University of Groningen
Studies on Anthriscus sylvestris L. (Hoffm.) Hendrawati, Oktavia
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Download date: 02-10-2021 Studies on Anthriscus sylvestris L. (Hoffm.) Metabolic engineering of combinatorial biosynthesis of podophyllotoxin
Oktavia Hendrawati This PhD project was carried out in the Department of Pharmaceutical Biology, Department of Molecular Biology of Plants and Department of Plant Physiology according to the requirements of the Graduate School of Science (Faculty of Mathematics and Natural Sciences, University of Groningen). This work was financially supported by Ubbo Emmius Fund of the University of Groningen, the Netherlands ISBN: 978-94-6182-027-3 Cover design: Hester Nijhoff, www.hesternijhoff.nl Layout and printing: Off Page, www.offpage.nl This thesis is also available in electronic format at: http://dissertations.ub.rug.nl/ Copyright © 2011 by O. Hendrawati. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without prior permission of the author. RIJKSUNIVERSITEIT GRONINGEN
Studies on Anthriscus sylvestris L. (Hoffm.) Metabolic engineering of combinatorial biosynthesis of podophyllotoxin
Proefschrift
ter verkrijging van het doctoraat in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus, dr. E. Sterken, in het openbaar te verdedigen op vrijdag 28 oktober 2011 om 14.30 uur
door
Oktavia Hendrawati geboren op 29 oktober 1977 te Surabaya, Indonesië Promotores: Prof. dr. O. Kayser Prof. dr. W.J. Quax Copromotor: Dr. H.J. Woerdenbag Beoordelingscommissie: Prof. dr. R. Verpoorte Prof. dr. J.T.M. Elzenga Prof. dr. E.M.J. Verpoorte
The soul filled by love neither tires others nor grows tired
Taize
Didedikasikan untuk papa, mama, Januar Hendrawati, Yuniarto dan Aprilarto Hendronoto Tjandra Paranimfen: Melanie Foeh Christina Avanti Contents
Scope of the thesis 9
Chapter 1 Metabolic engineering strategies for the optimization of medicinal and aromatic plants: realities and expectations 11
Chapter 2 Seasonal variations in the deoxypodophyllotoxin content and yield of Anthriscus sylvestris L. (Hoffm.) grown in the field and under controlled conditions 45
Chapter 3 Identification of lignans and related compounds in Anthriscus sylvestris by LC-ESI-MS/MS and LC-SPE-NMR 63
Chapter 4 In vitro regeneration of wild chervil (Anthriscus sylvestris L.) 79
Chapter 5 Agrobacterium mediated transformation of Anthriscus sylvestris with human cytochrome P450 3A4 followed by regeneration 93
Summary 111 Samenvatting 113 Ringkasan 116 Acknowledgments 119
Scope of the thesis
Podophyllotoxin is a lignan, which is used as a precursor of the anticancer drugs etoposide and teniposide. Both drugs are important in the treatment of lung and testicular cancers, Ewing’s sarcoma, lymphoma, glioblastoma and non-lymphomatic leukaemia. Three different methods are known for the production of podophyllotoxin: isolation from Podophyllum and Linum species, production by plant cell cultures, and organic synthesis. To date, podophyllotoxin is commercially only obtained by extraction of the rhizome of Podophyllum species. The availability of Podophyllum species, however, is limited and the continuous demand of podophyllotoxin jeopardizes the natural sources. Podophyllum species are already listed on the endangered species list in India. Using plant cell cultures or organic synthesis for production purposes is not feasible, as the yields are limited and the price cannot compete with the collection of plants from wild habitats. In the near future, the availability of podophyllotoxin will become a major bottleneck in supplying pharmaceutical needs. An alternative source of podophyllotoxin may be obtained from the hydroxylation at the C-7 position of the closely related lignan deoyxpodophyllotoxin yielding (epi)podophyllotoxin, the diastereoisomer of podophyllotoxin. The Apiaceae species Anthriscus sylvestris L. (Hoffm.) is a wild plant generally occurring in northern Europe containing deoxypodophyllotoxin as its main lignan constituent. The aim of this thesis is to create and explore an alternative source of (epi) podophyllotoxin by production from deoxypodophyllotoxin. Current engineering strategies for the optimization of medicinal and aromatic plants are discussed in the introductory chapter 1. Deoxypodophyllotoxin is found in all parts of A. sylvestris at concentrations between 0.03 and 0.15% (dw). To get a clear picture of the deoxypodophyllotoxin content over the developmental stages of the plant, we studied the variations of deoxypodophyllotoxin during different developmental stages. The results are described in chapter 2. We followed one biannual life cycle of A. sylvestris collected from 13 different locations in Europe that were grown in the field and in a climate room. Based on the results, we could indicate the best harvesting time of the plant for deoxypodophyllotoxin isolation and for choosing a suitable candidate plant for on-going cultivation. In chapter 3, we identified 14 compounds in the root extract of A. sylvestris using combined method of LC-ESI-MS/MS and LC-SPE-NMR. Based on these results, we propose a hypothetical biosynthetic pathway of 6-hydroxy-aryltetralin lignans in A. sylvestris. A. sylvestris allows an interesting approach for genetic modification to directly produce (epi)podophyllotoxin in the plant. Human cytochrome P450 3A4 was cloned in A. sylvestris via Agrobacterium tumefaciens. For transformation purposes we first needed to establish a regeneration protocol for A. sylvestris. Different media and combinations of auxins and cytokinins were used for regeneration and the outcome is discussed in chapter 4. The transformation of A. sylvestris with human cytochrome P450 3A4 was achieved and discussed in chapter 5. The findings and the interpretation of the results of our study are highlighted in the summary.
9
Chapter
Metabolic engineering strategies for the optimization of medicinal and aromatic plants: realities and expectations
Oktavia Hendrawati Herman J. Woerdenbag Jacques Hille 1 Oliver Kayser
Journal of Medicinal and Spice Plants 2010; 15(3): 111-126 1
Metabolic engineering strategies engineering Metabolic Abstract
In recent years, strategies and techniques for the production of natural compounds (plant derived fine chemicals) and/ or the breeding of medicinal and aromatic plants has expanded. Efficient production of high value natural products with medicinal and cosmetic purpose (e.g. essential oils, paclitaxel, artemisinin, and vincristine) is the main target. Metabolic engineering and pathway optimization with the aim to reduce costs and increase productivity are the main focus of academia and industry. Until now, only a limited number of plant cell cultures and isolated enzymes gave sufficiently high production for commercial purposes. Therefore research strategies have been shifted to metabolic engineering. Engineering of microorganisms has proven to be a valuable tool and the concept has been transferred to plant science opening new promising perspectives. Engineering has been conducted for crop plants, but the application of this technique to medicinal plants has not yet been explored well so far. Nowadays the cloning and expression of multiple genes and genomic integration are of high interest. This allows the reconstitution of biosynthetic pathways in heterologous organisms, being either plants or microorganisms. Combining basic science and applied engineering in this research area has been named combinatorial biosynthesis and later as synthetic biology. Synthetic biology comprises a large number of subareas, including enzymology, protein assembly and interactions, metabolomics, gene regulation, signal transduction and computational biology and is considered as an important future approach for biotechnological plant optimization. Synthetic biology has exciting perspectives for the exploitation of medicinal and aromatic plants, in order to increase the level of desired natural products, to gain insight in metabolic pathways even for new similar chemicals, to improve nutritional and health promoting effects of foods (nutraceuticals), and to reduce the amount of undesired side products with potential toxic or allergic activities.
Keywords: synthetic biology, metabolic engineering, plant breeding, plant genetics, medicinal and aromatic plants
Oktavia Hendrawati1, Herman J. Woerdenbag2, Jacques Hille3, Oliver Kayser1,4
1Department of Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 2Department of Pharmaceutical Technology and Biopharmacy, University of Groningen Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 3Department of Molecular Biology of Plants, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands; 4Technical University Dortmund, Technical Biochemistry, Emil-Figge-Strasse 66, 44227 Dortmund, Germany
Journal of Medicinal and Spice Plants 2010; 15(3): 111-126
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1. Introduction strategies engineering Metabolic
Plants are a rich source of bioactive compounds. Compounds of plant origin are used as drugs and precursors of semisynthetic drugs, and may provide valuable leads for novel drug design. Furthermore, plant extracts are still being used to prevent, and to treat a number of diseases although the mechanism of action is frequently unknown. Finally, there is a global demand for “greener” manufacturing processes that are economically attractive to be available in a timely manner.1 Worldwide more than 50,000 plant species are used for medicinal purposes.2 The World Health Organization (WHO) estimated that more than 80% of the population in the world in less developed countries depends primarily on herbal medicine for basic healthcare needs.3 The current herbal drug market has reached a level of US $62 billion, which is forecast to grow to US $5 trillion in 2050.4 The world market for herbal medicines shows an annual growth of 5-15%.5 In the UK, more than 25% of the population uses herbal medicines on a regular basis.3 In the past 30 years, more than 25% of the new drug entities approved was based on a molecule of plant origin and about one third of the approximately 980 new pharmaceuticals originated from or were inspired by natural products.6, 7 About 50% of the top-selling chemicals are derived from the knowledge on plant secondary metabolism.7 About 40% of the pharmaceuticals in the US and Europe use plants as raw source material.8 Besides plants and plant extracts, pure compounds derived from plants play an important role in contemporary pharmacy and medicine. Typical plant compounds (table 1 and figure 1), commonly used drugs, are terpenoids, alkaloids, polyketides, phenylpropanoids, and flavonoids. For examples, morphine and codeine from Papaver somniferum L., artemisinin from Artemisia annua L., paclitaxel from Taxus brevifolia Nutt, genistein from Glycine max L. (Merr.), scopolamine from Dubosia species, camptothecin from Camptotheca acuminata Decne, and podophyllotoxin from Podophyllum species. Despite the use of and demand for plant-derived compounds, their availability is a major bottleneck in supplying the pharmaceutical needs. Most of these compounds are secondary metabolites, which are present only in low amounts from natural sources. Most medicinal plants are not cultivated, but are collected from the wild and some of them are slowly growing. Because of intensive collection from the wild the current extinction rate of medicinally used plants are estimated to be 100 to 1000 times higher than for other plants. As many as 15,000 out of 50,000 to 70,000 medicinal plant species are now threatened with extinction.9 Currently between 4,000 and 10,000 medicinal plants are on the endangered species list and this number is expected to increase in the future.10 There are a number of limitations to obtain plant-derived compounds. They may be restricted to one species or genus and might be formed only during a particular stage of growth or development or under specific seasonal, stress or nutrient availability conditions.11, 12 Chemists have also been challenged to synthesize plant-derived
13 1 Metabolic engineering strategies engineering Metabolic
Ref. 13 14-16 17 18 14, 19 Reason for combinatorial biosynthesis Availability in nature is limited Chemical synthesis – economically not feasible Green manufacturing Cottonseed free from gossypol for protein source of human diet Low production in nature Slowly growing tree The bark is nonrenewable – harvesting the bark results in the death of the tree Chemical synthesis – economically not feasible Endangered species Chemical synthesis – economically not feasible
Price $US/kg 1,000 12 (synthetic) 30-120 (vanilla pods) Unknown? 28,000 1,490 Currentproduction E. coli chemical synthesis Isolation from plants Plant cell culture ESCA genetics (USA); Phyton Catalytic (USA/ Germany); Nippon Oil (Japan); Samyang Genex (Korea) Plant cell culture (Nippon oil – Japan) Demand (tons/ year) 120 > 10,000 36,000 0.3 species Plants source Artemisia annua (0.01 – 0.86% in aerial parts) Taxus planifolia Vanilla Gossypium hirsutum Podophyllum species (4.3% d.w.) Activity / function Anti- malarial Antitumor Flavor Fiber Antitumor Overview of the production of the plant-derived and medicinally relevant compounds with their metabolic engineering strategies Compound Dihydroartemisinic acid (Terpenoid) Paclitaxel (Terpenoid) Vanillin (Phenylpropanoid) Genistein (Flavonoid) Podophyllotoxin (Lignan) Table 1. Table
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Metabolic engineering strategies engineering Metabolic Ref.
14, 20, 21 16, 22 23 Reason for combinatorial biosynthesis Multiple chiral centres – chemical synthesis – economically not feasible Multiple chiral centres – chemical synthesis – economically not feasible Multiple chiral centres – chemical synthesis – economically not feasible Higher yield
Price $US/kg Unknown? Unknown? 1,400 spp. spp. (HnH6H & Currentproduction Transgenic hairy root culture of Hyoscyamus niger NtPMT) – 411.2 mg/L Duboisia Sumitomo Chemical Industries (Japan) Isolation from plants Isolation of plants Demand (tons/ year) 27,8 0.3 species (20% d.w. Plants source Duboisia (1.2 – 2.4% in leaves) Papaver in latex; 1.23-2.45 whole% d.w. plant extracts) Catharanthus roseus (0.0003 in% d.w. whole plant) Activity / function Anticho- linergic Analgesic Antitumor Overview of the production of the plant-derived and medicinally relevant compounds with their metabolic engineering strategies Compound Scopolamine (Alkaloid) Morphine (Alkaloid) Vincristin (Alkaloid) Table 1. Table
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Metabolic engineering strategies engineering Metabolic compounds via organic chemistry. This is often hampered by the chemical complexity, specific stereochemistry and the economic feasibility. Metabolic engineering may offer prospects to overcome the lack of availability of such compounds, through the advancement of the molecular biology techniques, including cloning, recombinant DNA and knowledge of the plant biosynthetic pathways. In this review, we discuss the major strategies in plant metabolic engineering and their principle approaches and its prospects and limitations for the production of drugs and fine chemicals. Case studies are used as illustrations.
Figure 1. Chemical structures of important plant derived compounds.
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2. The plant as a source for natural products strategies engineering Metabolic 2.1. Plant Cell Cultures In principle, whole plants, plant organs and even single cells can be used for the production of natural products. Plant cell culturing was initiated in the 1930s24 and would offer alternatives to improve the production of the secondary metabolites, since natural harvest is sometimes bulky and not feasible from an economic point of view. The main advantages of plant cell culturing are easy up-scaling, simple purification schemes due to product secretion, environmental friendliness, and amenability to strict control in regards to meet FDA manufacturing standards.25 Plant cell cultures are also not subject to changes in environmental conditions, thus the production of the desired compounds could take place at any location and season.26 In 1959, plant cells were first cultured in a 10 L glass or steel bioreactor27 and later, in 1977, a first larger scale of a 20 L stirred tank bioreactor of N. tabacum cells was reported.28 Today, undifferentiated plant cell suspension cultures can easily be scaled up for commercial production purposes, but the productivity is often hampered by the fact that the compounds of interest are not produced in the undifferentiated cells. Currently 14 plant cell cultures have been commercialized for secondary metabolites production for pharmaceutical, food and cosmetic purposes.14, 29 Examples are scopolamine from Dubosia spp (Sumitomo Chemical Industries, Japan), ginsenosides from Panax ginseng (Nitti Denko, Japan), and paclitaxel from Taxus spp. (Phyton Biotech, USA and Samyang Genex, Korea).14 One success story of a plant cell culture produced drug is paclitaxel (Taxol® Bristol Myers Squibb). While the plant itself, Taxus brefolia, only produces paclitaxel at approximately 0.01% of the dry weight of the bark,30 the plant cell suspension culture has been shown to produce stably in the range of 140-295 mg/L, reaching 295 mg/L at a maximum under two-stage culture with the elicitation of methyl jasmonate and high density conditions.15 Main constraints of using plant cell cultures for the production of secondary metabolites include slow growth of plant cells in comparison to microorganisms, no accumulation of desired metabolites in undifferentiated cultures, compartmentalization of the production of secondary metabolites, low and variable yields, and the decrease of metabolite accumulation as the cell line ages.25, 31-33 Differentiated cells produce the same product as the plant itself, but in large-scale production aiming at an economically attractive way the yield remains a bottleneck, especially for slowly growing plants. A variety of approaches such as the growth of differentiated cells (roots and shoot cultures) and the induction of pathways by elicitors had limited success so far.12 The plant production of secondary metabolites is controlled in a tissue-specific manner, thus the dedifferentiation results in loss of production capacity12 and undifferentiated cell cultures which are genetically unstable, often lose, partially or totally, their ability to produce secondary products.34, 35 For example, artimisinin, a potent antimalarial drug, was not found in cell suspension cultures of Artemisia annua, while considerable amounts were detected in
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Metabolic engineering strategies engineering Metabolic shoot cultures.36, 37 Deoxypodophylltoxin, the main lignan in Anthriscus sylvestris was also detected in trace amounts in callus and cell suspension cultures.38
2.2. Transgenic plants In 1907, Smith & Towsend reported the cause of crown gall disease of paris daisy (Chysanthemum frustescens) by Bacterium tumefaciens. Later on the bacterium was classified asPhytomonas tumefaciens and finally asAgrobacterium tumefaciens, a gram- negative soil dwelling bacterium.39 In the end of the 1970s, it was reported that the T-DNA of this microorganism was covalently integrated into the plant nuclear genome in tobacco teratoma cell lines.40, 41 This led to many studies up to date. Since 1994, transgenic technology is being used and commercialized to produce new crop products with herbicide tolerance, insect resistance, virus resistance, and improved post-harvest quality.42 Transgenic approaches can be applied to target a rate-limiting step through manipulation of the expression of individual structural genes.5 There are two transformation approaches commonly used to produce recombinant pharmaceuticals in plants. First to subject plants to Agrobacterium-mediated transformation, particle bombardment, electroporation, and second, to infect plants with recombinant viruses that express transgenes during their replication in the host.43-46 Genetic transformation of medicinal plants is usually carried out using Agrobacterium rhizogenes to obtain hairy root cultures, or using Agrobacterium tumefaciens to produce transformed cells that can be maintained in cell cultures or can be regenerated as whole plants.2 In principle, the wounded plant tissues caused by insect or mechanical damage, produce phenolic compounds, which attract Agrobacterium by chemotaxis to infect the plant cell on the wounded site and allow the transfer of T-DNA from Agrobacterium into the plant nuclear chromosome. The T-DNA contains genes that encode enzymes directing the plant cells to produce peculiar amino acids called opines, and express genes to direct the plant cells to produce plant hormones such as cytokinin and auxin. Opines are used as primary sources of carbon and nitrogen by the cohabiting bacteria, and cytokinins and auxin promote cell division and tumor formation, providing a steadily increasing supply of nutrients for the bacteria.47 The infection from A. rhizogenes in the wounded site will cause a number of small roots protrude as fine hairs grow and proliferate rapidly, causing hairy root.48 T-DNA carries the rol and aux genes. The rol genes are responsible for the phenotype of hairy roots and the aux genes are involved in root induction by directing auxin synthesis.49 The major drawbacks of this approach are the unstable gene expression, instability of cell lines that often lose their capacity to produce target molecules over time, and high cost of bioreactors.2 For example, the alkaloid accumulation in transgenic Catharanthus roseus cell cultures resumed quickly to the level of nontransgenic ones.50 The capacity to regenerate whole plants from single cells without changing the genetic features of the cells and the gene transfer mechanism via Agrobacterium tumefaciens facilitate efforts to engineer secondary metabolic pathway.2, 51 The constraint is the
18 1 subsequent regeneration of transgenic plants, which remains problematic and time strategies engineering Metabolic consuming. Unwanted somaclonal variation may be introduced through the tissue culture regeneration system in some cases.52 Plants have been and are used as a host to produce genuine and recombinant proteins and enzymes of industrial and pharmacological value.53 More than 200 novel antibody-based potential products are in clinical trials worldwide, and the market demand will constrain the capabilities of existing production systems.54 One would expect that the biopharmaceuticals from transgenic plants are safer and less expensive than those from animal-based sources, which have the potential for contamination with human pathogens.43 Enhanced productivity of valuable secondary plant metabolites can also be achieved via hairy root cultures.26 Hairy root culture can be obtained from transformed root cultures using Agrobacterium rhizogenes, a gram-negative soil dwelling bacteria. The term “hairy root” was introduced in 190055 and the first transformation of higher plants using A. rhizogenes was achieved in 1973.56 Hairy root cultures are genetically stable, capable of unlimited growth without additional hormones and have an increased capacity for secondary metabolites formation and accumulation.25 Genetically transformed root cultures have been shown to produce levels of secondary metabolites comparable to that of an intact plant. It has further been shown that hairy root cultures can accumulate secondary metabolites that normally occur only in aerial part of the plant. An example is artemisinin in Artemisia annua.57 The transformation ofArtemisia annua using A. rhizogenes carrying the cDNA encoding FDS (farnesyl diphosphate synthase) under the 35S CaMV promoter yielded 4-fold higher artemisinin accumulation compared to untreated control plants.58 The transformation of Atropa belladonna with H6H (hyoscyamine 6b-hydroxylase) from Hyoscyamus niger under the control of the 35S CaMV promoter in a binary plasmid via A. rhizogenes mediated transformation resulted in an accumulation of scopolamine up to 5-fold higher compare to untreated control plants.59 Other examples of hairy root cultures producing secondary metabolites can be found in Srivasta and Srivasta.26 Another advantage is that transformed roots are able to regenerate whole viable plants, maintain their genetic regeneration, and in addition produce secondary metabolites that are not present in the parent plant.60 Furthermore, they show fast auxin-independent growth and are suitable for adaptation to bioreactor system.26 In addition to production of secondary metabolites, hairy roots are also used to produce human therapeutic proteins, vaccines and diagnostic monoclonal antibodies. For example, hairy root cultures of potato carrying pBSHER containing the hepatitis B surface antigen (HBsAg)’s gene expressed higher level of HBsAg compared to control cultures.59 Despite discussed potentials, challenges during large-scale cultivation like unusual rheological properties of hairy root cultures have to be addressed. Non-optimal fermentation made it necessary to investigate novel approaches to apply hairy root cultures to fermentor26 and process design.25
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Metabolic engineering strategies engineering Metabolic In conclusion, the use of hairy roots as factories for the production of novel plant- based bioactive compounds, vaccines, antibodies and other therapeutic protein offers good prospects for feasibility of commercial production.
3. Optimizing biochemical pathways 3.1. Strategies and goals of metabolic engineering Metabolic engineering is generally defined as the redirection of one or more enzymatic reactions to produce new compounds in an organism, to improve the production of existing compounds, or to mediate the degradation of compounds.61 Metabolic engineering of plants offers interesting perspectives to improve the productivity of the plant as a cell factory. This approach may create new opportunities in agriculture, environmental applications, production of chemicals, and medicines.12, 52 The main goal of metabolic engineering in general is to produce the desired natural products in a sustainable and economically attractive way.62 Several more specific goals of metabolic engineering are listed in table 2. The production level of a compound of interest which is present in trace amounts can be enhanced by increasing the flux of precursors, by blocking a competitive (parallel) pathway using the same precursor or intermediate compound, by introducing new routes of metabolism, by overcoming rate limiting steps, by reducing flux through enhancing competing pathways, by over-expressing regulatory genes or transcription factors that induce the pathway, and by inhibiting or limiting catabolism of the molecule or increasing the number of specialized cells producing the compound.2, 63 Some of the scientific challenges comprise a better understanding of the partly known secondary metabolite biosynthetic pathways on a genetic level, the generation of heterologous organisms with desirable biosynthetic characteristics, and optimised tools for pathway manipulation like vectors, synthetic genes and regulating elements.63 Moreover, biosynthetic pathways are often species-specific. Features like cell compartmentalization, tissue differentiation, and multi-enzyme complexes, will make the outcomes unpredictable.
3.2. Metabolic pathways of interest A comprehensive understanding of different metabolic pathways and their genetic control is essential for the application of a genomics approach to the improvement of medicinal plants.5 In this review we confine to the metabolic pathway of medicinal compounds among other pathways of interest (figure 2). Most secondary metabolites are derived from the shikimate, terpenoid and polyketide pathways. The shikimate pathway is the major source of phenylpropanoids and aromatic compounds,65, 66 such as flavonoids, coumarins, isoquinoline and indole alkaloids, lignans, lignins, and anthocyanins. The terpenoid pathway leads to more than one-third of all known secondary metabolites, including mono-, sesqui-, di-, tri- and tetraterpenes. It is also the source
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Table 2. Important goals of metabolic engineering in general. strategies engineering Metabolic
Some important Physiological understanding goals of metabolic engineering Novel compounds To yield a novel compound in a plant and other precursors by introducing the appropriate heterologous genes.2 To give a new trait (colour, taste, smell) to food, flowers or ornamental plants.12 To increase To improve production of a desired compound or enzyme in a cell culture and also in the plant itself To achieve production in a related plant species or even in microorganism To improve agronomic traits, such as resistance of a plant to various stresses, pests, diseases and to increase the seed yield of a crop plant through the expression of certain metabolites.12, 64 To decrease To decrease levels of noxious or antinutritional factors in food and feed crops.2 Regulatory understanding To improve our understanding of pathways regulation and flux when some of the intermediate pathways increase in abundance beyond their usual concentration range.64
of the C5-building block (isoprene) in many skeletons from other biosynthetic origin, such as anthraquinones, naphtoquinones, cannabinoids, furanocoumarins, and terpenoid indole alkaloids.67 The polyketide pathway is a rich source of bioactive molecules such as anthranoids. It is attractive as a model for metabolic engineering studies because the complex structure results from simple C2 units combined in different ways and the modular construction of enzymatic catalysts allows control of enzyme structure.63 The complexity of a metabolic pathway and some strategies to engineer the pathway are illustrated in figure 3. It is supposed that a basic skeleton S (substrate) is present in which three functional groups can be introduced. If highly specific enzymes would catalyze all steps, 12 enzymes (E1 until E12) could be involved in the formation of three different products with one functional group, three different products with two functional groups, and one final product with all three functional groups. If the specificity of the substrate is broad, it is likely that three different enzymes will be adequate. Heterologous genes (E13) can also be introduced into plant metabolic pathway which could catalyze all three functions of the substrate (S1) into product “S1,2,3.”
3.3. Synthetic Biology Synthetic biology is a rapidly growing multidisciplinary field among biologists, chemists, physicists, engineers and mathematicians.69 It is defined as the design and construction or engineering driven building of new or artificial biological components or increasingly complex biological entities, such as enzymes, genetic circuits, and cells, or the redesign of existing biological systems for novel applications.70, 71 The goals are
21 of medicinal plants.5 In this review we confine to the metabolic pathway of medicinal compounds among other pathways of interest (figure 2). 1 Metabolic engineering strategies engineering Metabolic
Figure 2. Simplified biosynthetic pathways of primary and secondary metabolism in plants (adapted from Kumar et al.5). Figure 2. Simplified biosynthetic pathways of primary and secondary metabolism in plants (adapted from Kumar et al.5). to build complex systems into specific hosts,71 to engineer synthetic organisms,71, 72 to improve understanding of biological systems, and to produce bio-orthogonal systems Most with new secondary functions. metabolites 69 are derived from the shikimate, terpenoid and polyketide The distinguishing pathways. element The that shikimate differentiates pathway synthetic is the biology major from source traditional of phenylpropanoids metabolic engineering and is aromatic the focus comp on theounds design,65, 66andsuch technological as flavonoids, construction coumarins, of core components (part of enzymes, genetic circuits, metabolic pathways, etc), which isoquinoline and indole alkaloids, lignans, lignins, and anthocyanins. can be modelled, understood and tuned to meet specific criteria. The assembly of these components into integrated systems which enables a systematic forward-engineering The of (parts terpenoid of) biological pathway systems leads for to improved more than and onenovel-third applications of all known is a second secondary key issue of synthetic biology.70, 71 metabolites, including mono-, sesqui-, di-, tri- and tetraterpenes. It is also the Synthetic biology is categorized into two broad classes. One uses unnatural source molecules of to the reproduce C5-building emergent block behaviours (isoprene) from in natural many biology, skeletons with the from goal other of biosynthetic creating artificial origin, life. such The other as anthraquinones, seeks interchangeable naphtoquinones, parts from natural cannabinoids, biology to assemble into systems that function unnaturally.73 The knowledge about these tools and methods may enable synthetic biologists to design, fabricate, integrate, test and construct artificial biological systems that came from the insights discovered by experimental biologists and their holistic perspectives.72
22 13 furanocoumarins, and terpenoid indole alkaloids.67 1 Metabolic engineering strategies engineering Metabolic
Figure 3. Schematic biosynthetic network, S: basic skeleton to which functional group 1, 2 and 3 are added. E1-13: enzymes that catalyze biosynthetic steps (adapted from Verpoorte et al.68). Figure 3. Schematic biosynthetic network, S: basic skeleton to which functional group 1, 2 and 3 are added. E1-13: enzymes that catalyze biosynthetic steps (adapted from Verpoorte Although synthetic biologyet al. offers68) promising applications for novel compounds and novel approaches, the success so far is rather limited since it is quite a young science. It is further hindered by the fact that the production processes of the most effective biological The components polyketide (promoters, pathway gene, is plasmids, a rich etc) source have been of bioactive patented. Royalty molecules payments such will as 70 anthranoids. It is attractiveincrease the costs, which makeas a model for metabolic engineering studies because it economically no longer attractive. Another drawback is that living systems are highly complex. Currently biologists lack information about the complex structure results from simple C2 units combined in different ways and how integration of living systems works.72 The success of synthetic biology depends on the its capacity modular to surpass construction traditional of engineering. enzymatic It catalysts should blend allows the best control features of of natural enzyme structuresystems with.63 artificial designs that are extensible, comprehensible, user-friendly, and implement stated specifications to fulfill user goals.72
The complexity of a metabolic pathway and some strategies to engineer the pathway are illustrated in 4. Metabolic engineeringfigure 3. It is supposed that a basic skeleton S (substrate) strategies and techniques in is present medic in in which al pla three nt functional biotech groups nology can be introduced. If highly specific The major metabolic engineering strategies and techniques applied in medicinal plant biotechnology are discussed in detail in this paragraph (see also figure 1). They include up or down regulating of pathways, redirecting common precursors, targeting metabolites
23
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Metabolic engineering strategies engineering Metabolic to specific cellular compartments, and creating of storage of overproducing secondary metabolites. Examples of techniques used and their application are given in table 3.
Table 3. Techniques used in metabolic engineering and their applications
Techniques Genes/ Plant species Target compounds/ Ref. Enzymes goals Single transgene codeinone reductase Papaver Increase of morphine 82 (biotransformation) (COR) somniferum CYP80B3 Papaver Increase of morphine 83 somniferum alkaloid Taxadiene synthase Solanum Production of taxadiene 84 lycopersicum Polycistronic Cholera toxin Nicotiana Production of cholera 85, 86 vectors (artificial b-subunit (CTB gene) tabacum toxin b-subunit chromosomes) Transcription factor ORCA Catharanthus Increase of terpenoid 79 roseus indole alkaloid Sense/antisense antisense CYP80B3 Papaver Decrease of 83 suppression somniferum benzylisoquinoline alkaloids up to 84% of total alkaloid Virus Inducing Gene Phytoene desaturase Papaver Reduction of transcript 87 Silencing (VIGS) (PapsPDS) somniferum level of endogenous PapsPDS and photobleach phenotype; and assessing gene function T6ODM (thebaine Papaver Increase of thebaine as a 88 6-O-demethylase) somniferum precursor of important and CODM (codeine pharmaceuticals O-demethylase) (oxycodone, naltrexone, naloxone, buprenorphine) RNAi berberine bridge Eschscholzia Accumulation of (s)- 89 enzyme (BBE) californica reticuline salutaridinol Papaver Accumulation of 90 7-O-acetyltransferase somniferum salutaridinol (SalAT) d-cadiene synthase Gossypium Reduction of gossypol 18 hirsutum
4.1. Upregulating of pathways (overexpression) Transcription factors (in multienzyme pathways) are regulatory proteins that can be used to regulate multiple steps or even to modulate an entire pathway in order to produce a significant yield of a desired product through sequence-specific DNA binding and protein-
24 1 protein interactions.64, 74 They can act as activators or repressors of gene expression, which strategies engineering Metabolic mediate respectively an increase or a decrease in the accumulation of messenger RNA.75 They are also able to regulate steps for which the enzymes are unknown.74 Using this approach, it is often necessary to increase precursor availability and to understand the coordination of multiple branches or sections of the metabolic pathway. The use of transcription factors requires integrated information from genomics, transcriptomics, proteomics, and metabolomics.25 Several transcription factors have now been identified. A relevant example is transcription factor MYB12, a flavonol-specific regulator of the phenylpropanoid biosynthesis in developing seedlings. Total flavanol content of the seed was increased when MYB12 was expressed in developing Arabidopsis thaliana seedlings. The expression of the genes encoding the four flavonoid biosynthetic enzymes was upregulated, increasing the flux through the flavanone pathway.76 Three transcription factors: ORCA1, ORCA2, and ORCA3 (octadecanoid-responsive Catharanthus AP2-domain) have been identified in the medicinal plant Catharanthus roseus and are involved in biosynthesis of terpenoid indole alkaloids. They belong to the AP2/ERF transcription factor family. The overexpression of ORCA3 in C. roseus cultured cells increased the expression of the terpenoid indole alkaloid biosynthesis genes TDC (tryptophan decarboxylase), STR, CPR (cytochrome P450 reductase), D4H (desacetoxyvindoline 4-hydroxylase)77 and SLS (secologanin synthase).78 Moreover, ORCA3 also regulated two genes encoding enzymes (ASa : a subunit of anthranilate synthase and DXS: D-1- deoxyxylulose 5-phosphate synthase) in the primary metabolism leading to terpenoid indole alkaloid precursor formation.79 Next to well-studied pathways, such as the phenylpropanoid biosynthesis, and the well- characterized MYB transcription factor family, finding a transcription factor that acts on specific pathway genes is very challenging.64 Transcription factors are difficult to identify in non-model species.74 An alternative is to design synthetic transcription factors, which target one or more genes of choice.80 As example, the expression of the ZFP-TF (zinc finger protein transcription factor) increased the activity of native g-methyltransferase (VTE4) and the a-tocopherol content in Arabidopsis thaliana seeds.81 Transcription factors, natural or synthetic, are used only if the pathway is endogenous to the plant.64
4.2. Redirecting common precursors Many branching points are found in a biosynthetic pathway where enzymes compete for a common precursor. Increasing and redirecting the precursor pool towards the biosynthesis of the target compounds can theoretically increase their production. This can be achieved by blocking the competitive pathway or by inducing overexpression of genes in the precursor pathway.67 GGPP (geranylgeranyl diphosphate) is normally utilized for making carotenoids in tomato. By overexpressing the gene that encodes taxadiene synthase in the tomato that lacks the ability to utilize GGPP for carotenoid production allowed GGPP to be re-routed for the production of taxadiene. The production was 660-20,000 times higher than in Arabidopsis thaliana.84 By overexpressing genes in precursor pathways in both
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Metabolic engineering strategies engineering Metabolic peppermint91 and lavender92 an increase in the monoterpene fraction of the essential oils was found. However, due to tight regulation of metabolite accumulation, this approach may also have a limited impact on target products. The increase of intermediate precursor resulted in a limited accumulation of alkaloid target product in C. roseus.93 In this case, the direct overexpression of related genes in the alkaloid pathway was shown to be more effective in increasing the alkaloid accumulation in C. roseus.94 The effect seems to be temporary. It might be due to a result of the same factors, which induce variability in nontransgenic plants.25
4.3. Targeting metabolites to specific plant cell compartments Targeting gene expression to a specific cellular compartment or organelle that contains the precursors could increase the level of the target compounds. Plants are able to express the transgene with organelle targeting signals from the nuclear DNA and the resulting recombinant proteins will be targeted to the appropriate organelles. Specific amino acid sequences required for targeting of proteins to particular organelles and for retention of proteins in organelles have been identified.52 Thus targeting the enzymes to the compartment of substrate seems feasible. However, the products formed may cause toxicity problems in another compartment than usual.67 Using this approach, overexpression of a target gene either in plastids or the cytosol allows transport of a sufficient pool of common precursors into the right direction and led to an more than 1,000-fold increase in concentration of the sesquiterpenes patchouli alcohol and amorpha-4,10-diene and a 10-30-fold increase of the monoterpene limonene in transgenic tobacco plants compared to untreated control plants.95
4.4. Creation of storage of overproduced secondary metabolites A plant may have the capacity to produce secondary metabolites but sometimes it lacks a proper subcellular compartment to store them.96 Modifications to metabolic storage of products or secondary metabolic pathways have been generally more successful than manipulations of primary and intermediary metabolism.97, 98 The genes controlling the formation of subcellular compartments have been isolated and characterized in plants.99 The expression of the Or gene encoding a DnaJ cysteine-rich domain-containing protein led to the formation of large membranous chromoplasts in cauliflower curd cells.99 The expression of the same gene in transgenic potato under the control of a potato granule-bound starch synthase promoter increased the total carotenoid up to 6-fold compared to the original, non transgenic plants.99
4.5. Downregulating of pathways (silencing) The production of a certain compound can be reduced by decreasing the flux towards that product by reducing the level of enzyme in the pathway, increasing catabolism and increasing flux into competitive pathways.2, 68 A particular step in the pathway that leads to undesirable compounds can be blocked by suppressing genes that upregulate the pathway or by increasing their catabolism.2
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Antisense, co-supression and RNA interference (RNAi) methods are used to block, to strategies engineering Metabolic reduce or to eliminate levels of undesirable compounds. This so called silencing can be targeted to specific plant tissues and organs with minimal interference of the normal plant life cycle, by using tissue or organ-specific RNAi vectors. Mutants with the RNAi effect have been shown to be stable for at least 20 generations.100
5. Challenges in plants metabolic engineering 5.1. Unexplored regulation of secondary metabolism The lack of complete understanding of the regulation of secondary metabolism, especially in the complex alkaloid biosynthesis, hinders the determination of an effective metabolic engineering strategy to achieve a specific production phenotype. The complexities comprise pathway compartmentalization, the existence of sometimes multiple biosynthetic pathways and the regulatory control mechanisms.101 Up to date, only four biosynthetic routes of alkaloid subclasses have been partially characterized in particular, the benzylisoquinoline, monoterpenoid indole, purine and tropane alkaloids.101 This could be ascribed to limited genome/cDNA sequence information of medicinal plants.5
5.2. Pathways are often species-specific A number of genes encoding enzymes, that control key steps of secondary metabolic pathways, has been cloned from a number of a medicinal plant species using classical and modern genomics approaches.5 However this represents a small fraction of a total of about 1,000 plant genes known to function in secondary metabolism.102 The progress in isolating genes involved in secondary metabolism is limited due to species specificity, the difficulty in producing large numbers of mutants, their intermediate precursor availability, their analysis, and to the instability of secondary metabolites caused by environmental factors.103 The major bottleneck for secondary metabolism will remain per definition species specific. Only early parts of pathways are common to most plants, for example in the flavonoid and terpenoid biosynthetic pathways, thus homology between genes can be used for strategies to clone genes from other plants.103 The genes encoding enzymes involved in the more specific ‘decoration’ of the basic skeletons only can be studied at the level of the very producing plant.104
5.3. Cell compartmentalization and tissue differentiation Plant cells have a complicated intercellular organization with metabolite flow between compartments highly regulated and orchestrated depending on the biosynthetic needs of the plants.105 They have numerous organelles of which some are not found in mammalian or yeast cells.52 The highly compartmentalized nature of enzymes, substrate precursors, and metabolic intermediates also contributes to the complexity of secondary metabolites production, which is regulated at a different level.2
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Metabolic engineering strategies engineering Metabolic Plants also have numerous specialized and differentiated organs in which physiological processes and gene expression may differ substantially. Next to organelles, the compartmentalization of secondary metabolite pathways also occurs at the subcellular level.106 Furthermore, temporal and developmental processes can profoundly influence whether and when a transgene is active. Thus the issues of compartmentalization complicate the targeting gene strategy. Moreover if the engineered plants are going to be propagated as crops, environmental effects may add to the level of variability and unpredictability which is not encountered in a fermentor based system.52 There is increasing evidence that intra- and intercellular translocation of enzymes are one of the key elements in secondary metabolite production. Localization of enzymes to diverse cellular compartments showed the importance of protein targeting in the assembly of the alkaloid pathway.2 Alkaloids are generally stored in specific types of compartments due to their cytotoxicity and probable role in plant defence responses. The subcellular compartmentalization of alkaloid pathway enzymes is extremely diverse and complex as the cell type-specific localization of the gene transcripts, enzymes, and metabolites.107 Other examples are phenylpropanoid derivatives. Their biosynthesis occurs in the cytoplasm, but the precursors are derived from metabolism in other organelles, including the chloroplasts and mitochondria.105
5.4. Unpredicted or unexpected outcome The use of metabolic engineering approaches in medicinal plant species to improve the yield of pharmaceutical products has been and is a challenge. There are several limitations such as gene silencing, unpredictable results due to complex network genes, and no increase in concentration of desirable metabolites up to the level of commercialization.5 Techniques used to introduce new genes into plants also do not allow a prediction about the site of integration and the level of gene expression, even when a strong promoter is used.67 It is often hard to accurately guess what are the actual biological roles of certain enzymes solely based on bioinformatics, due to promiscuity towards substrates and the relatively ease to change substrate or product specificity by introducing minor changes in sequence of the enzymes.108 Single-enzyme perturbations of alkaloid pathways resulted in unexpected metabolic consequences suggesting the existence of key rate-limiting steps, potential multi-enzyme complexes, or unsuspected compartmentalization.107 Over-expression of COR1 (codeinone reductase), the final enzyme in morphine biosynthesis, increased the morphine and codeine contents in transgenic poppy.82 However, thebaine, an upstream metabolite in the 23 branch pathways, was also unexpectedly significantly increased. The knock down of COR1 with RNAi technology would expect to suppress 23 upstream biosynthetic steps and the accumulation of codeinone and morphinone, the immediate precursor of COR. The amount of morphinan alkaloids decreased, while the biosynthesis of (S)-reticuline, an early upstream metabolite in the pathway, was increased instead of the target compounds codeinone and morphinone.109
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The complexity and redundancy of many biosynthetic pathways coupled to incomplete strategies engineering Metabolic knowledge of their regulation could lead to an unpredictable outcome from a targeted metabolic engineering strategy.25 Selected case studies using different approaches and strategies in metabolic engineering are discussed in the next paragraph.
6. Metabolic engineering applications in medicinal plant biotechnology 6.1. Case study: Podophyllotoxin production in Anthriscus sylvestris Anthriscus sylvestris (L.) Hoffm. (Apiaceae) is a common wild plant in northwest Europe that accumulates considerable amounts of lignans. Deoxypodophyllotoxin, an aryltetralin-lignan as the main attractive constituent which is much more abundant in the plant kingdom than podophyllotoxin, can be used as a precursor for the production of podophyllotoxin. Podophyllotoxin is used as a precursor for the semi-synthesis anticancer drugs: Etoposide phosphate and Teniposide.110 To date, podophyllotoxin is obtained by isolation from Podophyllum species. In the future, the availability of podophyllotoxin from this source is likely to become a major bottleneck. Podophyllum species are on the endangered species list, proving that the increasing demand of podophyllotoxin is a serious threat for the plant.111 An alternative source of podophyllotoxin may be obtained by (biotechnological) hydroxylation of deoxypodophyllotoxin at the C7 position (see figure 1). Human cytochrome P450 3A4 in E.coli DH5a selectively hydroxylates deoxypodophyllotoxin at the C7 position yielding podophyllotoxin.112 Studies to transform A. sylvestris with this cytochrome are in progress.
6.2. Case study: Scopolamine biosynthesis in Nicotiana tabacum Scopolamine and hyoscyamine are tropane alkaloids. They form an important class of plant derived anticholinergic compounds occurring in several genera of the Solanaceae like Hysoscyamus, Atropa, Duboisia, Scopolia, and Datura.16, 107 Scopolamine has a higher commercial market value than hyoscyamine but has a lower yield from plants than hyoscyamine.16 The world demand of scopolamine is estimated to be about 10 times higher than hyoscyamine and its racemic form atropine. The main source of raw material worldwide are Duboisia leaves containing 2-4% of total alkaloids, with more than 60% scopolamine and 30% hyoscyamine.20 Up to 6% of scopolamine has been achieved by conventional cultivation of selected varieties in Australia, Equador, and Brazil, producing 1 t/ha of plant material for industrial alkaloid extraction.20 The heterologous expression of PMT (putrescineN -methyltranferase) from Nicotiana tabacum in Scopolia parviflora yielded a 8-fold increase in scopolamine and a 4.2-fold increase in hyoscyamine production.113 A similar effect has been achieved inHyoscyamus muticus and Datura metel.114 Surprisingly, this PMT expression has no effect on alkaloid production when it is expressed in other tropane alkaloid producing hairy root cultures
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Metabolic engineering strategies engineering Metabolic of Hyoscyamine niger, Atropa belladonna, and Duboisiana hybrid.21, 115, 116 It was suggested that PMT expression in the roots was insufficient to boost the tropane alkaloid synthesis of these plants. Overexpression seems to be species-related due to a different, specific post-translational regulation of the endogenous enzyme in respect to the foreign one.116 The constitutive expression of H6H (hyoscyamine 6b-hydroxylase) fromHyoscyamus niger in Atropa belladonna, a plant that normally accumulates hyoscyamine, converts hyoscyamine into scopolamine up to 1.2% dry weight.117 The alkaloid composition of aerial parts of mature plants changed from over 90% hyoscyamine in controls and wild type plants, to almost exclusively scopolamine in transgenics.117 In transgenic hairy root of Atropa belladonna, up to a 5-fold scopolamine increase was observed.118 In Hyoscyamus muticus hairy root expressing the H6H gene, up to a 100-fold increase of scopolamine was found, while the hyoscyamine content remained unaltered.119 Transgenic tobacco plants expressing constitutively H6H were fed with hyoscyamine and 6b-hydroxyhyoscyamine. These precursors were converted into scopolamine in the leaves of the plants.117 The hairy root cultures of Nicotina tabacum, which do not produce hyoscyamine, were used to express the H6H gene from Hyoscymanus niger. The cultures successfully converted added hyoscyamine into scopolamine. They showed efficient uptake of hyoscyamine (average of 95%) from the culture medium and a higher rate of bioconversion of hyoscyamine into scopolamine (10-45%). Up to 85% of the total scopolamine was released into the culture medium.120 This was in contrast to the normal metabolic behaviour of tropane alkaloid-producing hairy roots in which the scopolamine remained accumulated in the root tissues.62 Feeding exogenous hyoscyamine to cell suspension cultures, which were obtained from the hairy root, showed considerable capacity to convert hysocyamine into scopolamine and the product was secreted into the culture medium.121 The scaling up of the transgenic cells grown in a 5 L turbine stirred tank reactor in a batch mode yielded scopolamine up to a 1.6-fold higher than the small-scale cultures. Almost 18% of the hyoscyamine added to the medium was transformed into scopolamine, which showed 65% of increase with respect to the same alkaloid obtained by bioconversion in shakes flasks.20 The constitutive co-expression of genes encoding the rate-limiting upstream enzyme PMT (putrescine N-methyltransferase) and the downstream enzyme H6H of scopolamine biosynthesis yielded only a modest increase in alkaloid accumulation when it was expressed alone, but exhibited a synergistic effect on alkaloid levels when expressed together.21 It resulted in the highest production of scopolamine in hairy root culture reported of 411 mg/L. It is a 10-fold increase over control cultures and a 2-3-fold increase over cultures, which expressed only H6H.21
6.3. Case study: Genistein production in transgenic arabidopsis, tobacco, lettuce, corn, petunia, and tomato Genistein is a common precursor of the isoflavonoids biosynthesis especially occurring in the subfamily Papilionoideae of the Fabaceae.122 Isoflanoids are interesting because of their pharmaceutical and nutraceutical activity that attract considerable interests in the prospect of introducing them into vegetables, grains, and fruits for dietary disease
30 1 prevention.123 Genistein production in nonlegume plants has been performed but yet strategies engineering Metabolic with unsatisfactory yields. It might be due to the competitive use of naringenin between isoflavon syntase (IFS) and the endogenous flavonoid pathway.123-125 Soy products are the major dietary sources of isoflavonoids (genistein) for human. The IFS isolated from soybean has been introduced into Arabidopsis thaliana, corn (Zea mays) and tobacco (Nicotiana tabacum).125 There was no accumulation of free genistein in Arabidopsis, but genistein was glycosylated to glucose-rhamnose-genistein and rhamnose-genistein.123 The overexpression of soybean IFS in tobacco, petunia (Petunia hybrida Vilm) and lettuce (Lactuca sativa L.) resulted in genistein accumulation in transgenic plants.126 Another approach was the introduction of a heterogenous phenylalanine ammonia- lyase (PAL) and IFS into genetically manipulated plants. This increased the genistein content in tobacco petals (1.80-fold) and lettuce leaves (1.5-fold).126 The overexpression of IFS soybean in tomato (Solanum lycopersicum L) resulted in the presence of genistein 7-O-glucoside as the major isoflavone metabolite in the transgenic plants.127
6.4. Case study: Expression of spearmint limonene synthase in lavender Essential oil quantity and quality can be regulated by metabolic engineering.91 In principle, it is possible to engineer the biosynthesis of monoterpenes in order to increase or to modify the essential oil profiles in the target plant.128 For example, the expression of a sense of the 1-deoxy-D-xylulose-5-phosphate (DXP) reductoisomerase cDNA, and with an antisense of menthofuran synthase cDNA under the control of CaMV 35S promoter, resulted in up to 50% more essential oil in Mentha × piperita L. without changing the composition of the monoterpenes as compared to the wild- type.91 Meanwhile the expression of DXP synthase in Lavandula latifolia increased the essential oil up to a 3.5-fold in leaves and up to a 7-fold in flowers as compared to control, without obvious deleterious effects on plant development and fitness.92 Spike lavender (Lavandula laftifolia Med.) is an aromatic shrub that is cultivated worldwide for oil production, which has limonene as a minor constituent (0.5-2%). Overexpression of the LS gene from spearmint (Mentha spicata) in spike lavender under the regulation of the CaMV35S constitutive promoter showed more than 450% increase of limonene content in developing leaves as compared to the control.128 The expression of lemon basil (Ocimum basilicum L. cv. Sweet Dani) geraniol synthase under the regulation of the tomato polygalacturonase promoter in tomato increased the monoterpenes (limonene) and sesquiterpenes content at the expense of reduced lycopene accumulation.129, 130
6.5. Case study: Artemisinin biosynthesis in Artemisia annua In the early 1980s, efforts started to establish Artemisia annua L. cultures producing artemisinin.131 A range of variable but always low artimisinin levels were found in callus, shoot and root cultures but no artemisinin in cell suspension cultures, suggesting that some degree of differentiation is required for the production.132 Transformation of Artemisia annua with Agrobacterium rhizogenes resulted in hairy root cultures that
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Metabolic engineering strategies engineering Metabolic produced artemisinin and currently many efforts are directed toward optimizing production in hairy root cultures.133 Several key genes involved in the biosynthesis of artemisinin have been introduced in A. annua. Approaches in genetic engineering have been focused on the overexpression of cloned key enzymes involved in the biosynthesis, such as farnesyl diphosphate synthase (FPS)134 and amorpha-4,11-diene synthase (AMS).135 Genetic transformation and regeneration of A. annua has been established to introduce genes of interest via A. tumefaciens.136 A. annua expressing FPS from Gossypium arboreum accumulated higher level of artemisinin compared to A. annua expressing the FPS from A. annua. A. annua expressing FPS accumulated up to 10.08 mg/g d.w. artemisinin.136-138 Hairy root cultures of A. annua were established by transforming it via A. rhizogenes carrying the farnesyl diphosphate synthase (FDS) gene. The artemisinin content in the transgenic plants, which were regenerated from the hairy root cultures, was significantly higher than in the control plant.95 Despite all the genetic engineering attempts, the mean of production of artemisinin is still mainly from the plant itself. Recently, the FDA has approved Coartem® (Novartis) as the first artemisinin-based combination treatment (ACT) for malaria in the USA.139 Novartis has stimulated the cultivation of Artemisia annua of more than 1,000 hectares in Kenya, Tanzania and Uganda. In addition, it has also cultivated in China, in total it reaches up to 10,000 hectares.140
6.6. Case study: Morphine and Thebaine biosynthesis in Papaver somniferum Papaver somniferum remains to be the sole source of morphine. The commercial chemical synthesis of morphine, codeine and other benzylisoquinoline alkaloid is not economically feasible due to the complexity of the molecule and multiple chiral centres.16 Reticuline is an essential precursor leading to the biosynthesis of benzylisoquinoline alkaloids like codeine, berberine and morphine. One of the strategies to increase the flux into morphinan alkaloid is by blocking the BBE (berberine bridge enzymes). Blocking the BBE will increase the (S)-reticuline concentration. The expression of an antisense-BBE construct in transgenic opium poppy plants indeed showed increased flux into the morphinan and the tetrahydrobenzylisoquinoline branch pathway.141 Another strategy is to increase the precursor pool leading to the formation of (S)-reticuline, which is (S)-N-methylcoclaurine 3’-hydrolase. The overexpression of cytochrome P450 monooxygenase (S)-N-methylcoclaurine 3’-hydrolase (CYP80B3) resulted in an up to 450% increase of total morphinan alkaloids.83 The suppression of this gene by an antisense construct led to a reduced total alkaloid content in the transgenic poppy.83 The existence of multi-enzyme complexes has been proposed for flavonoid142-144 and polyamine metabolism.145 The occurrence of multi-enzyme complex as seems also to exist in the morphine biosynthesis,107 therefore the metabolic engineering strategies
32 1 have to be developed carefully. However, not all enzymes of the morphinan branch are strategies engineering Metabolic necessarily involved in such a macromolecular complex.146 A further approach is to increase salutaridinol, a precursor of thebaine, by overexpressing salutaridinol 7-O-acetyltransferase (SaIAT) and salutaridine reductase (SaIR). RNAi-silenced SalAT in opium poppy plants showed an accumulation of salutaridine instead of salutaridinol, which is normally not abundant in the plants.90 Salutaridine may be channelled to thebaine through an enzyme complex that includes salutaridine reductase (SaIR) and SaIAT. Recent results showed that there is an interaction between SaIR and SaIAT.146 Morphine, codeine, and thebaine levels were increased in both saIAT over-expressing and saIAT RNAi plants.90 The codeinone reductase (COR) converts codeinone into codeine. Theoretically, the morphine production can be increased by blocking this enzyme using RNAi technique. On the contrary, there was an accumulation of (S)-reticuline instead of morphine, codeine, oripavine and thebain.109 The reasons are unknown, but there were some speculations. It was suggested that there was a feedback mechanism preventing intermediates from the general benzylisoquinoline synthesis entering the morphine-specific branch.2 The impairment of a required metabolic channel composed of morphinan branch pathway enzymes resulted in accumulation of alkaloid intermediates produced by enzymes that were not part of the same complex.107 The COR could be part of a multi-enzyme complex, which cannot function if one of the enzymes is removed.16 It might be that the side effect of silencing COR was the suppression of 1,2-dehydroreticuline reductase.107 The potential homology between the two reductases could lead to cosilencing.107 The COR seems to be an important target for metabolic engineering. The overexpression of COR in Papaver somniferum yielded a 15 % increase of benzylisoquinoline alkaloids as compared to the high-yielding control genotypes and a 30% increased as compared to the non-transgenic control.82 Recent example is the engineering of thebaine in opium. Thebaine is the natural precursor used in the synthesis of several pharmaceuticals such as oxycodone, naltrexone, naloxone and buprenorphine. Virus inducing gene silencing (VIGS) of T6ODM (thebaine 6-O-demethylase) and CODM (codeine O-demethylase) in opium resulted an efficient blockage of the metabolism at thebaine and codeine, respectively, which increased the thebaine production in transgenic opium up to 95% as compared to control.88
7. Crossing borders – heterologous production of plant compounds in microorganisms 7.1. Artemisinic acid One of the success stories of using the synthetic biology approach is related to artemisinic acid. It is a naturally occurring precursor of artemisinin, used as an antimalarial drug. Malaria causes nearly a million deaths each year, mostly of children below 5 years. The World Health Organization (WHO) estimated 247 million malaria cases among
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Metabolic engineering strategies engineering Metabolic 3.3 billion people at risk in 2006.147 This leads to a demand to supply artimisinin in an economically attractive and environmental friendly way. The relatively low yield (0.01- 0.6%) of artemisinin from Artemisia annua is unable to supply the world demand.136 The total chemical synthesis of artemisinin is difficult and costly.148 However, the semi- synthesis of artemisinin or any derivatives from microbial sourced artemisinic acid and its immediate precursor gives an alternative for availability and economic feasibility.149 Using the synthetic biology approach with the use of appropriate promoters and an expression vector resulted in the production of artemisinic acid up to 300 mg/L in the yeast Saccharomyces cerevisiae. 70, 150
7.2. Stilbenes Stilbenes are polyketides, produced by plants. Resveratrol, as a representative of stilbenes and known as constituent of red wine, which has possible interesting biological activities as anti-cancer agent,151 inhibitor of inflammation, tumor promotion, angiogenesis and metastasis, and regulation of cell cycle progression.152 The biosynthetic pathway and the enzymes have been characterized and metabolic engineering has been achieved in plants, microbes and animals.153 E. coli cells carrying PAL (phenylalanine ammonia-lyase), 4CL (4-coumarate:CoA ligase), STS (stilbene synthase), and ACC (acetyl CoA carboxylase) produced 40 mg/L resveratrol (1 h) from tyrosine The PAL is from the yeast Rhodotorula rubra, 4CL is from actinomycete S. coelicolor A3 (138), and STS is from Arachis hypogaea.154, 155 Resveratrol yield were > 100 mg/L in E.coli expressing 4CL and STS.156 Stilbenes are rapidly absorbed and metabolized when given orally. The modification of the resveratrol scaffold by hydroxylation and methylation enhanced its bioactivities. The recombinant E. coli carrying PAL, 4CL, STS, ACC and OsPMT (pinosylvin methyltransferase in rice) with the addition of tyrosine resulted in the production of 18 mg/L pinostilbene and 6 mg/L pterostilbene. Addition of phenylalanine resulted in production of pinosylvin monomethyl ether and pinosylvin dimethyl ether almost in the same yield of 27 mg/L.157
7.3. Curcuminoids Curcumin, bisdemethoxycurcumin, and dicinnamoylmethane are called curcuminoids.158 Curcumin is the active ingredient of turmeric (Curcuma longa), which has a surprisingly wide range of beneficial claims, not clinically proven yet. Its use is related to traditional medicine as anti-inflammatory, antioxidant, anti-HIV, chemopreventive, and chemotherapeutic agent. These actions are partly supported by preclinical pharmacology.159, 160 Horinouchi et al., 2009 discovered a type III polyketides synthase (PKS) in Oryza sativa (rice) that can synthesize curcuminods via p-courmaroyl-CoA.157 This PKS, named CUS (curcuminoid synthase), as part of an artificial biosynthetic pathway for production of curcuminoids in E. coli.161 The E. coli expressing PAL, 4CL, CUS, and ACC with the additional supply of 1mM each of the phenylpropanoid acid (p-coumaric acid, cinnamic acid or ferulic acid) yielded about 100 mg/L of curcumin
34 1 or dicinnamoylmethane, and bisdemethoxycurcumin, respectively.157 E. coli carrying strategies engineering Metabolic 4CL, ACC and CUS with the addition of ferulic acid isolated from 1 g of rice bran pitch yielded 60 mg curcumin. Rice bran pitch is a dark and viscous oil, which is a waste from the production of rice edible oil from rice bran. Rice bran pitch (1 g) contains about 22 mg ferulic acid.158
7.4. Flavonoids For the first time the complete flavonoid pathway from a plant has been successfully transferred into a microorganism.157 Genes from various organisms were assembled in E. coli on a single pET plasmid for the production of flavanones. They are PAL from the yeast Rhodotorula rubra, 4CL or ScCCL from the actinomycete S. coelicolor A3(2), CHS from the plant Glycyrrhiza echinata, and CHI from the plant Pueraria lobata.162, 163 The construction proved to be optimal using isopropyl b-D-thiogalactopyranoside (IPTG)-inducible T7 promoter and a synthetic ribosome-binding sequence in front of each of the four genes in a recA- host.163 The yield of pinocembrin from 3 mM phenylalanine exogenously added, and naringenin from 3 mM tyrosine were both 60 mg/L.154 Flavanone-3b-hydroxylase (F3H), flavonol synthase (FLS) and flavone synthase (FNS) were introduced into E. coli to modify flavanones into flavonols (kaempferol and galangin). The expression of the genes led to the production of kaempferol (15.1 mg/L) from 3 mM tyrosine and galangin (1.1 mg/L) from 3 mM phenylalanine.164 Cloning of a FNS gene from Petroselinum crispum into pACYC in the E.coli host led to production of flavones: apigenin (13 mg/L) from tyrosine and chrysin (9.4 mg/L) from phenylalanine.164
7.5. Vanillin An example of ‘white biotechnology’ is the production of vanillin as one of the most important aromatic flavour compounds used in foods, beverages, perfumes and pharmaceuticals. The production scale is more than 10,000 tons per year by chemical synthesis.17 The increasing demand of customers for natural flavours has shifted the interest of the flavour industry to produce vanillin from natural sources by biotransformation instead of organic synthesis.17 The aim of the biotransformation of vanillin is to avoid toxic and mutagenic solvents such as phenol and dimethyl sulfate and to avoid corrosive compounds such as hydrogen peroxide which are used for the organic synthesis.165 Many different possibilities have been investigated for the biotechnological production of vanillin using different kinds of bacteria and fungi and different precursors.17 The transformed E. coli BL21(DE3) cells carrying isoeugenol monooxygenase gene of Pseudomonas putida IE27 produced up to 28.3 g/L of vanillin from 230 mM isoeugenol, with a molar conversion yield of 81% at 20oC after 6 h.166 The growing knowledge regarding enzymes involved in biosynthetic pathways as well as the identification and characterization of the corresponding genes offers new opportunities for metabolic engineering and for the construction of genetically engineered production strains.17
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Metabolic engineering strategies engineering Metabolic 8. Conclusion and future prospective
Plants definitely play an essential role in modern pharmacy and medicine. Efforts to obtain the desired natural compounds to be used as drugs in an efficient way, are going on and included various approaches. Metabolic engineering has been applied to both plants and plant cell cultures. Plant cell cultures have been shown to be feasible for industrial production only limitedly, as shown for paclitaxel. Understanding secondary metabolism within cells and cell cultures is essential to use them as a means to supply natural products. The characteristics and metabolic capacities of plant cell/tissue and microbial systems are inherently different; therefore they can serve as complementary unit operations in order to solve the long- standing problem of robust secondary metabolites production.101 The lack of complete information about genomes of most medicinal plants is still an immense challenge for applying the appropriate metabolic engineering strategy. Up to date, only few plant genomes (e.g., Oryza sativa, Zea mays, and Arabidopsis thaliana), but none of the medicinal plant, have been fully sequenced. The challenges to unravel the unknown biosynthetic pathways, the encoding genes and the transcription factors are still there. However with the progressing sequencing techniques, it will likely be feasible to fully sequence medicinal plants in a shorter time. Yet the only main constraint will be the funding. Conventional breeding of medicinal plants is another way to enhance the concentration of the desired compounds. Breeding and genetic engineering are essential to go hand in hand and are necessary to ensure the availability of the desired compounds. Until now, it seems that there is limited success in engineering medicinal plants in which the product could be commercialized based on economic feasibility. However, genetic engineering strategies have been applied into crop plants such as rice, maize, soybean, and cotton with great significant success. The genetically modified crop plants with bt (Bacillus thuringiensis) toxin for pest resistance have been grown commercially in approximately 42 million hectares worldwide.167 In addition, Bt transgenic rice varieties are in field tests and are close to approval for commercialization.168 The advance of technology holds great promise for the future of plant metabolic engineering. Genomics approaches may lead to the identification of regulatory genes and proteomic approaches may explain why the expression levels of some biosynthetic genes do not correlate with the metabolites profile.107 Finding alternative ways to produce originally plant-derived compounds are still continuing. Microorganisms such as endophytes may serve as an alternative host for production of bioactive substances as reviewed by Staniek et al.169 The success of transferring the biosynthetic pathway from plants into microorganisms or other hosts for the production of artemisinic acid and flavonoids showed that it is feasible to engineer the entire pathway into microorganisms. The latest promising approach is through synthetic biology for optimizing the biotechnological production of the plant-derived compounds. However, well-
36 1 characterized biological components such as the knowledge of the biosynthetic strategies engineering Metabolic pathways, the genes involved, the promoters, and the precursors are essential to build the system. An integrated approach of synthetic biology and metabolic engineering will be necessary in the near future. For successful engineering, to enhance and optimize the production of the desired metabolites, crossing borders of different disciplines will be needed.
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147. WHO. World Malaria Report 2008. 159. Hatcher H, Planalp R, Cho J, et al. strategies engineering Metabolic Geneva, 2008. Curcumin: From ancient medicine to 148. Schmid G, Hofheinz W. Total synthesis current clinical trials. Cell Mol Life Sci of qinghaosu. J Am Chem Soc 2008;65:1631-1652. 1983;105:624-625. 160. Itokawa H, Shi Q, Akiyama T, et al. Recent advances in the investigation of 149. Haynes RKV. Cyclic peroxyacetal curcuminoids. Chin Med 2008;3:11. lactone, lactol and ether compound. US Patent 5,310,946. 1994. 161. Katsuyama Y, Matsuzawa M, Funa N, et al. Production of curcuminoids 150. Chang MCY, Eachus RA, Trieu W, et al. by Escherichia coli carrying an artifi- Engineering Escherichia coli for produc- cial biosynthesis pathway. Microbiol tion of functionalized terpenoids using 2008;154:2620-2628. plant P450s. Nat Chem Biol 2007;3:274- 277. 162. Hwang EI, Kaneko M, Ohnishi Y, et al. Production of plant-specific flavanones 151. Oliver Y, Joseph MJ. Nature’s assembly by Escherichia coli containing an artifi- line: biosynthesis of simple phenyl- cial gene cluster. Appl Environ Microbiol propanoids and polyketides. Plant J 2003;69:2699 - 2706. 2008;54:750-762. 163. Miyahisa I, Kaneko M, Funa N, et al. 152. Kundu JK, Surh YJ. Molecular basis Efficient production of (2 S )-flavanones of chemoprevention by resveratrol: by Escherichia coli containing an artificial NF-kappaB and AP-1 as potential targets. biosynthetic gene cluster. Appl Microbiol Mut Res 2004;555:65-80. Biotechnol 2005;68:498-504. 153. Halls C, Yu O. Potential for metabolic 164. Miyahisa I, Funa N, Ohnishi Y, et al. engineering of resveratrol biosynthesis. Combinatorial biosynthesis of flavones Trends Biotechnol 2008;26:77-81. and flavonols in Escherichia coli. Appl Microbiol Biotechnol 2006;71:53-58. 154. Katsuyama Y, Funa N, Miyahisa I, et al. Synthesis of unnatural flavonoids and 165. Schafer B. Naturstoffe der chemischen stilbenes by exploiting the plant biosyn- industrie. Munchen: Elsevier, 2007. thetic pathway in Escherichia coli. Chem 166. Yamada M, Okada Y, Yoshida T, et al. Biol 2007;14:613-621. Vanillin production using Escherichia 155. Yohei K, Nobutaka F, Sueharu H. Pre- coli cells over-expressing isoeugenol cursor-directed biosynthesis of stilbene monooxygenase of Pseudomonas putida. methyl ethers in Escherichia coli. Bio- Biotechnol Lett 2008;30:665-670. technol J 2007;2:1286-1293. 167. Fitt GP. Have Bt crops led to changes in insecticide use patterns and impacted 156. Watts K, Lee P, Schmidt-Dannert C. IPM? Integration of insect-resistant Biosynthesis of plant-specific stilbene genetically modified crops within IPM polyketides in metabolically engi- programs, Progress Biol Contr 2008:303- neered Escherichia coli. BMC Biotechnol 328. 2006;6:22. 168. Liu W. Effects of Bt transgenic crops on 157. Horinouchi S. Combinatorial biosyn- soil ecosystems: a review of a ten-year thesis of plant medicinal polyketides by research in China. Front Agric China microorganisms. Curr Opin Chem Biol 2009;3:190-198. 2009;13:197-204. 169. Staniek A, Woerdenbag HJ, Kayser O. 158. Horinouchi S. Combinatorial biosynthesis Endophytes: exploiting biodiversity for of non-bacterial and unnatural flavonoids, the improvement of natural product- stilbenoids and curcuminoids by microor- based drug discovery. J Plant Interact ganisms. J Antibiot 2008;61:709-28. 2008;3:75 - 93.
43
Chapter
Seasonal variations in the deoxypodophyllotoxin content and yield of Anthriscus sylvestris L. (Hoffm.) grown in the field and under controlled conditions
Oktavia Hendrawati Herman J. Woerdenbag 2 Jacques Hille Wim J. Quax Oliver Kayser
Journal of Agricultural and Food Chemistry 2011; 59 (15): 8132-9139 2
SEASONAL Abstract
Deoxypodophyllotoxin (DPT) is the main lignan in Anthriscus sylvestris. We carried out two sets of experiments with sixteen plants and seeds, collected from a wide V
ARIATIONS geographical range. The DPT content in roots was significantly lower (p < 0.05) when the plants were cultivated in a non-native environment. For field grown plants the highest DPT content was found in March (2nd year): 0.15 % w/w (dry weight) in roots; 0.03 % w/w in aerial parts. For plants grown in the climate room the highest concentration (0.14 % w/w) was observed in April (2nd year) in the roots and in July (1st year) in the aerial parts (0.05 % w/w). For the isolation of DPT roots are the most suitable part. The best harvest time is March (2nd year) for outdoor plants and April (2nd year) for indoor plants when height content and adequate biomass give the optimal DPT yield.
Keywords: lignan, deoxypodophyllotoxin, podophyllotoxin, Anthriscus sylvestris, environmental factors, plant cultivation; biosynthesis, etoposide, teniposide
Oktavia Hendrawati1, Herman J. Woerdenbag2, Jacques Hille3, Wim J. Quax1, Oliver Kayser1,4
1Department of Pharmaceutical Biology, University of Groningen, Groningen, The Netherlands; 2Department of Pharmaceutical Technology and Biopharmacy, University of Groningen, Groningen, the Netherlands; 3Department of Molecular Biology of Plants, University of Groningen, Haren, The Netherlands; 4Technical Biochemistry, Technical University Dortmund, Dortmund, Germany
Journal of Agricultural and Food Chemistry 2011; 59 (15): 8132-9139
46 2
Introduction SEASONAL
Anthriscus sylvestris (L.) Hoffm. (Apiaceae) is a common wild plant in northwest Europe, in parts of North America, Africa, Asia and New Zealand.1-3 The dried roots are V used in Korean and Chinese traditional medicine for the treatment of various diseases, ARIATIONS including bronchitis, as an antipyretic, cough remedy, and analgesic herbal drug.4-6 The plant accumulates considerable amounts of lignans, that are held responsible for the biological activity.7 Deoxypodophyllotoxin (DPT) is considered as the plant’s main lignan constituent.7 It has pharmacological properties such as antiproliferative, antitumor, antiviral, anti- inflammatory, anti-platelet aggregation and anti-allergic related disorders including asthma.8-16 The number of studies of DPT mechanism of action against cancer cells17 and other pharmacological properties are growing.4, 18-21 It also has anti-insecticidal properties.22, 23 The closely related podophyllotoxin is used for the semisynthesis of the cytostatic agents, etoposide and teniposide. These drugs are used for the treatment of lung and testicular cancers, Ewing’s sarcoma, lymphoma, glioblastoma and non- lymphomatic leukaemia.24 In several plant species, DPT serves as a biosynthetic precursor for podophyllotoxin (figure 1).25, 26 Feeding experiments with cultures of undifferentiated plant cells (Linum album) or fungi (Penicillium F-0543 and Aspergillus niger) have shown that DPT can be converted into podophyllotoxin.25, 27 To date, podophyllotoxin is obtained by extraction of the rhizome of Podophyllum species. The availability ofPodophyllum species is limited28 and the increasing demands of podophyllotoxin jeopardizes the natural sources. Podophyllum species are listed on the endangered species list in India.29, 30 In the near future, the availability of podophyllotoxin will be a major bottleneck in supplying pharmaceutical needs. Preliminary studies focusing on the question which factors may influence the production of DPT in A. sylvestris suggested that environmental factors highly determine the lignan profile and content.31, 32 It has also been reported that DPT content
Figure 1. Chemical structure of deoxypodohyllotoxin and podophyllotoxin.
47 2
SEASONAL differs at least twofold between the low and high altitude both in aerial (0.13 % d.w. in 900m, 0.33 % d.w. in 1200m) and root part (0.38 % d.w in 900m and 0.78% d.w. in 1200 m) of A. sylvestris.21 Different populations of A. sylvestris yielded different lignan
V patterns, and that there was no clear genetic factor determining the lignan profiles ARIATIONS when seeds from different locations were grown under identical conditions.31, 32 A major drawback of that study was the limited number of plants. Here we conducted a biannual experiment with a higher number of the collected plants and seeds, from a wider geographical range. The plants from the previous studies we included as well (table 2). All plants were grown under identical field conditions and in a climate room. DPT was the main important compound, therefore was used as the biosynthetic marker. The field resembles the natural weather conditions whereas the climate room resembles the controlled cultivation. The first objective of this study is to determine the DPT content of native and non- native A. sylvestris grown in the field and in a climate room, in order to get insight into the production rate of DPT in A. sylvestris. Second, we aimed to study the influence of growing conditions, both outdoor and indoor, on the DPT production. Furthermore, it is important to identify rate limiting ecological factors for optimal growing conditions of A. sylvestris for DPT production.
Results 1. DPT content of native and cultivated Anthriscus plants The DPT content of Anthriscus plants from their native location was compared to that of the plants from the seeds of the native location, grown in the botanical garden De Kruidhof. The native A. sylvestris from Iceland (Mogilsa) contained the highest DPT production in the root part (0.182 %) and the native A. sylvestris from Germany (Bonn) contained the highest DPT production in the aerial (0.025 %). For the cultivated plants, the highest DPT production in the root part was the A, sylvestris from Bonn (0.081%) and Coventry (0.062 %), whereas in the aerial part was the A. sylvestris from Olst (0.018%). The results are shown in figure 2. The DPT content of all field plants cultivated in the Netherlands in 2009 was used for the correlation analysis. There was a significant negative correlation between the DPT content in the aerial part of the field plants with the rainfall (r = -0.624, p < 0.01), with the duration of sun (r = -0.402, p < 0.01) and with the temperature (r = -0.643, p < 0.01). There was also a significant negative correlation between the DPT content in the root part of the field plants with the duration of sun (r = - 0.611, p < 0.01) and with the temperature (r = - 0.599, p < 0.01). In the climate room plants, there was a significant negative correlation between the DPT content in aerial part with the rainfall (r = -0.430, p < 0.01) and with the temperature (r = -0.190, p < 0.01). There was also a significant negative correlation between the DPT content in the root part with the duration of the sun (r = -0.228, p < 0.01), with the temperature (r = -0.464, p < 0.01), and with the rainfall (r = -0.362, p < 0.01). There was a positive correlation between
48 2 SEASONAL V ARIATIONS
Figure 2. Deoxypodohyllotoxin content of floweringA. sylvestris collected in their native location and the flowering A. sylvetris cultivated from their native fruits in the same field (botanical garden de Kruidhof, the Netherlands). Note: seeds from Hrisey and Mogilsa did not germinate; therefore no data could be recorded in 2009.
the DPT content in the aerial and in the root of the field plant (r = 0.315, p < 0.01) and the climate room plant (r = 0.374, p < 0.01). There was a significant positive correlation between the total yield of DPT in the aerial part of the field plants with the duration of sun (r = 0.221, p < 0.01). There was a significant negative correlation between the total yield of the DPT in the root part of the field plants with the duration of sun (r = -0.573, p < 0.01) and temperature (r = -0.507, p < 0.01). Thus, a lower temperature and less sun result in a higher DPT production in A. sylvestris.
2. DPT content of the field plants (outdoor plants) The experiments in the field with A. sylvestris plants grown from seeds of the various origins (uncontrolled condition – outdoor plants) and in the climate room (controlled condition – indoor plants) were carried out in parallel. The DPT content variation over the developmental stages was measured and compared both for the aerial (figure 3a) and the root parts (figure 3b). A. sylvestris is a biannual plant, therefore we started sampling in the second year when they develop biomass and flower. The DPT content in the roots of the field plants was up to 0.15 % and in the aerial parts up to 0.03 %. The highest DPT content in aerial part was found in March for all plants and in the root part was found in April, except A. sylvestris from Enebyberg and Egilstaffr, which were in March. The lowest was between July and September 2009. The highest yield of DPT per plant in the field plants was 22.23 mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009 (figure 3c and 3d). Data are summarized in table 1.
49 September 2009. The highest yield of DPT per plant in the field plants was 22.23 September 2009. The highest yield of DPT per plant in the field plants was 22.23 September 2009. The highest yield of DPT per plant in the field plants was 22.23 mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009 mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009 September 2009. The highest yield of DPT per plant in the field plants was 22.23 (figure 3c and 3d). Data are summarized in table 1. (mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009 figure 3c and 3d). Data are summarized in table 1.
(figure 3c and 3d). Data are summarized in table 1. a 2 a 0,05
SEASONAL a 0,05
0,05 0,04
0,04
0,04 0,03 V
ARIATIONS 0,03
0,020,03 Concentration (%) Concentration (%) 0,02 Concentration (%) 0,010,02 Concentration (%) 0,01
0,000,01 Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr 0,00 Location Bonn Tartu Coventry Suffolk Buitenpost OlstLocationDiever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 0,00 Bonn Tartu Coventry Suffolk Buitenpost Olst LocationDiever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr b March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 b Location March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 b 0,25
b 0,25
0,20 0,25
0,20
0,15 0,20
0,15 0,10 0,15 Concentration (%) Concentration (%)
0,10 0,05 Concentration (%) 0,10 Concentration (%) 0,05 0,00 Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegein Reykjavik Enebyberg Oudeschans Groningen Egilsstafr 0,05 Location c 0,00 Location Bonn Tartu Coventry March 2009Suffolk BuitenpostApril 2009 May 2009Olst Diever June 2009NieuwegeinJuly 2009 ReykjavikAug 2009 Enebyberg Oudeschans Groningen Egilsstafr 300,00 c c Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegein Reykjavik Enebyberg Oudeschans Groningen Egilsstafr Location March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 c 30 Location 3025 March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 30 25 2520 25 20 2015 Yield (mg) 20 15 1510
Yield (mg) Yield (mg) 15 10 10 5 Yield (mg)
10 5 5 0 Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr 5 Location 0 0 March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 BonnBonn TartuTartu CoventryCoventry SuffolkSuffolkBuitenpostBuitenpost Olst Olst Diever Diever NieuwegienNieuwegienReykjavikReykjavikEnebybergEnebybergOudeschansOudeschansGroningenGroningenEgilsstafrEgilsstafr 0 LocationLocation Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr March 2009March 2009April 2009April 2009May 2009May 2009June 2009June 2009July 2009July 2009Aug 2009Aug 2009 Location d March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 d d 100 90 Figure 3. A. sylvestris d 100 100 80 90 grown in the field. (a) 90 100 70 80 80 90 Deoxypodophyllotoxin 60 70 70 80 content in the aerial part. 50 60 60 70 Yield (mg) (b) Deoxypodophyllo- 40 50 50 60 30 toxin content in the root Yield (mg) Yield (mg) 40 40 50 20 part. (c) Deoxypodophyl-
Yield (mg) 30 30 40 10 lotoxin yield in the aerial 20 20 30 0 part. (d) Deoxypodo- 10 Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegein Reykjavik Sverige Oudeschans Groningen Egilsstafr 10 20 phyllotoxin yield in the 0 Location 0 10 BonnBonn TartuTartu CoventryCoventry SuffolkSuffolkMarch Buitenpost2009BuitenpostApril 2009Olst OlstMay Diever 2009Diever June Nieuwegein2009NieuwegeinJuly Reykjavik2009ReykjavikAug Sverige2009SverigeOudeschansOudeschansGroningenGroningenEgilsstafrEgilsstafr root part. 0 LocationLocation Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegein Reykjavik Sverige Oudeschans Groningen Egilsstafr March March 20092009April April 20092009May May 20092009June June 20092009July 2009July 2009Aug 2009Aug 2009 Figure 3. (a) Deoxypodohyllotoxin content in Location the aerial part of A. sylvestris grown in the field. ( b) Deoxypodohyllotoxin content in the root part of March 2009 April 2009 May 2009 June 2009 A.July sylvestris2009 Aug 2009 grown in the field. (c) FigureAerial masFigure50 3. 3(.as of ) (aDeoxypodohyllotoxin ) A.Deoxypodohyllotoxin sylvestris grown in the field. ( content content in in the the d) Root mass of aerial aerial part part of of A.A. A. sylvestris sylvestris sylvestris grown grown in the grown in in the the field. (field. field. ( bAll) Deoxypodohyllotoxin content in the root part of b ) Deoxypodohyllotoxin content in the root part of DPT contents and yields significantly differ (p<0.01)A. A.sylvestris sylvestris comparing grown in the field. ( grown in the field. ( the indoor andc) c ) ( ) Deoxypodohyllotoxin content in the aerial part of A. sylvestris grown in the Aerial masoutdoorAerial masFigure plants. 3s of . s of a A. A.sylvestris sylvestris grown in the field. ( grown in the field. (d) Root mass of d) Root mass of A. A.sylvestris sylvestris grown in the grown in the field. field. field. (AllAll bDPT) Deoxypodohyllotoxin content in the root part of DPT contents contents and and yields yields significantly significantly differ differ (p<0.01) (p<0.01)A. sylvestris comparing comparing grown in the field. ( the the indoor indoor and and c) outdoorAerial mas plants.s of A. sylvestris grown in the field. (d) Root mass of A. sylvestris grown in the outdoor plants. field. All DPT contents and yields significantly differ (p<0.01) comparing the indoor and outdoor plants.
September 2009. The highest yield of DPT per plant in the field plants was 22.23 a mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009 September 2009. The highest yield of DPT per plant in the field plants was 22.23 (figure 3c and 3d). Data are summarized in 0,07 table 1. mg in the aerial part in June 2009 and 68.87 mg in the root part in March 2009
(figure 3c and 3d). Data are summarized in 0,06 table 1. a a 0,05 2 0,05 a 0,040,07 SEASONAL
0,06 0,03 0,05 0,04
Concentration (%) 0,05 0,02 0,04
0,03 V 0,04 0,01 ARIATIONS
0,03 0,03 0,00 0,02 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen Concentration (%) Concentration (%) 0,02 0,02 Location 0,01 June 2008 July 2008 August 2008 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 Sept 2009 Concentration (%) 0,01
0,01 0,00 0,00 b BonnBonn TartuTartu CoventryCoventry SuffolkEssexBuitenpostBuitenpostOlst Diever Olst NieuwegienDiever ReykjavikNieuwegienEnebybergReykjavikOudeschansOudeschansGroningen EgilsstafrGroningen Location 0,00 Location March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 Bonn June 2008Tartu July 2008Coventry August 2008Suffolk BuitenpostMarch 2009Olst April 2009Diever NieuwegienMay 2009 ReykjavikJune 2009EnebybergJuly 2009OudeschansAugust 2009Groningen Sept 2009Egilsstafr Location b 0,20 March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 0,18 b b 0,25 0,16
0,25 0,14 0,20
0,120,20
0,180,20 0,100,15
0,080,16
Concentration (%) 0,15 0,14 0,060,10 Concentration (%) 0,040,12 0,10 0,020,100,05 Concentration (%) c 0,000,08
Concentration (%) 0,05 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen c 0,060,00 5 Bonn Tartu Coventry Suffolk Buitenpost Olst LocationDiever Nieuwegein Reykjavik Enebyberg Oudeschans Groningen Egilsstafr c c 0,045 June 2008 July 2008 August 2008 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 Sept 2009 0,00 Location 0,02 Bonn Tartu Coventry SuffolkMarch 2009BuitenpostApril 2009Olst May 2009Diever June 2009NieuwegeinJuly 2009ReykjavikAug 2009Enebyberg Oudeschans Groningen Egilsstafr c 4530 0,004 Location Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen 30 March 2009 April 2009 May 2009 June 2009 July 2009 Aug 2009 25 Location 34 3 June 2008 July 2008 August 2008 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 Sept 2009 25 20
Yield (mg) 32 20 Yield (mg) 2 15 Yield (mg)
Yield (mg) 1215 10 1 Yield (mg)
10 01 5 0 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen 5 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen 0 Location 0 Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegien Reykjavik Enebyberg Oudeschans Groningen Egilsstafr June 2008 July 2008 August 2008 March 2009 April 2009LocationMay 2009 June 2009 July 2009 August 2009 Sept 2009 Bonn Tartu Coventry Essex BuitenpostLocationOlst Diever Nieuwegien Reykjavik Oudeschans Groningen 0 June 2008 July 2008 August 2008 March 2009 April 2009 May 2009 June 2009 July 2009 August 2009 Sept 2009 Bonn Tartu Coventry SuffolkMarch 2009BuitenpostApril 2009Olst May 2009Diever June 2009NieuwegienJuly 2009ReykjavikAug 2009Enebyberg Oudeschans Groningen Egilsstafr d LocationLocation Figure 4. A. sylves- d June 2008 July 2008 August 2008March 2009 March 2009April 2009 May 2009April 2009June 2009May 2009July 2009June 2009Aug 2009July 2009 August 2009 Sept 2009 20 tris grown in the d d 20 18 climate room. (a) d 18100 2016 Deoxypodophyl- 1690 1814100 lotoxin content in 1480 90 1612 the aerial part. (b) 1270 80 1410 Deoxypodophyllo- 1060 70 Yield (mg) 128 toxin content in the Yield (mg) 50 860 106 Yield (mg) 40 root part. (c) Deox- 650 Yield (mg) 84
Yield (mg) 30 ypodophyllotoxin 440 62 20 230 yield in the aerial 40 10 020 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen part. (d) Deoxypo- 2 Bonn Tartu Coventry Essex Buitenpost Olst Diever Nieuwegien Reykjavik Oudeschans Groningen 0 Location 10 dophyllotoxin yield Bonn Tartu Coventry Suffolk Buitenpost Olst Diever Nieuwegein Reykjavik Sverige Oudeschans Groningen Egilsstafr 0 Location 0 Bonn June 2008Tartu July 2008CoventryAugust 2008Essex March Buitenpost2009 LocationApril 2009Olst May 2009Diever June 2009NieuwegienJuly 2009ReykjavikAugust 2009OudeschansSept 2009Groningen in the root part. Bonn June Tartu2008 July Coventry2008 SuffolkAugust 2008BuitenpostMarch 2009Olst April Diever 2009 NieuwegeinMay 2009 ReykjavikJune 2009SverigeJuly 2009OudeschansAugust Groningen2009 Sept Egilsstafr2009 March 2009 April 2009 May 2009LocationJune 2009 July 2009 Aug 2009 Location June 2008 July 2008 August March 20082009 March April 20092009 May April 20092009June May 20092009July 2009June 2009Aug 2009July 2009 August 2009 Sept 2009 FigureFigure 43. . ((aa) ) Deoxypodohyllotoxin content content in in the the aerial aerial part part of A. of sylvestrisA. sylvestris grown grown in the in the Figureclimate roomfield. ( b4) Deoxypodohyllotoxin content in the root part of . (a) (Deoxypodohyllotoxin b). Deoxypodohyllotoxin content in the root part of content in the aerial A. sylvestris part of A.grown in the field. (A. sylvestrissylvestris grown grown in the c) in the 51 Figure 3. (a) Deoxypodohyllotoxin content in the aerial part of A. sylvestris grown in the climate roomAerial mass of ((bA.).. Aerial mass of Deoxypodohyllotoxin content in the root part of sylvestris grown in the field. (A. sylvestris grown in thed) Root mass of climate roomA. sylvestrisA. sylvestris ( ).grown in the Root mass of grown in the A. field. (b) Deoxypodohyllotoxin content in the root part of c) A. sylvestris grown in the field. (d c) sylvestrisFigureclimate roomfield. All 4. DPTgrown in the climate room(a) ( c)Deoxypodohyllotoxin contents. Aerial mass of and yieldsA. significantlysylvestris content in grown in the differ the aerial (p<0.01) part climate room comparing of A. sylvestris ( thed). indoorRoot mass of grown and in the A. sylvestrisclimate roomoutdoorAerial mas plants. grown in the climate rooms of (b ).A. Deoxypodohyllotoxin content in the root part of sylvestris grown in the field. ( d) Root mass of A. sylvestrisA. sylvestris grown in the grown in the field. All DPT contents and yields significantly differ (p<0.01) comparing the indoor and climate room ( . Aerial mass of A. sylvestris grown in the climate room ( ). Root mass of A. outdoor plants.c) d sylvestris grown in the climate room
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SEASONAL Table 1. Summary of the highest and lowest DPT content, biomass and the DPT yield of Anthriscus sylvestris (figure 3 and 4)
Field Climate room V
ARIATIONS Aerial Root Aerial Root Highest DPT content 0.033 0.151 0.051 0.144 (% w/w, dry weight) Enebyberg Nieuwegein Tartu Bonn Mar 2009 Mar 2009 Jul 2008 Apr 2009 Lowest DPT content 0.001 0.008 0.008 0.012 (% w/w, dry weight) Nieuwegein Reykjavik Essex Buitenpost Jul 2009 Sep 2009 Jun 2009 Sep 2009 Highest mass 173.4 108.9 7.0 16.4 (dry weight in g) Nieuwegein Oudeschans Buitenpost Olst May 2009 Jun 2009 Apr 2009 Apr 2009 Lowest mass 1.5 8.2 2.0 0.8 (dry weight in g) Suffolk Egilstaffr Bonn Tartu Aug 2009 Apr 2009 Jun 2008 Jun 2008 Highest yield 22.23 mg 68.87 mg 2.81 12.60 mg (dry weight in mg) per plant Oudeschans Bonn Buitenpost Bonn Jun 2009 Mar 2009 Apr 2009 Apr 2009 Lowest yield 0.01 mg 0.73 mg 0.12 mg 0.32 mg (dry weight in mg) per plant Coventry Reykjavik Essex Coventry Jul 2009 Sep 2009 Jun 2009 Sep 09
3. DPT content of the climate room plants (indoor plants) Samples were taken during two years following the developmental stages of the life cycle of A. sylvestris. The DPT content and yield were measured and compared with outdoor grown plants of the same seed origin (figure 4). The DPT content of the climate room plants was up to 0.144% in the roots and up to 0.051% in the aerial part. The highest yield of DPT per plant in the field plants was 2.81 mg in the aerial part and 12.60 mg in the root part in April 2009 (table 1). In the first year, the highest DPT content in the roots was found inA. sylvestris from Bonn (0.053%) in July 2008. In the aerial parts the highest content of DPT was found in A. sylvestris from Tartu (0.051%) also in July 2008. In the second year, in general the highest DPT content both in aerial as well as root parts were found in April 2009 for all plants except A. sylvestris from Bonn and Oudechans for aerial part and A. sylvestris from Reykjavik and Oudeschans (figure 4a and 4b). At this time the plants started to grow after the cold dormancy period. Indoor A. sylvestris did not flower at the same time as the outdoor plants. All A. sylvestris plants from Bonn and Nieuwegein already started to flower by mid-April 2009, whereas only about 50% of plants from the other origins started to flower at this time point. TheA. sylvestris plants from Estonia did not flower at all by mid-April 2009. By end of May 2009, all plants have flowered. In the Netherlands, A. sylvestris flowers between April and May.
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In the first year, the highest DPT yield in the root part was in August and September SEASONAL 2008 for all plants, but in the aerial parts the highest yield was in July 2008 for all plants. In the second year, the highest DPT yield in the aerial as well as root part was in April 2009, except the root part of A. sylvestris from Groningen (figure 4c and 4d). V ARIATIONS There is a significant difference comparing the DPT content of the field and climate room plants (p < 0.01). There is also a significant different comparing the total yield of the field and climate room plants (p < 0.01).
Discussion
Anthriscus sylvestris is a biannual plant meaning that a life cycle takes 2 years. In the first year, the rosettes remain in the vegetative phase and form a basal rosette with a taproot. Vernalization will lead to flowering during the next growing season. After flowering, the seeds are produced and then the life cycle is completed.33 The biomass of the aerial and root of the field plants reached the highest in May in the second year for all plants, but the highest DPT content was in March for field plants, both in aerial and root part. However, only the aerial part of the field plants has the highest yield following the highest biomass in May for all plants except A. sylvestris from Oudeschans. The highest yield of the root part for all field plants was in March when the highest DPT content was reached (table 1). DPT as the main lignan in A. sylvestris was used as a marker to study its metabolic variation over the developmental stages. This is the first study reporting results of climate room experiments covering the entire life cycle of two years. In general, the DPT content in the roots was higher than in the aerial parts.
Native versus cultivated The first experiment was dedicated to compare the DPT content of plants of the native location with that of the same plants grown on the non-native location (Buitenpost). There were significant differences (p < 0.05) comparing the DPT content in the root parts of all plants except A. sylvestris from Enebyberg and Coventry (figure 2). The DPT content in the aerial part differed moderately over time. Meanwhile the DPT content in the roots decreased except in A. sylvestris from Coventry, UK. It seems that the A. sylvestris from Coventry were adapted easily to the Dutch soil. This is reflected in a more or less equal DPT content (0.007 % in aerial native compared to 0.005 % in aerial cultivation; 0.064% in root native compared to 0.062 % in root cultivation). The DPT content of theA. sylvestris from Bonn, DE, was moderately higher (significantly different of the DPT concentration in the root part, p < 0.05) compared to others (0.025% in aerial native compare to 0.017 % in aerial cultivation; 0.146% in root native compared to 0.081% in root cultivation). Based on these results, A. sylvestris from Coventry and Bonn were chosen as candidates for further cultivation. The DPT content in roots from the cultivated plants from Groningen was 7.5 fold decreased (0.087 % in roots native compared to 0.012 % in roots cultivation). This high producing plant at its
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SEASONAL native location became a low producing one when cultivated in a foreign environment. Interestingly, the DPT content in the root parts of Anthriscus from the local area of the botanical garden (Buitenpost) also decreased fivefold (0.119% in root native compare
V to 0.024% in root cultivation). In general, the decrease of DPT content in the cultivated ARIATIONS root parts varied with a factor between 7.5 and 1 compared to the native plants (0.087 % in roots native compared to 0.012 % in roots cultivation in Groningen Anthriscus, 0.064% in roots native compared to 0.062% in roots cultivation in Coventry plant). These results clearly show that environmental factors play an important role in the DPT content in Anthriscus. The statistical analysis showed that there is a significant negative correlation among the DPT content, the rainfall, the temperature and the duration of sun. Both in the aerial and root part, the DPT content is expected to increase with decreasing temperature and duration of sun. The DPT in aerial part is also influenced by rainfall. The DPT in aerial part is also expected to increase with decreasing rainfall. There is also a positive significant correlation between the DPT content in the root and aerial part. It means that the DPT in the aerial part is increase with increasing DPT in the root.34 This correlation could explain the significant differences (p < 0.05) found in DPT content of the root part of all plants (except A. sylvestris from Enebyberg and Coventry) from the Netherlands in 2007 and the Dutch cultivated plants in 2009. These plants originated from Buitenpost, Olst, Groningen, Diever and Nieuwegein. The DPT content of the cultivated plants became reduced up to 7.5 times in the root parts and up to 3 times in the aerial parts. The DPT content in the root would decrease when the duration of sun and the temperature were increased. In May 2007 the temperature was 1.7oC higher and there was 38 h less sun as compared to May 2009. This may have caused the DPT content in the root to decrease as shown in figure 2. Whereas in the aerial part, the DPT content would decrease when there were less sun, rainfall and temperature. In 2007, the weather in the Netherlands was unusual as there was no rain in March 2007, but there was 73 mm more rain in May 2007 compared to May 2009. The more abundant rainfall and higher temperature contributed to the decrease of the DPT in aerial part, however the less duration of sun contributed to the increase of the DPT in the aerial part. This might explain why the DPT content was reduced only up to 3 times in the aerial compared to up to 7.5 times in the root part.
Outdoor versus indoor The second experiment was to grow all plants in the same field, under the same environmental conditions. In parallel, we also grew the plants under controlled conditions in the climate room. The A. sylvestris grown in the field (outdoor) received influences from abiotic and biotic stress, such as temperature, light, drought, wind, and insects, and has more space to grow compared to the plants in the climate room. For experiments of controlled cultivation in a climate room we expect that differences found are mainly to be ascribed to genetic factors, as growing conditions are standardized. Furthermore, it is important to identify rate limiting ecological factors for improved cultivation either outdoor or indoor.
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In the climate room experiment, there was a decrease of DPT production during SEASONAL the vegetative period in the 1st year (August – February) and also after the plants had flowered (2nd year). This biosynthetic profile was also observed in Podophyllum hexandrum. When the plant gets older, the podophyllotoxin content in the rhizome V ARIATIONS also decreases.35 The DPT content in A. sylvestris increased again in the spring (March – April 2nd year). Interestingly, the DPT pattern over the entire period in the climate room was in general similar for all plants (figure 4). The DPT profiles of both the indoor and the outdoor plants were comparable, however there were differences in the mass of the aerial and root parts which influenced the yield and also in the flowering time of the indoor plants. There is a significant difference (p< 0.01) either of the DPT content or the DPT yield between indoor and outdoor plants. The differences found in DPT production between indoor and outdoor plants were comparable to a previous study from our group31 and from others.36 The inter-individual variability of the DPT content in the root parts of the outdoors plants was higher than of the indoor plants (e.g. 0.151 % - 0.007% versus to 0.144% - 0.012 % - see table 1). In contrast, the inter-individual variability of the DPT content in the aerial part of the indoor plants was higher than of the outdoor plants (e.g. 0.051% % - 0.008% versus to 0.033 % - 0.001% - see table 1). Previous research showed that the indoor plants contained higher DPT contents in aerial parts than in the roots.31 We now confirm these results as several indoor plants from Estonia (0.051 % in aerial, 0.045% in root), Buitenpost (0.031 % in aerial, 0.024% in root), and Olst (0.028 % in aerial, 0.023% in root), all sampled in July 2008, had higher a DPT content in the aerial part compared to the roots. The differences found in the flowering time of the indoor plants points towards variations even though the plants were grown under identical conditions. These variations might point to differences in genotype at different geographical locations. The similarity in the DPT content observed under controlled conditions suggested that these genetic differences, if any do not influence the DPT production. However the significant differences in the DPT content and the yield between outdoor and indoor plants suggests that there might be environmental factor that play a role on the DPT production and yield. The root mass of the outdoor plants was up to 8 times higher than that of the indoor plants and the aerial mass was up to 30 times higher than that of the indoor plants. This influenced the DPT yield. The DPT yield of the outdoor plants was up to 8 times higher in the aerial part and up to 5 times higher in the root part than that of the indoor plants. This variation in the root and aerial mass of the indoor plants was also observed in the previous study.31 In summary, these results show the DPT content over time for both indoor and outdoor plants. The best time to harvest plants for the DPT isolation is when the plants reach the optimal DPT production together with an adequate biomass. For indoor plants this was in April (2nd year) in both aerial and root part. For outdoor plants this was in March (2nd year) for the root part and in June (2nd year) for the aerial part. TheA. sylvestris from Bonn showed constant production of DPT in the field over the season
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SEASONAL and may be a suitable candidate for on-going cultivation and breeding for production purposes and commercial isolation of DPT (figure 3). Another candidate isA. sylvestris from Coventry which showed a similar DPT content when cultivated elsewhere
V (figure 2), but further work to optimise growing conditions have to be carried out. ARIATIONS
Materials and Methods Chemicals Deoxypodophyllotoxin (DPT) was a gift from Dr. M. Angeles Castro (Salamanca University, Salamanca, Spain) and was synthesized chemically. The identity and purity of DPT were checked by using HPLC (100 %). Acetonitrile and methanol were HPLC grade from Biosolve (Valkenswaard, the Netherlands). Dichloromethane is from Fisher Scientific (Landsmeer, the Netherlands).
Plant Material The fruits (ripe mericarps, hereafter called seeds) and plants of Anthriscus sylvestris L. were obtained from different sources (table 2). Vouchers specimens are deposited in our department coded Asylv2007-1 until Asylv2007-16. The identity of the seeds was verified and samples were stored in the reference collection of the Groningen Institute of Archaeology. A. sylvestris plants were collected at the flowering stage between May and June 2007, from the locations in the Netherlands and other European countries (table 2), and used for analysis. From the same plants and origin, seeds were collected. Plants were grown from these seeds (identical condition) in the Botanical Garden De Kruidhof (Buitenpost, the Netherlands, 53o 15’ 52” N, 06o 07’ 41” E) and sampled in 2009. The roots were separated immediately from the aerial parts. The plant material was dried at room temperature prior to grinding and extraction.
Plant cultivation in the field (outdoor) The seeds were sown in December 2007 on soil in trays for cold stratification at botanical garden De Kruidhof and germinated in February 2008. These seedlings were transferred to the field in May 2008. The field samples were collected in the second year (2009) on a monthly basis, from March until August. The data (table 3) of the weather conditions in the Netherlands during this experiment in 2007 - 2009 were taken from KNMI (the Netherlands Meteorology Institute) website (www.knmi.nl).
Plant cultivation in the climate room (indoor) The seeds were sown in December 2007 on soil at the botanical garden De Kruidhof and germinated in February 2008. The seedlings were transferred into individual pots and placed under day-night regime (16 hours light and 8 hours dark) at 20-22oC in May 2008. In the first year (2008), samples were collected in June, July and August. During the subsequent winter period (September 2008 – February 2009), the plants were placed in an open green house to induce a cold dormancy period. In March of the
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Table 2. Origin of the collected Anthriscus plants and seeds SEASONAL
No Origin Country Location amsla Collector 1 Nieuwegeinb The 52o 00’ 50” N 05o 06’ 68” E 1 Oktavia Hendrawati V
Netherlands ARIATIONS 2 Olstb The 52o 32’ 97” N 06o 10’ 21” E 3 Oktavia Hendrawati Netherlands 3 Dieverb The 52o 85’ 95” N 06o 32’ 91” E 9 Oktavia Hendrawati Netherlands 4 Groningenb The 53o 11’ 34” N 06o 37’ 04” E 1 Oktavia Hendrawati Netherlands 5 Buitenpost The 53o 15’ 52” N 06o 07’ 41” E 1 Jan W. Zwart Netherlands 6 Oudeschans The 53° 08’19” N 07° 08’ 34” E 1 Rene J.T. Cappers Netherlands 7 Bonn Germany 50o 45’ 04” N 07o 06’ 39” E 60 Frank Klingenstein 8 Tartu Estonia 58o 36’ 60” N 26o 69’ 25” E 79 Christina Birnbaum 9 Coventry United 52° 24’ 03” N 01° 30’ 40” W 76 Dalila Martins Kingdom 10 Essex United na na 38 Kew Garden, accession Kingdom No: 0039420 11 Suffolk United na na na Kew Garden, accession Kingdom No: 0053121 12 Enebyberg Sweden 59° 26’ 06” N 18° 01’48” E 20 Renata Alnsatter 13 Reykjavik Iceland 66° 21’ 25” N 21° 71’ 29” W 15 Sigurdur H. Magnusson 14 Egillstafr Iceland 64° 59’ 57” N 14° 17’ 22” W 34 Sigvardur Eirnarsson 15 Hrisey Iceland 66° 01’ 03” N 18° 23’ 69” W 5 Bjarni E. Gudleifsson 16 Mogilsa Iceland 66° 21’25” N 21° 71’ 29” W 65 Sigurdur H. Magnusson aabove mean sea level (m) bsame locations as in the preliminary studies31, 32 second year (2009), they were placed back into the climate room and samplings were continued every month, from March until August.
Sample preparation and extraction method All sampling were from three individual plants (triplicate) and randomly selected. The samples were divided into aerial part and the root part. Subsequently, the biomass (fresh weight) of aerial and root part was weighed for every plant. The biomass data was an average of three individual plants. The samples from field and climate room experiment were freeze-dried and pulverized for analysis. The fresh weight - dry weight ratio was calculated based on an average of six plants. The ratio for the aerial part was 0.1891 and for the root part 0.2840. The yield was calculated based on DPT concentration and total dry weight of the biomass per plant. The extraction method
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SEASONAL Table 3. Data on rainfall, temperature and duration of sun in the Netherlands in 2008 and 2009 (www.knmi.nl)
Month V
ARIATIONS 1 2 3 4 5 6 7 8 9 10 11 12 Rainfall 2007 (mm) 104 68 85 0 138 90 161 42 97 32 58 77 Rainfall 2008 (mm) 96 39 92 34 33 40 127 114 100 92 91 24 Rainfall 2009 (mm) 54 55 48 20 65 54 107 47 34 90 120 84 Temperature 2007 (°C) 7.1 6.0 8.0 13.1 14.1 17.5 17.0 17.1 13.8 10.1 6.9 3.8 Temperature 2008 (°C) 6.5 5.1 5.9 8.9 15.7 16.5 18.1 17.4 13.6 10.1 6.9 2.4 Temperature 2009 (°C) 0.8 3.3 6.3 12.2 13.9 15.6 18.1 18.5 15 10.7 9.5 2.2 Duration of sun 2007(h) 50 57 157 284 198 172 193 199 116 130 62 72 Duration of sun 2008 (h) 50 128 117 185 260 233 182 163 147 134 54 85 Duration of sun 2009 (h) 101 48 142 227 236 232 233 226 160 123 51 60
was as described by Koulman et al.31 Shortly, 100 mg dried plant material were weighed in a sovirel tube. A 2.0 ml portion of 80% methanol was added and the mixture was
sonicated during 1 hour. Subsequently 4.0 ml of dichloromethane and 4.0 ml H2O were added. The mixture was vortexed and centrifuged at 1,000 g for 5 minutes. The aqueous layer was discarded and 2.0 ml of organic layer were transferred into a 2 mL Eppendorf tube. The organic layer was left in the fume hood until dried. The residue was redissolved in 2.0 ml methanol and filtered over a 0.45 µm HPLC syringe filter (nylon). The samples were submitted to HPLC analysis.
HPLC analysis The HPLC analysis was as described by Vasilev et al.37 with some modifications. We used a Shimadzu-VP system consisting of a LC-10AT pump, a Kontron 360 auto sampler, a SPD M10A DAD detector, a FCV-10AL low pressure gradient mixer, a SCL-10A system controller, a FIAtron system CH-30 column heater, operated with LC Solution software, version 1.2. The column used was Zorbax Eclipse C18 (150 x 4.6 mm, 5 µm), together with Phenomenex guard cartridge C18 (4 x 3 mm) Phenomenex, Bester,
The Netherlands. The detection wavelength was 240 nm. Mobile phase A [H2O: ACN
(95:5)] and B [ACN: H2O (95:5)] were both in 0.1% formic acid and 2 mM ammonium formate. The injection volume was 5 µL. The flow rate was 1 mL/min using a gradient program of 30 min consisting of 1 min of B 30%, followed by a linear gradient until 15 min B 90%, at 20 min B 90%, at 25 min B 30% and at 30 min B 30%. Concentrations of metabolites were calculated using a calibration curve established with the reference compound (DPT).
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Statistical analysis SEASONAL Statistical calculations were carried out with the SPSS 16.0. Pearson correlation was used for correlation analysis and T-test was used for significant testing. P values < 0.05 were considered to be significant. V ARIATIONS
Acknowledgements
We thank M. A. Castro for giving us pure DPT as a reference compound, J.T.M. Elzenga for the climate room facility, J.W. Zwart and H. Drost for the A. sylvestris cultivation in the field at the Botanical garden De Kruidhof. We also thank J.J. Hogendorf, G. Telkamp, B. Farahanikia and E.J.J. Berm for their technical support. Financial support by the Ubbo Emmius fund, University of Groningen, is acknowledged.
References 1. Jeong G, Kwon O, Park B, et al. Lignans 8. Kozawa M, Baba K, Matsuyama Y, et al. and coumarins from the roots of Anthr- Components of the root of Anthriscus iscus sylvestris and their increase of sylvestris Hoffm. II. Insecticidal acitivity. caspase-3 activity in HL-60 cells. Biol Chem Pharm Bull 1982;30:2885-2888. Pharm Bull 2007;30:1340-1343. 9. Charlton JL. Antiviral activity of lignans. 2. Magnusson, S.H. NOBANIS – Invasive J Nat Prod 1998;61:1447-1451. alien species fact sheet – Anthriscus 10. Jin M, Moon TC, Quan Z, et al. The sylvesris – From: online database of the naturally occurring flavolignan, de- north European and Baltic network oxypodophyllotoxin, inhibits lipopol- on Invasive alien species – NOBANIS. Available from: www.nobanis.org. 2006 ysaccharide-induced iNOS expression (accessed 06.09.2011) through the NF-kappaB activation in RAW264.7 macrophage cells. Biol Pharm 3. Hulten E, Fries M. Atlas of north Bull 2008;31:1312-1315. European vascular plants north of the tropic of cancer. Konigstein: Koeltz Sci- 11. Jin M, Lee E, Yang JH, et al. Deoxypo- entific Books, 1986. dophyllotoxin inhibits the expression of intercellular adhesion molecule-1 4. Yong Y, Shin S, Lee Y, et al. Antitumor induced by tumor necrosis factor-alpha; activity of deoxypodophyllotoxin in murine lung epithelial cells. Biol isolated from Anthriscus sylvestris: Pharm Bull 2010;33:1-5. Induction of G2/M cell cycle arrest and caspase-dependent apoptosis. Bioorg 12. Chen J, Chang Y, Teng C. et al. Anti- Med Chem Lett 2009;19:4367-4371. platelet aggregation alkaloids and lignans from Hernandia nymphaeifolia. Planta 5. Wong S, Tsui S, Kwan S, et al. Identifica- Med 2000;66:251-256. tion and characterization of Podophyllum emodi by API-LC/MS/MS. J Mass Spec 13. Gordaliza M, Castro MA, García- 2000;35:1246-1251. Grávalos MD, et al. Antineoplastic and antiviral activities of podophyllotoxin 6. Koulman A, Kubbinga ME, Batterman S, et al. A phytochemical study of lignans in related lignans. Archiv der Pharmazie whole plants and cell suspension cultures 1994;327:175-179. of Anthriscus sylvestris. Planta Med 14. Lee SH, Son MJ, Ju HK, et al. Dual inhi- 2003;69:733-738. bition of cyclooxygenases-2 and 5-lipox- 7. Koulman A, Bos R, Medarde M, et al. A ygenase by deoxypodophyllotoxin in fast and simple GC MS method for lignan mouse bone marrow-derived mast cells. profiling in Anthriscus sylvestris and bio- Biol Pharm Bull 2004;27:786-788. synthetically related plant species. Planta 15. Sudo K, Konno K, Shigeta S, et al. Inhibi- Med 2001;67:858-862. tory effects of podophyllotoxin deriva-
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SEASONAL tives on herpes simplex virus replication. 6-hydroxylase, a key enzyme for the Antivir Chem Chemother 1998;9:263-267. formation of 6-methoxypodophyllotox- 16. Ikeda R, Nagao T, Okabe H, et al. Anti- in. Phytochem 2007;68:1397-1406. proliferative constituents in umbelliferae 26. Jackson DE, Dewick PM. Aryltetralin V plants. III. Constituents in the root and lignans from Podophyllum hexandrum ARIATIONS the ground part of Anthriscus sylvestris and Podophyllum peltatum. Phytochem Hoffm. Chem Pharm Bull 1998;46:871- 1984;23:1147-1152. 874. 27. Kondo K, Ogura M, Midorikawa Y, et al. 17. Shin SY, Yong Y, Kim CG, et al. De- Conversion of deoxypodophyllotoxin to oxypodophyllotoxin induces G2/M cell podophyllotoxin-related compounds by cycle arrest and apoptosis in HeLa cells. microbes. Agric Biol Chem 1989;53:777- Cancer lett 2010;287:231-239. 782. 18. Choi H, Lee J, Shin H, et al. Deoxypo- 28. Choudhary DK, Kaul BL, Khan S. Culti- dophyllotoxin reduces skin pigmenta- vation and conservation of Podophyllum tion of brown guinea pigs. Planta Med hexandrum—an overview. J Med Aromat 2004;70:378-380. Plant Sci 1998;20:1071-1073. 19. Suh S, Kim J, Jin U, et al. Deoxypodo- 29. Nayar MP, Sastry APK. Red data book of phyllotoxin, flavolignan, fromAnthriscus Indian plants. Calcutta, 1990. sylvestris Hoffm. inhibits migration and 30. Giri A, Narasu ML. Production of MMP-9 via MAPK pathways in TNF- podophyllotoxin from Podophyllum [α]-induced HASMC. Vasc Pharmacol hexandrum: a potential natural product 2009;51:13-20. for clinically useful anticancer drugs. Cy- 20. Lin CX, Lee E, Jin MH, et al. Deoxy- totechnol 2000;34:17-26. podophyllotoxin (DPT) inhibits eosi- 31. Koulman A, Batterman S, van Putten nophil recruitment into the airway and FMS, et al. Lignan profiles of indoor-cul- Th2 cytokine expression in an OVA- tivated Anthriscus sylvestris. Planta Med induced lung inflammation. Planta Med 2006;72:786-791. 2003;69:959-961. 21. Dall’Acqua S, Giorgetti M, Cervellati R, 32. Koulman A, Hendrawati O, Batterman et al. Deoxypodophyllotoxin content S, et al. The seasonal variations of lignan and antioxidant activity of aerial parts of profiles in Anthriscus sylvestris (L.) Anthriscus sylvestris Hoffm. Z Naturfor- Hoffm. Planta Med 2007;73:P_112. sch C 2006;61:658-62. 33. van Mierlo JEM, van Groenendael 22. Rong G, Congfen G, Xuan T, et al. Insec- JMA. Population dynamic approach to ticidal activity of deoxypodophyllotoxin, the control of Anthriscus sylvestris (L.) isolated from Juniperus sabina L, and Hoffm. J Appl Ecol 1991:128-139. related lignans against larvae of Pieris 34. Field A. Discovering statistics using rapae L. Pest Manag Sci 2004;60:1131- SPSS. London: SAGE Publications, 2005; 1136. 125-129 23. Xu H, Wang JJ. Natural products-based 35. Pandey H, Nandi S, Kumar A, et al. Po- insecticidal agents 5. Design, semisyn- dophyllotoxin content in Podophyllum thesis and insecticidal activity of novel hexandrum Royle plants of known age of 4’-substituted benzenesulfonate deriva- seed origin and grown at a lower altitude. tives of 4-deoxypodophyllotoxin against Acta Phys Plant 2007;29:121-126. Mythimna separata Walker in vivo. Bioorg 36. Robinson AR, Ukrainetz NK, Kang K, Med Chem Lett 2010;20:2500-2502. et al. Metabolite profiling of Douglas-fir 24. Ayres DC, Loike JD. Lignans: chemical, (Pseudotsuga menziesii) field trials reveals biological and clinical properties. strong environmental and weak genetic Cambridge, UK: Cambridge University variation. New Phytol 2007;174:762-773. Press, 1990. 37. Vasilev NP, Julsing MK, Koulman A, et 25. Federolf K, Alfermann AW, Fuss E. al. Bioconversion of deoxypodophyllo- Aryltetralin-lignan formation in two toxin into epipodophyllotoxin in E. coli different cell suspension cultures of using human cytochrome P450 3A4. J Linum album: deoxypodophyllotoxin Biotechnol 2006;126:383-393.
60
Chapter
Identification of lignans and related compounds in Anthriscus sylvestris by LC-ESI-MS/MS and LC-SPE-NMR
Oktavia Hendrawati Herman J. Woerdenbag Paul J.A. Michiels 3 Herald G. Aantjes Annie van Dam Oliver Kayser
Phytochemistry 2011; in press 3 I D Abstract ENTI
F The aryltetralin lignan deoxypodophyllotoxin is much more widespread in the plant ICATION kingdom than podophyllotoxin. The latter serves as a starting compound for the production of cytostatic drugs like etoposide. A better insight into the occurrence
O of deoxypodophyllotoxin combined with detailed knowledge of its biosynthestic F F
LIGNANS pathway(s) may help to develop alternative sources for podophyllotoxin. Using HPLC combined with electrospray tandem mass spectrometry and NMR spectroscopy techniques, we found lignans and related structures in roots of Anthriscus sylvestris (L.) Hoffm. (Apiaceae), a common wild plant in temperate regions of the world. Podophyllotoxone, deoxypodophyllotoxin, yatein, anhydropodorhizol, 1-(3’-methoxy- 4’,5’-methylenedioxyphenyl)1-ξ-methoxy-2-propene, and 2-butenoic acid, 2-methyl- 4-[[(2Z)-2-methyl-1-oxo-2-buten-1-yl]oxy]-, (2E)-3-(7-methoxy-1,3-benzodioxol-5- yl)-2-propen-1-yl ester, (2Z)- were the major compounds. α-Peltatin, podophyllotoxin, β-peltatin, isopicropodophyllone, β-peltatin-a-methylether, (Z)-2-angeloyloxymethyl- 2-butenoic acid, anthriscinol methylether, and anthriscrusin were present in lower concentrations. α-Peltatin, β-peltatin, isopicropodophyllone, podophyllotoxone, and b-peltatin-a-methylether have not been previously reported to be present in A. sylvestris. Based on our findings we propose a hypothetical biosynthetic pathway of aryltetralin lignans in A. sylvestris.
Keywords: Anthriscus sylvestris L. (Hoffm.), Apiaceae, cow parsley, wild chervil, LC-ESI-MS/MS, LC-SPE-NMR, aryltetralin lignans, biosynthetic pathway, deoxypodophyllotoxin
Oktavia Hendrawati1, Herman J. Woerdenbag2, Paul J.A. Michiels3, Herald G. Aantjes3, Annie van Dam4, Oliver Kayser1,5
1Department of Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 2Department of Pharmaceutical Technology and Biopharmacy, University of Groningen Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 3Spinnovation Analytical BV, Nijmegen, the Netherlands; 4Mass Spectrometry Core Facility, University of Groningen, Groningen, The Netherlands; 5Technical University Dortmund, Technical Biochemistry, Emil-Figge-Strasse 66, 44227 Dortmund, Germany
Phytochemistry 2011; in press
64 3 I Introduction D ENTI
Anthriscus sylvestris L. (Hoffm.) (Apiaceae) is a perennial herb that grows in Europe F ICATION and in parts of North America, Africa, Asia and New Zealand.1-3 The aryltetralin lignan deoxypodophyllotoxin (6) is an interesting constituent of the plant because it can be
4 used as a precursor for the production of podophyllotoxin (2). Podophyllotoxin (2) is O F F important as a semi-synthetic precursor for the anticancer drugs etoposide, teniposide, LIGNANS and etopophos.5 To date, 2 is obtained by isolation from Podophyllum species. In the future, the availability of 2 from this source is likely to become a major bottleneck. Podophyllum species have been listed on the endangered species list in India, proving that the continuous demand of 2 is a serious threat for their existence.6 An alternative source of 2 may be found by the (biotechnological) hydroxylation of 6 at the C7 position.7 Compound 6 is much more widespread in the plant kingdom than 2. 1-4 A better insight into the occurrence of 6 combined with profound knowledge of its biosynthetic pathway(s) may help to develop alternative sources for the desired lignans. In addition to 6, several other compounds have been reported to occur in A. sylvestris, including monoterpenes, anthricinol, angeloyl butenoid acid, anthriscusin (13), anthricin, isoanthricin and crocactone.8-10 The objective of the present study was to further investigate the occurrence of lignans and related structures in A. sylvestris. A better insight into the phytochemistry of A. sylvestris will increase our understanding of possible biosynthetic pathways for podophyllotoxin and related lignans and contribute to the development of alternative sources for the desired compounds. LC-SPE-NMR and LC-ESI-MS/MS techniques were used for the identification and structure elucidation.
Results and Discussion
A typical HPLC chromatogram of the aerial and the root parts of A. sylvestris is shown in figure 1. Because the underground parts contained more compounds and at higher concentrations compared to the aerial parts, we used the root extract for the separation, isolation and identification of lignans and related structures, 14 in total. Compounds 1, 2, 3, and 6-9 were identified based on comparison with pure reference compounds using HPLC, molecular weights and fragment ions by LC-MS/ MS. Compound 4, 5, and 10-14 were identified based on molecular weights, fragment ions, 13C NMR and 1H NMR spectra. The chemical structures are shown in figure 2. The molecular weights and the fragment ions are summarized in table 1. The comprehensive and detailed assignment of the multiplicity and coupling constants of 13C NMR and 1H NMR spectra are summarized in table 2. We are the first to report on the presence of a-peltatin (1), b-peltatin (3), isopicropodophyllone (4), podophyllotoxone (5) and b-peltatin-a-methylether (9) in A. sylvestris.
65 3 I D ENTI F ICATION
O F F LIGNANS
Figure 1. UV chromatograms obtained at 240 nm of aerial parts and root extract of Anthriscus Figure 1. UV chromatograms obtained at 240 nm of aerial parts and root extract of sylvestris. Anthriscus sylvestris
Compound 1 (mw: 400), 2 (mw: 414), 3 (mw: 414), and b-peltatin-a-methylether Compounds(9, mw: 428) 1are, 2 aryltetralin, 3, and 6 lignans.-9 were The identified general basedfragmentation on comparison ions were with produced pure + by loss of the pendant phenyl substituent [B+H] and subsequent loss of CO2 from the + 11 referencelactone ring compounds [B-CO2+H] using. The HPLC, latter molecular fragment is weights either andnot fragmentobserved or io nsvery by weak. LC- + + 11 [B+H] shows the dehydration product [B-H2O+H] with somewhat higher intensity. MS/MS. Compound 4, 5, and 10-14 were+ identified based+ on molecular+ weights, The fragment ions of1 are 247 [B+H] , 229 [B+H-H2O] , and 185 [A] . The fragment + + + + ions of 2 are 31313 [A+H] , 247 1[B+H] , 229 [B+H-H O] , and 185 [B+H-H O-CO ] . fragment ions, C NMR and H NMR spectra. The2 chemical structures are2 shown2 + Compound 3 has the same fragmentation as 1 with additional 203 [B-CO2+H] . The + + infragment figure ions 2. The of compond molecular 9 are weights 261 [B+H] and and the 217 fra [B-COgment2 +H] ions. The are summarizedconcentration inof these peltatins in A. sylvestris were low and hardly detectable by HPLC. However using tcombinedable 1. The LC-MS/MS, comprehensive a technique and more detailed sensitive assignment than HPLC-UV of the multiplicityalone, we could and 11 couplingconfirm constantsthe identity of of13 Ccompounds NMR and 1, 1 H2, 3NMR and 9spectra, also in are comparison summarized to the in literature.table 2. Compounds 4 and 5 have the same molecular weight of 412 and the same fragment + + ion patterns, 245 [B+H] and 201 [B-CO2] . We further identified the stereochemistry by 1H-NMR and 13C-NMR and compared it to the literature.12, 13 The coupling constant and multiplicity of especially H-7’, H-8’, H-8 and H-9 determine the stereochemistry. The signals of H-7’ of compound 4 and 5 appear as doublets at δ 4.72 (J = 6.3 Hz) and δ 4.84 (J = 4.6 Hz), respectively. These results are not in agreement with picropodophyllone13 which has a singlet for this proton resonance. The multiplicity of H-8’ of compound 4 is multiplet at δ 3.77 whereas this signal in compound 5 appears
66
3 I Table 1. LC-ESI-MS and LC-ESI-MS/MS data of the compounds identified in root extract of D Anthriscus sylvestris. ENTI F No Compound MW Molecular Ions Fragment ions ICATION + of [M+NH4] or [M+H]+ion
O
1 α-Peltatin 400 418 247, 229, 185 F LIGNANS 2 Podophyllotoxin 414 432 313, 247, 229, 185 3 β-Peltatin 414 432 247, 229, 203, 185 4 Isopicropodophyllone 412 430 245, 201 5 Podophyllotoxone 412 430 245, 201 6 Deoxypodophyllotoxin 398 416 231, 187 7 Yatein 400 418 223, 181 8 Anhydropodorhizol 398 416 231, 135 9 β-Peltatin-a-methylether 428 446 261, 217 10 (Z)-2-angeloyloxymethyl-2-butenoic acid 198 199 181 11 Anthriscinol methyl ether 222 223 191, 161 12 1-(3’-methoxy-4’,5’- 222 229d 191, 161 methylenedioxyphenyl)1-ς-methoxy-2- propene 13 Anthriscrusin 388 406 191 14 2-butenoic acid, 2-methyl-4-[[(2Z)- 388 406 191 2-methyl-1-oxo-2-buten-1-yl]oxy]-, (2E)-3-(7-methoxy-1,3-benzodioxol-5-yl)- 2-propen-1yl ester, (2Z)- a Unknown 428 b Unknown 416 c Unknown 392 d[M+Li]+ as a doublet of doublets (dd) at δ 3.77 (J = 15.6, 4.6 Hz). The multiplicity of H-8 of compound 4 is multiplet at δ 3.83 whereas this signal in compound 5 appears as a doublet of doublets (ddd) at δ 3.59 (J = 15.6 and 4.7 Hz). The multiplicity of H-9 of compound 4 is multiplet at δ 3.87 and triplet at δ 4.50 (J= 7.9 Hz) whereas this signal in compound 5 appears as a doublet of doublets (dd) at δ 4.31 (J=10.3 and 8.4 Hz) and triplet at δ 4.49 (J=7.9 Hz). The 13C-NMR spectra also showed characteristic values distinguishing these stereochemistry at C-3, C-7, C-8, C-9, C-8’, and C-9’. These values are similar with the reported data.12, 13 The main lignan in A. sylvestris is deoxypodophyllotoxin (6). The identity of this compound was based on comparison of the retention time of reference compound by HPLC, the molecular weight (398), the fragment ions, and the 13C NMR and 1H NMR spectra. Our data are in agreement with literature.14
67 3 I D ENTI F ICATION
O F F LIGNANS
Figure 2. Chemical structures of compounds in the root extract of Anthriscus sylvestris. Figure 2. Chemical structures of compounds in the root extract of Anthriscus sylvestris
We identified compound 10 as (Z)-2-angeloyloxymethyl-2-butenoic acid, an acyloxycarbocyclic acid, based on the molecular weight (198), and 1H-NMR and 13C-NMR spectra. Our proton NMR data (table 2) are in agreement with those
published by Kozawa who isolated this compound from A. sylvestris.8 TableCompound 1. LC-ESI-MS 11 and was LC identified-ESI-MS/MS as anthriscinoldata of the compounds methyl ether, identified a phenylpropanoid in root extract derivative, based on the molecular weight (222), the 1H-NMR and 13C-NMR spectra. of TheAnthriscus NMR spectrasylvestris were confirmed with reported literature.15 Compound 11 has been reported to display weak insecticidal activity.16 The molecular weight of compound 12 is 222. The 13C NMR and 1H NMR data No Compound MW Molecular Ions of Fragment ions 13 + compared with the literature confirmed that compound[M+NH 124] is or 1-(3’-methoxy-4’,5’- 15 methylenedioxyphenyl)-1ξ-methoxy-2-propene. The isolation[M+H]+ion and uses of compound 1 12 inα -A.Peltatin sylvestris are for prevention or treatment400 of cancer 418or condyloma.247,17 229, 185
68
3 I The molecular weight of compounds 13 and 14 is 388 and showed similar fragment D ENTI ions in LC-MS data. The NMR data and compared with data from the literature9, 15 F suggested that compound 13 is O-[(Z)-2-angeloyloxymethyl-2-butenoyl]-3-methoxy- ICATION 4,5-methylendioxyamyl alcohol (anthriscusin). It is a phenylpropanoid ester derived from 16 13 1
anthriscinol and compound 10. Based on our intepretation of C NMR and H NMR O data, we propose that compound 14 is 2-butenoic acid, 2-methyl-4-[[(2Z)-2-methyl-1- F LIGNANS oxo-2-buten-1-yl]oxy]-, (2E)-3-(7-methoxy-1,3-benzodioxol-5-yl)-2-propen-1-yl ester, (2Z)-. Selective 1D NOE experiments were carried out to identify the NOE long range coupling for the 4’’ CH to the 3’’ CH3 group. The NOE was difficult to identify in the 2D NOESY experiment because it overlapped with the large NOE between 3’’’ and 4’’’. The weak NOE between CH2 and the CH3 could be explained by spin-diffusion because it is very far away through space. The biological study, isolation and uses of compound 14 in A. sylvestris for prevention or treatment of cancer or condyloma were patented.17 However there was no NMR or MS data reported in the patent. The major compounds in the roots were compounds 5-8, 12 and 14. Compound 1 and 3 were isolated from P. hexandrum for the first time.18 In A. sylvestris, we now report and structure elucidated these compounds for the first time. Trace amounts of compound 2 (< 0.01 µg/mg d.w.) have been reported in A. sylvestris.19 Compounds 10 and 13 have been isolated earlier from the roots of A. sylvestris.8, 9 Compound 6 was isolated for the first time from the roots of A. sylvestris.10 Compound 7, 11, 12 have been isolated from the roots of A. sylvestris.15 Compound 7 and 12 were also isolated from the fruit of A. sylvestris.20 The low concentration of 1 and 3 might be due to the fact that A. sylvestris was collected after having flowered in May 2007. A decrease of these compounds after flowering has also been shown in Podophyllum species.21 The loss of 1 and 3 during growth might due to metabolic turnover.21 The lignans isolated in this study (1-9) may be involved in the late biosynthesis pathway of aryltetralin lignans in A. sylvestris. Federolf et al.22 has recently proposed hypothetical pathway of 2 in Linum album. Combined with our findings, we propose a biosynthetic pathway of 6 and related lignans in A. sylvestris (figure 3). Matairesinol was incorporated effectively into 1, 2, 3, 4’-demethylpodophyllotoxin, and 4’-demethyldeoxypodophyllotoxin in P. hexandrum root, P. peltatum leaves and Diphylleia cymosa leaves.23 In A. sylvestris, matairesinol may be incorporated into 7, 8, 4’-demethylyatein (putative intermediate) and other compounds24 which are further metabolized into 6, 2, 5, 1, 3, and 9 (figure 3). Feeding experiments with labelled 6 and 4’-demethyldeoxypodophyllotoxin in P. hexandrum showed that these compounds are the likely precursors of 1 and 3 respectively, by hydroxylation in the aromatic ring.21 The transformation of compound 6 into 2 and 3 has been shown in a feeding experiment in P. hexandrum.21 In P. hexandrum, it has been shown that 2 is derived from 6 by hydroxylation. Further oxidation yielded 5, the later reaction being reversible.18, 25 Compound 5 may be also reduced in vivo into 2.25 In our studies with A. sylvestris, 2 was detected in low amount together with its oxidation products, 5 and its diasteoisomer, 4 were present.
69 Table 2. NMR spectroscopic data (500MHz, d6-DMSO) for metabolites identified in Anthriscus sylvestris root extracts by LC- 3 SPE-NMR. I D
ENTI 2 4 5 6 Position δ C δ H δ C δ H δ C δ H δ C δ H F ICATION (J in Hz) (J in Hz) (J in Hz) (J in Hz) 1 166.9 128.0 127.9 131.0 6.49, dt (15.8) 2 127.3 140.0 141.6 124.9 6.25, dt
(15.8, 5.8, 5.8) O
F F 3 137.1 6.10, qq 108.0 6.86, s 109.4 6.85, s 71.9 4.00, dd LIGNANS (6.0, 1.8) 4 15.2 1.88, dq (7.4, 1.8, 152.7 152.4 1.6, 1.5) 5 20.0 1.81, q (1.45, 1.57, 147.6 147.6 1.62, 1.46) 6 104.7 7.31, s 104.4 7.40, s 7 195.0 192.4 8 44.2 3.83, m 42.8 3.59, ddd (15.6, 4.7) 9 68.5 3.87, m, 4.50, 66.4 4.31, dd t (7.9) (10.3, 8.4) and 4.49, t (7.9) 1’ 64.7 4.71, s 135.1 133.2 131.3 2’ 128.5 106.3 6.35, s 107.5 6.37, s 106.7 6.72, d (1.6) 3’ 141.1 6.41, q (7.5, 7.2) 152.6 152.4 143.4 4’ 15.2 2.00, d (7.2) 136.8 136.8 134.5 5’ 167.2 152.6 152.4 148.8 6’ 12.67, s 106.3 6.35, s 107.5 6.37, s 99.4 6.77, d (1.1) 7’ 42.7 4.72, d (6.3) 43.6 4.84, d (4.6) 8’ 43.5 3.77, m 44.8 3.77, dd (15.6, 4.6) 9’ 175.4 173.6
OCH2O 102.6 6.13, d (0.8), 102.9 6.16, d (0.8), 6.16, 101.0 5.97, s 6.13, d (0.8) d (0.8) C-3’, 55.5 3.63, s 55.6 3.65, s 56.0 3.83, s
OCH3 C-4’, 60.1 3.62, s 59.8 3.63, s
OCH3 C-5’, 55.5 3.63, s 55.6 3.65, s
OCH3 C-3, 57.0 3.27, s
OCH3
70 7 8 12 13 3 Position δ C δ H δ C δ H δ C δ H δ C δ H I D
(J in Hz) (J in Hz) (J in Hz) (J in Hz) ENTI 1 130.6 83.1 4.58, d (6.6) 133.2 6.57, dt (15.9, < 1) 133.1 6.61, dt (15.9, < 1) F ICATION 2 129.1 138.7 5.86, ddd 122.0 6.26, dt (15.9, 6.2) 122.1 6.31, dt (15.9, 6.3) (17.1, 10.3, 6.6)
O
3 119.6 6.51, s 115.3 5.14 ddd 64.5 4.77, m (nd) 64.7 4.78, dd (6.2, 1.2) F
(10.3, 1.8, LIGNANS 1.1); 5.25, ddd (17.2, 1.8, 1.3) 4 145.9 5 145.9 6 108.2 6.81, s 7 31.8 2.75, dd (15.4, 11.7); 3.03, dd (16.4, 5.1) 8 32.3 2.62, m 9 71.3 3.96, dd (10.6, 8.2) ; 4.42, t (7.6) 1’ 137.1 135.7 131.0 130.8 2’ 108.0 6.30, s 106.1 6.58, d (1.3) 106.9 6.71, d (1.4) 107.1 6.76, d (1.4) 3’ 152.1 143.1 142.9 143.2 4’ 136.3 134.1 134.9 134.9 5’ 152.1 148.4 148.8 148.8 6’ 108.0 6.30, s 100.2 6.51, d (1.3) 99.7 6.75, d (1.3) 99.7 6.80, d (1.4) 7’ 42.8 4.52, d (5.3) 8’ 45.9 2.99, dd, (13.5, 5.2)
OCH2O 99.8 5.94, d (0.9) 100.0 5.95, s 101.0, 5.96, s 100.6 5.96, s 5.97, d (0.9) CH2 C-3’, 55.6 3.64, s 56.0 3.79, s 56.1 3.83, s 56.1 3.84, s
OCH3 C-4’, 59.7 3.62, s
OCH3 C-5’, 55.6 3.64, s
OCH3 C-1, 55.3 3.20, s
OCH3 1’’ 165.3 166.2 2’’ 127.2 128.4 3’’ 143.1 6.53, qt (7.2, < 1) 19.3 1.93, tq (5.3, 1.6nd) 4’’ 15.6 2.03, dt (7.2, < 1) 138.1 6.18, tq (5.3, 16)
5’’ 64.6 4.78, m (nd) 61.8 5.02, dq (5.3, 1.8)
1’’’ 166.8 167.0
2’’’ 127.2 127.2
3’’’ 137.5 6.07, qq (7.2, 1.5) 137.8 6.14, qq (7.2, 1.5)
4’’’ 15.3 1.85, dq (7.2, 1.5) 15.5 1.92, dq (nd, 1.5)
5’’’ 20.1 1.78 , p (1.5) 20.1 1.85, p (1.5) nd: not determined due to overlap
71 present. Compound 4 was first isolated in nature from P. pleianthum.26
Compounds 4 and 5 have been reported to be present in P. pleianthum, P.
hexandrum and P. peltatum.27 Since 5 is readily isomerised to 4 by heat, the latter
compound may well be an artefact from 5 in Podophyllum extracts.26 Compound 4
is quite likely to be an artefact formed from 5. 3 I
D Figure 3. Proposed biosynthetic pathway of ENTI deoxypodophyllotoxin and related lignans in
F Anthriscus sylvestris (additional compounds: ICATION 1-5, 8, and 9, nd = not detectable).
O F F LIGNANS
Compound 4 was first isolated in nature fromP. pleianthum.26 Compounds 4 and 5 have been reported to be present in P. pleianthum, P. hexandrum and P. peltatum.27 Since 5 is readily isomerised to 4 by heat, the latter compound may well be an artefact from 5 in Podophyllum extracts.26 Compound 4 is quite likely to be an artefact formed from 5. Compound 7 has been reported to be an earlier precursor of deoxypodophyllo- toxin,25 while compound 3 is the product of the metabolization of 6 according to the hypothetical biosynthetic pathway of lignans which has been reported previously.18, 22 Broomhead et al.23 proposed 4’-demethylyatein and 4’-demethyldeoxypodophyllotoxin as putative intermediates between matairesinol and 1 in P. hexandrum root, P. peltatum leaf and Diphylleia cymosa leaf. Although 4’-demethylyatein and 4’-demethyldeoxypodophyllotoxin were not detected in the root extract of
72 3 I A. syvlestris, these compounds may be putative intermediates between matairesinol D ENTI and 1 (figure 3). However, we could not trace these earlier precursors such as F matairesinol and later products of lignan biosynthesis detected in other plants, such as ICATION 6-methoxypodophyllotoxin.22 18, 22
In the late biosynthetic pathway of podophyllotoxin, we suggest a role of other O
(or: additional) compounds related to the formation of podophyllotoxin in A. sylvestris F LIGNANS (figure 3). Our results add to what is known about the biosynthetic pathway of lignans in A. sylvestris. Additional experiments to further unravel this biosynthetic pathway of lignans in A. sylvestris are needed. In summary, the combination of the liquid chromatography, electrospray ionization mass spectrometry (LC-ESI-MS/MS), and LC-SPE-NMR techniques are proven to be powerful tools to elucidate the structures unknown compounds in A. sylvestris extracts. In total, we identified 14 compounds in the root extract of A. syvlestris which may be involved in the late biosynthesis pathway of aryltetralin lignans as shown in figure 3. We identified the 6-methoxy lignans (1 and 3) as new side pathway, which previously was not known.
Material and Methods Chemicals Deoxypodophyllotoxin was a gift from Dr. M. Angeles Castro (Salamanca University, Salamanca, Spain). Anhydropodorhizol, yatein, α-peltatin, β-peltatin and β-peltatin- a-methylether were kindly provided from Prof. M. Medarde (Salamanca University, Salamanca, Spain). Podophyllotoxin was from Sigma Aldrich (Zwijndrecht, the Netherlands). The identity and purity of these reference compounds were checked using HPLC. Acetonitrile and methanol were HPLC grade from Biosolve, Valkenswaard, the Netherlands. Dichloromethane was from Fisher Scientific, Landsmeer, the Netherlands. Formic acid and ammonium formate were from Sigma Aldrich, Zwijndrecht, the Netherlands. Deuterated DMSO (99.96 %) was from Eurisotop, Saint Aubin Cedex, France.
Plant Material Anthriscus sylvestris L. Hoffm. (Apiaceae) plants at the flowering stage were collected in Groningen, the Netherlands (53o 11’ 34” N and 06o 37’ 04” E) in May 2007. Voucher specimen have been deposited in our department, encoded Asylv2007-4. The roots were separated from the aerial parts and the material was dried at room temperature after harvesting and prior to extraction.
Sample preparation The extraction method was as described by Koulman et al.19 Shortly, 100 mg dried plant material were weighed into a Sovirel tube. A 2.0 mL portion of 80% methanol was added and the mixture was sonicated during 1 hour. Subsequently 4.0 mL of dichloromethane
73 3 I D and 4.0 mL H2O were added. The mixture was vortexed and centrifuged at 1,000 g for ENTI 5 minutes. The aqueous layer was discarded and 2.0 mL of organic layer were transferred F ICATION into a 2 mL Eppendorf tube. The organic layer was left in the fume hood until dried. The residue was redissolved in 2.0 mL methanol and filtered over a 0.45 µm HPLC
syringe filter (nylon). The samples were submitted to HPLC analysis. For LC-MS/MS O
F F and LC-SPE-NMR analysis 1 g dried root material was used and the aliquot residue was LIGNANS reconstituted in methanol at a concentration corresponding to 1 g dried plant material.
HPLC-UV analysis The HPLC analysis was as described by Vasilev et al.7 with some modifications. A Shimadzu-VP system was used, consisting of an LC-10AT pump, a Kontron 360 auto sampler, an SPD M10A DAD detector, an FCV-10AL low pressure gradient mixer, an SCL-10A system controller, an FIAtron system CH-30 column heater, operated with LC Solution software, version 1.2. The column used was Zorbax Eclipse C18 (150 x 4.6 mm, 5 µm), together with Phenomenex guard cartidge C18 (4 x 3 mm) Phenomenex,
Bester, The Netherlands. The detection wavelength was 240 nm. Mobile phase A [H2O:
ACN (95:5)] and B [ACN: H2O (95:5)], both in 0.1% formic acid and 2 mM ammonium formate. The injection volume was 5 µL with a flow rate of 1 mL/min using a gradient program of 30 min consisting of 1 min of B 30%, followed by a linear gradient until 15 min B 90%, at 20 min B 90%, at 25 min B 30% and at 30 min B 30%.
LC-ESI-MS/MS analysis HPLC was performed using a Shimadzu LC system, consisting of 2 LC-20AD gradient pumps and a SIL-20AC autosampler. The LC system was coupled to an API 3000 triple- quadrupole mass spectrometer (Applied Biosystems/MDS Sciex) via a TurboIonSpray source. Data were collected and analyzed by Analyst 1.4.2 data acquisition software (Applied Biosystems/MDS Sciex). Chromatographic separation was achieved on an Alltima C18 (Grace Davison) narrow-bore guard column (2.1 x 150 mm, 5 µm). The mobile phase and the gradient system were the same as used for the HPLC analysis. The flow rate was 0.2 mL/min. The injection volume was dependent on the expected analyte concentration. The ionization was performed by electrospray in the positive + + mode, which resulted in the formation of (M+H) and/or (M+NH4) adduct ions. The source temperature was set to 450°C. The instrument was operated with an ionspray voltage of 5.2 kV. Nitrogen was used both for curtain gas and nebulizing gas. Full scan mass spectra were acquired at a scan rate of 1 scan/sec with a scan range of 100-1100 amu and a step size of 1 amu. Defined product ion scans were acquired in specified time windows.
LC-SPE isolation HPLC was applied for the isolation of the individual compounds in pure form. Mobile
phase A consisted of 0.1% formic acid in H2O, mobile phase B consisted of 0.1% formic acid in acetonitrile. The following method with gradient was applied with a flow-rate of 1 mL/min: 5 min isocratic at 32% B, followed by a linear gradient until 15 min B
74 3 I 86%, quick increase in 0.1 min to 95% B, where kept constant for 5 min and followed D ENTI by a quick descent in 1 min to 32% B, where kept for 5 min of equilibration prior to F the next analysis. The purification was carried out on an Agilent 1200 system (Agilent ICATION Technology, SantaClara, USA) equipped with a Prospekt 2 (Spark Holland), using an
Agilent column; Zorbax Eclipse XDB-C18, (150 x 4.6 mm, 5 µm). Compounds were O trapped on general purpose (GP) cartridges (Spark Holland) and dried for at least 40 F LIGNANS min under nitrogen air flow. Elution was performed using 600 mL of acetonitril, the purified fraction was dried under nitrogen air flow and dissolved in deuterated DMSO prior to NMR analyses.
NMR spectroscopy NMR analysis was performed on a Bruker Avance III 500MHz spectrometer equipped with a 5-mm CPTCI cryo-probe (1H-13C/15N/2H + Z-gradients) operating at 303 K. The structure identification of the purified compounds was based on a selection of 11D H, 1D selective NOE, 1H-1H-DQF-COSY, 1H-1H-TOCSY, 1H-13C-HSQC, 1H-13C-HMQC, and 1H-1H-NOESY spectra based on complexity or quantity of the sample. The proton and carbon chemical shifts were referenced to the internal reference TMS (proton, d = 0.00 ppm; carbon, d = 0.00 ppm). The data were processed using Topspin 2.1 pl5 and analysed with Mnova 6.2.1.
Acknowledgements
Financial support by the Ubbo Emmius Fund, University of Groningen, and the Müggenburg Foundation is greatly acknowledged.
References 1. Hulten E, Fries M. Atlas of north synthetically related plant species. Planta European vascular plants north of the Med 2001;67:858-862. tropic of cancer. Konigstein: Koeltz Sci- 5. Ayres DC, Loike JD. Lignans: chemical, entific Books, 1986. biological and clinical properties. 2. Jeong G, Kwon O, Park B, et al. Lignans Cambridge, UK: Cambridge University and coumarins from the roots of Anthr- Press, 1990. iscus sylvestris and their increase of 6. Nayar MP, Sastry APK. Botanical survey caspase-3 activity in HL-60 cells. Biol of India. Calcutta, 1990. Pharm Bull 2007;30:1340-1343. 7. Vasilev NP, Julsing MK, Koulman A, et 3. Magnusson, S.H. NOBANIS – Invasive al. Bioconversion of deoxypodophyllo- alien species fact sheet – Anthriscus toxin into epipodophyllotoxin in E. coli sylvesris – From: online database of the using human cytochrome P450 3A4. J north European and Baltic network Biotechnol 2006;126:383-393. on Invasive alien species – NOBANIS. 8. Kozawa M, Morita N, Hata K. Chemical Available from: www.nobanis.org. 2006 components of the roots of Anthris- (accessed 06.09.2011) cus sylvestris HOFFM. I. Structures of 4. Koulman A, Bos R, Medarde M, et al. A an acyloxycarboxylic acid and a new fast and simple GC MS method for lignan phenylpropanoidester, anthriscusin. profiling in Anthriscus sylvestris and bio- Yakugaku Zasshi 1978;98:1486-1490.
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D 9. Kozawa M, Morita N, Hata K. Structure sylvestris for cancer or condyloma. In: ENTI of anthriscusin, a new phenylpropa- Koho JKT, JP 09194369. Japan, 1997. noid ester from the roots of Anthriscus F 18. Jackson DE, Dewick PM. Aryltetralin ICATION sylvestris HOFFM. Chem Pharm Bull lignans from Podophyllum hexandrum 1978;26:1337-1338. and Podophyllum peltatum. Phytochem 10. Kurihara T, Kikuchi M, Suzuki S, et al. 1984;23:1147-1152.
O Studies on the constituents of Anthris- 19. Koulman A, Kubbinga ME, Batterman S, F F cus sylvestris HOFFM. I. On the com- LIGNANS et al. A phytochemical study of lignans in ponents of the radix. Yakugaku Zasshi whole plants and cell suspension cultures 1978;98:1586-1591. of Anthriscus sylvestris. Planta Med 11. Schmidt TJ, Hemmati S, Fuss E, et al. 2003;69:733-738. A combined HPLC-UV and HPLC-MS 20. Ikeda R, Nagao T, Okabe H, et al. Anti- method for the identification of lignans proliferative constituents in Umbellif- and its application to the lignans of erae plants. IV. Constituents in the fruits Linum usitatissimum L. and L. bienne of Anthriscus sylvestris HOFFM. Chem Mill. Phytochem Anal 2006;17:299-311. Pharm Bull 1998;46:875-878. 12. Ayres DC, Harris JA, Jenkins PN, et al. 21. Kamil WM, Dewick PM. Biosynthesis of Lignans and related phenols. Part XII. the lignans α- and β-peltatin. Phytochem Application of nuclear magnetic double 1986;25:2089-2092. resonance to the aryltetrahydronaphtha- lene class. J Chem Soc, Perkin Transac- 22. Federolf K, Alfermann AW, Fuss E. tions 1 1972:1343-1350. Aryltetralin-lignan formation in two different cell suspension cultures of 13. Miguel del Corral JM, Gordaliza M, López J-L, et al. Reassignment of the Linum album: Deoxypodophyllotoxin configuration of several keto-cyclolig- 6-hydroxylase, a key enzyme for the nans prepared from podophyllotoxin. formation of 6-methoxypodophyllotox- Helv Chim Act 1995;78:1793-1796. in. Phytochem 2007;68:1397-1406. 14. Pullockaran AJ, Kingston DGI, Lewis 23. Broomhead AJ, Rahman MMA, Dewick NG. Synthesis of stereospecifically deu- PM, et al. Matairesinol as precursor terated desoxypodophyllotoxins and of Podophyllum Lignans. Phytochem 1H-NMR assignment of desoxypodo- 1991;30:1489-1492. phyllotoxin. J Nat Prod 1989;52:1290- 24. Sakakibara N, Suzuki S, Umezawa T, et al. 1295. Biosynthesis of yatein in Anthriscus syl- 15. Ikeda R, Nagao T, Okabe H, et al. Anti- vestris. Org Biomol Chem 2003;1:2474- proliferative constituents in Umbelliferae 2485. plants. III. Constituents in the root and 25. Kamil WM, Dewick PM. Biosynthetic re- the ground part of Anthriscus sylvestris lationship of aryltetralin lactone lignans HOFFM. Chem Pharm Bull 1998;46:871- to dibenzylbutyrolactone lignans. 874. Phytochem 1986;25:2093-2102. 16. Kozawa M, Baba K, Matsuyama Y, et al. 26. Chang FC, Chiang C, Aiyar VN. Isopicro- Components of the root of Anthriscus syl- podophyllone from Podophyllum pleian- vestris HOFFM. II. Insecticidal activity. thum. Phytochem 1975;14:1440-1440. Chem Pharm Bull 1982;30:2885-2888. 27. Jackson DE, Dewick PM. Tumour- 17. Nishimura K, Umehara K, Nakamura inhibitory aryltetralin lignans from M. Cell differentation-inducing 1,3-di- Podophyllum pleianthum. Phytochem oxobenzene derivatives from Anthriscus 1985;24:2407-2409.
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Chapter
In vitro regeneration of wild chervil (Anthriscus sylvestris L.)
Oktavia Hendrawati Jacques Hille Herman J. Woerdenbag Wim J. Quax 4 Oliver Kayser
In Vitro Cellular & Developmental Biology – Plant 2011: in press 4
In v In Abstract i tro Anthriscus sylvestris (L.) Hoffm. (Apiaceae) is a common wild plant that accumulates
regeneration the lignan deoxypodophyllotoxin. Deoxypodophyllotoxin can be hydroxylated at the C-7 position in recombinant organisms yielding podophyllotoxin, which is used as a semi-synthetic precursor for the anticancer drugs, etoposide phosphate and teniposide. As in vitro regeneration of A. sylvestris has not yet been reported, development of a regeneration protocol for A. sylvestris would be useful as a micropropagation tool and for metabolic engineering of the plant. Calli were induced from hypocotyl explants and transferred to shoot induction medium containing zeatin riboside. Regenerated shoots were obtained within six months and were transferred onto growth regulator- free root induction medium containing 1% sucrose. Regenerated plants transferred to soil and acclimatized in a greenhouse. Plants were transferred to the field with a 100% survival rate. Regenerated plants flowered and were fully fertile. This is the first report of complete regeneration of A. sylvestris via shoot organogenesis from callus.
Keywords: organogenesis, micropropagation, regeneration, tissue culture, deoxypodophyllotoxin
1 2 3 1 1,4 Oktavia Hendrawati , Jacques Hille , Herman J. Woerdenbag , Wim J. Quax , Oliver Kayser
1Department of Pharmaceutical Biology, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands; 2Department of Molecular Biology of Plants, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands; 3Department of Pharmaceutical Technology and Biopharmacy, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands; 4Department of Technical Biochemistry, Technical University Dortmund, Emil-Figge-Strasse 66, 44227 Dortmund, Germany.
In Vitro Cellular & Developmental Biology – Plant 2011: in press
80 4
Introduction v In i Anthriscus sylvestris (L.) Hoffm. (Apiaceae) is a common wild plant, native to tro
Europe, North America, Africa, Asia and New Zealand1-3 that accumulates the lignan regeneration deoxypodophyllotoxin, especially in the roots. The dried root of A. sylvestris is used in Korean and Chinese traditional medicine for the treatment of various diseases.4 Deoxypodophyllotoxin is structurally closely related to the lignan podophyllotoxin, which is obtained from Podophyllum species and is used for the synthesis of the anticancer drugs, etoposide phosphate and teniposide. Podophyllotoxin is obtained from Podophyllum species, but the supply of podophyllotoxin from this source is likely to become a major bottleneck because Podophyllum species have been listed on the endangered species list in India.5 An alternative and more sustainable source of podophyllotoxin may be obtained by the biotechnological hydroxylation of deoxypodophyllotoxin at the C-7 position. This conversion has already been achieved in E. coli DH5α transfected with the human cytochrome P450.6 Although gene transfer via Agrobacterium can facilitate efforts to engineer secondary metabolic pathways,7, 8 this approach has not yet been evaluated for A. sylvestris. Plant regeneration from tissue cultures of many plant species has been reported, but some groups, families and genera are still regarded as recalcitrant.9 While there are no reports on regeneration of A. sylvestris, regeneration of the following members of the Apiaceae family has been documented: Daucus carota,10 Apium graveolens,11 Thapsia garganica,12 Pimpinella anisum,13 Ammi majus,14 Carum carvi,15 Coriandrum sativum,16 and Dorem ammoniacum.17 Regeneration from callus and suspension cultured cells of many crop plants, both by organogenesis18 and in vitro embryogenesis.19 Using information on the initiation of A. sylvestris calli and suspension cultures,20 cells from callus tissue were used to establish a regeneration protocol for A. sylvestris. Dormancy problems from A. sylvestris seeds presented an additional concern.21 The main objective of our study was to establish a regeneration protocol for A. sylvestris. This regeneration protocol can subsequently be used either as a micropropagation tool to bypass the dormancy in the seeds or for metabolic engineering of A. sylvestris. Different concentrations and combinations of auxins and cytokinins were used to induce shoots from callus tissue and to induce root formation from the regenerated shoots.
Results Seed germination Following chlorine gas sterilization (figure 1a), the seeds did not germinate immediately or at the same time prior to cold stratification at 1oC. The sterilized seeds started to germinate after a 3-months cold stratification (figure 1b) with an average germination rate of 39%. In vitro sterile seedlings were successfully obtained for callus induction (figure 1c).
81 4 In v In i tro regeneration
FigureFigure 1. RegenerationRegeneration of of A. A. sylvestris sylvestris L. (Hoffm.).L. (Hoffm.). a. Ripea. Ripe seeds, seeds, b. Germination b. Germination of the of sterile the o sterileseeds after seeds 3 aftermonths 3 1o monthsC, c. In vitro 1 C, youngc. In seedling, vitro young d. Leaves seedling, and d.hypocotyls Leaves explants, and hypocotyls e. Callus explants,growth after e. Callus 2 months growth induction, after 2 months f. Shoot induction, regeneration f. Shoot in Z10 regeneration media, g. Furtherin Z10 media, developed g. Furthershoot regeneration, developed shooth. In regeneration, vitro rooting ofh. shoots,In vitro i.rootin Youngg of regenerated shoots, i. Young plantlets, regenerated j. Ex vitro plantlets,acclimatization j. Ex vitroof young acclimatization regenerated of plantlets, young regenerated k. Field planting plantlets, of the k. Fieldregenerated planting plants, of the l. regenerated plants, l. Flowering of the regenerated plants, m. Seed pods of regenerated A. Flowering of the regenerated plants, m. Seed pods of regenerated A. sylvestris. Bars equal to 0.5 sylvestris. Bars equal to 0.5 cm in all figures. cm in all figures.
RootCallus formation induction and acclimation Calli were induced from leaf, hypocotyl (figure 1d) and root explants from in vitro- For complete plantlet development, regenerated shoots were rooted on plant grown seedlings. Several media were evaluated for callus induction in -1 addition to growththe one regulatorreported- freepreviously Gamborg for A. B5 sylvestris medium20 (table supplemented 1). The best with callus 10 g formation l sucrose. was Afterobtained 2 months, from roots roots with developed 75% induction (figure 1h), using and Gamborg's regenerated B5 medium plants were supplemented obtained (figure 1i). Twenty regenerated plants were transferred to small plastic pots for acclimatization in a growth room for 2 weeks before transfer to bigger pots (figure Table 1. Effects of different concentrations of auxins and cytokinins for callus induction from 1j).roots, After hypocotyls 3 months and, leavesthe regenerated explants of A. plants sylvestris were planted in the field (figure 1k) in June 2010Growth with a regulators100% survival (mg l-1 rate.) Callus induction (%) (x + SD)a Auxins Cytokinins Explants b c Flowering2,4-D andNAA seed formationBA (R1)Z Hypocotyls Roots Leaves 2.0 1.0 36.1 + 28.3 28.5 + 35.7 1.33 + 1.16 After 2-4 months in the field, 55% of the regenerated plants (11 out of 20) flowered 2.0 1.0 30.5 + 19.7 61.0 + 39.3 nad (figure 1l), formed seed pods (figure 1m) and eventually shed seeds. The 2.0 0.2 12.5 + 13.8 75.0 + 43.3 nad phenotype of the regenerated plants was similar to wild type except for the flowers, aMean and standard deviation b,cMeans in this column do not significantly differ from each other (p < 0.05) dMean and standard deviation not available
82
4 -1 -1 with 2.0 mg l NAA and 0.2 mg l Z (table 1). The best callus induction from hypocotyl v In -1 i explants was 36% using Gamborg's B5 medium supplemented with 2.0 mg l 2,4-D and tro 1.0 mg l-1 BA (table 1). Calli were formed, on average, after 2 months and 1-2 additional regeneration months were required to obtain sustained growth (figure 1e) before transferring to shoot induction media. Calli were either green, friable or compact.
Shoot formation In general, media supplemented with Z yielded better callus quality, and their growth rate was 2-5.6-fold compared to media supplemented with Kin or BA (table 2). The growth rate of calli in the shoot induction media with BA was 1.9-2.6, and the quality score was 1.3-3.2. Use of media containing Kin gave a similar growth rate between 1.7 and 2.5 but with better callus quality (1.0-3.9). However, none of these media led to shoot induction after 6 months. The quality of calli was improved using media with Z (from 3.0 up to 4.8). The best media (Z15 and Z16), yielding the fastest callus growth (4.7- and 5.6-fold) and the best callus quality (4.8 and 4.7), did not induce shoot formation within 6 months. Among the media used, only Gamborg's B5 medium supplemented with 2.0 mg l-1 Z and 1.0 mg l-1 IBA was able to induce shoot formation (figure 1f-g). The shoot induction period required up to 6 months, but the number of regenerated shoots was relatively high (> 100) once shoot induction was obtained. Shoots were regenerated from 3 independent calli from hypocotyl explants, taken from different in vitro seedlings. Although shoot-like structures were observed after 4 months, some shoots seemed stressed (purple-whitish color) and died, but some of them survived and eventually regenerated shoots. The elongation of shoots took 2 months.
Root formation and acclimation For complete plantlet development, regenerated shoots were rooted on plant growth regulator-free Gamborg's B5 medium supplemented with 10 g l-1 sucrose. After 2 months, roots developed (figure 1h), and regenerated plants were obtained (figure 1i). Twenty regenerated plants were transferred to small plastic pots for acclimatization in a growth room for 2 weeks before transferring to bigger pots (figure 1j). After 3 months, the regenerated plants were planted in the field (figure 1k) in June 2010 with a 100% survival rate.
Flowering and seed formation (R1) After 2-4 months in the field, 55% of the regenerated plants (11 out of 20) flowered (figure 1l), formed seed pods (figure 1m) and eventually shed seeds. The phenotype of the regenerated plants was similar to wild type except for the flowers, which showed a reduced apical dominance (figure 2). The regenerated plants flowered in the branches and at the basal part (figure 2c-f), whereas wild-type plants flower in the apical part (figure 2a-b). Seeds (R1) from the regenerated plants were collected, dried and placed at 1oC for germination. After a 2-3 months period of cold stratification, seeds from 4
83 4
In v In Table 2. Effects of different concentrations of auxins and cytokinins for shoot regeneration of A. sylvestris i tro
-1 a
regeneration Growth regulators (mg l ) Shoot Growth rate Quality of c b Auxins Cytokinins formation (x + SD) calli (x + SD)c 2,4-D NAA IAA IBA BA Z Kin C 2.0 1.0 - 2.92 + 1.13 3.31 + 0.69 S3 0.1 2.0 - 1.94 + 1.37 2.20 + 0.45 S5 0.1 2.0 - 1.94 + 0.50 2.67 + 1.03 S14 0.05 3.0 - 2.01 + 0.67 2.50 + 0.97 S15 0.01 0.3 - 1.59 + 0.40 1.33 + 0.58 S16 0.1 2.0 - 2.62 + 1.46 3.24 + 1.22 S12 0.1 2.0 - 2.56 + 0.81 3.84 + 0.60* S9 0.2 2.0 - 2.80 + 0.66 4.30 + 0.56* S10 0.1 2.0 - 2.33 + 0.68 3.70 + 1.08 S11 0.1 2.0 - 2.55 + 0.64 3.95 + 0.86* S17 0.1 2.0 - 2.54 + 0.80 3.88 + 1.08 S18 0.2 2.0 - 2.10 + 2.17 3.38 + 1.33 S19 0.05 3.0 - 2.40 + 1.22 3.57 + 0.79 S20 0.01 0.3 - 1.89 + 0.61 2.25 + 0.46 S22 0.1 2.0 - 1.68 + 0.55 1.00 + 0.00 S21 0.1 2.0 - 2.39 + 0.80 3.00 + 0.86 Z3 0.1 2.0 - 2.71 + 0.99 3.00 + 0.97 Z4 1.0 2.0 - 2.60 + 0.71 4.29 + 0.75* Z5 0.05 2.0 - 2.18 + 0.60 2.42 + 0.84* Z6 0.1 1.0 - 2.81 + 1.06 3.05 + 1.28 Z7 0.5 1.0 - 3.01 + 1.05 4.25 + 0.68* Z8 0.05 1.0 - 2.30 + 0.72 3.10 + 1.09 Z10 1.0 2.0 + 4.39 + 1.11* 4.55 + 0.00* Z11 0.05 2.0 - 3.03 + 0.88* 4.00 + 0.97* Z12 0.1 1.0 - 3.13 + 0.57* 4.33 + 0.59* Z13 0.5 1.0 - 3.67 + 1.82* 4.41 + 1.23* Z14 0.05 1.0 - 3.16 + 1.10* 4.25 + 0.93* Z15 1.0 2.0 - 4.72 + 1.46* 4.79 + 0.41* Z16 1.0 2.0 - 5.58 + 1.15* 4.68 + 0.48*
a Growth rate : the weight of the calli after 4 weeks divided by the initial weight. The initial weight was 2 g per petri dish. b Quality of calli : score of the greenish appearance (5: all five calli were green and proliferating, 3: average, 1: all five calli were brown/dead). cmean and standard deviation. All data were recorded monthly for at least a 6 months period (n = 30). All media were supplemented with 40 g l-1 sucrose and 8 g l-1 agar. An asterisk (*) shows a significant difference (p < 0.05) compared to control (C).
84 which showed a reduced apical dominance (figure 2). The regenerated plants flowered in the branches and at the basal part (figure 2c-f), whereas wild-type plants flower in the apical part (figure 2a-b). Seeds (R1) from the regenerated plants were collected, dried and placed at 1oC for germination. After a 2-3 months period of cold stratification, seeds from 4 regenerated plants germinated. Twenty regenerated seedlings (R1) of each regenerated plant (R0) were grown in the greenhouse. 4 In v In i tro regeneration
FigureFigure 2.2. FloweringFlowering ofof A. A. sylvestris sylvestris. a.. a.Wild Wild type type b. Wildb. Wild type type (no (no flower flower at theat the bottom bottom part). part).c-d. c-Reducedd. Reduced apical apical dominance dominance flowering flowering in the inbranches the branches of the regeneratedof the regenerated plants. e-f. plants. Flowering e-f. floweringin the bottom in the part bottom of the part regenerated of the regenerated plants. Arrows plants. show Arrows the differences. show the Barsdifferences. equal to Bars10 cm equal(a-b) andto 10 1 cm (c-f).(a-b) and 1 cm (c-f).
Deoxypodophyllotoxin content Theregenerated DPT content plants of germinated. the aerial Twentypart of theregenerated regenerated seedlings plants (R1) was of betweeneach regenerated 0.6-1.2 plant (R0) were grown in the greenhouse. µg/mg dry weight (d.w.). In the root part of the regenerated plant, the DPT content wasDeoxypodophyllotoxin 0.3-0.7 µg/mg d.w. The content DPT content of the aerial part of the wild type was 0.3- 0.5The µ g/mgDPT content d.w.; inof the the aerial root part of 1.4 the-1.5 regenerated µg/mg d.w. plants4 There was between was no 0.6-1.2 difference µg/mg dry weight (d.w.). In the root part of the regenerated plant, the DPT content was 0.3-0.7 observed on the profile of metabolites of the regenerated plants compared to the µg/mg d.w. The DPT content of the aerial part of the wild type was 0.3-0.5 µg/mg d.w.; wildin the type. root part 1.4-1.5 µg/mg d.w.4 There was no difference observed on the profile of metabolites of the regenerated plants compared to the wild type. Discussion In general, 3 phases can be distinguished in regeneration (organogenesis) in vitro. Discussion The first is dedifferentiation in which the tissue becomes competent to respond to In general, 3 phases can be distinguished in regeneration (organogenesis) in vitro. the organogenic stimulus. It is generally initiated by culturing on an auxin-rich The first is dedifferentiation in which the tissue becomes competent to respond to the callusorganogenic-inducing stimulus. medium It andis generally may involve initiated a period by culturing of callus on growth. an auxin-rich The second callus- is inductioninducing mediumin which andcells may become involve determined a period of tocallus form growth. either aThe root second or a shoot.is induction The explantsin which arecells cultured become ondetermined a shoot- inducingto form either medium a root or or root a -shoot.inducing The medium explants that are cultured on a shoot-inducing medium or root-inducing medium that contains a specific auxin/cytokinin ratio combination. The third is the realization in which the explants grow to an organ.9, 22 Initially, seeds of Anthriscus sylvestris (figure 1a) were dormant and have underdeveloped embryos. The embryos of the seeds grow to maturity during cold stratification. Germination frequency increased with the length of the cold stratification period. Approximately 30% of the non-sterilized seeds germinated after 8 weeks of cold stratification at 1oC and then warm stratification at 15oC/6oC or 20oC/10oC or 25oC/15oC.21 The germination increased to 77% with the increased duration of the cold stratification (12 weeks). Most A. sylvestris embryos completed growth during a 12-weeks period of cold stratification at 1oC.21
85 4
In v In The surface sterilization treatment with chlorine gas yielded on average 39% i
tro germination, which is approximately half the germination obtained from the non- surface sterilized seeds.21 regeneration Depending on the plant species, only a limited number of cells in an explant show the organogenic response.22 Therefore, different explants from hypocotyls, leaves and roots from 1-2 months young seedling were used for callus induction. The root explants showed the best callus induction (75%) using Gamborg's B5 medium supplemented with 0.2 mg l-1 Z and 2.0 mg l-1 NAA. However, use of seedlings to obtain root explants was not practical because 3 months were needed to obtain in vitro seedlings. Hypocotyl explants were preferred because they are renewable, and the 36% callus induction was sufficient for our purpose. The callus medium contained Gamborg's B5 salts and vitamins, supplemented with 2.0 mg l-1 2,4-D and 1.0 mg l-1 BA (table 1). Callus induction from leaf explants was low compared to hypocotyl and root explants. Callus tissue was formed on the cut sections after 2 months, but a further 1-2 months was required to obtain consistent growth of green friable or compact calli. There are differences in the organogenetic potential between plant families, genera, species and genotypes, and different genotypes of a species may show widely different responses.23 For example, Capsicum species that belong to the Solanaceae have been shown to be recalcitrant to differentiation and plant regeneration under in vitro conditions compared to Nicotiana tabacum, Lycopersicum esculentum and Solanum tuberosum, which belong to the same family.24 Although plant regeneration, somatic embyrogenesis and genetic transformation have been reported for several Apiaceae family members, tissue culture regeneration systems for different genotypes or species may not generally be applicable to all members of the same family. Among the 28 different media used, only Gamborg's B5 medium supplemented with 2.0 mg l-1 Z and 1.0 mg -1 IBA led to shoot formation after 6 months (table 2). Among 3 different cytokinins, use of Z led to a better callus quality (score 4.8) and growth rate (up to 5.6). We obtained 3 independent regenerants from different calluses from hypocotyls of different in vitro seedlings. The regenerated plants were planted in the field in the beginning of June 2010, with a 100% survival rate. In the Netherlands, the flowering season is between April and May. Interestingly, 55% of the regenerated plants flowered between August and October in their first year (figure 2). Daucus carota and A. sylvestris are biennual plants from the Apiaceae family that flower after exposure to a period of cold (vernalization), generally during the second year of growth.21, 25 Carrot roots, transformed by A. rhizogenes, converted from biennial to annual without vernalization.26, 27 A similar phenomenon was observed in endive plants (Cichorium intybus) containing Ri T-DNA.28 Natural genetic transformation by A. rhizogenes might provide genes that allow flowering in the absence of a cold treatment.26 Annualism was correlated with the segregation of a truncated transferred DNA (T-DNA) insertion. Root locus (rolC) was the primary promoter of annualism.26 Expressin of rolC in transgenic plants mainly leads to a modification of the cytokinin
86 4 29 balance and causes developmental, physiological and morphological alterations. In v In i
A. sylvestris regenerants, the observed annualism may be caused by the effects of tissue tro culture as reported for Chichorium intybus28 and long-term growth in shoot induction regeneration media containing high a cytokinin concentration. The regenerated plants in the field showed wild-type phenotypes except that they flowered on the secondary branches (figure 2c-d) and at the base of plants (figure 2e-f), as opposed to the apical flowering of the wild-type plants (figure 2a-b). This phenomenon may be caused by somaclonal variation as a result of tissue culture30 and/ or cytokinin imbalance from the long-term growth in shoot induction media. R1 seeds were germinated in February 2011 and grown in the field. Recalcitrance and somaclonal variation are the 2 main problems in plant regeneration via tissue culture. They are complex, multifactorial phenomena based on genotype, media and environmental interaction.30 Calli of A. sylvestris did not produce DPT20 and whole plants were required. Therefore, it is essential to achieve the differentiated form to restore the capability of the cell to produce DPT for metabolic engineering purposes. The DPT content of the aerial part of the regenerated plant was comparable with the root part of the wild-type plants. This is beneficial for the isolation of the bioconversion product for the metabolic engineering purpose. The ability of the regenerated plant to produce secondary metabolites, especially DPT, was not altered. In conclusion, this is the first report on the regeneration of A. sylvestris plants in vitro. This may provide a valuable tool in creating new opportunities to produce metabolically engineered A. sylvestris.31 Further optimization is needed to increase the efficiency and frequency of regeneration and to reduce the total regeneration period.
Material and Methods Plant material The fruits (ripe mericarps, hereafter called seeds) of Anthriscus sylvestris L. (Hoffm.) were collected from wild habitat in June 2007 in Groningen, the Netherlands (53o 13’ 34” N and 6o 32’ 43” E). The seeds were surface sterilized with chlorine gas for 3.5 h and subsequently cultured on 25 mL 10 g l-1 water agar (Duchefa, Haarlem, the Netherlands) in Petri dishes (94/16, Greiner Bio One, Alphen aan de Rijn, the Netherlands). To overcome dormancy, the seeds were kept in the Petri dishes at 1oC under fluorescent light illumination for for at least 3 months until the seeds germinated. The germinated seedlings were transferred to Gamborg's B5 medium32 supplemented with 8 g l-1 agar in a sterile container, OS 140 box and ODS filter (Duchefa, Haarlem, the Netherlands) and incubated in a climate room at 22oC/20oC under a 16-h light/8-h dark period (day/ night) (60 μmol m-2 s-1 fluorescent and incandescent light).
87 4
In v In Callus induction i
tro After 2 months, root, hypocotyl and leaf explants from young sterile in vitro-obtained seedlings were excised and cultured on Gamborg's B5 media supplemented with either regeneration 2.0 mg l-1 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg l-1 6-benzylaminopurine (BA)20 or 2 mg l-1 α-naphthaleneacetic acid (NAA) and 0.2 or 1.0 mg l-1 zeatin riboside (Z) (table 1). All media contained 40 g l-1 sucrose and 8 g l-1 agar (pH 5.7). The calli induced from various explants were subcultured on the same medium every 4 weeks.
Plant regeneration from callus cultures After 3 months, calli were cut into 400 mg pieces and transferred to Gamborg's B5 medium containing various concentrations of auxins such as 2,4-D, NAA, IBA (Indole- 3-butyric acid), Indole-3-acetic acid (IAA), and cytokinins such as BA, Z, kinetin (Kin) to induce shoot formation (table 2). Each treatment consisted of at least 5 Petri dishes with 5 calli in each dish. The growth rate and the quality of the calli of each treatment were recorded monthly for at least 6 months. The growth rate was defined as the ratio of the weight of the calli after 4 weeks divided by the initial weight. The quality of calli was given a score from 1 to 5 (5: all 5 calli were green and proliferating, 3: average, 1: all 5 calli were brown/dead). The score in table 2 was the average of at least 6 months data for both the growth rate and the quality of the calli.
Rooting and acclimatization Regenerated shoots measuring about 2 cm in length were transferred into rooting medium. The rooting medium contained Gamborg's B5 salts and vitamins supplemented with 10 g l-1 sucrose and no growth regulators. After 2 months, the rooted plantlets were thoroughly washed with tap water to remove the agar and transferred to sterile soil in small pots and covered with plastic to maintain high humidity. Plantlets were placed in a growth chamber with a 14-h light/10-h dark period, photosynthetic photon flux density 100 μmol m−2 s−1 at 22°C. After 2 weeks, the humidity was reduced by removing the plastic, and 20 plants were transferred to bigger pots and kept for another 2-3 months. Eventually, the plants were transferred to the field. The regeneration experiment was conducted with 3 replicates from 3 different independently obtained calli.
Plant extraction and HPLC analysis Deoxypodophyllotoxin (DPT) was a gift from Dr. M. Angeles Castro (Salamanca University, Salamanca, Spain). Acetonitrile and methanol were HPLC grade from Biosolve (Valkenswaard, the Netherlands). Dichloromethane was obtained from Fisher Scientific (Landsmeer, the Netherlands). Samples for HPLC analysis were taken from 10 randomly selected individual young regenerated plantlets, which were divided into an aerial part and a root portion. Plant material was dried at room temperature prior to grinding and extraction. The extraction method was as described by Koulman et al.20 and the HPLC analysis was as described by Hendrawati et al.4
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Statistical analysis v In i
The Student’s t-test (p < 0.05) was used to determine statistical significance compared tro to the control (SPSS software, version 16.0, 2008). regeneration
Acknowledgements
The authors would like to express their gratitude to Margriet Ferwerda for her advice concerning the plant tissue culture, J.T.M. Elzenga, Ger Telkamp, and Jacob J. Hogendorf for the climate room and the field facility. Financial support by the Ubbo Emmius fund, University of Groningen, is acknowledged.
References 1. Jeong G, Kwon O, Park B, et al. Lignans 9. Ochatt SJ, Atif RM, Patat-Ochatt EM, et and coumarins from the roots of Anthr- al. Competence versus recalcitrance for iscus sylvestris and their increase of in vitro regeneration. Notulae Bot Hort caspase-3 activity in HL-60 cells. Biol Agrobot Cluj-Napoca 2010;38:102-108. Pharm Bull 2007;30:1340-1343. 10. Steward FC, Mapes MO, Mears K. 2. Magnusson SH. NOBANIS - Invasive Growth and organized development alien species fact sheet - Anthriscus syl- of cultured cells. II. Organization in vestris – From: online database of the cultures grown from freely suspended north European and Baltic network cells. Am J Bot 1958;45:705-707. on invasive alien species. Available 11. Catlin D, Ochoa O, McCormick S, et al. from: www.nobanis.org. 2006 (accessed Celery transformation by Agrobacterium 06.09.2011). tumefaciens - cytological and genetic 3. Hulten E, Fries M. Atlas of north analysis of transgenic plants. Plant Cell European vascular plants north of the Rep 1988;7:100-103. tropic of cancer.Koeltz Scientific Books, 12. Jäger A, Schottländer B, Smitt U, et al. Konigstein. Germany, 1986. Somatic embryogenesis in cell cultures of Thapsia garganica. Plant Cell Rep 4. Hendrawati O, Woerdenbag J, Hille J, et 1993;12:517-520. al. Seasonal variations in the deoxypodo- phyllotoxin content and yield of Anthris- 13. Salem KMSA, Charlwood BV. Accumu- cus sylvestris L. (Hoffm.) grown in the lation of essential oils by Agrobacterium field and under controlled conditions. J tumefaciens-transformed shoot cultures Agri Food Chem 2011;59:8132-8139. of Pimpinella anisum. Plant Cell Tiss Org Cult 1995;40:209-215. 5. Nayar MP, Sastry APK. Botanical Survey 14. Purohit M, Pande D, Datta A, et al. of India. Calcutta, 1990. Enhanced xanthotoxin content in re- 6. Vasilev NP, Julsing MK, Koulman A, et generating cultures of Ammi majus al. Bioconversion of deoxypodophyllo- and micropropagation. Planta Med toxin into epipodophyllotoxin in E. coli 1995;61:481,482. using human cytochrome P450 3A4. J 15. Krens FA, Keizer LCP, Capel IEM. Trans- Biotech 2006;126:383-393. genic caraway, Carum carvi L.: a model 7. Birch RG. Plant transformation: species for metabolic engineering. Plant problems and strategies for practical ap- Cell Rep 1997;17:39-43. plication. Annu Rev Plant Physiol Plant 16. Wang Y, Kumar PP. Heterologous expres- Mol Biol 1997;48:297-326. sion of Arabidopsis ERS1causes delayed 8. Gómez-Galera S, Pelacho A, Gené senescence in coriander. Plant Cell Rep A, et al. The genetic manipulation of 2004;22:678-683. medicinal and aromatic plants. Plant Cell 17. Irvani N, Solouki M, Omidi M, et al. Rep 2007;26:1689-1715. Callus induction and plant regeneration
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In v In in Dorem ammoniacum D., an endan- 26. Limami MA, Sun LY, Douat C, et al. gered medicinal plant. Plant Cell Tiss Natural genetic transformation by Agro- i tro Org Cult 2010;100:293-299. bacterium rhizogenes. Annual flowering in two biennials, Belgian endive and regeneration 18. Flick CE, Evans DA, Sharp WR. Or- ganogenesis. In: Evans DA, Sharp, WR, carrot. Plant Physiol 1998;118:543-550. Ammirato PV, Yamada Y, ed. Handbook 27. Tepfer D. Transformation of several of plant cell culture. Volume 1. New York: species of higher plants by Agrobacteri- Macmillan Publishing Co., 1983:13-81. um rhizogenes: sexual transmission of the 19. Brown DCW, Finstad KI, Watson EM. transformed genotype and phenotype. Somatic embryogenesis in herbaceous Cell 1984;37:959-967. dicots. In: Thorpe TA, ed. In vitro em- 28. Sun LY, Touraud G, Charbonnier C, et bryogenesis in plants. Volume 20. al. Modification of phenotype in Belgian Dordrecht: Kluwer Academic Publishers, endive (Cichorium intybus) through The Netherlands 1995:345-416. genetic transformation by Agrobac- 20. Koulman A, Kubbinga ME, Batterman S, terium rhizogenes: conversion from et al. A phytochemical study of lignans in biennial to annual flowering. Transgen whole plants and cell suspension cultures Res 1991;1:14-22. of Anthriscus sylvestris. Planta Med 29. Estruch JJ, Chriqui D, Grossmann K, 2003;69:733,738. et al. The plant oncogene rolC is re- 21. Baskin CC, Milberg P, Andersson L, et sponsible for the release of cytokinins al. Deep complex morphophysiological from glucoside conjugates. EMBO J dormancy in seeds of Anthriscus sylves- 1991;10:2889-95. tris (Apiaceae). Flora 2000;195:245-251. 30. Cassells A, Curry R. Oxidative stress and 22. De Klerk G, Arnholdt-Schmitt B, physiological, epigenetic and genetic Lieberei R, et al. Regeneration of roots, variability in plant tissue culture: impli- shoots and embryos:physiological, bio- cations for micropropagators and genetic chemical and molecular aspects. Biol engineers. Plant Cell Tiss Org Cult Planta 1997;39:53-66. 2001;64:145-157. 23. George EF. Plant propagation by tissue 31. Hendrawati O, Woerdenbag HJ, Hille J, culture: part 2 - in practice. Basingstoke: et al. Metabolic engineering strategies Exegetics, England,1996. for the optimization of medicinal and 24. Ochoa-Alejo N, Ramirez-Malagon R. In aromatic plants: realities and expecta- vitro chili pepper biotechnology. In Vitro tions. J Med Spice Plants 2010;15:111- Cell Dev Biol - Plant 2001;37:701-729. 126. 25. Punja ZK, Jayaraj J, Wally O. Carrot. In: 32. Gamborg OL, Miller RA, Ojima K. Pua E, Davey MR, ed. Transgenic crops Nutrient requirements of suspension IV. Volume 59: Springer Berlin Heidel- cultures of soybean root cells. Exp Cell berg, 2007:277-294. Res 1968;50:151-158.
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Chapter
Agrobacterium mediated transformation of Anthriscus sylvestris with human cytochrome P450 3A4 followed by regeneration
Oktavia Hendrawati Jacques Hille Herman J. Woerdenbag 5 Heribert Warzecha Frank J. Dekker Wim J. Quax Oliver Kayser
(Manuscript in preparation) 5
Agrob Abstract
Metabolic engineering offers interesting perspectives to improve the productivity of the a
cter plant as a cell factory. The recently demonstrated conversion of deoxypodophyllotoxin a
i into epipodophyllotoxin upon expression of human P450 3A4 in E. coli DH5 , has um um prompted us to investigate the activity of P450 3A4 in planta. Because of the endogenous trans production of deoxypodophyllotoxin in A. sylvestris, transformation of this plant may result in the production of (epi)podophyllotoxin. A. sylvestris callus tissue was f or successfully transformed with Agrobacterium tumefaciens carrying the human P450 m
ation 3A4 gene and the cells were subsequently regenerated. The presence of the P450 3A4 gene in the regenerated transgenic A. sylvestris was confirmed by PCR. The transgenic plants were shown to form epipodophyllotoxin in low amounts whereas the wild type (control) plants do not. This opens the route for a novel plant source for the semi- synthesis of the important anticancer drugs etoposide and teniposide.
Keywords: Anthriscus sylvestris, epipodophyllotoxin, podophyllotoxin, deoxypodophyllotoxin, organogenesis, transformation, regeneration, human P450 3A4, CYP3A4
Oktavia Hendrawati1, Jacques Hille2, Herman J. Woerdenbag3, Heribert Warzecha4, Frank J. Dekker5, Wim J. Quax,1, Oliver Kayser1,6
1Department of Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 2 Department of Molecular Biology of Plants, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands; 3Department of Pharmaceutical Technology and Biopharmacy, University of Groningen Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands; 4Department of Plant Biotechnology and Metabolic Engineering, Technische Universitaet Darmstadt, Schnittspahnstrasse 3-5, 64287 Darmstadt, Germany; 5Department of Pharmaceutical Gene Modulation, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands; 6Technical University Dortmund, Technical Biochemistry, Emil-Figge-Strasse 66, 44227 Dortmund, Germany
(Manuscript in preparation)
94 5
Introduction Agrob
Plants are a rich source of bioactive compounds. Compounds of plant origin can be a used as drugs or as precursors of semisynthetic drugs, and may provide valuable leads cter
for novel drug design. The amounts of secondary metabolites in plants are often low and i um um the availability can often be a major bottleneck in furnishing the pharmaceutical needs. Chemists have in specific instances succeeded to synthesize typical plant compounds trans via organic synthesis, but often this is hampered by the high chemical complexity, f specific stereochemistry and the economic feasibility. Metabolic engineering of plants or m
offers interesting perspectives to improve the productivity of the plant as a cell factory. ation This approach may create new opportunities in agriculture, environmental applications, production of chemicals, and medicines.1, 2 Podophyllotoxin (PPT), obtained from Podophyllum species, is used for the semisynthesis of the anticancer drugs etoposide and teniposide. PPT and its derivatives are now intensively investigated for their use in anticancer therapy especially in combination treatment.3 Up to now, three different ways are known for the production of podophyllotoxin: direct isolation from Podophyllum species, via plant cell cultures, and by organic synthesis. Using organic synthesis or plant cell cultures is economically unfeasible. To date, PPT is only obtained by isolation from Podophyllum species. In the future, the availability of PPT from this source is likely to become a major bottleneck, as Podophyllum species have been listed on the endangered species list.4 An alternative and more sustainable source of PPT may be obtained by (biotechnological) hydroxylation of deoxypodophyllotoxin (DPT) at the C7 position (figure 1) yielding epipodophyllotoxin (epi-PPT), the diastereoisomer of PPT. This conversion has been achieved already on laboratory scale in E. coli DH5a transfected with the human cytochrome P450 3A4.5 Both epi-PPT and PPT can be used as a semisynthetic precursor for etoposide and teniposide. In many plants, DPT serves as the precursor of PPT.6, 7 DPT is the main constituent of Anthriscus sylvestris (L.) Hoffm. (Apiaceae). A. sylvestris accumulates up to 1.5 mg/ mg dried weight (d.w.) of DPT in the root part8 and trace amounts of PPT (<0.01 mg/mg d.w) in the aerial part.9 As a wild plant and generally occurring weed native to northwest Europe, the availability of A. sylvestris is hardly limited, in contrast to Podophyllum species. The human P450 3A4 gene has been used to create different recombinant systems such as in the yeasts Schizosaccharomyces pombe10 and Saccharomyces cerevisiae,11 in the bacterium E. coli,5, 12 and in the insect cells Sf21 Spodoptera frugiferda.13 The transformation of human P450 3A4 has been achieved in plant cells, but so far only in Nicotiana tabacum.14, 15 For functional activity of the 3A4 P450 enzyme a P450 reductase has to be expressed from endogenous or exogenously added DNA. The main objective of this study was to transform the human P450 3A4 gene in A. sylvestris plants and to determine the capacity of this system to in vivo transform deoxypodophyllotoxin into epipodophyllotoxin (see figure 1).
95 5 Agrob a cter i um um trans f or m ation
Figure 1. Scheme of Anthriscus sylvestris transformed with human P450 3A4. The expression of P450 3A4 is expected to result in the hydroxylation of deoxypodophyllotoxin (DPT) into epipodophyllotoxin (epi-PPT) based on the observed activity of E. coli produced 3A4 P450. The formation of its diastereoisomer, podophyllotoxin (PPT), is not expected to be catalysed by 3A4.
Results Feeding of DPT to CYP3A4 expressing N. tabacum cells N. tabacum cells were transformed with the human full length CYP3A4 cDNA as described15 and the results of the feeding of DPT to transformed and to wild type cells are presented in table 1. The transformed cells (CYP3A4) as well as the wild type (control) cells were able to hydroxylate DPT into epi-PPT, the diastereoisomer of PPT.
Table 1. DPT and Epi-PPT concentrations, means are given + SD (n=3), (mg/mg d.w. in cells and mg/ml in media) in tobacco plant cell suspension cultures of wild type (WT) and CYP3A4 (3A4) at different time points after feeding with DPT.
means + SD* Day 4 Day 7 WT DPT cells (mg/mg d.w.) 0.102 + 0.030 0.103* + 0.026 3A4-DPT in cells (mg/mg d.w.) 0.077 + 0.002 0.035*+ 0.006 WT DPT media (mg/ml) 1.316 + 0.178 1.302 + 0.138 3A4-DPT in media (mg/ml) 0.721 + 0.124 0.598 + 0.144 WT epi-PPT cells (mg/mg d.w.) 0.029 + 0.008 0.035 + 0.034 3A4-Epi-PPT in cells (mg/mg d.w.) 0.038 + 0.020 0.102 + 0.017 WT epi-PPT media (mg/ml) 1.062 + 0.109 2.940* + 0.455 3A4-Epi-PPT in media (mg/ml) 1.843 + 0.244 4.748* + 0.270
An asterisk (*) indicates a significant difference between wild type and 3A4 (p<0.05)
96 5
N. tabacum does not contain the DPT. Therefore the epi-PPT formation was due to the Agrob addition of DPT. On day 7, the conversion of DPT into epi-PPT in the medium was
significantly higher in transformed cells as compared to wild type cells. a cter In general, the concentration of epi-PPT was higher in the media than in the cells for i both wild type and transgenic cells. Although the wild type was able to form epi-PPT, um
the conversion was 3 times lower than in the transformed cells and 1.5 fold lower in the trans media of the transformed cells on day 7 compared to the media of the wild type cells.
In the transformed cells, the highest epi-PPT production was seen on day 7, in the cells f or
(0.1 µg/mg d.w.) and in the media (4.8 µg/ml). The high concentration of the product m in the medium as compared to the intracellular concentration suggests that there is an ation efficient secretion mechanism for the epi-PPT formed. within 3 months while wild type would die. The non-transformed calli eventually died and the transformedPlant transformation calli grew well and (figure regeneration 2d). About ofa hundredA. sylvestris transformed We initiated callus cells from young sterile in vitro seedlings (figure 2a-b). The calli calli clumps were subcultured to shoot-inducing medium (figure 2e) for up to 1 year were obtained by aseptically excising the hypocotyls of in vitro seedlings (figure 2c). and the regeneratedThe calli shoots were (figuretransformed 2f) were byA. subcultured tumefaciens in harboringthe root-inducing the binary media plasmid pGreen029- (figure 2g) for3A4 3 months. (figure Eventually3). YFP was the fused transformed to the P450 plants 3A4 were as an transferred additional into selection marker for the greenhousevisualization (figure 2h) besides and grownthe kanamycin under controlled resistant gene. conditions. After 8the After co-cultivation two for 2 days, independent theAgrobacterium calli were - subculturedmediated transformations on shoot-inducing on medium callus cells, containing five kanamycin for transformant selection and carbenicillin for elimination of overgrowth Agrobacterium. kanamycin-resistant plantlets from two independent transformations were The transformed calli will survive on antibiotics selection. Every 4 weeks, the calli were analyzed.
Figure 2. Anthriscus syl- vestris transformation and regeneration. (a) Seeds of A. sylvestris. (b) Young sterile in vitro seedling. (c) Callus induction by aseptically excised hypocotyls of the young sterile in vitro seedlings. (d) Transformed callus selection on kanamycin and carbenicillin callus medium. (e) Shoot formation of trans- formed calli grown in shoot- inducing medium. (f) Elon- gation of shoot formation. (g) Root formation in shoot- inducing medium. (h) Young transformed plantlets grown in the green house. Bars equal to 1 cm (a-d, f, g), 0.5 cm (e) and 10 cm (h).
Figure 2. Anthriscus sylvestris transformation and regeneration. (a) Seeds of A. sylvestris. 97 (b) Young sterile in vitro seedling. (c) Callus induction by aseptically excised hypocotyls of the young sterile in vitro seedlings. (d) Transformed callus selection on kanamycin and carbenicillin callus medium. (e) Shoot formation of transformed calli grown in shoot-inducing medium. (f) Elongation of shoot formation. (g) Root formation in shoot-inducing medium. (h) Young transformed plantlets grown in the green house. Bars equal to 1 cm (a-d, f, g), 0.5 cm (e) and 10 cm (h). 5
Agrob subcultured to fresh medium. The selection on kanamycin required 3 months and the elimination of Agrobacterium required up to 6 months. Kanamycin 100 mg/L was
a sufficient to kill the non-transformed cells within 3 months while wild type would die. cter The non-transformed calli eventually died and the transformed calli grew well (figure 2d). i um um About a hundred transformed calli clumps were subcultured to shoot-inducing medium
trans (figure 2e) for up to 1 year and the regenerated shoots (figure 2f) were subcultured in the root-inducing media (figure 2g) for 3 months. Eventually the transformed plants were 8 f transferred into the greenhouse (figure 2h) and grown under controlled conditions. or
m After two independent Agrobacterium-mediated transformations on callus cells, five ation kanamycin-resistant plantlets from two independent transformations were analyzed.
Figure 3. Schematic map of plasmid construct used for Anthriscus sylvestris transformation; LB: left border, D 35 S: double CaMV 35S promoter, YFP: yellow fluorescence protein fused with human P450 3A4 gene, NOS: nos polyadenylation signal (black), NOS: nos promoter (orange),Figure nptII: 3. Schematic kanamycin map resistance of plasmid gene.construct used for Anthriscus sylvestris transformation; LB: left border, D 35 S: double CaMV 35S promoter, YFP: yellow fluorescence protein fused with human P450 3A4 gene, NOS: nos polyadenylation signal (black), NOS: nos promoter (orange), nptII: kanamycin resistance gene.
Figure 4. (a) PCR-amplified human P450 3A4 gene of 561 bp. (b) PCR-amplified kanamycin gene of 687 bp. (c) PCR-amplified YFP gene of 739 bp from two wild type plants (WT) and five Figure 4. (a) PCR-amplified human P450 3A4 gene of 561 bp. (b) PCR-amplified transformed plants (Lane 1 – 5). M= molecular weight marker. kanamycin gene of 687 bp. (c) PCR-amplified YFP gene of 739 bp from two wild type plants (WT) and five transformed plants (Lane 1 – 5). M= molecular weight marker.
We tested that the transformed plants were free from Agrobacterium by growing
the calli and the transformed plants in LB medium at 28oC for 3 days. No grow of We Agrobacterium tested that the was transformed observed. The plants presence were of the free P450 from 3A4, Agrobacterium YFP and kanamycin by growgene ing the incalli the and transformed the transformed plants was confirmedplants in LBby PCRmedium (figure at 4).28o CThe for gene 3 fragmentdays. No could grow be of amplified from the aerial part of the transformedAnthriscus , whereas no band appeared Agrobacteriumfrom the wild was type observed. aerial part The of Anthriscus presence (negative of the P450 control), 3A4, confirming YFP and kanamycinthat the genetransformed in the transformed plants could be plants considered was as confirmed transgenic byplants. PCR The (figure YFP expression 4). The of gene transformed plants was low and the differences compared to the wild type were not fragment could be amplified from the aerial part of the transformed Anthriscus, clear (not shown). whereas no band appeared from the wild type aerial part of Anthriscus (negative control), confirming that the transformed plants could be considered as transgenic plants. The YFP expression of transformed plants was low and the differences 98 compared to the wild type were not clear (not shown).
Epi-PPT content in the transformed plants DPT, PPT or epi-PPT contents in the transformed and wild type plants are summarized in table 2. Figure 5 shows a typical HPLC chromatogram of A. 5
Epi-PPT content in the transformed plants Agrob DPT, PPT or epi-PPT contents in the transformed and wild type plants are summarized in table 2. Figure 5 shows a typical HPLC chromatogram of A. sylvestris extracts. The a cter enhanced formation of epi-PPT in transgenic A. sylvestris is clearly seen at a retention i time of 7.65 min. The transformed plants were able to form epi-PPT and PPT. Wild um 9
type Anthriscus contained trace amounts of PPT in concert with earlier reports but no trans epi-PPT was formed. The PPT content in the transformed plants was slightly higher
than in the wild type (areal part). No epi-PPT could be detected in the wild Anthriscus f sylvestris extracts. The enhanced formation of epi-PPT in transgenic A. sylvestris is or plant (figure 5). No obvious changes could so far be observed in the phenotype of the m in vitroclearly transformed seen at a regenerated retention time plants. of 7.65 min. The transformed plants were able to ation form epi-PPT and PPT. Wild type Anthriscus contained trace amounts of PPT in concert with earlier reports9 but no epi-PPT was formed. The PPT content in the Table transformed2. DPT, PPT, plants epi-PPT was contentsslightly higher in regenerated than in the wild wild type,type (arealregenerated part). Notransformed epi-PPT and wild type plants. could be detected in the wild Anthriscus plant (figure 5). No obvious changes could so far be observed in the phenotypeRange of concentration the in vitro transformed (mg/mg d.w.)regenerated plants. Transformed plant Wild type (control) plant Table 2. DPT, PPT,Aerial epi-PPT contents in Root regenerated wild type,Aerial regenerated transformedRoot and wild type plants. DPT 0.105 – 0.230 Range* concentration (µg/mg0.3 –d.w.) 0.5 1.4 – 1.5 TransformedD plant Wild type (control)D plant D PPT 0.006 – 0.133Aerial Root* 0.006Aerial – 0.011 <0.01Root – 0.019 DPT 0.105 – 0.230D * 0.3 – 0.5 1.4 – 1.5 Epi-PPTPPT 0.00060.006 – 0.036 – 0.133∆ ** 0.006 – -0.011∆ <0.01 – 0.019- ∆ Epi-PPT 0.0006 – 0.036∆ * - - *not determined*not determined Dthe concentration∆the concentration was was calculated calculated fromfrom highly highly concentrated concentrated extracts extracts
FigureFigure 5. HPLC 5. HPLC chromatograms chromatograms of of transgenic transgenic and and wild wild type type Anthriscus Anthriscus. Epi.- PPT Epi-PPT (epipodophyllotoxin), PPT (podophyllotoxin), DPT (deoxypodophyllotoxin). (epipodophyllotoxin), PPT (podophyllotoxin), DPT (deoxypodophyllotoxin).
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Agrob Discussion
The production of bioactive compounds through in vitro transformed callus or cell a
cter cultures has been carried out in several plant species, especially in medicinal plants.16
i The expression of human P450 genes in transgenic plants may lead to the formation of um um new secondary compounds.12 trans It has been reported that P450 3A4 can be expressed in plant cells (N. tabacum) in an active form.15 Feeding experiments with loratadine to N. tabacum suspension culture f or cells expressing P450 3A4 led to the formation of desloratadine, an active metabolite m
ation of loratadine that is also used as a drug compound. Another feeding experiment with indole in N. tabacum suspension culture cells expressing human cytochrome P450 2A6 and 3A4 led to the production of indican, a metabolite that is usually exclusively present in indigoferous dye plants,14 but not in N. tabacum. Based on the examples mentioned, it is illustrated that the human cytochrome P450 3A4 in N. tabacum may transform exogenously provided DPT into epi-PPT. In our studies, we showed that N. tabacum cell suspension cultures expressing the human P450 3A4 were able to hydroxylate DPT to epi-PPT with the highest concentration of epi-PPT in the cells and medium on day 7. Also the epi-PPT formation in medium was significantly higher on day 7 in transformed cells compared to wild type cells. Possibly, epi-PPT was excreted into the medium because it is toxic for the cells. Interestingly, the wild type tobacco cell suspension cultures were also capable of converting DPT into epi-PPT, although at a much lower level. We used the Agrobacterium transformation technique to introduce the human P450 3A4 gene in the callus cells of A. sylvestris. Since callus of A. sylvestris lost the capacity of producing DPT because they are in undifferentiated form,9 it is crucial to induce differentiation in order to restore the capability of the cell to produce DPT. We have developed a regeneration protocol of A. sylvestris17 that indeed after regeneration does restore the ability of the cells to produce DPT. There was no obvious somaclonal variation with respect to DPT production. The transformed Anthriscus plants were able to form clearly detectable amounts of epi-PPT and small amounts of PPT as well (figure 5). Wild type Anthriscus has been reported to contain trace amounts of PPT (<0.01 mg/mg d.w.).9 We found PPT (0.006- 0.011 mg/mg d.w.) in wild type Anthriscus which is in line with this previous finding. The PPT content in the transformed plants was slightly higher than in wild type, however, the involvement of P450 3A4 in this conversion is unlikely. It was reported that DPT can be converted into PPT in Linum album cell cultures,18 but the enzyme responsible for the hydroxylation has never been identified. The transformation efficiency of A. sylvestris was low (about 1%) compared to N. tabacum (about 30%). Five transgenic plants from two independent transformations were obtained. The shoot regeneration of A. sylvestris required up to a year in the transformed cells instead of 6 months in the wild type plant.17 This might due to carbenicillin which is extensively used for eliminating Agrobacterium. Carbenicillin has a broad spectrum of activity against bacteria and only low toxicity to eukaryotes.19
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Inhibition of callus growth and shoot regeneration has been observed in several Agrob plants such as Daucus carota,20 Malus domestica,21 Populus species,22 and Lycopersicon 23 esculentum. Carbenicilin was removed from the medium once there was no a cter Agrobacterium growth observed. Rooting took about 3 months which is similar to i the wild type plant. Kanamycin showed no inhibition either in the transformed calli um
growth or the shoot and root formation. trans We are the first to show the heterologous expression of the human cytochrome
P450 3A4 in A. sylvestris. The construct under the control of a 35S promoter should f or
provide constitutive expression in all parts of A. sylvestris plant. Fusion of a cytochrome m P450 and a fluorescence protein has been reported in mammalian cells24 and plants.25 ation However, the YFP expression was low in our transformed plants (data not shown). This may explain why the amounts of epi-PPT formed in transformed plants are limited. Reverse transcriptase PCR will be carried out to confirm the transcription of the P450, YFP and kanamycin gene in the transformed plants and further work to screen high expression level of P450 3A4 is still in progress. In addition, the progeny will be screened on kanamycin and the segregation analysis will be done. For more effective biotransformation and high level of epi-PPT and / or PPT production, it is necessary to optimize the constructs used such as the promoter, the P450 3A4 gene, and the targeting signal peptide to the compartment where the DPT is produced. To the best of our knowledge, there is no report regarding where in the cell the DPT is produced. Recent papers suggest that the shikimate pathway occurs in the plastids because the shikimate enzymes are generally synthesized as precursors containing a plastid transit peptide that directs them to the plastids.26, 27 Thus, DPT may be synthesized in the plastids. The 3A4 expression construct used in the Anthriscus study was devoid of any targeting signal as the original human signal sequenced was not copied in the PCR fragment. It should be noted that the construct used for expression in N. tabacum did contain an additional endoplasmic reticulum targeting signal.
Material and Methods Chemicals Epipodophyllotoxin (epi-PPT) was a gift from Dr. M. Angeles Castro (Salamanca University, Salamanca, Spain). The identity and purity of the compound was checked using HPLC. Acetonitrile and methanol were HPLC grade from Biosolve (Valkenswaard, the Netherlands). Dichloromethane was from Fisher Scientific (Landsmeer, the Netherlands). Formic acid, ammonium formate, podophyllotoxin, deuterated CDCl3 (99.96 %) were from Sigma Aldrich (Zwijndrecht, the Netherlands). DPT was synthesized chemically from PPT as described below. PPT (98% purity by HPLC) was obtained from Sino Future Pharmaceutical Company (Xi’an, China).
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Agrob Synthesis of deoxypodophyllotoxin from podophyllotoxin Glacial acetic acid (100 mL) was added to PPT (5.0 g, 12 mmol) and Pd/C 10% (0.25 g,
a 2.4 mmol). The resulting suspension was reacted under hydrogen (H ) atmosphere (3.0
cter 2 bar) at 50oC for 16 h in a Parr apparatus. The suspension was diluted with ethyl acetate i um um (200 mL) and filtered over Celite. The solvents were evaporated under reduced pressure
trans and the residue was purified using column chromatography using ethyl acetate: hexane (1:1, v/v). The pure product was obtained as white powder in quantitative yield (85 %). 1 28, 29 13 f H-NMR spectra are in agreement with the reported literature. C NMR spectra or 29 + m are in agreement with the reported literature. MS ESI-MS m/z [M+H] C22H23O7 calc
ation + + 399.4, found 399.2, [M+NH4] C22H26O7N calc 416.4, found 416.1. [M+Na] C22H22O7Na calc 422.4, found 422.1.
Plant material and callus induction Fruits (ripe mericarps, hereafter called seeds) of Anthriscus sylvestris L. (Hoffm.) were collected from wild habitat in June 2007 in Groningen, the Netherlands (53o 13’ 34” N and 6o 32’ 43” E). Voucher specimen of the plants used have been deposited in our department, encoded Asylv2007-4. In vitro plants were grown and the calli were initiated as described recently.17
Plasmid construction The cDNA encoding human P450 3A4 was a gift from F.P. Guengerich (Vanderbilt University School of Medicine, Nashville, USA). The plasmid construct used for Anthriscus transformation is shown in figure 3. Human cDNA devoid of the endoplasmic reticulum retention signal was amplified by PCR to create an overlapping sequence with YFP (pMON999, Monsanto, Missouri, USA), using a set of primers, a forward primer 5’-GCTTAGGAGGTCCATGGCTCTGTTATTAGCAGTTTTTCT-3’ and a reverse primer 5’ CCTTGCTCACCATTCAGGCTCCACTTACGGTGCCATCCCTTGACT-3’. YFP gene was amplified by PCR to introduce an overlapping sequence with cDNA and an XmaI restriction site at the 3’-end, using a set of primers, a forward primer 5’-GGATGGCACCGTAAGTGGAGCCT- GAATGGTGAGCAAGGGCGAGGAGC-3’ and a reverse primer 5’-GGCCGCCGGGCGATCTAGTAACATAGATG-3’. The second round of PCR was performed to create cDNA::YFP::NOS with a set of primers, a forward primer 5’-GCTTAGGAGGTCCATGGCTCTGTTATTAGCAGTTTTTCT-3’, and a reverse primer 5’-GGCCGCCGGGCGATCTAGTAACATAGATG-3’. All PCR was performed using phusion polymerase (Biolabs, Leiden, the Netherlands) and confirmed by sequencing. Thus, P450 3A4 and YFP were fused in frame. We cloned this sequence to plasmid pJIT145, which contained a double 35S promoter (a gift from Mark Smedley, John Innes Centre, UK). The plasmid was cut with KpnI and XmaI and cloned to pGreen029.30 The binary pGreen029 contains thenptII gene for kanamycin selection of transformed plant cells. The resulting plasmid (pGreen029-3A4) was cloned and transformed into Escherichia coli DH5a and mobilized into Agrobacterium tumefaciens EHA 105 (a gift from P.J.J. Hooykaas, Leiden University) using the electroporation method (pulse cells at 1.8 KV in 1 cm cuvette, 600 W and 10 mF capacitance).
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Callus transformation and regeneration Agrob Agrobacterium strain EHA 105 harboring the pGreen029-3A4 was grown overnight in -1 -1 LB medium supplemented with rifampicin (50 mg l ) and kanamycin (100 mg l ) in a cter a rotary shaker (225 rpm, 28oC). The Agrobacterium culture was centrifuged at 3000 i g for 5 min and the pellet resuspended in Gamborg's B5 medium supplemented with um ‑1
40 g l sucrose. Transformation was achieved by infecting A. sylvestris callus cells with trans Agrobacterium. Calli were dried on sterile filter paper, transferred to callus medium o and incubated for 2 days at 24 C. Incubated calli were subcultured to callus medium f or -1 -1 supplemented with kanamycin (100 mg l ) and carbenicillin (250 mg l ). Shoots were m regenerated on shoot-inducing medium as described,17 supplemented with kanamycin ation (100 mg l-1) and carbenicillin (250 mg l-1). Kanamycin was added to callus, shoot and root-inducing media. Carbenicillin was used until no Agrobacterium growth was observed (up to 6 months). Regenerated shoots measuring about 2 cm in length were transferred into root-inducing medium.17 The rooted plantlets were thoroughly washed with tap water to remove the agar and transferred to sterile soil in small pots and covered with plastic to maintain high humidity. They were placed in a climate chamber with 14-h light/10-h dark regimen, photosynthetic photon flux density 100 μmol m−2 s−1 at 22°C. After 2 weeks, the humidity was reduced to the climate room level by removing the plastic cover and 5 plants were transferred to bigger pots and kept in the green house. The efficiency of the transformation was about 1%.
Nucleic acid isolation and detection Plasmid isolation was performed using Nucleospin Plasmid Isolation kit (Macherey- Nagel). Total plant DNA was isolated using a DNA purification kit (NucleoSpin® Plant II, Macherey-Nagel). The presence of P450 3A4 in transformed plants was confirmed by PCR using a primer pair, a forward primer 5’-AACAGCCTGTGCTGGCTATC-3’ and a reverse primer 5’-GTGTATCTTCGAGGCGACTT-3’ giving a product of 561 bp of an internal fragment of the P450 3A4 cDNA. The primer pair for YFP gene is 5’-GGAATTCCATATGGTGAGCAAGGGCGAGGAGCT-3 and 5’-CGGGATCCTTACTTG- TACAGCTCGTCCATGC-3’ giving a product of 739 bp. The primer pair for kanamycin gene is 5’-GGAGCGGCGATACCGTAAAG-3’ and 5’-CGGCTATGACTGGGCACAAC-3’ giving a product of 687 bp. Plant genomic DNA was used as a template. The PCR condition was as follows: initial denaturation at 98oC for 5 min followed by 35 cycle of amplification at 98oC for 30 sec, annealing at 65oC for 30 sec, and extension at 72oC for 30 sec. The final extension step was at 72oC for 10 min.
Feeding experiments with Nicotiana tabacum suspension cultures Nicotiana tabacum cv. Petit Havana suspension cultures were cultivated in a volume of 120 mL in 300 mL Erlenmeyer flasks, and subcultured on a weekly basis by transferring 60 mL of old culture to 60 mL of fresh LS medium.14 The P450 3A4 cDNA was cloned into the binary plasmid pPSI and cell suspension cultures of N. tabacum cv. Petit Havana were transformed as described.14 The cells transformed with human cytochrome P450 3A4 (CYP3A4) as well as the wild type (control) cells were used for the feeding
103 5 15 Agrob experiment. One day after subculture, one set of flasks of CYP3A4 and wild type were supplemented with 2.0 mg DPT in 100 µl DMSO and further cultivated until 7 days.
a A set of three flasks was used for each feeding experiment. The cells and the supernatant cter (media) were harvested on day 4, and 7 for analysis. Cells were separated with a nylon i um um mesh in a Büchner-funnel and frozen in liquid nitrogen. Both media and cells were
trans freeze-dried prior to extraction.
f Extraction, HPLC, LC-MS-MS and NMR analysis or
m The extraction method of the plant material and the media was as described by Koulman ation et al.9 Shortly, 100 mg dried cells were weighed in a sovirel tube and all the supernatant were used for extraction. A 2.0 ml portion of 80% methanol was added and the mixture was sonicated during 1 hour. Subsequently 4.0 ml of dichloromethane and 4.0 ml
H2O were added. The mixture was vortexed and centrifuged at 1,000 g for 5 minutes. The aqueous layer was discarded and 2.0 ml of organic layer were transferred into a 2 mL Eppendorf tube. The organic layer was left in the fume hood until dried. The residue was redissolved in 2.0 ml methanol and filtered over a 0.45 mm HPLC syringe filter (nylon). The samples were submitted to HPLC analysis. DPT, PPT and epi-PPT were analyzed by HPLC, LC-MS/MS and NMR analysis as described.31
YFP visualization Calli of the transformed and wild type plants (control) were used to check the YFP expression. Visualization of the YFP expression was performed by using a Zeiss Axioskop fluorescence microscope (Zeiss Netherlands B.V. Weesp, The Netherlands).
Statistical treatment of data All data presented in this study are the mean + SD, of at least three independent experiments. Comparative statistical analyses of groups were performed using the student’s t-test. All statistical tests were considered significant at p values < 0.05.
Acknowledgement
The authors would like to express their gratitude to Margriet Ferwerda for her advice concerning the plant tissue culture, Paul D. Dijkwel and Marcel J.G. Sturre for their advice concerning the construct, J.T.M. Elzenga, Ger Telkamp, and Jacob J. Hogendorf for the climate room and the field facilities. Financial support by the Ubbo Emmius fund, University of Groningen, is acknowledged.
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Summary Samenvatting Ringkasan Acknowledgement &
&
Summary S u mm
In recent years, strategies and techniques for the production of natural compounds ary (plant derived fine chemicals) and / or the breeding of medicinal and aromatic plants have expanded. The aspiration for efficient production of high value natural products with medicinal purpose (e.g. paclitaxel, artemisinin, and vincristine) has triggered novel approaches. Metabolic engineering and pathway optimization with the aim to reduce costs and increase productivity have become a main focus of academia and industry. Until now, only a limited number of plant cell cultures and isolated enzymes have yielded sufficiently high productivity to allow commercial exploitation. Engineering of microorganisms has proven to be a valuable tool and the concept of metabolic engineering has been transferred to plant science opening promising perspectives. Although pathway engineering has been used for crop plants, but the application of this technique to medicinal plants has not yet been explored well. An overview of the current production of plant-derived and medicinally relevant compounds with their metabolic engineering strategies is presented in chapter 1. In addition, common strategies and techniques in medicinal plant biotechnology and challenges in plants metabolic engineering with several relevant case studies are also discussed in chapter 1. In this thesis, we focus on the lignan (epi)podophyllotoxin. We aimed to engineer Anthriscus sylvestris (Apiaceae), which contains deoxypodophyllotoxin (DPT) as its main lignin constituent, to produce (epi)podophyllotoxin. A. sylvestris is a wild plant to northern Europe and in other temperate regions of the world. To get a clear picture of the deoxypodophyllotoxin content over the developmental stages of the plant, we studied the variations of deoxypodophyllotoxin during different developmental stages (chapter 2). Two sets of experiments were carried out with sixteen collected plants and seeds, originating from a wide geographical range in Europe. Firstly, we compared the DPT content in various organs of the natively grown plants with that of the same plants now grown under identical conditions in the field. Secondly, we compared the DPT content between controlled climate room and field grown plants during one life cycle. The DPT concentration in both aerial and root parts dropped when the plants were cultivated in their non-native environment. The DPT contents of the climate room and the field plants were comparable, but the biomass and flowering time differed considerably. Environmental factors appear to be an important determinant for the DPT production in A. sylvestris. For field grown plants the highest DPT content was found in March (2nd year) for both root and aerial part (0.15 % w/w dried weight (d.w.) roots; 0.03 % w/w d.w. aerial material). For plants grown in the climate room the highest concentration was observed in April (2nd year) in the root and in July (1st year) in the aerial part (0.14 % w/w d.w. roots; 0.05 % w/w d.w. aerial material). The root part is suggested to be used for the optimal isolation of DPT and the best time to harvest is in April (2nd year) for both indoor and outdoor plants when the plants reach the optimal DPT production and an adequate biomass. A better insight into the occurrence of DPT combined with profound knowledge of its biosynthestic pathway(s) may help to develop alternative sources for podophyllotoxin
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u (chapter 3). Using HPLC combined with electrospray tandem mass spectrometry and mm NMR spectroscopy techniques, we identified 14 lignans and related structures in roots ary of A. sylvestris. Podophyllotoxone, deoxypodophyllotoxin, yatein, anhydropodorhizol, 1-(3’-Methoxy-4’,5’-methylenedioxyphenyl)1-ξ-methoxy-2-propene, and 2-butenoic acid, 2-methyl-4-[[(2Z)-2-methyl-1-oxo-2-buten-1-yl]oxy]-, (2E)-3-(7-methoxy-1, 3-benzodioxol-5-yl)-2-propen-1-yl ester, (2Z)- were the major compounds. α-Peltatin, podophyllotoxin, β-peltatin, isopicropodophyllone, β-peltatin-a-methylether, (Z)-2-angeloyloxymethyl-2-butenoic acid, anthriscinol methylether, and anthriscrusin were present in lower concentrations. α-Peltatin, β-peltatin, isopicropodophyllone, podophyllotoxone, and β-peltatin-a-methylether have not been previously reported to be present in A. sylvestris. Based on our findings we propose a hypothetical biosynthetic pathway of aryltetralin lignans in A. sylvestris (figure 3 in chapter 3). A. sylvestris allows an interesting approach for genetic modification to directly produce (epi)podophyllotoxin in the plant, because of the high content of DPT and its close biosynthetic relationship with podophyllotoxin. Human cytochrome P450 3A4 in E.coli DH5α selectively hydroxylates DPT at the C7 position yielding epipodophyllotoxin, the diastereoisomer of podophyllotoxin. Human cytochrome P450 3A4 was transferred in A. sylvestris via Agrobacterium tumefaciens. For transformation purposes, a regeneration protocol of A. sylvestris was established first (chapter 4). Plants were regenerated from callus material. Calli were induced from hypocotyl explants in Gamborg's B5 medium supplemented with 40 g l-1 sucrose, 2 mg l-1 2,4-dichlorophenoxyacetic acid and 1 mg l-1 6-benzylaminopurin. Subsequently, calli were transferred to shoot induction medium, Gamborg's B5 containing 40 g l-1 sucrose, 2 mg l-1 zeatin riboside and 1.0 mg l-1 indole-3-butyric acid. Regenerated shoots were obtained within 6 months and transferred into root induction medium, Gamborg's B5 supplemented with 10 g l-1 sucrose for 2 months. Regenerated plants were acclimatized in soil and grown in the greenhouse. Eventually they were transferred to the field with 100% survival. Regenerated plants flowered and shed fertile seeds. This protocol facilitates regeneration of genetically transformed plant cells with Agrobacterium. Feeding DPT to Nicotiana tabacum cell suspension cultures carrying the human P450 3A4 gene led to the bioconversion of DPT to epipodophyllotoxin (chapter 5). The A. sylvestris callus tissue was transformed with Agrobacterium tumefaciens carrying the human P450 3A4 gene and the cells were regenerated. The transformed regenerated plants now were able to form epipodophyllotoxin in low amounts. These results emphasize a future prospect of engineering A. sylvestris for (epi) podophyllotoxin production. Further optimization of the plasmid construction such as the promoter, P450 3A4 gene, and targeting signal peptide are needed to increase the level of expression of human P450 3A4 gene which should lead to a higher level of (epi)podophyllotoxin production. This engineering strategy may be applied to other plants producing DPT.
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Samenvatting S a m De afgelopen jaren is het arsenaal aan methoden en strategieën dat beschikbaar is voor en v de productie van plantenstoffen en voor het kweken van medicinale en aromatische atting planten uitgebreid. De wereldwijde ambitie om natuurstoffen voor medische toepassing op efficiënte wijze te produceren (bijvoorbeeld paclitaxel, artemisinine en vincristine) heeft de ontwikkeling van nieuwe technieken gestimuleerd. ‘Metabolic engineering’ en ‘pathway optimization’, met als doel kostenbesparing en productiviteitsverhoging te bewerkstelligen, zijn belangrijke benaderingen die worden toegepast door universiteiten en industrieën. Tot nu toe is met slechts een beperkt aantal plantencelcultures en geïsoleerde enzymsystemen een productieproces ontwikkeld dat rendabel genoeg is voor commerciële toepassing. ‘Engineering’ van micro-organismen is een waardevolle aanpak gebleken en wordt nu ook toegepast in planten, hetgeen de nodige perspectieven biedt. ‘Pathway engineering’ is tot nu toe vooral gebruikt voor planten die als voedingsmiddel dienen; de toepassing ervan voor medicinale planten is nog niet goed onderzocht. In hoofdstuk 1 geven wij een overzicht van de huidige productiemogelijkheden van (medisch relevante) plantenstoffen met behulp van ‘metabolic engineering’. Verder bespreken we in dit hoofdstuk meer algemene benaderingswijzen en technieken in de plantenbiotechnologie, en uitdagingen die het terrein van de ‘metabolic engineering’ biedt. Ter illustratie beschrijven we een aantal case-studies uit de literatuur. In dit proefschrift richten we ons op het lignaan (epi)podofyllotoxine. We hebben geprobeerd om de plant Anthriscus sylvestris (fluitenkruid), behorend tot de familie van de schermbloemigen (Apiaceae), te onderwerpen aan ‘engineering’-technieken, met als doel het belangrijkste lignaan in de plant, deoxypodofyllotoxine (DPT), om te laten zetten in het chemisch nauw verwante (epi)podofyllotoxine. A. sylvestris komt in het wild voor in Noord-Europa en in andere gematigde gebieden over de hele wereld. Om een helder beeld te krijgen van de variatie aan deoxypodofyllotoxine gedurende de groei van de plant, hebben we het gehalte ervan gemeten in verschillende ontwikkelingsstadia (hoofdstuk 2). Twee sets aan experimenten zijn uitgevoerd met zestien verschillende planten en zaden, afkomstig uit een breed verspreidingsgebied binnen Europa. Eerst vergeleken we het DPT-gehalte in verschillende organen van planten die geoogst waren op de plaats waar ze van nature voorkomen met dat van dezelfde planten die waren gekweekt onder gelijke condities in het veld. Daarna vergeleken we het DPT-gehalte in planten die onder gecontroleerde omstandigheden in kassen waren opgegroeid met dat van planten in het veld, gedurende een hele levenscyclus (twee jaar). Het DPT-gehalte nam af in zowel bovengrondse delen als in wortels van planten die waren gekweekt in een andere omgeving dan waar ze van nature groeiden. De DPT-gehaltes in de planten uit de kassen en die van het veld waren vergelijkbaar, maar de hoeveelheid gevormde biomassa en de bloeitijd verschilden aanzienlijk. Omgevingsfactoren bleken bepalend voor de DPT-productie in A. sylvestris. Voor planten die waren opgegroeid op het veld vonden we het hoogste DPT-gehalte in maart van het tweede jaar, zowel in
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a de wortels als in de bovengrondse delen (0,15% w/w op basis van drooggewicht (dw) m
en in de wortels en 0,03% w/w dw in bovengrondse delen). In kasplanten vonden we
v het hoogste DPT-gehalte in april van het tweede jaar in de wortels (0,14% w/w dw) en atting in juli van het eerste jaar in de bovengrondse delen (0,05 % w/w dw). De beste tijd om wortelmateriaal te oogsten voor de isolatie van DPT is in april van het tweede jaar van de levenscyclus van d e plant. Productie en biomassa zijn dan optimaal. Goed inzicht in het voorkomen van DPT in combinatie met kennis van de biosyntheseroute(s) voor deze verbinding kan nuttig zijn om alternatieve bronnen voor podofyllotoxine te vinden (hoofdstuk 3). Door gebruik te maken van HPLC in combinatie met electrospray tandem massaspectrometrie en NMR-spectroscopie, konden we 14 lignanen en gerelateerde verbindingen in de wortels van A. sylvestris identificeren. Podofyllotoxon, deoxypodofyllotoxine, yateine, anhydropodorhizol, 1-(3’-methoxy-4’,5’-methyleendioxyfenyl)1-ξ-methoxy-2-propeen, en 2-buteenzuur, 2-methyl-4-[[(2Z)-2-methyl-1-oxo-2-buteen-1-yl]oxy]-,(2E)-3-(7-methoxy-1, 3-benzodioxol-5-yl)-2-propeen-1-yl ester, (2Z)- waren hoofdcomponenten. α-Peltatine, podofyllotoxine, β-peltatine, isopicropodofyllon, β-peltatine-a-methylether, (Z)-2-angeloyloxymethyl-2-buteenzuur, anthriscinolmethylether, en anthriscrusine waren in geringere hoeveelheden aanwezig. Het voorkomen van α-peltatine, β-peltatine, isopicropodofyllon, podofyllotoxon, en β-peltatine-a-methylether in A. sylvestris was niet eerder gerapporteerd. Gebaseerd op deze resultaten presenteren we een hypothetische biosyntheseroute voor aryltetralinelignanen in A. sylvestris (figuur 3 in hoofdstuk 3). A. sylvestris is een interessante kandidaat voor genetische modificatie, om te komen tot een directe productie van (epi)podofyllotoxine in de plant, vanwege het hoge gehalte aan DPT en de sterke overeenkomst met podofyllotoxine in biosynthese en chemische structuur. Humaan cytochroom P450 3A4 in E.coli DH5α kan DPT op de C7-positie selectief hydroxyleren, waardoor epipodofyllotoxine, de diastereoisomeer van podofyllotoxine, ontstaat. Humaan cytochroom P450 3A4 is ingebracht in A. sylvestris met behulp van Agrobacterium tumefaciens. Voor transformatiedoeleinden hebben we een regeneratieprotocol voor A. sylvestris opgezet (hoofdstuk 4). Planten werden geregenereerd uit callusmateriaal. Callus werd geïnduceerd uit hypocotyl-explantaten in Gamborg's B5 medium met 40 g l-1 sucrose, 2 mg l-1 2,4-dichloorfenoxyazijnzuur en 1 mg l-1 6-benzylaminopurine. Vervolgens werden de calli overgebracht in een scheut-inducerend medium, Gamborg's B5 met 40 g l-1 sucrose, 2 mg l-1 zeatineriboside en 1 mg l-1 indool-3-boterzuur. Na zes maanden kregen we geregenereerde scheuten die werden overgebracht in een medium dat wortelvorming induceert, Gamborg's B5 met 10 g l-1 sucrose voor een periode van twee maanden. Gevormde regeneranten werden geacclimatiseerd in potgrond en groeiden verder in een kas. Uiteindelijk werden zij overgebracht naar het veld. Er was 100% overleving. Geregenereerde planten bloeiden en vormden vruchtbaar zaad. Dit protocol wordt gebruikt voor de regeneratie van met Agrobacterium genetisch getransformeerde plantencellen. Het toevoegen (‘feeding’) van DPT aan celsuspensiecultures van Nicotiana tabacum waarin het humane P450 3A4 gen was ingebouwd, resulteerde in de bioconversie
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van DPT in epipodofyllotoxine (hoofdstuk 5). Callusweefsel van A. sylvestris a m
werd getransformeerd met Agrobacterium tumefaciens voorzien van het humane en
P450 3A4 gen en de cellen werden geregenereerd. De getransformeerde regeneranten v atting bleken in staat om kleine hoeveelheden epipodofyllotoxine te maken. Deze resultaten tonen aan dat het in de toekomst mogelijk kan zijn om via ‘engineering’ van A. sylvestris (epi)podofyllotoxine te produceren. Om deze benadering succesvol te maken, moet het plasmideconstruct verder worden geoptimaliseerd, via de promoter, het P450 3A4 gen, en een signaalpeptide. Dit is nodig om een hoger expressieniveau van het gen te krijgen, hetgeen zou moeten leiden tot een hogere productie van (epi) podofyllotoxine. Deze strategie van ‘engineering’, ten slotte, kan ook worden toegepast bij andere planten die DPT maken.
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R Ringkasan ingkasan Beberapa tahun terakhir ini, strategi dan teknik untuk produksi senyawa alami (bahan kimia yang berasal dari tanaman) dan / atau pengembangbiakan tanaman medisinal dan tanaman penghasil senyawa aromatik berkembang sangat pesat. Strategi baru untuk memproduksi secara efisien senyawa alami yang digunakan untuk obat (misalnya paclitaxel, artemisinin, dan vincristine) telah melahirkan banyak pendekatan baru. Fokus utama riset di bidang akademia dan industri adalah untuk menurunkan biaya produksi dan meningkatkan produktivitas. Sampai saat ini, jumlah kultur sel tanaman dan enzim dengan produktivitas yang tinggi yang bisa dikomersialkan jumlahnya masih sangat terbatas. Rekayasa mikroorganisme telah terbukti menjadi sarana yang penting, lebih lanjut lagi penerapan konsep metabolic engineering di tanaman telah mampu membuka peluang baru yang menjanjikan. Metode engineering pathway banyak digunakan untuk pembiakan tanaman pangan, namun penerapan teknik tersebut untuk tanaman obat masih belum optimal. Pembahasan mengenai produksi terkini dari senyawa obat yang berasal dari tanaman dengan teknik metabolic engineering dibahas di bab 1. Selain itu, beberapa strategi dan teknik umum bioteknologi tanaman medisinal dan permasalahannya dilengkapi dengan beberapa contoh kasus studi juga didiskusikan lebih lanjut di bab 1. Fokus tesis ini adalah senyawa lignan (epi)podopyllotoxin. Tujuan penelitian ini adalah untuk merekayasa tanaman Anthriscus sylvestris yang secara alami mengandung senyawa utama deoxypodophyllotoxin (DPT) agar dapat digunakan untuk memproduksi senyawa (epi)podophyllotoxin. A. sylvestris (Apiaceae) merupakan tanaman liar di Eropa utara dan beberapa tempat beriklim sedang di dunia. Untuk mendapatkan gambaran tentang kandungan DPT, dilakukan perbandingan tentang variasi kandungan DPT di berbagai tahap perkembangan tanaman di lahan (bab 2). Penelitian ini dibagi dalam dua tahap eksperimen dengan 16 origin tanaman dan biji dari berbagai daerah di Eropa. Pertama, kandungan DPT tanaman yang tumbuh di lingkungan alaminya (native) dibandingkan dengan tanaman dengan daerah asal yang sama yang dikultivasi di lahan (non-native). Kedua, kandungan DPT antara tanaman yang dikultivasi di ruangan dengan iklim terkontrol dibandingkan dengan tanaman yang dikultivasi di lahan selama satu siklus. Hasil eksperimen menunjukkan bahwa kandungan DPT pada bagian aerial dan pada akar tanaman native menurun bila tanaman dikultivasi di lingkungan yang non-native, sedangkan kandungan DPT tanaman di ruangan dengan iklim terkontrol dan di lahan sebanding, namun terdapat perbedaan pada biomasa dan waktu mulai berbunga. Dapat disimpulkan bahwa faktor lingkungan tampaknya menjadi faktor penting untuk produksi senyawa DPT di A. sylvestris. Untuk tanaman di lahan, kandungan DPT tertinggi untuk bagian akar dan aerial adalah pada bulan Maret di tahun kedua (0,15% w/w dibagian akar; 0,03 % w/w di bagian aerial). Tanaman yang di ruangan dengan iklim terkontrol, kandungan DPT tertinggi diperoleh pada tahun kedua di bulan April untuk bagian akar (0,14% w/w) dan di tahun pertama bulan Juli untuk bagian aerial (0,05% w/w). Untuk mengoptimalkan isolasi DPT, disarankan untuk mengambil bagian akar. Waktu terbaik untuk panen
116 & adalah pada saat tanaman mencapai produksi DPT secara optimal dan menghasilkan R ingkasan biomasa yang cukup yaitu di tahun kedua pada bulan April baik untuk tanaman di ruangan dengan iklim terkontrol maupun tanaman di lahan. Pemahaman mengenai terbentuknya DPT dikombinasikan dengan pemahaman mengenai jalur biosintesis yang dijabarkan pada bab 3 dapat digunakan untuk mengembangkan strategi baru dalam memproduksi senyawa (epi)podophyllotoxin secara efisien. Sebanyak 14 senyawa lignans dan senyawa lainnya telah berhasil diisolasi dari bagian akar A. sylvestris dan diidentifikasi menggunakan HPLC yang dikombinasikan dengan ESI-MS (Electrospray Ionization – Mass Spectrometry) dan NMR (Nuclear Magnetic Resonance). Podophyllotoxone, deoxypodophyllotoxin, yatein, anhydropodorhizol, 1-(3’-methoxy-4’,5’-methylenedioxyphenyl)1-ξ-methoxy- 2-propene dan 2-butenoic acid, 2-methyl-4-[[(2Z)-2-methyl-1-oxo-2-buten-1-yl] oxy]-, (2E)-3-(7-methoxy-1,3-benzodioxol-5-yl)-2-propen-1-yl ester, (2Z)- adalah merupakan senyawa utama. Sedangkan, α-Peltatin, podophyllotoxin, β-peltatin, isopicropodophyllone, β-peltatin-a-methylether, (Z)-2-angeloyloxymethyl-2-butenoic acid, anthriscinol methylether and anthriscrusin merupakan senyawa minor. Senyawa α-Peltatin, β-peltatin, isopicropodophyllone, podophyllotoxone, dan β-peltatin-a- methylether pada A. sylvestris belum pernah dilaporkan sebelumnya. Berdasarkan penemuan ini, kami mengusulkan hipotesis jalur biosintetik lignan aryltetralin di A. sylvestris (gambar 3 bab 3). A. sylvestris diduga dapat dimodifikasi secara genetik untuk memproduksi langsung senyawa epi(podophyllotoxin) di tanaman karena kandungan DPT yang tinggi dan kedekatan jalur biosintetis dengan podophyllotoxin. Gen P450 3A4 yang diisolasi dari hati manusia dapat menghidroksilasi DPT pada posisi C-7 menghasilkan epipodophyllotoin (diastereoisomer dari podophyllotoxin) di bakteri E. coli DH5α. Gen P450 3A4 dapat ditransfer ke dalam A. sylvestris melalui Agrobacterium. Protokol regenerasi tanaman A. sylvetris untuk proses transformasi ini perlu dikembangkan terlebih dahulu (bab 4). Tanaman diregenerasi dari kalus sel. Kalus sel diinduksi dari eksplan hipokotil di media Gamborg's B5 ditambah dengan 40 g/l sukrosa, 2 mg/l 2,4-dichlorophenoxyacetic acid dan 1 mg/l 6-benzylaminopurin. Kemudian, kalus sel dipindahkan ke media induksi untuk kultur pucuk (tunas), media Gamborg's B5 ditambah dengan 40 g/l sukrosa, 2 mg/l zeatin riboside dan 1,0 mg/l indole-3-butyric acid. Kultur pucuk diperoleh dalam waktu enam bulan dan kemudian ditransfer ke media induksi akar selama dua bulan, yaitu media Gamborg's B5 ditambah dengan 10 g/l sukrosa. Tanaman baru yang terbentuk dikultivasi di rumah kaca dan kemudian diaklimatisasi di lahan. Setelah beberapa bulan, tanaman baru dipindahkan ke lahan dengan tingkat kesuksesan 100%. Tanaman hasil kultur jaringan berbunga dan menghasilkan biji yang subur. Protokol regenerasi tanaman ini akan memfasilitasi regenerasi sel tanaman yang telah ditransformasi dengan Agrobacterium. DPT yang ditambahkan (feeding) ke kultur sel suspensi Nicotiana tabacum yang telah ditransformasi dengan gen P450 3A4 dari hati manusia menghasilkan biokonversi dari DPT menjadi epipodophyllotoxin (bab 5). Jaringan kalus A. sylvestris ditransformasi dengan Agrobacterium tumefaciens yang mengandung gen P450
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R 3A4 dan kemudian jaringan kalus tersebut diregenerasikan menjadi tanaman utuh ingkasan yang mengandung gen P450 3A4. Tanaman hasil transformasi dan regenerasi dapat menghasilkan epipodophyllotoxin dengan konsentrasi yang rendah. Hasil penemuan ini membuka prospek baru untuk memproduksi senyawa epipodophyllotoxin melalui rekayasa genetika tanaman A. sylvetris. Konstruksi plasmid, seperti promoter, gen P450 3A4 dan penggunaan target signal peptida perlu dioptimasi lebih lanjut agar dapat meningkatkan produksi senyawa (epi)podophyllotoxin. Strategi rekayasa genetika ini dapat juga diaplikasikan untuk jenis tanaman lain yang juga memproduksi DPT.
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Acknowledgments A cknowle
Finally this is it. Despites all challenges and struggling, I have finally completed my studies. d First of all, I would like to acknowledge Prof. dr. Wim J. Quax who welcomed me to his ge m department. I thank you very much for your continued support throughout my studies, ents your critical views on my manuscripts and to let me join the IAPB 2010 conference. This conference was very significant to my subject and it was the highlight of my PhD studies. I would also like to thank Prof. dr. Oliver Kayser for this PhD project. My deep gratitude goes to Prof. dr. Jacques Hille for his supervision, guidance, and patience in assisting me in the field of plant tissue cultures and the transformation work. I also thank you for your critical views on my manuscripts. I did enjoy the coffee breaks and our chat in the coffee room. I am grateful to Dr. Herman J. Woerdenbag for being my co-promotor because of his help organizing the paper works, the public defense ceremony, and translating the summary in Dutch language. You were always thorough with your feedback on my manuscripts. I do appreciate your structured writing, level of detail and critical views on my manuscripts. I would also like to express my thanks to Prof. dr. J.T.M. Elzenga for his support and hospitality in plant physiology department and also for being one of the reading committee members. My special thanks go to the other members of the reading committee, Prof. dr. Robert Verpoorte and Prof. dr. E.M.J. Verpoorte for their time and remarks on my thesis. I am grateful for Janita Zwinderman and Yvonne Vergnes, for their kind assistance on the administrative works during my PhD. I thank Dr. Paul. J. Dijkwel, Marcel J. G. Sturre and Margriet Ferwerda for their intellectual and technical supports in the beginning of my research in the Department of Molecular Biology of Plant. Paul, I thank you for your help and supervision in the beginning of my research at MBP. Marcel, I thank you for your help that was available any time and your advice concerning plant works. Margriet, I thank you for your help and patience for ‘making my finger green.’ My special thanks go to the entire lab fellows at the MBP, Reza, Jos, Tsanko, Aukje, Bert, Ijaz, Sujeeth, Kamran, Eelco and Jan, I enjoyed a lot the free lab trips, baby visits, BBQ at Jacques’ house, cakes for any occasion and the ultimate Christmas dinner. I would also like to thank Jacob, Ger, and Martin for their help in providing the green house and climate room stuffs. I thank people who collected the Anthriscus plants and sent it to me: Frank Klingenstein, Christina Birnbaum, Dalila Martins, Sigurdur H. Magnusson, Rene J.T. Cappers, Renata Alnsatter, Sigvardur Eirnarsson, and Bjarni E. Gudleifsson. Without your help, there would not be chapter 2. My special thanks go to Dalila for collecting the plants and the seeds. I also thank you for our friendship. To my students, Lisette and Behnaz, I thank you for doing some of the extraction works. My deep thanks go to Dr. Wouter Hinrichs for all the help with the freeze-drying when our machine was broken.
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A I thank our collaborators, Prof. dr. Heribert Warzecha for the plasmids and the cknowle Nicotiana works, Paul J.A. Michiels and Herald G. Aantjes for the NMR works, and Dr. Frank. J. Dekker for the DPT synthesis.
d I am grateful to Jan W. Zwart, Hein Drost, Kees and Katja who helped me for ge the field experiment in De Kruidhof botanical garden in Buitenpost. Hein, hartelijk m
ents bedankt voor je advies en je hulp bij het groein van de planten. Ik begrijp je wel, maar Ik moet ‘heel veel’ denken als ik met je wil praten in het Nederlands. Het is goed om mijn nederlands te verbeteren. I am thankful to Annie van Dam for her patience and her help on measuring my always ‘urgent samples.’ I thank all my colleagues in the Department of Pharmaceutical biology. Many people have come and gone, nevertheless, it was nice to meet you all. I always enjoyed ‘the cake moment.’ I thank the plant group people, Anna-Margareta, Remco, Torsten, Agata, Magda, Elena, Gany, Insanu, Nizar, Eko and the other groups as well, Gerrit, Robbert, Mariana, Anja, Carlos, Mark, Edzard, Jandre, Marianne, Vinod, Hans, Yufeng, Bert-Jan, Ellen, Gudrun, Ilse, Pol, Luis, Harshwardhan, Mehran, Jan Ytzen, Mariette, Aart, Dan, Ingrid, Anna, and Evelina. Special thanks go to Mariana Wahjudi for your support, tips and tricks in cloning and for our friendship. The highlight of the activities for me was the ski trip to Austria in 2009. Many thanks go to Gudrun who organized it. I am grateful to all the technicians: Sieb, Rita, Ronald & Pieter. Rita, I thank you for your help during my accident and moving Anthriscus plants to Buitenpost. Ronald, I thank you for your support and help in ordering the chemicals. I am very grateful to Christina Avanti and Melanie Foeh for being my paranymphs. I would like also to thank Melanie’s family, Peter and Michael for your friendship and support. My HOST mates, Adri & Kelly, Byeong Ui & Su Jung, Anieljah, Roeland, Gineke, Ben, Corien, Ingrid, Rio, John, Willy, Anieljah, Sarah, Giulia, Jie Lin, Hong You, Nancy, Christian, Geert, Aga, Marije, Michelle, Trix, Martijn, Dirk-Jan, Elisabeth, Magda, Eline, Linda, Erik, Johnson, Lydia, Paulina, Olubunmi, Ivana, Paulina, Louise, Danica, Amy and many others, my deepest thanks go to you for your support, friendships, colorful, and enjoyable moments that we have shared together. I would like to thank Elissa & Nico, Petur & Maartje, Ajay & Kanika, for the BBQ, cooking, baking and eating activities together. Maartje, Kanika & Elissa, girls I did enjoy our shopping trips, as I was always the one who ended up with countless shopping bags. I also enjoyed watching movies together with you. My special gratitude goes to Hester Nijhoff, who designed the cover thesis. My fellow PhD friends, Dr. Johana Nayoan, you are the first who got the degree. I thank you for your help in editing the Indonesian summary. My special thanks go to Tita Alissa Listyowardojo who made me register to the gym and now I’m kind of addicted to it and have become healthier, also for your valuable inputs on my CV and for all the talks. Special thanks go to Yunia Sribudiani for friendship, companionship, and for being a nice travel buddy, to Laura & Agnes for the sharing and friendships.
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My special thanks go to my fitness buddies, Maria, Alijca, Wictor, Ridwan, Justina, A cknowle Saras, Tita, Klara, Sita, Shinta, Lorenza, Agata for joining the classes and sometimes for having dinner together. Maria, I enjoyed talking to you and joining the body step
or body jam classes together. Alijca & Wictor, I did enjoy the sailing very much, thanks d a lot. Justina, I thank you for the meal invitations. To Ridwan, I thank you for the gym ge m exercise together and sometimes dinner afterwards. Mbak Saras, Klara, Sita, Tita and ents Shinta, I thank you all for the gym companionship. My sincere thanks go to the Indonesian community in Groningen (Shanti, Mira, Neng, Ari, Mas Yayok, Mbak Lia, teh Nisa, Kang Nandang, Adit, Pipit, Wangsa and many others) and the patrimonium group (Stephanie, Wisnu, Yuli, Tita, Dani, Meta, Laura, Daniel, Astrid, Bang Mangarai, Jerome, Kenzie, Agnes, Rosalina W., Mbak Roga, Mbak Ika, Mbak Erna and others). Special thanks go to Rosalina Wisastra (Ocha) who also helped me editing the Indonesian summary. My very special thanks go to my parents, sister and brothers for all their supports and love. Finally, my appreciation goes to all people who cannot be mentioned one by one for their contribution to my research projects and my personal life in Groningen. Thank you for everything and God bless you all.
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“I believe in the sun, even when it is not shining. I believe in love, even when I don’t feel it. I believe in God, even when there is silence.” *
* Graffiti found in 1945 on the wall of a basement in Koln, Germany, where a Jewish believer is thought too have been hiding from the gestapo.