Genetic and Molecular Basis of Petal Pigmentation in Floriculture Crops: a Review

Available online at www.ijpab.com Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 DOI: http://dx.doi.org/10.18782/2320-7051.5192 ISSN: 2320 – 7051 Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) Review Article

Genetic and Molecular Basis of Petal Pigmentation in Floriculture Crops: A Review

Sunita Dhakar1* and Anjali Soni2 1Division of Floriculture and Landscaping, ICAR- IARI, New Delhi 110012, India 2Division of Fruits and Horticultural Technology, ICAR-IARI, New Delhi 110012, India *Corresponding Author E-mail: [email protected] Received: 11.07.2017 | Revised: 19.08.2017 | Accepted: 26.08.2017

ABSTRACT Flower colours are of paramount importance in the ecology of plants and their ability to attract pollinators and seed dispersing organisms. The primary pigments occurring in plants are chlorophylls and carotenoids accumulated in plastids, anthocyanins and betalains, which are dissolved in vacuolar sap. Flavonoids and carotenoids are widely distributed in plant pigments. Among the factors influencing flower colour, anthocyanin biosynthesis has been the most extensively studied. Each plant species usually accumulates limited kinds of anthocyanins and exhibits limited flower colour. For example, roses and carnations lack violet/blue colour because they do not accumulate delphinidin-based anthocyanins and petunia and cymbidium lack brick red/orange colour due to the lack of pelargonidin-based anthocyanins. Different approaches are used for development of novel flower colour in floricultural crops like hybridization, mutation and genetic engineering. Advances in molecular biology and plant transformation technology have made possible the engineering of an anthocyanin biosynthetic pathway by the overexpression of heterologous flavonoid biosynthetic genes or the down-regulation of endogenous genes in transgenic plants. Transgenic carnations and a transgenic rose that accumulate delphinidin as a result of expressing a flavonoid 3’, 5’-hydroxylase gene and have

novel blue hued flowers have been commercialized.

Key words: Carotenoids, Flavonoids, Flower colour, Hybridization, Mutation, Genetic engineering

INTRODUCTION promotion of wind pollination13. Flower and There are many beautiful flowers in nature and fruit colour are important in the attraction of they show a variety of shapes and colours. pollinators and organisms for seed dispersal Such diversity is acquired through and thus for critical factors in plant survival evolutionary processes to ensure successful organisms26. reproduction by attracting pollinators or by

Cite this article: Dhakar, S. and Anjali Soni, A., Genetic and Molecular Basis of Petal Pigmentation in Floriculture Crops: A Review, Int. J. Pure App. Biosci. 6(1): 442-451 (2018). doi:

http://dx.doi.org/10.18782/2320-7051.5192

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 From a horticultural point of view, flower red, orange and yellow colour on flower when colour is one of the most important targets for they are present. These lipid-soluble pigments plant breeders and many different coloured found embedded in the membranes of cultivars have been bred using natural mutants chloroplasts and chromoplasts. In addition, a or genetically related species. Ornamentals third class of pigment is betalains, it contribute were among the first plants to be hybridized to red and yellow colour. Betalains can be found alter specific colour traits, and fruit and flower only in certain plants from 10 families of the colour have contributed to make clear order Caryophyllales (including beetroot and fundamental genetic principles. Today, the several important genera such as Amaranthus, market for ornamental plants and cut flowers Celosia, Gomphrena, Iresine, etc.) and in is rapidly expanding and totals over $70 some higher fungi such as fly agaric (Amanita billion in annual sales. Although increasing muscaria)6. postharvest life, altering scent, and modifying Major plant pigments flower shape are areas where progress is being Primary function of pigments in flowers is to actively pursued, much of the novelty in the attract insects and other animals which help in cut flower industry continues to be targeted cross pollination. The different roles of colour toward the generation of new colours. other than attraction of pollinators are function Generally speaking, flower colour is in photosynthesis, protecting tissue against predominantly determined by two classes of photo oxidative damage, provide resistant to pigments: flavonoids and carotenoids. biotic and abiotic stress and symbiotic plant- Flavonoids and their coloured class microbe interaction. It acts as intermediary for anthocyanins are the most common flower other compounds and also shows antibacterial, pigments contributing to a wide range of antifungal, antitumor and anti-inflammatory colours are yellow, orange, red, magenta, properties. Chlorophylls and Carotenoids are violet, purple, blue. Carotenoids are synthesizing in the Plastid of the cell while ubiquitously distributed in plant as essential Anthocyanins and Betalins are synthesize in components of photosynthesis and confer a vacuole of plant cell.

Table 1: Major plant pigments and their occurrence Pigment Compound Types Compound Examples Typical Colours Chlorophylls Chlorophyll Chlorophyll a and b Green Carotenoids Carotenes Lycopene, α-carotene, Yellow, β-carotene, γ-carotene etc. Orange, Red Xanthophylls Lutein,, Zeaxanthin, Neoxanthin, Yellow, Orange, Violaxanthin etc. Anthocyanins Cyanidin, Delphinidin, Malvidin, Red, Orange, Pelargonidin, Peonidin, Petunidin Blue, violet Flavonoids Flavones Flavonol Luteolin, Apigenin, Tangeritin Yellow Flavanone Quercetin, Kaempferol, Myricetin Yellow Flavanonol Hesperetin, Naringenin, Eriodictyol Colour less , Homoeriodictyol co- pigments Flavone Taxifolin , Dihydrokaempferol Colour less co- pigments Betalains Betacyanins Red - Violet Betaxanthins Yellow -Orange

Each plant species usually accumulates limited floricultural breeders have always sought kinds of anthocyanins and exhibits limited novel flower colours26. For example, roses, flower color by the expression of a specific set carnations and chrysanthemum, which are the of biosynthetic genes, the substrate specificity most important floricultural crops, do not of key enzymes and/or the temporal and accumulate delphinidin-based anthocyanins. spatial regulation of the biosynthetic genes. Thus, they lack violet/blue varieties. This is Therefore, it is rare for a single species to have attributed to their deficiency of flavonoid 3‟, the entire spectrum of flower color, although 5‟-hydroxylase (F3‟5‟H), a key enzyme in the Copyright © Jan.-Feb., 2018; IJPAB 443

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 synthesis of delphinidin. On the other hand, primarily based upon six common petunia and cymbidium lack brick red/orange anthocyanidins; pelargonidin, cyanidin, varieties due to the lack of pelargonidin-based peonidin, delphinidin, petunidin and malvidin. anthocyanins because their dihydroflavonol 4- In terms of biosynthesis, since peonidin is reductases (DFRs) do not utilize derived from cyaniding and petunidin and dihydrokaempferol as a substrate. Some malvidin are both derived from delphinidin, species that usually accumulate delphinidin- there are only three major anthocyanidins; based anthocyanins and do not accumulate pelargonidin, cyanidin and delphinidin pelargonidin-based anthocyanins in their (Figure- 1). Flavonoid biosynthesis has been petals, such as iris and gentian, are likely to well characterized in the flowers of petunia have DFRs with a similar substrate specificity and snapdragon, and in the kernels of maize, to that of petunia DFR. Rose DFR can utilize and is therefore one of the most well studied dihydromyricetin as a substrate on the basis of pathways among plant secondary feeding of dihydromyricetin to rose petals. So metabolisms20,16,29. Blue flowers tend to have for the breeding for colour various approaches delphinidin and intense red flowers tend to have been followed. have pelargonidin as the anthocyanidin base. Flavonoids An increase in the number of hydroxyl groups Flavonoids are the most common pigment in on the B-ring imparts a bluer colour to the flower tissue. Flavonoids are derived from anthocyanins derived from the anthocyanidin, phenyl-propanoid pathway with precursor while methylation of the 3‟ or 5‟-hydroxyl amino acid phenyl-alanine. Though hundreds group results in a slight reddening. of anthocyanins have been reported, they are

Fig. 1: Flavonoid biosynthetic pathway and flavonoid compounds accumulated in flowers. A simplified pathway derived from several plant species is depicted for ease of explanation. The painted colours shows image of each compound. ANS (Anthocyanidin synthase), AS (Aureusidin synthase), AT (Acyltransferase), C4’GT (Chalcone 4’-Oglucosyltransferase), C4H (Cinnamate-4-hydroxylase), CHI (Chalcone isomerase), CHS (Chalcone synthase), 4CL (4-coumarate:CoA ligase), DFR (Dihydroflavonol 4-reductase), F3H (Flavanone 3-hydroxylase), F3’H flavonoid 3’-hydroxylase, F3’5’H (Flavonoid 3’,5’- hydroxylase), FLS (Flavonol synthase), FNR (Flavanone 4-reductase), FNS (Flavone synthase), GT (Glycosyltransferase), MT (Methyltransferase), PAL (Phenylalanine ammonialyase)23. Copyright © Jan.-Feb., 2018; IJPAB 444

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 Table 2: Genes involve in pigment synthesis Enzyme Gene Species CHS (Chalcone synthase) Chs Antirrhinum, Chrysanthemum, Orchid, Rosa, Dianthus CHI (Chalcone isomerase) Chi Antirrhinum, petunia, Dianthus F3H (Flavone 3-hydroxylase) F3h Antirrhinum, Orchid, Dianthus, Chrysanthemum F3‟H (Flavonoid 3‟ hydroxylase) F3’h Antirrhinum, Petunia F3‟5‟H (Flavonoid3‟,5‟-hydroxylase) F3’5’h Calistephus, , Petunia FLS (Flavonol synthase) Fls Petunia, Rosa FNS (Flavone synthase) FnsII Antirrhinum, Gerbera DFR (Dihydroflavonol-4-reductase) Dfr Antirrhinum, Gerbera, Petunia, Dianthus, Orchid

Carotenoids of the yellow to orange flower colors in Carotenoids are a widespread family of plant ornamentals that include marigold (Tagetes), pigments, like flavonoids, play vital roles in daffodil (Narcissus), Freesia, Gerbera, Rosa, plant photosynthesis in chloroplasts. Lilium, and Calendula. More important and Carotenoids are also precursors for the less recognized is the ability of carotenoids to synthesis of the plant hormones abscisic acid, coexist with red or purple anthocyanins, strigolactone and gibberellin11,27; therefore, resulting in brown and bronze hues that neither their genetic manipulation is rather difficult. pigment would be able to provide by itself7.

Carotenoids are generally C40 terpenoid Classical geneticists identified carotenoid compounds formed by the condensation of mutants in maize, tomato, and Arabidopsis eight isoprene units. At the center of the during the early part of this century. However, molecule, the linkage order is reversed, so the difficulties with the biochemical properties of molecule as a whole is symmetrical. A set of the enzymes of the pathway and the generally conjugated double bonds is responsible for the poor viability of mutants affected in carotenoid absorption of light in the visible region of the biosynthesis during early stages of spectrum. Carotenoids protect photosynthetic development conspired to delay development organisms against potentially harmful of the field. Genetic studies of carotenoid photooxidative processes and are essential biosynthesis in bacteria have played a structural components of the photosynthetic fundamental role in the cloning and reaction. Carotenoids are responsible for most characterization of plant carotenoid genes.

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 A simplified biosynthetic pathway. The yellow flower colour from yellow-flowered colours indicate the prevalent colour of the carnations (2n.2x.30) and Dianthus knappii compounds in nature. Compounds before δ- (2n.2x.30) to a white-flowered cultivar of the carotene do not absorb light in the visible garden pink, Dianthus plumarius (2n.6x.90). region of the spectrum. The colour of These hybrids were difficult to make but a compounds in nature does not necessarily small number were produced from both cross correspond to the colours of purified combinations. All the progeny from the compounds in solution due to interactions with crosses with carnations were pink but those other components of chromoplast membranes from crosses with D. knappii were pale cream- and to concentration effects. The first steps of yellow, with some variation in intensity the pathway are condensation reactions that between plants. Analysis of the flower result in the formation of geranylgeranyl pigments showed that the yellow flower colour diphosphate (geranylgeranyl pyrophosphate, of D. knappii resulted from the presence of GGPP). Phytoene synthase (PSY) catalyzes high levels of flavone and flavonol glycosides the condensation of two molecules of GGPP whereas those of yellow carnations were into prephytoene pyrophosphate and then into chalcones9. phytoene (Figure-2). A series of desaturation Mutation Breeding reactions results in the synthesis of lycopene, Ornamental plants appear to be ideal systems which is then cyclized into carotene. for application of mutation induction Zeaxanthin and violaxanthin, the two main techniques as many characters of economical compounds of the xanthophyll cycle. interest that is flower traits or the growth habit Breeding approaches to change flower are easily monitored after mutagenic colour treatment. Furthermore, many ornamental 1. Hybridization species are heterozygous and often propagated 2. Mutation vegetatively thus allowing the detection, 3. Interspecific Hybridization and selection and conservation of mutants within Polyploidy the M1-generation. Since the beginning of 4. Genetic Engineering practical mutation breeding in the 1930s, this Interspecific and Polyploidy breeding: technique has been applied to ornamental Interspecific hybridisation and polyploidy are plants. One of the first officially released recognized as the most important sources of commercial mutant cultivars has been evolution and domestication of flowering produced in tulip (cv. „Faraday„) by De Mol plants. In ornamental plant breeding these 1949. It expressed an altered flower colour and phenomena go hand in hand and can be resulted from irradiation of cv. „Fantasy„in observed in the breeding history of many 1936. In recent decades, mutation induction ornamental crops (Rosa, Chrysanthemum, has been used for the development of 'sport- Gladiolus, Alstroemeria, Lilium, orchids etc). families' in several ornamental crops, for The role of interspecific hybridisation is the example in Alstroemeria, Dahlia, most important source for variation in Dendranthema, Dianthus, Euphorbia and ornamental breeding. Interspecific hybrids Streptocarpus. Flower colour is one of the have the potential to capture hybrid vigour as most prominent features of ornamentals and well as combine traits that do not occur within there are numerous reports on alterations a single species. Because breeder rather than arising after mutagenic treatment. Evaluation geneticist always want to add a new type of of the literature shows, that 55% of the records characteristics to the current cultivars, concerne changes in flower colour. As interspecific hybridisation is indispensable to compared to the knowledge on the molecular combine diverse gene pools. Red gentian basis and genetics of flower colour available cultivars have been made by interspecies today, practical mutation breeding has been hybridization. It is also used in transferring undertaken from an empirical point of view. Copyright © Jan.-Feb., 2018; IJPAB 446

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 The majority of reports is purely descriptive Pusa centenary, Pusa kesari and Pusa and devoid of analytical data on mutated arunodaya. genes. But profound experience of breeders Genetic Engineering and evaluation of derivation of sports allow It is manipulation of plant genome through the selection of promising starting genotypes, recombinant DNA technology to alter plant from which most of the colours known in the characteristics. Genetic engineering can be species of question can be derived. For used to create genetically altogether a new example in chrysanthemums, mutagenic plant of desired nature. It is possible to treatment of pink flowering genotypes renders introduce genes from quite unrelated the chance to obtain a wide spectrum of flower organisms like bacteria, fungi, yeasts into the colours as bronze, brown, yellow, white, red plants to modify their traits. Novel plants with and orange. On the other side, yellow desirable characters created through genetic flowering genotypes normally do not give rise engineering methods are called “Transgenic to flower colour mutants. In several plants”. Creation of transgenic plant utilises ornamental crops, so-called sport families the genetic engineering technology through solely diverging in flower colour have been tissue culture methods. derived from selected genotypes. They allow Colour modification in ornamental plants the production of an assortment of flower are by following mechanisms: colours under identical environmental  By the over expression of structural genes conditions. Most prominent examples for the to colour intensification use of such sport families are found in  By the use of sense or antisense enzyme chrysanthemums, carnations and roses. construct Mutation breeding in India:  By suppressing the expression of certain Beside IARI, New Delhi, BARC, Mumbai, gene of the phenyl propanoid pathway that TNAU, Coimbatore, NBRI, Lucknow and is Flavonoid biosynthesis pathway other Mutation breeding work is going on. The  By blocking the anthocyanin synthesis at success story of mutation breeding in different stage ornamentals in India is impressive. Alone in  By inhibiting the production of key Chrysanthemum 46 mutants are commercially biosynthetic enzyme and released. (Source: Current Science, Vol.89,  By adding an enzyme of a particular th No. 2, 25 July 2005). Recently released biosynthetic step to modify its pathway Chrysanthemum variety from IARI through mutation induced by gamma rays; Pusa anmol,

Table 3: Examples of flower colour modifications by regulating flavonoid biosynthesis Plant Produced Original colors species Gene sources Methods flower References

colors Red to Viola sp. Over Rosa hybrida Bluish 17 pale cyanic F3’5’H expression Mazus pumilum Dominat Petunia hybrid Blue Pale blue 12 CHS negative Torenia Endogenous White to pale Blue RNAi 21 hybrida ANS blue Cyclamen F3‟5‟H Purple Endogenous Red to pink 3 persicum Antisense Gentiana sp . Blue Endogenous CHS Antisense White 23 Lilac to pale Gentiana sp Blue F3‟5‟H Endogenous RNAi 22 blue Lotus japonicus Over Petunia hybrid Red Variegated red 24 PKR expression

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 Genes affecting the pattern of petal shown to direct production of a blue hue in pigmentation flowers of petunia and tobacco14. The cellular expression of the biosynthetic Over-expression of a petunia F3'5'H gene genes in uniformly pigmented petal tissue under the control of a constitutive promoter in affect the pattern of petal pigmentation. a pelargonidin producing carnation variety However, within the petal, production of produces petals in which delphinidin pigment may be patterned. Some patterns are derivatives contribute to about 70% of total seen in natural isolates and other patterns arise anthocyanins. However, there was only a through mutation. Patterns may arise by loss of slight colour change toward blue. In order to function of a regulatory gene that has a pattern increase the content of delphinidin derived to its area of activity within the flower. In this anthocyanins it was necessary to avoid case, pigmentation will be lost in those areas competition for substrates between two key with an absolute requirement for the endogenous enzymes of the anthocyanin transcription factor but not in those areas in pathway (DFR and F3'H) and the introduced which the regulator is not active or in which it enzyme (F3'5'H). To achieve this white can be substituted for by another factor. A carnation cultivars were selected that were pattern mutation may also arise in a specifically deficient in the DFR gene. biosynthetic gene itself if the mutation is in a Expression of petunia F3'5'H (under the regulatory region of the gene (the promoter) control of a promoter region from the such that it interferes with the interaction snapdragon CHS gene) and Petunia DFR genes between a regulatory gene product and the in one such DFR mutant resulted in exclusive biosynthetic gene (for example, by accumulation of delphinidin derivatives and modification of a cis-acting protein binding significant colour change toward blue motif in a biosynthetic gene promoter2. In this (Florigene Moondust, the first genetically respect, pattern mutants are common in the modified floricultural crop to be sold in the CHS (Nivea) and DFR (Pa//ide) genes world). Expression of a pansy F3'5'H gene expressed in Antirrhinum flowers but are very (under the control of a promoter region from uncommon in the CHS (C2) and DFR (Al) the snapdragon CHS gene) and a petunia DFR- genes expressed in maize aleurone, despite the A gene (under the control of its own promoter presence of mutagenic transposon insertions in and terminator regions) resulted in transgenic all of these genes. plants which also exclusively accumulated Generating blue flowers delphinidin but at a higher concentration. Most blue flowers contain aromatically These flowers had a dark violet colour acylated delphinidin derivatives. Rose, (Florigene Moonshadow). Florigene chrysanthemum and carnation make up over Moonvista, Florigene Moonshade, Florigene 50% of the world cut flower market but only Moonlite and Florigene Moonaqua are accumulate pelargonidin and cyanidin standard carnations that have been developed derivatives that are not modified with aromatic using the same strategy and are currently sold acyl groups. Thus they have become targets in North America, Australia and Japan are for attempts at engineering the synthesis of being trialled25. Petunia has a cytochrome b5 delphinidin derivatives with the hope of that specifically transfers electrons to F3'5'H eventually generating blue flowers. The by which petunia can efficiently synthesize absorbance of anthocyanin shifts towards 3',5'-hydroxylated flavonoids. Expression of a longer wavelengths (blue) by about 10 nm petunia F3'5'H (Hf1) gene along with a petunia with each hydroxylation of the B ring and by 4 cytochrome b5 gene in a carnation cultivar nm following an aromatic acylation10. As producing cyanidin derivatives resulted in described previously, the key enzyme in the efficient production of delphinidin based biosynthesis of delphinidin is F3‟5‟H. F3’5’H anthocyanins and subsequent colour change genes from petunia and lisianthus have been petals. In this case, it was not necessary to use Copyright © Jan.-Feb., 2018; IJPAB 448

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 a carnation line mutant in DFR to achieve gentian and iris do not accumulate exclusive accumulation of delphinidin. pelargonidin derived pigments and thus lack Roses are the most important flowers flowers with an intense red colour. Genetic in today‟s global flower market and have been modification methods should be an alternative the center of attraction for consumers and solution to achieving red flower colours. breeders for hundreds of years. Modern roses Though down-regulation of the F3'H and (Rosa hybrida) have resulted from extensive F3'5'H genes in combination with over hybridization of wild rose species and have expression of a correctly identified DFR gene various flower colours, except those in the should generate gentian flowers producing violet to blue range28,15. Delphinidin pelargonidin based pigments. Sophisticated production is a major breakthrough in the optimization of gene expression or pathway achievement of blue roses15. The expression of engineering may be necessary to accumulate a viola F3’5’H genes produced delphinidin5. large amount of pelargonidin, and intense red The overexpression of a viola F3’5’H gene flower colour. Furthermore, Agrobacterium resulted in the efficient accumulation of mediated transformation of gentian occurs at a delphinidin and colour changes with a novel low efficiency and the promoter of the 35S blue hue in a rose cultivars. Furthermore, the cauliflower mosaic virus, a commonly used down-regulation of the rose DFR gene and constitutive promoter, is prone silencing by overexpression of the iris DFR gene, as well as methylation in gentian19. the overexpression of the viola F3’5’H gene, Effect of regulatory genes on flower resulted in more efficient and exclusive pigmentation: delphinidin production and a bluer flower An increase in anthocyanin levels has been colour. Suppression of the endogenous DFR achieved by over expression of genes encoding gene was achieved by RNAi23. such transcription factors. For example, the Aida et al.1 observed that the flowers maize Lc allele gene (bHLH) under the control of torenia harbouring an antisense DFR gene of an essentially constitutive (CaMV35S) were bluer than those harbouring an antisense promoter led to an increase in the amount of CHS gene because incomplete down- anthocyanins in tobacco flowers. Expression regulation of DFR lead to an accumulation of of the same genes also resulted in increased flavones and the resulting copigmentation anthocyanins levels in floral and vegetative effect with the remaining anthocyanins shifted tissues, including the leaves of transgenic the flower colour towards blue. petunias. These leaves were purple due to Genetic Modification for Red Flowers accumulation of anthocyanins, and may Accumulation of pelargonidin based represent a novel ornamental plant of anthocyanins in flowers confers an intense red commercial value4. or orange colour, which is very desirable Other factors affecting flower colouration commercially. Attempts have therefore been Co-pigment made to obtain such colours by genetic Flavonols and flavones are common co- engineering. In petunia down regulation of the pigments that stabilize and lend bluing to F3'H gene in conjunction with over-expression anthocyanins by forming complexes with of rose DFR yielded transgenic petunia whose them10. Flavonols are derived from flowers accumulated pelargonidin based dihydroflavonols by the activity of flavonol anthocyanins. Down regulation of F3'5'H and synthase (FLS). The genes encoding FLS have F3'H genes and over-expression of been cloned from various plants18. Flavones pelargonium DFR in blue torenia (which are synthesized from flavanones by flavone normally produces delphinidin based synthase (FNS). Interestingly there are two anthocyanins) resulted in transgenics with pink kinds of FNS, a dioxygenase type (FNSI) and flowers accumulating anthocyanins based on a cytochrome P-450 type (FNSII). The FNSII pelargonidin. Some cut flower species such as gene has been cloned from torenia, Copyright © Jan.-Feb., 2018; IJPAB 449

Dhakar and Soni Int. J. Pure App. Biosci. 6 (1): 442-451 (2018) ISSN: 2320 – 7051 snapdragon, gerbera and perilla. A parsley patterns in Antirrhinum majus. Genes Dev, FNSI gene has also been cloned. 3: 1756-1767 (1989). Vacuolar pH 3. Boase, M.R., Lewis, D.H., Davies, K.M., Vacuolar pH, that is most often maintained as Marshall, G.B., Patel, D., Schwinn, K.E. weakly acidic, is critical to anthocyanin and Deroles, S.C., Isolation and antisense stability and colour. Although higher (neutral) suppression of flavonoid 3‟, 5‟- pH generally yields bluer flower colours, hydroxylase modifies flower pigments and anthocyanins are less stable at higher pH and colour in cyclamen. BMC Plant Biol, 10: must be stabilized with 4 more than one 107 (2010). glycosyl and aromatic acyl group. Genetic 4. Bradley, J.M., Davies, K.M., Deroles, control of petal vacuolar pH is known in S.C., Bloor, S.J. and Lewis, D.H., The petunia and morning glory. The only structural maize Lc regulatory gene up-regulates the gene shown to regulate vacuolar pH to date flavonoid biosynthetic pathway of Petunia. encodes a Na+/H+ antiporter (Purple) in Plant J., 13: 381-392 (1998). morning glory8. The gene is highly expressed 5. Brugliera, F., Tanaka, Y. and Mason, J., just before flower opening, which elevates pH Flavonoid 3‟, 5‟-hydroxylase gene from 6.5 to 7.5 and changes the colour from sequences and uses therefor. purple to blue. Homologues have been isolated WO2004/020637 (2004). from petunia, torenia and Nierembergia but 6. Ewa Młodzinska, Survey of plant their function in vivo is unclear. Higher pigments: molecular and environmental vacuolar pH has been shown to be specific to determinants of plant colours. Acta epidermal cells where anthocyanins Biologica Cracoviensia Series Botanica, accumulate. 51(1): 7-16 (2009). 7. Forkmann, G., Flavonoids as flower CONCLUSION pigments: the formation of the natural Flower colour is mainly determined by the spectrum and its extension by genetic ratio of different pigments and other factors engineering. Plant Breed., 106: 1-26 1991. such as vascular pH, co-pigments and metal 8. Fukada-Tanaka, S., Inagaki, Y., ions. Knowledge at the biochemical and Yamaguchi, T., Saito, N. and Iida, S., molecular level has made it possible to Colouring-enhancing protein in blue develop novel colour which are otherwise petals. Nature, 407: 581 (2000). absent in nature. Genetic engineering is 9. Gatta, M.K., Hammettb, K.R.W., providing a valuable means of expanding the Markhamc, K.R. and Murraya, B.G., floriculture gene pool. Generally, genetically Yellow pinks: interspecific hybridization modified (GM) flowers are more acceptable to between Dianthus plumarius and related consumers than GM food crops; therefore species with yellow flowers. Scientia many floricultural plants are at advanced Horticulturae, 77: 207-218 (1998). stages of development. 10. Goto, T. and Kondo, T., Structure and molecular stacking of anthocyanins-ﬂower REFERENCES color variation. Angrew. Chem. Int. Ed. 1. Aida, R., Yoshida, K., Kondo, T., Engl., 30: 17-33 (1991). Kishimoto, S. and Sibata, M., 11. Grotewold, E., The genetics and Copigmentation gives bluer flowers on biochemistry of floral pigments. Annu Rev transgenic torenia plants with the antisense Plant Biol, 57: 761-780 (2006). dihydroflavonol-4-redutase gene. Plant 12. Hanumappa, M., Choi, G., Ryu, S. and Sci, 160: 49-56 (2000). Choi, G., Modulation of flower colour by 2. Almeida, J., Carpenter, R., Robins, T.P., rationally designed dominant-negative Martin, C., and Coen, E.S., Genetic chalcone synthase. J Exp Bot, 58: 2471- interactions underlying flower color 2478 (2007). Copyright © Jan.-Feb., 2018; IJPAB 450

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