Public Understanding of Life Sciences / Chemical Ecology PULS/CE 17

Newsletter April 2011

Host Change Alters Toxic Cocktail Due to a gene modification leaf larvae attacking trees produce toxic cocktails that differ from the ones produced by conspecifics living on … p. 3

Small Genetic Changes with Major Consequences Small changes have big consequences, some of which may lead to the development of new weapons in the evolutionary arms race between plants and herbivores … p. 4

Antibiotics in situ Scientists are looking for antibiotics produced by microbial symbionts of leaf-cutting ants and study their function in the ecosystem … p. 5 PULS/CE 17 2

Newsletter April 2011 | Editorial

PULS/CE 17 reports on two particular stories in- volving small molecular differences which have important consequences. A leaf beetle species has been shown capable of turning to birch trees instead of willows as hosts because of a minor “malfunction” in processing genetic information.

A second example demonstrates that today’s Brassicaceae species can defend themselves successfully against herbivory by producing cer- tain glucosinolates after an amino-acid-produc- Amino acid sequence comparison of salicyl alcohol oxidases in different leaf : a vacancy is ing enzyme switches from producing leucine to visible in the amino acid sequence of lapponica beetles feeding on birch (red area) . synthesizing glucosinolates (their strong taste More information on this topic is available on page 3. Picture: PNAS and smell is typical of cabbage) just because its polypeptide chain is shortened.

Although Alice Schwarzer and molecular biology Little Differences seem to have nothing in common, you should be reminded that males and females have only one tiny genetic difference – tiny as far as the basic Dear Readers! course of development for a human ovum after fertilization is concerned: Only the composition of “The little difference and its huge consequences” the 23rd chromosome pair in Homo sapiens deter- was the title of one of the most successful books mines the developing embryo’s sex. This little XX to come out of the young Bonn republic. Alice versus XY difference has had huge consequenc- Schwarzer‘s ground-breaking work was published es, sociological and biological. We are a long way in 1975, when West Germany was democratically from understanding all of them. maturing and – despite its 26 years of peaceful existence – still somehow unsettled.

Although Schwarzer had something completely Enjoy a beautiful spring and our new PULS/CE different in mind than the topics in this month‘s issue! newsletter – she was fighting for equal rights between men and women – “little differences can have major consequences“ is true in many contexts. Jan-W. Kellmann  PULS/CE 17

Research Highlight | Newsletter April 2011

means that birch feeders lack the enzyme salicyl Host Change alcohol oxidase (SAO), which is responsible for the oxidation from alcohol to aldehyde,” explains Alters Toxic Roy Kirsch, PhD student in the Department of Bio- Cocktail organic Chemistry and author of the study. Biochemical analyses revealed that the gland secretions of salicylaldehyde-producing Leaf beetles fascinate us because of their amaz- beetles contain this enzyme in strikingly large ing variety of shapes and rich coloring. Their amounts. The scientists labeled it SAO-W (W: larvae, however, are dangerous plant pests. willow). Using corresponding DNA sequence Beetle larvae are part of a food chain; they are data, they isolated and characterized the SAO- A leaf beetle larva (Chrysomela attacked by predatory and parasites. To B (B: birch) encoding gene from birch feeders. lapponica) emits toxic secretions, protect themselves, they emit substances from They found that the amino acid sequences of visible as vesicles, from its defensive their defensive glands. These defensive secre- both enzymes are 97 percent identical. However, glands as a chemical protection against tions contain toxins, such as butyric acid esters or SAO-B is inactive because 27 amino acids at the predators. Photo: Kerstin Ploss, MPI-CE salicylaldehyde, which the larvae sequester from beginning of the polypeptide chain are missing. chemical precursors they have ingested with their Further studies on the defensive glands of birch food. Most leaf beetle species use only one plant feeders have shown that the amount of messen- species for feeding and reproducing on. Larvae of ger RNA (mRNA) in the SAO-B gene was reduced the leaf beetle Chrysomela lapponica attack two by 1000-fold compared to that in willow beetles; different tree species: willow and birch. On the the protein and its enzyme activity were below one hand, the uptake of special plant molecules the detection level. The lack of enzyme activity is as substrates for toxin-producing enzymes is eco- caused by a mutation in the SAO-B gene located nomical for the beetle larvae; on the other hand, near the second exon/intron junction. The muta- the leaf beetles become strongly dependent on tion is responsible for changes in mRNA process- the host plant and its specific metabolites. Wil- ing, so-called alternative splicing, which leads to lows of the Salicaceae family have up to 5 per- the loss of 27 amino acids in the SAO-B enzyme. cent glycosylated salicyl alcohol (salicin) in their leaves, whereas birch trees contain none of these The scientists conclude that Chrysomela lappon- Roy Kirsch Photo: MPI-CE compounds. Hence, researchers have investigat- ica likely used willows exclusively as host plants ed how Chrysomela lapponica leaf beetles adapt- and later shifted to birch trees as well. “It is still ed to both birch and willow as host trees and unclear whether the gene mutation enabled the analyzed whether the loss of salicylaldehyde in host plant shift from willow to birch or whether it Original Publication: birch feeders is due only to the fact that the pre- was adapted in the course of evolution after the Kirsch, R., Vogel, H., Muck, A., cursor salicin is not available in birch. To test their shift to birch had occurred,” says Wilhelm Boland Reichwald, K., Pasteels, J. M., Boland, hypothesis, they offered willow leaves to hungry By not producing the costly enzyme, birch beetles W. (2011). Host plant shifts affect a leaf beetle larvae they had collected from birch can save resources .First and foremost the loss major defense enzyme in Chrysomela trees. “The beetles were able to ingest salicin of salicylaldehyde also means that birch-feeding lapponica. Proceedings of the from willow leaves; salicyl alcohol was also de- populations no longer betray themselves to their National Academy of Sciences USA, tected in their defensive secretions. However, the own enemies anymore, who can trace them be- 108, 4897-4901. alcohol was not transformed to an aldehyde; this cause of the odorous substance. [JWK, AO] PULS/CE 17 

Newsletter April 2011 | Research Highlight

sequence of the respective amino acids, chains Small Genetic Changes with are folded into helices, sheets or other shapes necessary for the polypeptide to perform its bio- Major Consequences logical function. To make sure that enzyme-medi- ated catalysis does not happen in an uncontrolled fashion, many enzymes are regulated by a feed- Plants are continually exposed to herbivore at- back mechanism. In IPMS, this mechanism is lo- tack. To defend themselves, they have developed cated in the last 120 amino acids of the polypep- sophisticated chemical defense mechanisms. tide chain. As soon as enough leucine is available, Plants of the mustard family, such as thale cress the production of leucine precursors is stopped. (Arabidopsis thaliana), produce glucosinolates (mustard oil glucosides) to protect themselves “We found that the missing 120 amino acids not against herbivory. If larvae feed on mus- only inactivate the regulation of enzyme activi- tard plants, glucosinolates are hydrolyzed to ties, but also change the architecture of MAM form toxic isothiocyanates. Chemists call this the completely,” Jonathan Gershenzon says. The Plants of the mustard family, such as “mustard oil bomb.” missing 120 amino acids cause a profound change cabbage, produce glucosinolates that in the active site: it expands and becomes able to help to fend off herbivorous insects. Special enzymes are responsible for catalyz- bind larger substrates, allowing it to produce new The enzyme MAM is responsible ing the synthesis of the side chains found in the products: the precursors of glucosinolates. for glucosinolate production. In the various glucosinolates. Jan-Willem de Kraker course of evolution the enzyme IPMS and Jonathan Gershenzon have isolated one of The researchers came across IPMS when they (three dimensional model), which is these enzymes from Arabidopsis thaliana and were looking for genes involved in glucosinolate involved in the formation leucine, was discovered a surprising new insight. The enzyme production. In the context of these studies, they converted to MAM: 120 amino acids methylthioalkylmalate synthase (MAM), which isolated and sequenced the IPMS gene. The scien- disappeared (represented as pale-col- catalyzes glucosinolate formation, strongly re- tists assume that after a duplication of the IPMS ored) and two mutations in the active sembles an enzyme with a completely different DNA sequence millions of years ago, the “twin site of the molecule occurred. Since function: IPMS (isopropylmalate synthase), which DNA” lost the fragment encoding the sequence of then, MAM’s role has been to synthe- is involved in the synthesis of the amino acid leu- the last 120 amino acids. In the course of evolu- size precursors of glucosinolates. cine. The scientists found two major structural tion, this probably happened when the mustard Photo: Angela Schneider, MPI-CE; differences between IPMS and MAM. The last family originated. The loss turned out to be very enzyme model based on Koon, PNAS 120 amino acids in IPMS were absent in MAM, advantageous for the plants: it enabled them to 101, 2004. and in the active site of the enzyme two amino produce glucosinolates as a defense against her- acids had been exchanged. bivores. The assumptions were confirmed by de Kraker and Gershenzon in extensive in vitro ex- Original Publication: IPMS encoding genes are present in eubacteria, periments. The way MAM emerged is probably De Kraker, J.-W., Gershenzon, J. archaebacteria, algae and higher plants, but not typical for the way new phenotypes arise from (2011). From Amino Acid to Glucosino- in . Therefore, we humans must ingest the variety of genetic information encoded and late Biosynthesis: Protein Sequence leucine as an essential amino acid with our food. stored in DNA, and offers another example of Changes in the Evolution of Methyl- In the model plant Arabidopsis thaliana, IPMS how small changes have big consequences, some thioalkylmalate Synthase in Arabidop- consists of a chain of 631 amino acids. In actual of which may lead to the development of new sis. The Plant Cell, 23, 38-53. enzymes, these amino acid chains, also called weapons in the evolutionary arms race between polypeptides, are not straight. Depending on the plants and herbivores.. [JWK, AO, HR]  PULS/CE 17

Research Highlight | Newsletter April 2011

Antibiotics in situ

Leaf-cutting ants cultivate the fungus Leucoag- aricus gongylophorus with harvested leaf mate- Microscopic image of an Acromyrmex echinatior leaf-cutting ant (left) and distribution of the antibiotic valino- rial. In turn the fungus garden serves the ants as mycin on the ant’s body (right; MALDI Image: green = little, red = high amounts of valinomycin) Images: PNAS themajor food source. However,this symbiosis, is threatened by invasive fungi, such as Escovopsis weberi, which can destroy the symbiotic fungus. cutting ants were then searched for in extracts In 1999 Currie et al. (Nature, 1999, 398, 701-704) of the microbial symbionts by targeted mass

found that bacterial symbionts on the leaf-cutting spectrometric profiling. Thus antimycins 1 A -A4, ants’ body support the leaf cutting ants to protect valinomycins and actinomycins were identified their fungus garden against harmful fungi invad- from microbial symbionts of leaf-cutting ants. ing their nests. Using MALDI imaging it was possible to obtain a Synergistic effect of antibiotics: Single In PULS/CE 13 (2009) we reported that Su- picture of the valinomycin distribution on the ant’s components (A-E) are hardly effective sanne Haeder and Dieter Spiteller had identified body. This is the first study that provides evidence in very low concentrations, in combina- candicidin macrolides as the first antibiotics from that antibiotic substances are directly present di- tion, however, they inhibit the growth of microbial symbionts of leaf-cutting ants. Candi- rectly on the leaf-cutting ant’s body. Escovopsis (F). Photo: PNAS cidin macrolides strongly inhibit the growth of E. weberi. Because many different bacteria are In order to study the ecological function of the found in the ecosystem of leaf-cutting ants, a identified antibiotics growth inhibition assays vast diversity of antibiotic substances can be ex- were performed. Actinomycins for example pected. Ilka Schoenian from Spiteller’s group now inhibited the growth of potentially competing developed a method to quickly identify further soil bacteria. Moreover, antibiotic mixtures of antibiotics produced by microbial symbionts of candicdin, antimycin, valinomycin and actinomy- leaf-cutting ants and studied their function in the cin are much more effective than the individual leaf-cutting ants’ nests. Together with colleagues comounds. Antibiotic mixtures inhibit the growth from Dortmund, Kaiserslautern and Panama, the of Escovopsis, even if the single components are Ilka Schoenian Photo: MPI-CE scientists studied the chemical basis of the syn- below the inhibitory concentration. ergism and antagonism in microbial communities Original Publication: in the nests of leaf-cutting ants. Further experiments are planned to study the Schoenian, I., Spiteller, M., Ghaste, M., diversity and functions of antibiotics in the eco- Wirth, R., Herz, H., Spiteller, D. (2011). Ilka Schoenian determined the relationship of mi- system of leaf-cutting ants in detail in order to Chemical basis of the synergism and crobial symbionts from leaf-cutting ants to known gain a better understanding of the interplay of antagonism in microbial communi- bacteria. Using database search the secondary secondary metabolites in nature. The studies ties in the nests of leaf-cutting ants. metabolite spectrum of these closest relatives may also lead to the discovery of new antibiot- Proceedings of the National Academy was identified. Such obtained putative candidate ics that could contribute to the fight against of Sciences of the United States of antibiotics of the microbial symbionts from leaf infectious diseases in humans. [JWK, AO, DS] America, 108, 1955-1960. PULS/CE 1617 

Newsletter April 2011 | IMPRS Project

Scent of a Poplar

The ability to communicate is essential for all liv- After analyzing and comparing the odors of poplar ing beings including plants. Plants may not emit trees emitted following herbivory by the two dif- sounds but they are fragrant, and odors are their ferent moth species and by two different larval language. They emit volatile organic compounds stages of the gypsy moth, we identified over 30 (VOCs) in response to herbivore attack; VOCs different chemical compounds. Interestingly, the attract the natural enemies of the herbivores, odor blends differed not in composition, only in such as predators and parasitoids. This process amount. The next step was to expose single com- is known as indirect defense – the plants’ cry for pounds to the wasp’s antennae to observe if they help. caused physiological responses; for this we used a method called electroantennographic detection. Gypsy moth larvae are common poplar Indirect defenses of trees have been poorly stud- Out of a set of 20 compounds, we observed physi- pests. Freshly hatched larvae can be ied in the past. Trees have several special fea- ological responses for at least 10. parasitized by Glyptapanteles liparidis tures, such as wood formation, perennial growth wasps. These tiny parasitoids are and seasonality, which makes them particularly These results suggest that poplars produce dif- attracted by volatile organic com- interesting and challenging to study. ferent odors depending on who is attacking them pounds emitted by attacked trees. and that the wasp’s antennae can perceive some Photo: C. Meyer, Beutenberg Campus The main objective of my Ph.D. research is to of the compounds which are differentially emit- determine if indirect defenses are functional ted upon different types of damage. However, mechanisms in the black poplar (Populus nigra). many other questions remain to be answered, We are using a model system which involves two such as the effect of single compounds on the common herbivores of black poplars: gypsy moths wasp’s behavior (attractant or repellant); wheth- (Lymantria dispar) and poplar hawk moths (Laothoe er behavioral effects are a result of individual populi). The third actor is a tiny parasitic wasp compounds or blend ratios; and ultimately, if this (Glyptapanteles liparidis), which lays its eggs only indirect defense mechanism works under natural gypsy moth larvae during their early larval stages conditions. ; the offspring of the wasp grow and develop in- A. McCormick side the small caterpillars, preventing them from growing and killing them within a few days.

Andrea Liliana Clavijo McCormick Some of the exciting questions we have asked so from Colombia holds a fellowship of far are: Is the odor emitted by poplar trees differ- the International Max Planck Research ent depending on which herbivore is attacking or School. Her PhD project in the Depart- even according to the larval stage of the gypsy ment of Biochemistry (project group moth? Can the wasps smell whether the plant is of Dr. Sybille Unsicker) focuses on being damaged by their potential host (the gypsy volatile-mediated indirect defenses of moth) or a non-host species, and whether gypsy poplar. Photo: MPI-CE moth larvae are still in their early larval stage?  PULS/CE 17

News | Newsletter April 2011

10th IMPRS PhD Symposium – more participants than ever

The annual symposium of the International Max Two lectures by invited speakers completed the Planck Research School at the old castle (Altes program: Dr. Corné Pieterse, University of Utre- Schloss) in Dornburg is becoming an increasingly cht, Netherlands, talked about plant hormones and important event. It provides scientific exchange not defense, and Dr. Martin Heil, CINVESTAV Mexico, only between PhD students, but also between the reported on the role of ants in indirect plant de- scientific departments of the MPI and the partici- fenses. pating institutes of Friedrich Schiller University. At the 10th IMPRS symposium prizes The symposium is an important part of the PhD were awarded for the best talks and More than 120 PhD students, supervisors and post- training offered by the IMPRS and provides a fa- posters. The awardees (from left to docs attended the symposium, the highest number miliar and at the same time critical environment right): Maria Heinrich, Andrea Mc- of participants ever. 24 PhD students presented where PhD students can present their research Cormick, and Elisabeth Eilers. their projects in talks, 33 presented posters. Both results, answer questions, or lead sessions profes- Photo: Angela Overmeyer, MPI-CE posters and talks were intensively discussed. sionally. Karin Groten

Bill Hansson Elected to the about 400 members. World-famous botanist and Royal Swedish Academy of zoologist Carl Linnaeus (1707-1778), the father of Sciences modern and considered by many to be one of the fathers of modern ecology, was one of The Royal Swedish Academy of Sciences in its founders. Stockholm has elected Prof. Bill S. Hansson as a member of the “class for biosciences”. The The induction ceremony took place during the an- society, which also awards the Nobel Prizes each nual meeting of the academy on March 31, 2011, Bill Hansson during the induction year, was founded in 1739 as an independent non- in Stockholm. [AO] ceremony into the Royal Swedish governmental scientific society and currently has Academy. Foto: Markus Marcetic, KVA

institute this year. Among the experiments they performed in the labs: analyses of their fingernails at the MPI in the isotope ratio mass spectrometer; compa- risons between natural and synthetic odors by What role do enzymes play in insects’ defense means of GC/MSl; and tests with bees and ants against plant toxins? How can DNA be made vi- using a confocal microscope. We hope that a lot sible? Am I what I eat? These were some of the of interest in and fascination with research was questions that were addressed in the hands-on stimulated in the participants. We are already The Forsche-Schüler-Tag provides an workshops the MPI organized for school kids looking forward to April 26, 2012, when the motto opportunity for girls and boys to get a at the “Forsche-Schüler-Tag” on April 14, 2011. will again be: “Looking for young researchers!” glimpse of scientific methods. 28 girls and 19 boys from 8th grade on visited the Angela Overmeyer Photo: Angela Overmeyer, MPI-CE PULS/CE 17 

Newsletter April 2011 | News & Events

XVI Int. Symposium on Olfaction and Taste Stockholm, Sweden, 23.-27. Juni 2012 http://www.isotxvi.com

MPI-CE Institute Symposium and Alumni Meeting

The annual institute symposium of the Max Planck Institute for Chemical Ecology will be held on September 22-23, 2011, in Lecture Hall 3, Friedrich Schiller University Jena, Carl-Zeiß-Straße 3, 07743 Jena. All former co-workers and alumni of the institute will be specifically invited this year.

www.ice.mpg.de

Impressum: PULS/CE is published semi-annually and can be downloaded free of charge on the homepage of the MPI for Chemical Ecology and is distributed electronically as PDF to subscribers. A print version will be sent on request. Editor: MPI-CE, Jena • Managing Director: Prof. Dr. Bill S. Hansson (viSdP). Editorial Staff: Dr. Jan-W. Kellmann, Research Coordination • Angela Overmeyer, M.A., Information and Communication • Emily Wheeler, Editing ISSN: 2191-7507 (Print), 2191-7639 (Online)