PULS/CE 23
Public Understanding of Life Sciences / Chemical Ecology
Newsletter April 2014
How leaf beetle larvae fend off predators
Poplar leaf beetle Chrysomela populi larvae transport salicin,
a substance from their leafy diet, from the midgut into the larvae’s
defensive glands, where it is converted into the defensive compound
salicyl aldehyde … p. 3
How banana plants kill root pests
By increasing local concentrations of plant toxins in infected root tissues,
banana plants protect themselves from the parasitic nematode Radopholus similis.
The toxins are stored in lipid droplets in the body of the nematode until the
parasite finally dies.... p. 4
Why fruit flies prefer laying their eggs on oranges
A single odorant receptor controls the choice of citrus fruits as an egg-laying substrate in Drosophila. Laying eggs on oranges is advantageous, because
parasitoid wasps feeding on Drosophila larvae avoid citrus fruits. The same smell
that is attractive to the flies also repels the wasps … p. 5
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Newsletter April 2014 | Editorial
Researchers of the future!
Young researchers present extracted
DNA from fruits, vegetables and
leaves in the “molecular kitchen“
Dear Readers!
Photo: Angela Overmeyer, MPI-CE
18 girls and 7 boys (here with their
workshop supervisors) were guests
at the MPI.
March 27, 2014 was the day of the 5th
“science day for kids” (Forsche-Schüler-Tag):
The Max Planck Institute for Chemical Ecology
again invited school kids from the 8 th grades of
area schools to join scientists in the labs for
hands-on experiments. Workshops focused on
research questions in chemical ecology, for example, why does mustard have such a pungent
flavor? what happens in insects’ brains when
they perceive odors? what are symbiotic bacteria
in our bodies or in those of insects good for? what
roles do proteins play in a plant?
surprise, even for the scientists who supervised
the experiment. Lena, Marie, Steffi and Georg had
travelled to Jena from Ohrdruf and brought seeds
of the horseradish tree Moringa oleifera. Using
high-performance liquid chromatography techniques, they were able to determine the amount
of glucosinolates in the seeds. Because of its
high contents of essential amino acids, minerals,
vitamins, and glucosinolates, the Moringa plant,
which is also called the “miracle tree”, is thought
to bring health. The four students will now continue to study the Moringa plant in more detail
and are happy that scientist Michael Reichelt has
offered to support their project.
In his concluding lecture “School is over – Now
life really begins” for the 120 young people who
had visited hands-on workshops in six campus
institutes, Jan-Wolfhard Kellmann, research coordinator of our institute, provided some career
guidance. In the context of a society which will
be made up of fewer and fewer young people and
more and more senior citizens, he encouraged the
young participants to be optimistic about their
professional futures, especially since their energy
and creative ideas will be urgently needed.
The young students particularly liked the handson workshops which included them as active
participants in the research labs and not just as
spectators. 17-year old-Katrin summarized what
many of the participants agreed on: “Organizing
such a day for school kids is important and should
continue in the future.”
Photo: Angela Overmeyer, MPI-CE
In the workshop “Natur vs. Douglas & Co. –
a comparison of natural and purchasable scents
by means of GC/MS”, students analyzed different
odors, including those of their favorite perfume.
Some of the substances they found were a real
Angela Overmeyer
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PULS/CE 233
Research Highlight | Newsletter April 2014
Leaf beetle
larvae defense
Leaf beetle larvae are part of food chains. To
protect themselves, some leaf beetle larvae emit
a deterrent from their defensive glands in the
form of little droplets on their back. The defensive substances in the secretion are synthesized
by the larvae from chemical precursors, such as
salicin, ingested when the larvae feed on leaves.
Salicin is present in the leaf tissues of poplars
and willows. A sophisticated transport network
carries the precursors from the gut into the defensive glands.
Anja Strauß, who wrote her PhD thesis in the
Department of Bioorganic Chemistry, unraveled
the mystery of this transport mechanism. She
studied gene transcripts in the secretory cells
of the poplar leaf beetle Chrysomela populi and
found a gene which is 7000 times more expressed
in the glandular tissue than in the gut tissue. Gene
sequence analysis revealed that the scientists
had cloned the gene for a so-called ABC transport
protein. Such transport proteins are widespread
and also mediate multi-drug resistance, transporting substances potentially dangerous for the
cell either away from the cell or into the tiniest
cell organelles where they are rendered harmless.
Large amounts of CpMRP − as the scientists
named the transporter − are located in the membranes of small bodies, the storage vesicles within glandular cells. As soon as the precursors of
defensive compounds are ingested and reach the
cells, they immediately accumulate in the cells’
abundant vesicles with the help of ATP, the molecular energy unit in the cell. This is where the
name ABC transporter comes from: ATP-binding
cassette transporter. The vesicles migrate within
the glandular cells towards the reservoir, where
they bind to the membrane of the large reservoir
and distribute their contents. The defensive compound salicyl aldehyde is then produced from the
salicin precursor. In case of danger, the repellent
is secreted from the tips of the glandular tubercles as the larvae assume a threatening posture.
CpMRP functions as a pacemaker in this process:
Thanks to its high carrying capacity, CpMRP lowers the concentration of salicin in the glandular
tissue. As a consequence, there is a continuous
and selective flow of salicin molecules via asyet-unknown transport proteins from the larvae’s
bodily fluid. Interestingly, ABC transporters form
a huge network within the glandular cells of
the leaf beetle larvae; this network efficiently
absorbs the toxins and traps them in storage
vesicles. In the insect, this is actually not a detoxification process, but rather a well-directed
accumulation of toxin precursors ingested when
the larvae feed on leaves and economically used
to fend off predators. [JWK/AO]
Immunofluorescence microphotograph of a glandular cell of the poplar
leaf beetle: CpMRP (green) spans a
huge network through the entire cell.
Image: Anja Strauß
Anja Strauß. Photo: MPI-CE
Original Publication
Strauß, A., Peters, S., Boland, W.,
Burse, A. (2013). ABC transporter
functions as a pacemaker for the
sequestration of plant glucosides in
leaf beetles. eLIFE, 2:e01096
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Newsletter April 2014 | Research Highlight
analysis and imaging techniques, the researchers
were able to identify and localize defense substances in banana roots: The plants accumulated
so-called phenylphenalenones only in infected
regions of their roots, not in healthy tissues. This
was the case in both the resistant and the susceptible banana variety. However, the concentration
of the most active compound, anigorufone, was
much higher in the immediate vicinity of lesions
on the roots of resistant bananas than in the infected root tissues of the nematode-susceptible
banana plants.
Toxic substances in banana
plants kill root pests
Root of the susceptible banana variety
Grande Naine (above) and the resistant banana Yangambi km5 (below):
visible are a few red, phenylphenalenone-containing regions on the
resistant banana within the predominantly healthy, pale root tissue. The
root of the susceptible Grande Naine
is covered in widespread dark areas.
This massive root damage will eventually cause the plant’s death.
Photo: Dirk Hölscher, MPI-CE.
Middle: Microscopic image of the
nematode Radopholus similis: Inside
the roundworm are lipid droplets that
store the phenylphenalenone
Bananas are among the world’s most important
food crops. In addition to fungi and insects, the
parasitic nematode Radopholus similis is also a
major banana pest. It attacks the roots of banana
plants, impeding growth and slowing development of the plant and fruit. In the
final stage of the disease, plants topple
over − often when already bearing an immature fruit bunch. Yield losses up to 75%
can be the result of R. similis infestation.
In order to control such pests in banana
plantations, high doses of synthetic pesticides are used which not only cause ecological damage but can also have severe
negative effects on the health of people
who are exposed to these chemicals.
anigorufone (yellow). Image: S. Dhakshinamoorthy, KU Leuven
Original Publication:
Hölscher, D., et al. (2014). Phenalenone-type phytoalexins mediate resistance of banana plants (Musa spp.) to
the burrowing nematode Radopholus
similis. PNAS, 111, 105-110
Scientists have now taken a closer look at the
plant-nematode interactions in the context of
resistance versus susceptibility. They compared
two banana varieties, a resistant and a susceptible one, and studied their defense responses to
Radopholus similis. Using modern spectroscopic
The toxic effect of anigorufone and other defensive substances was tested on living nematodes.
Anigorufone turned out to be the most toxic to
the pest. The researchers were able to visualize
the plant toxin within the body of the roundworm.
There the lipid-soluble anigorufone accumulated
in lipid droplets which increased in size as they
converged and finally killed the nematode. Why
these complex lipid droplets are formed
and why the nematodes cannot metabolize or excrete the toxin still needs to be
clarified. The scientists assume that the
growing lipid droplets displace the inner
organs of the nematode causing an eventual metabolic dysfunction.
The researchers will now try to find out
how resistant banana plants biosynthesize
and translocate the defense compounds on
the molecular level. Such insights will provide important clues for the development of banana varieties which are resistant to the nematodes. This
could help to minimize the excessive use of highly
toxic pesticides in banana plantations; these toxins jeopardize the environment and people’s lives.
[AO]
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Research Highlight | Newsletter April 2014
For egg-laying insects, selecting the best site
to lay eggs is crucial for the survival of the eggs
and larvae. Once the eggs have been deposited,
the maternal care of the female flies ends: eggs
and larvae are henceforth at the mercy of their
environment. Suitable food sources for the hungry larvae and protection against predators and
parasites are important selection criteria for egglaying substrates.
Researchers from the Department of Evolutionary Neuroethology wanted to know which oviposition substrates fruit flies preferred, so they
let the insects select among different ripe fruits.
An analysis of the behavioral assays showed that
female flies preferred to lay their eggs on oranges. Further selection experiments helped to identify the odor that determinded the flies’ choice:
the terpene limonene. Although citrus is not an
attractant for the flies, it elicits egg laying.
By performing electrophysiological measurements, the scientists were able to quantify the
flies‘ responses to limonene and to localize and
identify the olfactory sensory neurons responsible for detecting citrus. Subsequently, they
tested the flies’ responses to 450 different odors.
Valencene, another component of citrus fruit, also
triggered a strong response. Compounds that activated these particular sensory neurons induced
oviposition. In vivo calcium imaging of the flies’
brains stimulated with citrus enabled the researchers to identify the corresponding odorant
receptor.
In nature, a considerable proportion of Drosophila larvae are killed by enemies, mainly parasitoid wasps that lay their eggs inside the larvae.
Astonishingly, these wasps are repelled by citrus
Preference for oranges
protects flies from parasites
odors, although citrus would guide them to their
food source: Drosophila larvae. The parasitoid
wasp Leptopilina boulardii, which specializes in
Drosophila melanogaster, is repelled by valencene. Why wasps avoid citrus is not completely
understood; however, female fruit flies have
clearly learned to let their offspring grow on citrus fruits, because there the larvae are better
protected against parasites.
Drosophila on an orange peel. Photo:
Marcus C. Stensmyr, Universität Lund
Above: Researcher Hany Dweck
These research results provide important information about the criteria that insects use to select an oviposition site that guarantees the best
development of their offspring. There may be
similar odor responses in other insects and ways
to manipulate them. These insights may lead to
new ways to control insects, especially those that
destroy crops or transfer diseases. [AO]
with an odor collection: Drosophila
repsonses to 450 different odors were
analyzed. Photo: Anna Schroll
Original Publication
Dweck, H. K. M., Ebrahim, S. A. M.,
Kromann, S., Bown, D., Hillbur, Y.,
Sachse, S., Hansson, B. S., Stensmyr,
M.C. (2013). Olfactory Preference
for Egg Laying on Citrus Substrates
in Drosophila. Current Biology, 23,
2472–2480
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Newsletter April 2014 | News
Captive breeding for thousands of years has impaired
olfactory functions in silkmoths
Bombyx mori (left) and Bombyx mandarina (right) females. The domesticated moth has lost its camouflage
coloration as well as its ability to fly.
Photo: Markus Knaden, MPI-CE
Domesticated silkmoths Bombyx mori have a
much more limited perception of environmental odors compared to their wild relatives. A
new study on silkmoths revealed that the insects’ ability to perceive environmental odors
has been significantly reduced after about 5000
years of domestication by humans. This is what
scientists from the Department of Evolutionary
Neuroethology and their colleagues from Japan
found when they compared olfactory functions in
Bombyx mori and in their wild ancestors.
Nevertheless, the extremely sensitive olfactory
detection of pheromones in domesticated males
eager to mate remains unaltered. [AO]
Originalveröffentlichung:
Bisch-Knaden, S., Daimon, T., Shimada, T., Hansson, B.S.,
Sachse, S. (2014). Anatomical and functional analysis
of domestication effects on the olfactory system of the
silkmoth Bombyx mori. Proc. R. Soc. B, 281: 20132582
Division of labor in the test tube:
Bacteria grow faster if they feed each other
Bacteria that divide their metabolic
labor (left colony) grow faster than
bacterial cells that produce all amino acids on their own (right colony).
Humans know that divvying up the chores is more
efficient than doing it alone, and this is also true for
bacteria. Researchers from the Research Group
Experimental Ecology and Evolution and their colleagues at the Friedrich Schiller University came
to this conclusion when they performed experiments with microbes. The scientists worked with
bacteria that were deficient in the production of
a certain amino acid and therefore depended on
a partner to provide the missing nutrient. Bacterial strains that complemented each other’s need
by providing the required amino acid showed a
fitness increase (faster growth) of about 20%
relative to that of a non-deficient strain without
a partner. These results help to explain why cooperation is such a widespread model of success in
nature. [JWK/AO]
Photo: Samay Pande, MPI-CE
Original Publication:
Pande, S., Merker, H., Bohl, K.,
Reichelt, M., Schuster, S., de Figueiredo, L., Kaleta, C., Kost, C. (2013).
Fitness and stability of obligate crossfeeding interactions that emerge
upon gene loss in bacteria. The ISME
Journal. doi: 10.1038/ismej.2013.211
The Research Group Experimental Ecology and Evolution headed by Christian Kost (2nd from left). Photo: MPI-CE
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News | Newsletter April 2014
Tobacco hornworm larvae exhale a small fraction of nicotine from
ingested tobacco leaves to ward off predatory spiders
Caterpillars use different strategies to protect
themselves from their enemies; many are camouflaged, others use their bright colors as warning signals, have stinging hairs or secrete toxic
substances, or assume threatening postures.
Scientists from the Department of Molecular
Ecology have now discovered a previously unknown protective mechanism: Tobacco hornworm
larvae can exhale a small fraction of the nicotine
they have ingested while feeding on tobacco leaves. To do so, they transfer some of the ingested nicotine into their hemolymph (insect blood)
and from there into their respiratory system.
The “bad breath” that results repels major predators. These insights were made possible by combining molecular techniques with a natural history approach in field experiments in the tobacco’s
native habitat. [AO]
Original Publication:
Kumar, P., Pandit, S. S., Steppuhn, A., Baldwin, I. T. (2014).
A natural history driven, plant mediated RNAi based
study reveals CYP6B46’s role in a nicotine-mediated
Wolf spider Camptocosa parallela
anti-predator herbivore defense. PNAS, 111, 1245–1252
attacking a Manduca sexta larva in an
experimental assay.
Photo: Pavan Kumar, MPI-CE
Ants protect acacia plants against pathogens
The biological term “symbiosis” refers to what
economists and politicians usually call a win-win
situation: a relationship between two partners
which is beneficial to both. The mutualistic association between acacia plants and the ants that
live on them is an excellent example: The plants
provide food and accommodation in the form of
nutritious food bodies and nectar as well as hollow thorns which can be used as nests. The ants
return this favor by protecting the plants against
herbivores. Researchers have now found that
ants also keep harmful leaf pathogens in check.
The presence of ants greatly reduces bacterial
abundance on the surfaces of leaves and has a
visibly positive effect on plant health. The results
indicate that symbiotic bacteria colonizing the
ants inhibit pathogen growth on leaves. [AO]
Mutualistic Pseudomyrmex ferrugineus
ants on an acacia plant. The ants love
the nectar from the plant’s extrafloral
Original Publication:
nectaries. Photo: Martin Heil, CIN-
González-Teuber, M., Kaltenpoth, M., Boland, W. (2014).
VESTAV, Irapuata, Mexico
Mutualistic ants as an indirect defence against leaf
pathogens. New Phytologist, DOI 10.1111/nph.12664
The first insects could not smell so well
An insect’s sense of smell is vital to its survival.
Only if it can trace even tiny amounts of odor
molecules is it able to find food sources, communicate with conspecifics, or avoid enemies.
According to a new study, many proteins involved
in the highly sensitive odor perception of insects
emerged rather late in the evolutionary process.
The very complex olfactory system of modern insects is therefore not an adaptation to a terrestrial environment that appeared when insects first
migrated from water to land but, rather, an adaptation that appeared when insects developed the
ability to fly. [AO]
Original Publication:
Mißbach, C., Dweck, H., Vogel, H.,
Vilcinskas, A., Stensmyr, M. C., Hansson, B. S., Grosse-Wilde, E. (2014).
Evolution of insect olfactory receptors.
eLIFE, doi:10.7554/elife.02115
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Newsletter April 2014 | News & Events
Flowering plants need sugar transporter SWEET9
for nectar production
Ovary and nectary (orange) of a
Nicotiana attenuata flower.
Photo: Danny Kessler, MPI-CE
To make sure that flying pollinators such as insects, birds and bats come to the flowers to pick
up pollen, plants evolved special organs, the
nectaries, to attract and reward them. Scientists
from the Department of Molecular Ecology and
their colleagues from Stanford and Duluth (USA)
have identified the sugar transporter that plays
a key role in plants’ nectar production. SWEET9
transports sugar into the extracellular areas of
the nectaries where nectar is secreted. Thus,
SWEET9 may have been crucial for the evolution
of flowering plants, many of which attract and
reward pollinators with nectar. [AO]
Original Publication:
Lin, W., Sosso, D., Chen, L.-Q., Gase, K., Kim, S.-G.,
Kessler, D., Klinkenberg, P. M., Gorder, M., Hou, B.-H.,
Qu, X.-Q., Carter, C., Baldwin, I. T., Frommer, W. (2014).
Nectar secretion requires sucrose phosphate synthases
and the sugar transporter SWEET9. Nature, doi: 10.1038/
nature13082
Five new IMPRS PhD fellowships available in 2015
In April 2013, the International Max Planck Research School, the graduate program of the Max
Planck Institute for Chemical Ecology, was evaluated positively by four internationally renowned
scientists. Just before Christmas the institute
received confirmation that the program will be
extended for another six years, until 2021.
Thanks to new funding, the IMPRS will be able to
award new doctoral fellowships. Therefore, a
new round for submission of fellowship applications will open in July. The application deadline will be at the end of August 2014.
At the end of November, selected candidates will
be invited to Jena for interviews and give talks.
Even more than five new PhD students may be
hired, because the IMPRS will likely break its own
record of successfully completed PhDs this year:
Ten doctoral candidates have already successfully defended, ten more have submitted their
theses.
http://imprs.ice.mpg.de/ext/
Currently, the 74 doctoral students in
the IMPRS (here at their annual symposium in Dornburg) come from
17 different countries.
Photo: Karin Groten, MPI-CE
© Danny Kessler
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)