Trichomes, hair-like projections on leaves, are part of a plant’s defense against herbivores: they can be obstacles, traps, or reservoirs for toxic substances. The hairs of wild tobacco Nicotiana attenuata contain primarily acyl sugars, which are composed of the common sugar, sucrose, bound to branched chain aliphatic acids, compounds that give baby vomit its distinctive odor.
Freshly hatched Manduca sexta larva (tobacco hornworm) consuming trichomes of wild tobacco (Nicotiana attenuata). MPI Chemical Ecology: Ian Baldwin, Alexander Weinhold
A rough harvester ant (Pogonomyrmex rugosus) has located a caterpillar because of its smell and is carrying it back to its nest. The larva emits distinctive odors after it has consumed acyl sugars from trichomes. MPI Chemical Ecology: Ian Baldwin, Alexander Weinhold
Tiny, freshly hatched caterpillars consume these sweet secretions. However, consuming the sugary exudations from the plant hairs has unwanted side effects for the insects: the caterpillars develop a distinctive body odor, and so does their frass (the term entomologists use for “caterpillar poop”). The Max Planck researchers discovered that ants recognize the caterpillar’s body odor and use the aliphatic acids excreted by the caterpillars after ingestion of acyl sugars to locate their prey. These predatory ants locate the tiny larvae on the plants and carry them back to their nests to feed their young and co-workers. Thus plants use acyl sugars not only as sticky traps against aphids, leaf fleas or spider mites; they can also skillfully utilize them to tag voracious caterpillars with a distinctive smell which makes them easy prey to locate. (PNAS Early Edition, April 25-29, 2011, DOI: 10.1073/pnas.1101306108).
Striking features of animals can be fateful, because they may betray them to their enemies. Colorful feathers or incautious courtship behavior are examples of such attributes, as are involuntary body odors emitted by the organism itself or its excretions. Larvae of the silver-spotted skipper, Epargyreus clarus, are punctilious about removing feces from their shelter, so that predators won’t find them due to their telltale odors. Some plant species, on the other hand, take advantage of the predators’ preferences when they produce their compelling “green leaf volatiles” to protect themselves indirectly against herbivores. In a recent study, Ian Baldwin, head of the Department of Molecular Ecology at the Max Planck Institute for Chemical Ecology in Jena, Germany, and his colleagues showed that Manduca sexta larvae have a substance in their oral secretions that catalyzes the transformation of green leaf volatiles into dangerous attractants – with fatal consequences for the caterpillars. The attractant called (E)-2-hexenal lures predatory bugs that feed on Manduca sexta larvae and eggs. (see Press Release “Lethal Backfire: Green Odor with Fatal Consequences for Voracious Caterpillars”)
Knowing that trichomes are supposed to be defensive structures, replete with poisons and sticky substances, the researchers were surprised to observe that freshly hatched Manduca sexta larvae as well as larvae of two Spodoptera species did not just start feeding on the leaf tissue of wild tobacco Nicotiana attenuata; they directly consumed the hairs on the leaves and their contents (see also video on http://www.ice.mpg.de/ext/735.html). The reason for this behavior is probably that the trichomes contain large amounts of sucrose bound to fatty acids. This diet is rich in calories and the larvae thrive and prosper; toxic effect could not be discovered. However, when Alexander Weinhold, a PhD student in Ian Baldwin’s group studied the animals and their excretions, he found that their odor profile had significantly changed after digesting the sweet trichome secretions: the larvae’s bodies and excretions evaporated four volatile branched-chain aliphatic acids into the air; within two hours the considerable amount of 0.03 milligram emitted by the feces could be measured. Chemical analyses revealed that these aliphatic acids in the larvae’s midgut originated from the acyl sugars that the larvae had consumed with the trichomes.
“We were actually pretty sure that the volatile fatty acids would attract predators like bugs of the Geocoris genus, which would feed on the Manduca larvae and eggs,” says Baldwin. But control experiments that included Nicotiana glauca, a species which completely lacks trichomes on its leaves, did not confirm a significantly increased occurrence of the bugs. However, tiny larvae on leaves that had been additionally perfumed with branched-chain aliphatic acids became easier prey for predators, even though it was unclear who the attackers were. The scientists now suspected the many ant species, which are abundant in the Utah habitat.
To test the responses of the many different ant species which inhabit Nicotiana attenuata’s native habitat to branch-chain aliphatic acids, Ian Baldwin laid out cooked rice grains that had been marked with 0.03 milligram of volatile fatty acids – the exact amount that had been measured from the larval excretions. The result: ants from five different nests specifically headed for the rice grains and carried them away. The ants belonged to the Pogonomyrmex rugosus species; they feed on plant seeds as well as cicadas and small caterpillars. In further extensive experiments, designed to exclude the influence of visual features of the larvae, Baldwin used fresh versus heated (= free of aliphatic acids) frass as well as “aliphatic acid perfume” and thereby demonstrated that the ants respond specifically to the aliphatic acid scent of the young larvae - an odor with fateful consequences for the herbivores.
The scientists assume that wild tobacco plants trick their enemies by providing tasty sugar molecules with branched-chain aliphatic acids. This trick is beneficial for the plants because it betrays the herbivores to their own enemies. Experiments in the planning stages will examine whether this molecular strategy is an “indirect defense” in the ecological sense. These studies will include transgenic plants which can no longer produce acylated sugars in their trichomes. [JWK/AO/ITB]Original Publication:
Dr. Jan-Wolfhard Kellmann | Max-Planck-Institut
Unique genome architectures after fertilisation in single-cell embryos
30.03.2017 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
Transport of molecular motors into cilia
28.03.2017 | Aarhus University
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
30.03.2017 | Physics and Astronomy
30.03.2017 | Studies and Analyses
30.03.2017 | Life Sciences