Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Toxic Breath Keeps Spiders Away

02.01.2014
Tobacco hornworm larvae exhale a small fraction of nicotine from ingested tobacco leaves as a defense signal to deter predatory spiders

Caterpillars use different strategies to protect themselves from their enemies; many are camouflaged, while others use their bright colors as warning signals, have stinging hairs or secrete toxic substances, some even take threatening postures.


Interaction between the caterpillar Manduca sexta and the spider Camptocosa parallela. The caterpillars nicotin breath frigthens the spider.

Danny Kessler; Grafics: Pavan Kumar and Sagar Pandit, MPI chem Ökol.


Spider Camptocosa parallela attacks a caterpillar.
Pavan Kumar, MPI chem. Ökol.

Scientists at the Max Planck Institute for Chemical Ecology have now discovered a previously unknown protective mechanism: Tobacco hornworm larvae can exhale a small fraction of nicotine they ingest as they feed on tobacco leaves.

To do so, they transfer some of the nicotine they ingest into their hemolymph (insect blood) from which a “defensive halitosis” is created that repels a major predator.

These insights were made possible by combining molecular techniques with a natural history approach in field experiments in the native habitat of the study organisms. (Proceedings of the National Academy of Sciences of the United States of America, December 30; 2013, DOI 10.1073/pnas.1314848111)

The importance of the ecosystem for studying gene functions

Understanding the function of genes is a central objective of biological research. Ultimately, genes function at the level of the organism, where their influence on an organism’s Darwinian fitness determines whether a gene is retained, modified or lost from genomes over evolutionary time. Gene silencing is a successful research method used to identify the function of individual genes and their relevance for the survival and fitness of an organism.

In addition to a gene’s biochemical and physiological roles that can be studied in the laboratory, the ecological role of a gene needs to be studied, and for this, there can be no better laboratory than the organism’s natural habitat. Scientists from the Department of Molecular Ecology headed by Ian Baldwin pioneer this approach and call it an unbiased, “ask the ecosystem” approach.

“Nature is our most important teacher,” Ian Baldwin emphasizes. “Nature is the arbitrator of who survives. Elucidation of gene functions is only possible if you study organisms in their native environment − including all the unknowns of the wild.”

For their field experiments, researchers planted tobacco plants that were deficient in producing nicotine. In addition, they used a plant-mediated RNAi technique to silence a cytochrome P450 enzyme in the midgut of tobacco hornworm larvae (see press release “Yellow Biotechnology: Using plants to silence insect genes in a high-throughput manner”, February 2, 2012) which is usually activated by nicotine ingested when the larvae feed on tobacco leaves. The scientists then observed what happened to caterpillars feeding on nicotine-deficient plants in order to compare their fate with those caterpillars that had ingested nicotine but lacked the active catalyzer for the toxin in their midgut.

Predatory spider assists the process of elucidating a defense mechanism

The function of the cytochrome P450 proved hard to reveal by laboratory-based experiments, but then the researchers received unexpected support from a wolf spider Camptocosa parallela. Surprisingly, the nocturnal predator preferably preyed not only on larvae that fed on nicotine-free leaves, but also preyed on their cytochrome P450-silenced conspecifics that were deficient in their response to nicotine in the food. The gene must therefore have played an important role in a spider defense mechanism that usually excludes the spider from the list of Manduca sexta’s enemies.

Further analysis revealed that the enzyme plays a role in transporting the ingested nicotine from midgut to the hemolymph which allows the nicotine to be exhaled out the spiracles, the nose-equivalents of the caterpillars. Caterpillars exhale a small fraction of this nicotine. And this functions as an anti-spider signal. Other predators of Manduca sexta, such as bugs or antlions, seem to be completely insensitive to this defensive halitosis.

Nicotine, the defensive substance in their host plant, is too toxic for the larvae to sequester. Most of it is excreted. That the larvae repurposes only a tiny amount of the toxin for their own defense in order to ward off spiders with a kind of toxic halitosis came as a surprise for the scientists. “This case of toxic breath as a defense is unique,” says Ian Baldwin. The example of the wolf spider illustrates the importance of combining molecular biology and natural history to understand the function of genes at the level of the organism. [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 anti-predator herbivore defense. Proceedings of the National Academy of Sciences of the United States of America. DOI 10.1073/pnas.1314848111

http://dx.doi.org/10.1073/pnas.1314848111

Further Information:
Prof. Dr. Ian T. Baldwin, Max-Planck-Institut für chemische Ökologie, E-Mail baldwin [at] ice.mpg.de, Tel.: +49 3641 57 1101

Download of movies and high resolution pictures on www.ice.mpg.de/ext/735.html

Angela Overmeyer | Max-Planck-Institut
Further information:
http://www.ice.mpg.de/ext/735.html

More articles from Life Sciences:

nachricht A new molecular player involved in T cell activation
07.12.2018 | Tokyo Institute of Technology

nachricht News About a Plant Hormone
07.12.2018 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

Im Focus: Substitute for rare earth metal oxides

New Project SNAPSTER: Novel luminescent materials by encapsulating phosphorescent metal clusters with organic liquid crystals

Nowadays energy conversion in lighting and optoelectronic devices requires the use of rare earth oxides.

Im Focus: A bit of a stretch... material that thickens as it's pulled

Scientists have discovered the first synthetic material that becomes thicker - at the molecular level - as it is stretched.

Researchers led by Dr Devesh Mistry from the University of Leeds discovered a new non-porous material that has unique and inherent "auxetic" stretching...

Im Focus: The force of the vacuum

Scientists from the Theory Department of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science (CFEL) in Hamburg have shown through theoretical calculations and computer simulations that the force between electrons and lattice distortions in an atomically thin two-dimensional superconductor can be controlled with virtual photons. This could aid the development of new superconductors for energy-saving devices and many other technical applications.

The vacuum is not empty. It may sound like magic to laypeople but it has occupied physicists since the birth of quantum mechanics.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

Expert Panel on the Future of HPC in Engineering

03.12.2018 | Event News

Inaugural "Virtual World Tour" scheduled for december

28.11.2018 | Event News

 
Latest News

A new molecular player involved in T cell activation

07.12.2018 | Life Sciences

High-temperature electronics? That's hot

07.12.2018 | Materials Sciences

Supercomputers without waste heat

07.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>