Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cereals use chemical defenses in a multifunctional manner against different herbivores

06.12.2018

A team of scientists from the University of Bern (Switzerland) and the Max Planck Institute for Chemical Ecology and their partners have characterized multiple functions of benzoxazinoids in wheat: The toxic form of the substances makes the plant directly resistant to lepidopteran larvae, whereas a less toxic form regulates indirect defense mechanisms against aphids. Scientists have identified the “switch” between these different functions as a methyltransferase enzyme, which is activated by caterpillar feeding. This switch enables wheat plants to adapt their defense response to different herbivores.

A team of scientists from the University of Bern (Switzerland) and the Max Planck Institute for Chemical Ecology and their partners have characterized multiple functions of benzoxazinoids in wheat:


When wheat is attacked by aphids, the plant produces a less toxic form of benzoxazinoids, which regulates callose production. Callose makes it difficult for aphids to take up plant sap.

Beibei Li and Tobias Züst / University of Bern, Switzerland


Wheat plants which overexpress a maize methyltransferase gene (right) cannot regulate their defense adequately and become susceptible to aphid attack.

Beibei Li / University of Bern, Switzerland

The toxic form of the substances makes the plant directly resistant to lepidopteran larvae, whereas a less toxic form regulates indirect defense mechanisms against aphids. Scientists have identified the “switch” between these different functions as a methyltransferase enzyme, which is activated by caterpillar feeding.

This switch enables wheat plants to adapt their defense response to different herbivores. A comparison with maize shows that a methyltransferase also regulates defense processes in maize against different pest insects. However, the two enzymes in wheat and maize have evolved independently from each other (Science Advances, DOI: 10.1126/sciadv.aat6797, December 5, 2018).

In nature, plants are exposed to a multitude of enemies that feed on their leaves, stems and roots, or feast on their sap. In response to these threats, plants have evolved the capacity to produce secondary metabolites whose functions include preventing herbivores from feeding. Plants can use such defensive substances in a multifunctional manner.

A team of researchers led by Tobias Köllner from the Max Planck Institute for Chemical Ecology and Matthias Erb from the University of Bern has now characterized the function of benzoxazinoids in wheat. The researchers used previously obtained, detailed knowledge about the defensive functions of benzoxazinoids in maize.

In maize plants, the enzyme methyltransferase acts as a functional switch: it decides whether benzoxazinoids act as efficient toxins to protect the plant from caterpillar herbivory, or whether benzoxazinoids are less toxic, but induce callose production. Callose is used as a cell sealant that blocks sieve elements and makes it difficult for the aphids to suck phloem sap.

“Our approach was to introduce the maize switch into wheat and to permanently activate it. Together with our colleagues from the Leibniz Institute of Plant Genetics and Crop Plant Research, we made transgenic wheat plants which were no longer able to choose between toxin production and defense regulation, but constantly produced the toxic form of the benzoxazinoids. This enabled us to elucidate the functions of benzoxazinoids in wheat in detail,” explains Tobias Köllner.

The approach allowed for a thorough analysis of how switching between toxin production and defense regulation affects wheat resistance to lepidopteran larvae and aphids.

Moreover, the scientists were able to identify the corresponding switch in wheat and to analyze it from a biochemical and phylogenetic perspective. Although maize and wheat both produce benzoxazinoids -- their most important defense, via the same, conserved core biosynthetic pathway -- in both species, the genes responsible for switching between their toxic and regulative forms are only distantly related.

Thus, the two cereal species likely evolved this switch independently during the course of evolution. Scientists call this phenomenon “convergent evolution.”

“Convergent evolution is widespread in nature and results from the fact that different species evolve a solution for the same problem independently from each other. It is remarkable that two grasses which produce the same specialized defensive substances evolved the corresponding switch for their use independently of each other.

On one hand, this may be evidence that the ability to use benzoxazinoids for different functions has evolved relatively recently. On the other hand, it highlights the importance of the ability to adapt defense responses specifically to different herbivores.

In our opinion, what we are observing here is the emergence of new regulative mechanisms away from the conserved canon of phytohormones towards more specialized systems,” says Matthias Erb. “Interestingly, plants of the cabbage family also use defensive substances for callose regulation, suggesting that this type of multifunctionality is widespread in the plant kingdom.”

As a next step, the researchers would like to find out how benzoxazinoids control other defensive processes. They are particularly interested in finding an answer to whether there are receptors for benzoxazinoids. If so, these could well be classified as specialized hormones, thus further blurring the boundary between plant toxins and defense regulators. Ultimately, this research could contribute to answering why plants use toxins to regulate defenses in addition to classical plant hormones.

Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail overmeyer@ice.mpg.de
Download of high resolution images via http://www.ice.mpg.de/ext/downloads2018.html

Wissenschaftliche Ansprechpartner:

Prof. Dr. Matthias Erb, Tel. +41 31 631 86 68, E-Mail: matthias.erb@ips.unibe.ch, Institute of Plant Sciences, University of Bern, Switzerland

Dr. Tobias Köllner, Tel. +49 3641 57 1329, E-Mail: koellner@ice.mpg.de, Max Planck Institute for Chemical Ecology, Jena, Germany

Originalpublikation:

Li, B., Förster, C., Robert, C. A. M., Züst, T., Hu, L., Machado, R. A. R., Berset, J.-D., Handrick, V., Knauer, T., Hensel, G., Chen, W., Kumlehn, J., Yang, P., Keller, B., Gershenzon, J., Jander, G., Köllner, T. G., Erb, M. (2018). Convergent evolution of a metabolic switch between aphid and caterpillar resistance in cereals. Science Advances 4:eaat6797, DOI: 10.1126/sciadv.aat6797
https://doi.org/10.1126/sciadv.aat6797

Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
Further information:
http://www.ice.mpg.de/

More articles from Agricultural and Forestry Science:

nachricht Are cover crops negatively impacting row crops?
30.07.2020 | American Society of Agronomy

nachricht Space to grow, or grow in space -- how vertical farms could be ready to take-off
14.07.2020 | John Innes Centre

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

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

Im Focus: New Strategy Against Osteoporosis

An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.

Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...

Im Focus: AI & single-cell genomics

New software predicts cell fate

Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

Im Focus: NYUAD astrophysicist investigates the possibility of life below the surface of Mars

  • A rover expected to explore below the surface of Mars in 2022 has the potential to provide more insights
  • The findings published in Scientific Reports, Springer Nature suggests the presence of traces of water on Mars, raising the question of the possibility of a life-supporting environment

Although no life has been detected on the Martian surface, a new study from astrophysicist and research scientist at the Center for Space Science at NYU Abu...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Study clarifies kinship of important plant group

05.08.2020 | Life Sciences

Human cell-based test systems for toxicity studies: Ready-to-use Toxicity Assay (hiPSC)

05.08.2020 | Life Sciences

Molecular Forces: The Surprising Stretching Behaviour of DNA

05.08.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>