Discovery of wheat's clustered chemical defenses creates new avenues for research

Date:
April 13, 2022
Source:
John Innes Centre
Summary:
Research collaboration has helps to explain the chemical defenses
that protect wheat plants against disease.



FULL STORY ==========================================================================
A research collaboration has helped to explain the chemical defenses that protect wheat plants against disease -- opening potential new avenues
of study in this globally cultivated crop.


========================================================================== Researchers at the John Innes Centre leveraged recent advances in mapping
of bread wheat's complex genome to make the discovery.

The Osbourn and Uauy groups collaborated to generate data that led to
the discovery of several sets of genes in wheat that are switched on
when the plant is attacked by disease-causing microbes.

These genes are found in six so-called biosynthetic gene clusters in
the wheat genome. Gene clusters that produce defense molecules have also previously been found in other cereal crops such as oat and rice.

To find out what chemicals are produced by these clusters the researchers isolated genes of interest and introduced them into the plant Nicotiana benthamiana, a close relative of tobacco. This transient expression
technique enabled rapid analysis of the biochemical pathways encoded by
the clusters.

The researchers found that the clusters encoded a versatile set of
molecules including triterpenes, diterpenes and flavonoids, including
a previously unknown molecule which was named ellarinacin.



==========================================================================
The group are continuing their work on deciphering other molecules
produced by the gene clusters and understanding how they contribute to protection of wheat against pests and disease.

Wheat is one of the most important cereal crops and supplies one fifth
of the calories consumed by humans worldwide. Despite its agricultural importance, little is known about the chemicals wheat produces in response
to pest and pathogen attacks.

Knowing genetic pathways produce certain useful chemicals means that
these gene combinations could be bred into wheat varieties to make them
more resistant to diseases at a time when climate change is making this
more of a problem.

The study which appears in the journal PNAS also found that Brachypodium distachyon, a wild grass relative of wheat contained a pathogen-induced variation of the Ellarinacin cluster, which produces a structurally
similar compound, brachynacin.

The paper highlights the start of a significant new direction for wheat research explains Dr Polturak.

"Our genomics-driven approach has allowed us to identify compounds that
are produced in wheat only under certain conditions -- in this case
pathogen attack. Finding these molecules by the 'classical' approach of chemical analysis of wheat extracts would be challenging." Professor Anne Osbourn, a group leader at the John Innes Centre and an author of the
paper said: "From knowing little about wheat defense compounds, we have
now discovered six previously unknown pathways for biosynthesis of defence compounds in wheat, including entirely new chemicals that haven't been
reported before. Our work continues, to investigate what these molecules
are doing in wheat, how they contribute to defence against pathogens,
and how the whole network of pathogen-induced gene clusters is regulated."

========================================================================== Story Source: Materials provided by John_Innes_Centre. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Guy Polturak, Martin Dippe, Michael J. Stephenson, Rajesh Chandra
Misra,
Charlotte Owen, Ricardo H. Ramirez-Gonzalez, John F. Haidoulis,
Henk-Jan Schoonbeek, Laetitia Chartrain, Philippa Borrill,
David R. Nelson, James K.M. Brown, Paul Nicholson, Cristobal
Uauy, Anne Osbourn. Pathogen- induced biosynthetic pathways
encode defense-related molecules in bread wheat. Proceedings
of the National Academy of Sciences, 2022; 119 (16) DOI:
10.1073/pnas.2123299119 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413131207.htm

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