Scientists decode chemical defense against plant sap-sucking leafhoppers
Date:
February 3, 2022
Source:
Max Planck Institute for Chemical Ecology
Summary:
Given the sheer number of potential enemies, plants are
resistant to most pests, even if they can cause damage to other
plants. Researchers describe a newly discovered mechanism
that protects a wild tobacco species from plant sap-sucking
leafhoppers. By combining different genetic screening methods with
the study of chemical changes in tobacco leaves, they identified a
previously unknown defense substance important for the tobacco's
resistance to leafhoppers and characterized the genes for its
biosynthesis.
FULL STORY ========================================================================== Plants are at the bottom of the food chain and are continually threatened
by pathogens and herbivorous insects. But the vast majority of attackers
are unable to cause any damage due to a broadly based plant resistance,
also known as non-host resistance. This resistance is permanent
and effective. However, the mechanisms that lead to this resistance, particularly to herbivorous pests, are largely unknown. In a new study, researchers at the Max Planck Institute for Chemical Ecology were able to identify a chemical substance responsible for the resistance of Nicotiana attenuata plants to sucking leafhoppers (Empoasca spp.) and the genes
needed for its production. "Our research uncovered how native plants
use chemical reprogramming to defend themselves against opportunistic leafhoppers in nature," first author Yuechen Bai says, summarizing
the results.
==========================================================================
In 2004, scientists at the institute had already discovered in field
studies that tobacco plants impaired in their defense-signaling cascade
based on the plant hormone jasmonic acid were attacked by leafhoppers,
insects that are usually not able to harm tobacco plants with functional defenses. The work proved that, in nature, plants are permanently
"tested" by herbivorous insects in order to find out whether they can
serve as a food source; however, in most cases the plants are able to
defend themselves effectively. Consistent with these findings, another
study by the institute showed that leafhoppers colonized the very plants
in natural tobacco populations whose jasmonic acid signaling pathway
was weaker than in other tobacco plants. "However, at that time, it was
still unknown which specific defense mechanisms triggered by jasmonic acid
were responsible for resistance to the leafhoppers," explains Dapeng Li,
one of the study leaders.
To answer this question, the scientists crossed 26 genetically different natural parental lines. This population, which the research team had
crossed according to a fixed scheme over a total of nine years, was
planted out in its natural habitat in Arizona, USA, where it could be
attacked by opportunistic leafhoppers. When leafhoppers attacked these
plants, the severity of the damage helped identify the genetic basis
that made this particular plant a host plant for leafhoppers taking
advantage of weak defenses.
The researchers also investigated which chemical changes are elicited
in the plants after attack and which genes are activated. They
found a new unstable substance, for which they used the abbreviation
CPH (caffeoylputrescine-green- leaf-volatile compound), which was
responsible for permanent resistance to leafhoppers. Through bioinformatic detective work and by using plants that were specifically modified in
certain defense and signal transduction genes, they were able to show
which three metabolic pathways were involved in the production of this chemical. Finally, the researchers even succeeded in reconstituting the biosynthetic pathway for the defense substance CPH in two related plants,
the field bean Vicia faba and the tomato species Solanum chilense,
and demonstrating its efficacy against leafhoppers.
"By combining sophisticated molecular biology and chemical analysis
methods, we were able to identify and characterize not only a previously unknown defense substance, but also the genes responsible for its
synthesis," explains Ian Baldwin, and continues: "Our approach can be
described as "natural history- guided forward genetics. Natural history
and the observation of the feeding behavior of leafhoppers has driven our discovery process. Because when it comes to chemistry, nature remains
the mother of invention." In further studies, the researchers want to
find out how the synthesis of this chemical defense is coordinated in
the plant and which other factors and specific regulators are crucial
for its production, especially under natural conditions. Leafhoppers
of the genus Empoasca, especially the potato leafhopper Empoasca fabae,
can cause major crop damage by sucking on the leaves of young plants and transmitting viral diseases. Higher temperatures have led to a threatening spread of these insects. This basic research to control such a pest can
provide valuable insights with regard to permanently improved resistance
in crops, especially in the context of new demands on agriculture caused
by climate change.
========================================================================== Story Source: Materials provided by
Max_Planck_Institute_for_Chemical_Ecology. Note: Content may be edited
for style and length.
========================================================================== Journal Reference:
1. Yuechen Bai, Caiqiong Yang, Rayko Halitschke, Christian Paetz, Danny
Kessler, Konrad Burkard, Emmanuel Gaquerel, Ian T. Baldwin,
Dapeng Li.
Natural history-guided omics reveals plant defensive chemistry
against leafhopper pests. Science, 2022; 375 (6580) DOI:
10.1126/science.abm2948 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/02/220203160617.htm
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