Cereals use chemical defenses in a multifunctional manner against different herbivores

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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 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.