Plants are constantly attacked by insects, germs, and other pests, and activate sophisticated defense mechanisms as soon as the enemy is detected. It was thought that raising levels of jasmonates, a class of plant hormones, was necessary for the induction of defenses. By identifying a new class of oxidases acting on jasmonic acid when its levels are very low, the team of Thierry Heitz reveals an unprecedented mode of regulation of the responses controlled by the jasmonates. This work is published in the journal Molecular Plant.
A: In wild leaves (WT), the oxidase JAO2 forms the 12OH-JA derivative, limiting the activation of JA to JA-Ile, to keep the defenses repressed. When JAO2 is inactivated (mutant jao2), the metabolic flux is accentuated towards formation, catabolism and JA-Ile signaling, resulting in a high constitutive defense.
B: Permanent defense in jao2 plants results in high resistance to infection with the fungus Botrytis cinerea.