The function of Jasmonic acid in induced plant defence
茉莉酸在植物诱导防御中的作用

Jasmonic acid (JA) and methyl jasmonate (MeJA) are wound-related hormone and signal molecules found in most plants that, when applied exogenously, can stimulate the defensive genes to increase the chemical levels of induced defenses in the patterns similar to those induced by wounding or insect feeding. Numerous studies show that they can systemically activate the activity of proteinase inhibitors (PI) and polyphenol oxidases (PPO) in the treated plants, which appear to function as an anti-nutritive defense against herbivores. Jasmonic acid and methyl jasmonate can also increase the level of activity of other defensive proteins such as peroxidase (POX), Chitinase and lipoxygenase(LOX), resulting in the accumulation of some secondary metabolites, including alkaloid and phenolic compounds, as well as the emission of volatiles and the formation of defensive structures, such as trichomes and traumatic resin ducts. Thus, the toxic effect of the treated plants increases herbivore mortality while the volatiles attract more parasitoids and herbivore predators than uninduced plants. The airborne phase compound , methyl jasmonate, can realize long-distance signal transportation through hydrolyzing to jasmonic acid, enabling communication among the contiguous plants. Jasmonate consists of a cyclopentane ring with a ketone group. They have four possible stereoisomers respectively since the chiral center can have either an R or S absolute configuration. The cis orientation is more biologically active but less stable, and will epimerize to the more stable trans configuration (Z)-jasmone, a volatile metabolite of jasmonic acid and electrophysiologically active to insects, while its possible signaling role is qualitatively different from that of the biosynthetically related JA and MeJA.