Plant resistance to insects induced by application of exogenous jasmonic acid and methyl jasmonate

This article reviews the molecular structures of jasmonic acid (JA) and methyl jasmonate (MJA), the resistance to insects by plants induced by application of exogenous JA and MJA and the induction mechanisms. In many plants, defense systems against insect herbivores can be induced by application of exogenous JA or MJA. Exogenous JA or MJA can activate plant defense genes either via the octadecanoid pathway or acting directly on the genes. Activation of defense genes leads to metabolic reconfiguration to produce the following four types of responses: (1) direct defense: production of toxic compounds, proteinase inhibitors and oxidative enzymes, and behaviour_modifying volatiles against herbivores; (2) indirect defense: production of volatiles for recruiting natural enemies of herbivores; (3) no defense; and (4) negative defense: production of volatiles attractive to herbivores.