Chapter 12 - Jasmonates and Other Defense-Related Compounds

Abstract

Jasmonic acid (JA) and its methylated derivative, methyl jasmonate, play major roles in plant defense against insect herbivores and microbial pathogens. They do so by inducing the synthesis of enzymes such as proteinase inhibitors and chitinases, and volatile aldehydes and oxoacids. Jasmonates share many activities with abscisic acid, including inhibition of growth of stems and roots, inhibition of seed germination, and induction of some seed storage protein genes. They also share some responses with ethylene in fruit ripening and in senescence and abscission. Mutants in JA biosynthesis are known from tomato and Arabidopsis; both mutants are defenseless against insect herbivores because they cannot synthesize defense-related proteins. Many related compounds or JA metabolites occur naturally in plants. Except for some, their roles are uncertain. Tuberonic acid may have a role in tuber formation in crops such as potato and yam. Cucurbic acid, like JA, inhibits cell growth and is also reported to induce tuberization. A JA-related compound, 12-oxo-trans-10-dodecenoic acid, derived via the hydroperoxy lyase (HPL) pathway, acts similarly to traumatic acid in promoting cell divisions in a bioassay, but many other fatty acids and their derivatives also give a positive response in the bioassay. The role of these metabolites and related compounds in the regulation of endogenous levels of jasmonic acid is unclear.