Jasmonate

Jasmonate (JA) and its derivatives are lipid-based plant hormones that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herbivory and plant responses to poor environmental conditions and other kinds of abiotic and biotic challenges. Some JAs can also be released as volatile organic compounds (VOCs) to permit communication between plants in anticipation of mutual dangers. The isolation of methyl jasmonate (MeJa) from jasmine oil derived from Jasminum grandiflorum led to the discovery of the molecular structure of jasmonates and their name in 1962 while jasmonic acid itself was isolated from Lasiodiplodia theobromae by Alderidge et al in 1971. Biosynthesis is reviewed by Acosta and Farmer 2010, Wasternack and Hause 2013, and Wasternack and Song 2017. Jasmonates (JA) are oxylipins, i.e. derivatives of oxygenated fatty acid. They are biosynthesized from linolenic acid in chloroplast membranes. Synthesis is initiated with the conversion of linolenic acid to 12-oxo-phytodienoic acid (OPDA), which then undergoes a reduction and three rounds of oxidation to form (+)-7-iso-JA, jasmonic acid. Only the conversion of linolenic acid to OPDA occurs in the chloroplast; all subsequent reactions occur in the peroxisome. JA itself can be further metabolized into active or inactive derivatives. Methyl JA (MeJA) is a volatile compound that is potentially responsible for interplant communication. JA conjugated with amino acid isoleucine (Ile) results in JA-Ile ((+)-7-iso-jasmonoyl--isoleucine), which Fonseca et al 2009 finds is involved in most JA signaling - see also the review by Katsir et al 2008. However Van Poecke & Dicke 2003 finds Arabidopsiss emission of volatiles to not require JA-Ile, nor VanDoorn et al 2011 for Solanum nigrums herbivore resistance. JA undergoes decarboxylation to give cis-jasmone. Although jasmonate (JA) regulates many different processes in the plant, its role in wound response is best understood.