jasmonic

Jasmonic refers to jasmonates, a family of oxylipin plant hormones derived from linolenic acid. The best known member is jasmonic acid (JA); related compounds include methyl jasmonate (MeJA) and JA-Ile, the isoleucine conjugate. Collectively they regulate growth, development, and defense responses in plants, especially under biotic and abiotic stress.

Biosynthesis: In chloroplasts, alpha-linolenic acid is released by lipases and converted by lipoxygenase (LOX) to 13-hydroperoxylinolenic acid, then to an unstable allene oxide by AOS and AOC, forming OPDA. OPDA is transported to peroxisomes, reduced and processed to jasmonic acid. JA is subsequently conjugated with isoleucine by JAR1 to form JA-Ile, the bioactive form.

Signaling: JA-Ile binds the COI1-JAZ co-receptor complex, triggering ubiquitination and degradation of JAZ repressors. Free transcription factors, such as MYC2, regulate JA-responsive genes involved in defense proteins, protease inhibitors, and secondary metabolites. JA signaling interacts with other hormone pathways (ethylene, salicylic acid, abscisic acid) to coordinate responses.

Functions and significance: Primary role in plant defense against chewing insects and necrotrophic pathogens; wound response; can modulate root growth, reproductive development in many species; systemic signaling; widespread across land plants, with variation among species.

Applications and notes: MeJA is used in research and agriculture to induce defenses and secondary metabolite production. The jasmonate pathway is a model for plant signaling and has parallels to ethylene and SA pathways. Discovery traces to jasmonic acid in jasmine oil, giving rise to the name jasmonic.