Jasmonic acid

Jasmonic acid was first isolated in 1962 from the essential oil of Jasminum grandiflorum by the Swiss chemist Edouard Demole and colleagues, who identified its structure as a cyclopentanone derivative.¹ Its biosynthesis begins with α-linolenic acid released from chloroplast membranes, which is converted through the octadecanoid pathway: lipoxygenase (LOX) adds oxygen, allene oxide synthase (AOS) and allene oxide cyclase (AOC) form 12-oxo-phytodienoic acid (OPDA), and OPDA reductase plus three rounds of β-oxidation yield jasmonic acid.² The pathway is shared with the production of the volatile methyl jasmonate, which acts as an airborne signal between plants.

The active form of jasmonic acid is its conjugate with isoleucine, JA-Ile, which is perceived by the F-box protein COI1 as part of the SCF^COI1 E3 ubiquitin ligase complex.³ In the absence of JA-Ile, JAZ (jasmonate ZIM-domain) repressors bind to transcription factors such as MYC2 and inhibit their activity. When JA-Ile accumulates, it promotes the binding of COI1 to JAZ proteins, leading to JAZ ubiquitination and degradation by the 26S proteasome, thereby releasing MYC2 to activate jasmonate-responsive genes.⁴ This pathway is tightly regulated by negative feedback, including the induction of JAZ genes themselves, and is modulated by other hormones such as salicylic acid and ethylene.

Jasmonic acid orchestrates a wide range of developmental and stress responses. It is essential for reproductive development, including male fertility in Arabidopsis thaliana, where mutants defective in JA biosynthesis are male-sterile due to anther dehiscence failure.⁵ In defense, JA triggers the accumulation of proteinase inhibitors, alkaloids, and volatile organic compounds that attract natural enemies of herbivores. It also mediates resistance to necrotrophic pathogens, wounding responses, and systemic signaling. Additionally, JA influences root growth, senescence, and the formation of glandular trichomes.

Beyond its canonical roles, jasmonic acid has several niche functions. It is involved in the production of secondary metabolites such as nicotine in tobacco and artemisinin in Artemisia annua, making it a target for metabolic engineering.⁶ JA also modulates plant–microbe interactions, including mycorrhizal symbiosis and the suppression of beneficial rhizobacteria. In some species, JA promotes the closure of the Venus flytrap (Dionaea muscipula) after prey capture. Furthermore, methyl jasmonate is used in agriculture as an elicitor to enhance the production of bioactive compounds in cell cultures. The discovery of the COI1–JAZ co-receptor complex was a landmark in understanding hormone perception, and the pathway is conserved across land plants, including mosses.

JAZ proteins

Jasmonate ZIM-domain repressors that inhibit transcription factors until degraded upon JA-Ile perception.

Octadecanoid pathway

The biosynthetic route from α-linolenic acid to jasmonic acid via LOX, AOS, AOC, and β-oxidation.

Methyl jasmonate

A volatile derivative of jasmonic acid that acts as an airborne signal.