O-methyltransferase variation enables a specific volatile alarm call in rice

Plants emit volatile compounds that orchestrate complex ecological interactions, with methylated catabolites of interaction-induced phytohormones being common examples. Salicylic acid (SA) mediates plant antipathogen responses, while its methylated derivative, MeSA, broadly mediates plant-insect interactions without specificity. Here, we identified dimethyl salicylate (DMSA), an unappreciated dimethylated SA catabolite, emitted by rice when attacked by the major destructive pest, the brown planthopper. DMSA biosynthesis requires an O-methyltransferase cascade, BSMT1 (benzoic acid/salicylic acid carboxyl methyltransferase 1)-MSOMT (methyl salicylate O-methyltransferase), which is directly activated by a jasmonate (JA)-responsive MYC2-JAMYB transcriptional cascade. Natural variation in the MSOMT promoter confers its herbivory-induced expression in indica but not japonica cultivars. Functionally, DMSA acts as a specific volatile signal attracting the egg-parasitoid wasps of brown planthoppers (BPHs) without mediating direct resistance, which demonstrably suppresses BPH populations in paddy fields. DMSA is an optimized advance in SA signaling derived plant "alarm calls" with great potential in sustainable rice pest management.