A herbivore-inducible CYP82 catalyzes DMNT formation in Idesia polycarpa leaves

Herbivore-induced volatile organic compounds (HIPVs) are important components of plant defense, but the molecular basis of their biosynthesis in woody plants remains poorly understood. Among HIPVs, the homoterpenes (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are well-characterized herbivore-induced volatiles in herbaceous plants, whereas their biosynthesis in woody species remains largely unexplored. Here, we characterized herbivore-induced volatile emissions from Japanese orange cherry (Idesia polycarpa) leaves following feeding by gypsy moth caterpillars (Lymantria dispar) and investigated the molecular basis of homoterpene HIPV biosynthesis in this perennial woody species.

Herbivory substantially altered the volatile emission profile of I. polycarpa leaves, leading to strong induction of mono- and sesquiterpenes and particularly high emission of the C₁₁ homoterpene DMNT, whereas the C₁₆ homoterpene TMTT was not detected. These changes were accompanied by elevated jasmonic acid and jasmonate-derived metabolites in damaged leaves. Comparative transcriptome analysis identified a CYP82-family cytochrome P450 monooxygenase and two TPS-g terpene synthases as candidate genes involved in DMNT biosynthesis. Biochemical assays showed that IpCYP82L45 converts (E)-nerolidol into DMNT in vitro, while heterologous expression in Nicotiana benthamiana demonstrated that IpTPS15 and IpTPS3 produce (E)-nerolidol and linalool, respectively. Co-expression of IpTPS15 and IpCYP82L45 in N. benthamiana reconstituted DMNT production in planta. Furthermore, no diterpene synthase capable of producing (E,E)-geranyllinalool, the precursor of TMTT, was identified in I. polycarpa, consistent with the absence of TMTT emission.

These findings establish a likely jasmonate-associated DMNT biosynthetic pathway in I. polycarpa involving the coordinated activity of IpTPS15 and IpCYP82L45. This work advances the molecular understanding of herbivore-induced volatile biosynthesis in non-model woody species and provides new insights into terpene-mediated defense mechanisms in trees.