Involvement of a novel cytochrome P450 CYP6HX3 from a specialist herbivore, Pagiophloeus tsushimanus, in the metabolism of host-plant terpenoids

Abstract

Cytochromes P450 have been confirmed to be involved in plant terpenoid biosynthesis and the degradation and metabolism of exogenous terpenoids in herbivorous organisms. Nevertheless, the underlying molecular mechanisms of P450-mediated terpenoid metabolism in numerous non-model insects remain largely unclear, which impedes our understanding of the chemical interactions between plants and insects. Herein, we identified a novel P450 gene belonging to CYP6 family, designated as CYP6HX3, from a specialist herbivore on camphor trees, Pagiophloeus tsushimanus. CYP6HX3 transcripts were constitutively abundant in the gut and fat body of larvae, and its expression in various tissues (except for head) was significantly induced by specific terpenoids in camphor trees (D-camphor, linalool, and eucalyptol) to varying degrees. Additionally, the CYP6HX3 protein model was constructed accurately, and it could stably bind to the three terpenoid molecules mainly via hydrophobic forces. The capability of CYP6HX3 to metabolize the three terpenoids was verified using metabolic assays in vitro, and this monooxygenase catalyzed the epoxidation of linalool to (R/S)-furanoid-linalool oxide. These results will enhance our understanding of insect metabolic resistance to natural chemicals and offer new targets for pest management.