Functional characterization of the epoxidase gene, Li_epo1 (CYP341B14), involved in generation of epoxyalkene pheromones in the mulberry tiger moth Lemyra imparilis.

Epoxidation of alkenes derived from essential fatty acids is a key step in the biosynthesis of sex pheromones in moth species that utilize alkenyl sex pheromones. The position of the epoxy ring in the pheromone molecule differs depending on the species, thereby conferring diversities on sex pheromones. To date, only one pheromone gland (PG)-specific epoxidase, Hc_epo1 (CYP341B14), has been reported. Hc_epo1, which was identified from an arctiid moth Hyphantria cunea, catalyzes the epoxidation of a double bond at position 9 of the triene, Z3,Z6,Z9-21:H. In the present study, we investigated the PG-specific epoxidase from another arctiid, the mulberry tiger moth Lemyra imparilis, in order to verify whether cytochrome P450 in the CYP341B subfamily, to which Hc_epo1 belongs to, is responsible for the epoxidation of pheromone precursors at position 9 in moths other than H. cunea. A fragment of the Hc_epo1 homolog was amplified from cDNA prepared from the PG of L. imparilis by PCR with degenerate primers. The deduced amino acid sequence of the subsequently cloned homolog, Li_epo1, showed 88.5% identity to Hc_epo1. A functional assay using the Sf9 insect cell line-baculovirus expression system showed that Li_epo1 exhibited epoxidase activity with high selectivity to the double bond at position 9 of two trienes, Z3,Z6,Z9-21:H and Z3,Z6,Z9-23:H, precursors of epoxy diene sex pheromone components in L. imparilis.