Identification of an adult attractant for Anomala corpulenta by the reverse chemical ecology approach

Semiochemicals are dominant cues for insects to locate food, mates, predators, and oviposition sites. In the modern genomic era, semiochemicals have been identified not only by the conventional chemical ecology based on bioassay-guided protocols but also by reverse chemical ecology started with deorphanization of olfactory proteins with high olfactory sensitivity and selectivity. The Scarab beetle, Anomala corpulenta, is a polyphagous pest, posing a substantial economic burden to agricultural, horticultural, and forestry industries. Here, we focused on four odorant receptors (ORs) abundantly expressed in the antennae. We heterologously expressed them in Xenopus oocytes and examined their responses to a panel of 22 odorants. Of the ORs, AcorOR29 was specifically tuned to a common floral compound, phenethyl propionate (PEP). Further, gas chromatography coupled with electroantennographic detection showed that PEP elicited a strong electrophysiological response from antennae. Y-tube olfactometer assay and field trap experiment demonstrated that PEP is attractive for both sexes of A. corpulenta across a wide range of concentrations, potentiating PEP in practical applications. Our results show that the reverse chemical ecology approach is effective in identifying semiochemicals for A. corpulenta, which would help to formulate novel strategies to control this pest.