Odorant binding protein C12 is involved in the defense against eugenol in Tribolium castaneum

Tribolium castaneum (T. castaneum) is a worldwide pest of stored grain that mainly harms flour, and not only causes serious loss of flour quality but also leads to deterioration of flour quality. Chemical detection plays a key role in insect behavior, and the role of odorant-binding proteins (OBPs) in insect chemical detection has been widely studied. However, the mechanism of OBPs in insect defense against exogenous toxic substances is still unclear. In this study, biochemical analysis showed that eugenol, the active component of A. vulgaris essential oil, significantly induced the expression of the OBP gene OBPC12 from T. castaneum (TcOBPC12). The mortality of late larvae treated with eugenol was higher than that of the control group after RNA interference (RNAi) against TcOBPC12, which indicates that the OBP gene is involved in the eugenol defense mechanism and leads to a decrease in sensitivity to eugenol. Tissue expression profiling showed that the expression of TcOBPC12 in the epidermis, hemolymph, and intestine was higher than in other larval tissues, and TcOBPC12 was expressed mainly in the epidermis, head, and fat body of adults. The developmental expression profile showed that the expression of TcOBPC12 in late eggs, early and late larval stages, and late adult stages was higher than in other developmental stages. These data suggest that TcOBPC12 may be involved in the absorption of exogenous toxic substances by the larvae from T. castaneum. Our results provide a theoretical basis for the metabolism and degradation mechanism of exogenous toxic substances and help explore more potential target genes of insect pests.