Molecular Recognition of Kairomones with Two Olfactory-Related Proteins in the Bean Weevil (Callosobruchus chinensis)

Callosobruchus chinensis (Coleoptera: Chrysomelidae) is a significant pest of legumes, causing serious losses. Odorant-binding proteins play a crucial role in regulating the behaviors of insects, including mating and oviposition. In this study, we identified 11 novel CchiOBPs and analyzed the expression levels of these CchiOBPs in different tissues. Seven candidate CchiOBPs were selected by expression correlation analysis after 2,3-butanediol induction. Notably, silencing of CchiOBP6 and CchiOBP7 significantly diminished the behavioral and electroantennogram responses to 2,3-butanediol, suggesting the two CchiOBPs may participated in response to 2,3-butanediol. The fluorescence competitive binding assays indicated that the CchiOBP6 and CchiOBP7 proteins exhibited a strong binding affinity for 2,3-butanediol. The site-directed mutagenesis of CchiOBP6 and CchiOBP7 showed a significant reduction in binding affinity for 2,3-butanediol. These findings confirm that CchiOBP6 and CchiOBP7 play a significant role in recognition for 2,3-butanediol and could facilitate the novel RNAi targets for controlling C. chinensis in the future.