Screening of behaviorally active compounds based on the interaction between two chemosensory proteins and mung bean volatiles in Callosobruchus chinensis.

Chemosensory proteins (CSPs) are involved in the earliest steps of the olfactory process by binding and transporting odorants and play a crucial role in the insect's search for food and egg-laying sites. In the present study, the tissue expression profiles showed that both CchiCSP3 and CchiCSP5 of Callosobruchus chinensis were highly expressed in the adult antennae. Subsequently, the recombinant CchiCSP3 and CchiCSP5 proteins were analysed using fluorescence competitive binding assays, and both showed binding affinities for the three mung bean volatiles. Molecular docking and site-directed mutagenesis revealed four key amino acid residues in CchiCSP3 (L47, W80, Y81, and L84) and CchiCSP5 (Y28, K46, L49, and I72). Electroantennogram (EAG) and dual-choice biobehavioral assays showed that the antennae of adult C. chinensis were electrophysiologically active in response to stimulation with all three behaviorally active compounds and that octyl 4-methoxycinnamate and β-ionone had a significant luring effect on adult C. chinensis, whereas vanillin had a significant avoidance effect. Our study screened three effective behaviorally active compounds based on the involvement of two CchiCSPs in the recognition of mung bean volatiles, providing an opportunity to develop an alternative control strategy using behavioral disruptors to limit the impact of pests.