A Highly Expressed Antennae Chemosensory Protein 6 of Dastarcus helophoroides Is Involved in the Recognition of Herbivore-Induced Plant Volatiles

Dastarcus helophoroides, an ecologically friendly biocontrol vector, precisely locates hosts via olfaction-mediated chemoreception to complete its life cycle. Chemosensory proteins (CSPs) mediate this process by binding and transporting odorants. This study characterizes DhelCSP6's role in perceiving herbivore-induced plant volatiles (HIPVs) in D. helophoroides. Quantitative real-time PCR (qRT-PCR) and fluorescence competitive binding assays demonstrated that DhelCSP6, expressed specifically in antennae, binds four of the eight HIPVs. Three-dimensional (3D) structural modeling, molecular docking, and molecular dynamics (MD) simulations revealed that DhelCSP6 features six typical α-helices forming a hydrophobic ligand-binding pocket, with six key residues (Ile89, Leu67, Leu104, Met50, Tyr46, and Tyr108) stably interacting with the four ligands via van der Waals forces. Electroantennographic (EAG) and dual-choice biobehavioral assays demonstrated D. helophoroides perception of and response to p-cymene, γ-terpinene, and fenchone, while DhelCSP6 silencing abolished ligand perception. These findings establish DhelCSP6 as integral to olfactory recognition and chemoreception in D. helophoroides.