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

<i>Dastarcus helophoroides</i>, 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 <i>D. helophoroides</i>. 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 <i>D. helophoroides</i> perception of and response to <i>p</i>-cymene, γ-terpinene, and fenchone, while <i>DhelCSP6</i> silencing abolished ligand perception. These findings establish DhelCSP6 as integral to olfactory recognition and chemoreception in <i>D. helophoroides</i>.