Binding characteristics and physicochemical basis of C ‐minus odorant‐binding protein 8 in western flower thrips, Frankliniella occidentalis , with various host vegetable volatiles

Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a globally invasive polyphagous pest that relies on olfaction to sense host plants. Odorant‐binding proteins (OBPs) in insect sensillar lymph mediate interactions with plant volatiles. However, the physicochemical mechanisms by which OBPs in F. occidentalis bind to host‐plant volatiles, the key amino acid residues involved in these interactions and the structural characteristics of the preferred ligands remain unclear. Here, we cloned a novel OBP, Focc OBP8, which belongs to the C‐minus OBP subfamily based on sequence alignment and phylogenetic analyses. Competitive fluorescence binding assays using purified recombinant Focc OBP8 revealed broad binding interactions towards host‐plant volatiles. Notably, 4‐ethylacetophenone and ethyl isonicotinate showed the strongest binding affinity with dissociation constants ( K D ) of 2.00 and 2.46 μmol/L, respectively. Thermodynamic analyses indicated the binding processes were dynamic quenching processes and mainly driven by hydrophobic interactions, spontaneously. Molecular docking and the corresponding residue‐interaction energy heatmap analyses predicted that the conserved Gln4 residue contributed substantially to the ligand‐protein interactions. Molecule clustering and structural analyses predicted that the ligands containing aromatic moieties π–π conjugated with the carbonyl group or carbon–carbon double bond preferentially bound to Focc OBP8. This study elucidates the broad binding profiles of Focc OBP8 with ligands and their physicochemical basis, providing insights into the olfactory‐driven polyphagia of WFT and theoretical foundations for developing odour‐based attractants or repellents targeting this invasive pest.