Odorant-Binding Protein Interactions with Herbivore-Induced Volatiles Drive Behavioral Attraction of Harmonia axyridis (Coleoptera: Coccinellidae) to Tuta Absoluta-Infested Tomato Plant

Tuta absoluta severely constrains global tomato production. We investigated the behavioral attraction of Harmonia axyridis to infested plants and the molecular basis of herbivore-induced plant volatile (HIPV) recognition. Y-tube bioassays showed statistically significant attraction of H. axyridis to the infested plant (χ2 = 13.72, P < 0.05). Molecular docking showed strong HaxyOBP-HIPV interactions, with predicted binding energies reaching −7.6 kl mol–1 and ligand efficiencies of more than 0.30 kl mol–1 per heavy atom. HaxyOBP13, HaxyOBP19, and HaxyOBP23 were found to have the most stable complexes with 1,3-cyclohexadiene-1-carboxaldehyde, 2,6,6-trimethyl, 1-methyl-3-(1-methylethyl), and beta-phellandrene during 100 ns molecular dynamics simulations, maintaining RMSD values within 0.15–0.30 nm. The competitive binding assays confirmed micromolar affinities, with dissociation constants (Kd) ranging between 6.45 and 14.58 μM. These behavioral, computational, and biochemical findings define important OBPs that mediate the perception of HIPV in H. axyridis, which forms the basis of volatile-mediated improvement of biological control measures against T. absoluta.