Functional Divergence of Two General Odorant-Binding Proteins to Sex Pheromones and Host Plant Volatiles in Adoxophyes orana (Lepidoptera: Tortricidae)

Adoxophyes orana (Lepidoptera: Tortricidae) is a significant polyphagous leafroller that damages trees and shrubs in Rosaceae and other families. However, the molecular mechanisms by which this pest recognizes sex pheromones and host plant volatiles remain largely unknown. Tissue expression profiles indicated that two general odorant-binding proteins (AoraGOBP1 and AoraGOBP2) were more abundant in the antennae and wings of both sexes, with AoraGOBP1 being rich in the female head and abdomen. Temporal expression profiles showed that AoraGOBP1 was expressed at the highest level in 5 day-nmated adults, while AoraGOBP2 exhibited high expression in 5 day-unmated, 7 day-unmated, and mated female adults. Fluorescence competitive binding assays of heterologous expressed AoraGOBPs demonstrated that AoraGOBP2 strongly bound to the primary sex pheromone Z9-14:Ac, and two minor sex pheromones Z9-14:OH and Z11-14:OH, whereas AoraGOBP1 only showed a high binding affinity to Z9-14:Ac. What is more, AoraGOBP1 exhibited a broader binding spectrum for host plant volatiles than AoraGOBP2. Molecular dockings, molecular dynamic simulations, and per-residue binding free decompositions indicated that the van der Waals interaction was the predominant contributor to the binding free energy. Electrostatic interactions between aldehydes, or alcohols and AoraGOBPs stabilized the conformational structures. Phe12 from AoraGOBP1, and Phe13 from AoraGOBP2 were identified as the most important residues that contributed to bind free energy. Our findings provide a comprehensive insight into the molecular mechanisms of olfactory recognition in A. orana, facilitating the development of chemical ecology-based approaches for the control.