OBP2 in the Midlegs of the Male <i>Bactrocera dorsalis</i> Is Involved in the Perception of the Female-Biased Sex Pheromone 4-Allyl-2,6-dimethoxyphenol

Abstract

Short-range semiochemicals convey individual-specific information, which is important for final successful courtship and copulation. In this study, an electroantennography (EAG) instrument was used to determine the legs of male <i>Bactrocera dorsalis</i> that might participate in the perception of 4-allyl-2,6-dimethoxyphenol (4-DMP), a female-biased cuticular hydrocarbon (CHC) component. By performing comparative RNA-seq analysis, nine differentially expressed OBPs between 4-DMP-stimulated (M_4-DMP) and unstimulated (M) male flies were screened out. Among the four downregulated OBPs, <i>Bdor</i>OBP2 exhibited the strongest binding to 4-DMP than <i>Bdor</i>OBP4, <i>Bdor</i>OBP19a, and <i>Bdor</i>OBP56h. Functional analyses confirmed that the reduction in transcript abundance of <i>Bdor</i>OBP2 led to a significant decrease in behavioral responses of male flies to 4-DMP. <i>In silico</i> simulation revealed dramatic changes in the key residues and conformation between the two complexes, implying that <i>Bdor</i>OBP2 might activate different receptors after binding to 4-DMP or methyl eugenol (ME). The results of this study suggest that <i>Bdor</i>OBP2 mediates behavioral responses to 4-DMP and could be a promising molecular target for strategies of pest control.