Function and Characterization Analysis of BodoOBP8 from Bradysia odoriphaga (Diptera: Sciaridae) in the Recognition of Plant Volatiles and Sex Pheromones

SIMPLE SUMMARY: Bradysia odoriphaga (Diptera: Sciaridae) is an important underground pest in Chinese chives. Chemical pesticides are the main prevention and control method, however, but this method not only leads to the increase of the insect’s resistance, but also causes pesticide residues and pollutes the environment. Previous studies have shown that olfaction plays a crucial role in the recognition of plant volatiles and sex pheromones, but the mechanism of olfactory action is still unclear. In the present study, Real-time PCR (qRT-PCR) analysis revealed that BodoOBP8 was highly expressed in the antennae of both sexes, and speculated that it is very likely to participate in the olfactory process. Then we used prokaryotic expression, fluorescence competitive binding, homology modeling, and molecular docking to prove its olfactory function. The results of this study increase our understanding of the binding of BodoOBP8 with plant volatiles and sex pheromone, facilitating the development of novel ways to control B. odoriphaga. ABSTRACT: The belowground pest Bradysia odoriphaga (Diptera: Sciaridae) has a sophisticated and sensitive olfactory system to detect semiochemical signals from the surrounding environment. In particular, odorant-binding proteins (OBPs) are crucial in capturing and transporting these semiochemical signals across the sensilla lymph to the corresponding odorant receptors. In this study, we cloned a full-length cDNA sequence of BodoOBP8 from B. odoriphaga. Real-time PCR (qRT-PCR) analysis revealed that BodoOBP8 has the highest expression levels in males, with more pronounced expression in the male antennae than in other tissues. In this study, the recombinant protein BodoOBP8 was successfully expressed by a bacterial system to explore its function. Competitive binding assays with 33 host plant volatiles and one putative sex pheromone (n-heptadecane) revealed that purified BodoOBP8 strongly bound to two sulfur compounds (methyl allyl disulfide and diallyl disulfide) and to n-heptadecane; the corresponding dissolution constants (Ki) were 4.04, 6.73, and 4.04 μM, respectively. Molecular docking indicated that Ile96, Ile103, Ala107, and Leu111, located in the hydrophobic cavity of BodoOBP8, are the key residues mediating the interaction of BodoOBP8 with two sulfur compounds (methyl allyl disulfide and diallyl disulfide) and n-heptadecane. These results show that BodoOBP8 plays a role in the recognition of plant volatiles and sex pheromones, suggesting its application as a molecular target for the screening of B. odoriphaga attractants and repellents and facilitating a new mechanism of B. odoriphaga control.