Key amino acids in odorant-binding protein OBP7 enable Bradysia odoriphaga to recognize host plant volatiles

Bradysia odoriphaga (Diptera: Sciaridae) is a devastating underground pest that can cause serious economic losses. Odorant binding proteins (OBPs) are crucial components of the insect olfactory system, playing key roles in locating host plants, oviposition sites, and mates. Therefore, they are considered potential targets for pest control. Here, we obtained one OBP gene (BodoOBP7) from the antennal transcriptome of B. odoriphaga, and observed that the expression level of BodoOBP7 was primarily in the antennae of both sexes, with significantly higher expression level in females than in males. Fluorescence competitive binding assays indicated that BodoOBP7 exhibited strong binding affinities for the six host plant volatiles, including propyl disulfide, dipropyl trisulfide, dimethyl trisulfide, 2-tridecanone, 2-undecanone and alpha-ionone. Subsequently, homology modeling, molecular docking and site-directed mutagenesis revealed that four key amino acid residues (Phe79, Phe99, Ile96, Leu100) participate in the binding of BodoOBP7 with six host plant volatiles. Our results demonstrate that BodoOBP7 is involved in olfactory recognition in B. odoriphaga. These findings may enhance our understanding of the interaction mechanisms between host plants and B. odoriphaga, potentially offering new perspectives for the development of effective green control strategies.