Functional Characterization of Three Odorant-Binding Proteins in Sex Pheromones and Host Plant Volatiles Detection in Bradysia odoriphaga

The insect olfactory system serves as a critical detection mechanism, where odorant-binding proteins (OBPs) mediate recognition by binding odor molecules, thereby regulating behavioral responses. Here, we functionally characterized three male antennal-enriched OBPs (BodoOBP2, BodoOBP4, and BodoOBP8) from Bradysia odoriphaga . Fluorescence binding assays showed that these OBPs had significantly higher affinity for three sex pheromones than for five host plant volatiles, with BodoOBP8’s affinity for linolenic acid particularly outstanding ( K i = 0.44 μΜ, pH = 5.0). Molecular docking attributed these profiles to key pocket residues. RNA interference showed that dsRNA-treated males had significantly impaired female recognition. Furthermore, host-plant attraction assays showed a reduced Chinese chive orientation in dsBodoOBP2 - and dsBodoOBP4 -silenced adults. Our findings suggest that BodoOBP2 and BodoOBP4 mediate both pheromone communication and host-plant detection, while BodoOBP8 mainly transports pheromones. These results advance our understanding of olfactory mechanisms in Diptera and provide molecular targets for olfactory-based management of this pest.