Cyetpyrafen, chlorfenapyr and spirodiclofen affect the olfactory recognition of Dastarcus helophoroides by acting on DhelOBP4 and DhelOBP21.

The pine-forest guardian Dastarcus helophoroides mainly rely on olfaction to locate its host accurately and interact socially. Odorant binding proteins of D. helophoroides play an important role in olfactory recognition and transporting odors to olfactory receptors to trigger signal transduction. However, some compounds affect olfactory recognition of D. helophoroides by binding to odorant binding proteins. In this study, DhelOBP4 and DhelOBP21, which are involved in the recognition of plant volatiles, were expressed to explore compounds that affect olfactory recognition. The affinity of 24 compounds with DhelOBP4 and DhelOBP21 was investigated by vitro fluorescence competitive binding assays. It was found that cyetpyrafen, chlorfenapyr and spirodiclofen had high affinity with DhelOBP4 and DhelOBP21. At the same time, we found that these three pesticides had a good evasive effect on the D. helophoroides and elicited EAG response in a dose-dependent manner. Besides, it was found that silencing DhelOBP4 and DhelOBP21 would affect D. helophoroides identifying these three pesticides. Through homology modeling and molecular docking, we identified key amino acid sites involved in the binding of DhelOBP4 and DhelOBP21 to these three pesticides, which might revealed their specific binding molecular interactions. This study is helpful to provide a valuable addition of OBP-pesticide interactions of D. helophoroides.