The binding properties of Plus-C odorant binding protein 14 in Orius sauteri to host volatiles.

Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is a natural enemy of many pests, and also feeds and oviposits on plant material. Odorant binding proteins (OBPs) play an important role in the olfactory system of insects. The molecular mechanism of OBPs in O. sauteri to host volatiles is still unknown. Here, we observed by quantitative real-time polymerase chain reaction that the expression level of OsauOBP14 was primarily in the antennae. We performed a fluorescence competition binding assay, and the results showed that OsauOBP14 exhibited binding affinities to 5 host volatiles (hexanal, octanal, 1-octen-3-ol, 2-ethyl hexanol, and p-cymene). Subsequently, we conducted homology modeling, molecular docking, and site-directed mutagenesis, and the result showed that 2 key residues (W13 and R58) play a key role in the binding of OsauOBP14 to ligands. In subsequent Y-tube tests, olfactory behavioral assay revealed that hexanal was significantly attractive to male adults, octanal and 1-octen-3-ol were found to have significant attractant effects on female adults. Furthermore, RNA interference and Y-tube olfactometer confirmed that the attraction to the 3 host volatiles was significantly attenuated. Our study revealed that OsauOBP14 is involved in olfactory detection and helps to better understand the molecular mechanism of OBPs in O. sauteri to host plant volatiles.