The Female-Biased General Odorant Binding Protein 2 of Semiothisa cinerearia Displays Binding Affinity for Biologically Active Host Plant Volatiles.

Simple Summary: The moth Semiothisa cinerearia (Lepidoptera: Geometridae) is a major pest of Chinese scholar trees (Sophora japonica L.). Olfaction is very important for insects to locate host plants and oviposition sites. Here, we identified the binding abilities of ScinGOBP2 for host plant volatiles using fluorescence-based competitive binding assays. We also confirmed the key amino acid residues that bind to plant volatiles in ScinGOBP2 via three-dimensional structure modeling and molecular docking. The ScinGOBP2 ligands had attractive or repellent behavioral effects on S. cinerearia for oviposition. Overall, ScinGOBP2 may play important roles in detecting host plant volatiles, and ScinGOBP2 ligands could be used as candidate olfactory regulators for the management of S. cinerearia. Herbivorous insects rely on volatile chemical cues from host plants to locate food sources and oviposition sites. General odorant binding proteins (GOBPs) are believed to be involved in the detection of host plant volatiles. In the present study, one GOBP gene, ScinGOBP2, was cloned from the antennae of adult Semiothisa cinerearia. Reverse-transcription PCR and real-time quantitative PCR analysis revealed that the expression of ScinGOBP2 was strongly biased towards the female antennae. Fluorescence-based competitive binding assays revealed that 8 of the 27 host plant volatiles, including geranyl acetone, decanal, cis-3-hexenyl n-valerate, cis-3-hexenyl butyrate, 1-nonene, dipentene, α-pinene and β-pinene, bound to ScinGOBP2 (KD = 2.21–14.94 μM). The electrical activities of all eight ScinGOBP2 ligands were confirmed using electroantennography. Furthermore, oviposition preference experiments showed that eight host volatiles, such as decanal, cis-3-hexenyl n-valerate, cis-3-hexenyl butyrate, and α-pinene, had an attractive effect on female S. cinerearia, whereas geranyl acetone, 1-nonene, β-pinene, and dipentene inhibited oviposition in females. Consequently, it can be postulated that ScinGOBP2 may be implicated in the perception of host plant volatiles and that ScinGOBP2 ligands represent significant semiochemicals mediating the interactions between plants and S. cinerearia. This insight could facilitate the development of a chemical ecology-based approach for the management of S. cinerearia. [ABSTRACT FROM AUTHOR]