Molecular Characterization, Expression and Binding Specificity Analysis of the Odorant-Binding Proteins of Scleroderma sichuanensis Xiao (Hymenoptera: Bethylidae)

Odorant-binding proteins (OBPs) play an important role in the sense of smell in parasitoid wasps, especially for locating hosts and mates. Clarifying the role of OBPs in information exchanges between parasitoid wasps and their environment is beneficial for understanding the sense of smell in parasitoid wasps. To this end, we cloned the OBPs, SsicOBP1 and SsicOBP2 (GenBank accession numbers: AKP80533.1 and AKP80534.1), of Scleroderma sichuanensis Xiao and then proceeded to conduct prokaryotic expression and qPCR analysis, and determine the binding capacity of SsicOBP1 and SsicOBP2 with 18 types of volatiles from Pinus massoniana Lambert using competitive binding (with 1-NPN as fluorescent probes). We found that SsicOBP1 and SsicOBP2 are expressed at high levels in the antennae of Scleroderma sichuanensis Xiao. Of the 18 types of P. massoniana volatiles, SsicOBP1 could bind effectively with ocimene (binding constant of 12.82 µM) and β-pinene (binding constant of 15.57 µM). SsicOBP2 could bind effectively with α-pinene (with a binding constant of 13.52 µM), ocimene (binding constant of 14.38 µM) and β-pinene (binding constant of 14.51 µM). From this, we could infer that SsicOBP1 and SsicOBP2 are general odorant-binding proteins, which play an important role in sensing plant volatiles.