Binding characterization of odorant-binding protein BhorOBP29 in Batocera horsfieldi (Hope) with host-plant volatiles.

ABSTRACT

Odorant binding proteins (OBPs) are involved in odorant discrimination and act as the first filter in the peripheral olfactory system. Previous studies have shown that BhorOBP29 is potentially involved in olfactory perception in an important wood-boring pest Batocera horsfieldi (Hope) (Coleoptera Cerambycidae), however, its function remains unclear. Here, we investigated the ligand-binding profiles of recombinant BhorOBP29 with 22 compounds from its host plant using fluorescence competitive binding assays and fluorescence quenching assays. The results showed that BhorOBP29 could bind to five ligands relying mainly on hydrophobic interactions. Molecular docking analysis indicated that residues Ile48, Leu51, Met52, Trp57, Asn105, and Val119 were extensively involved in the interactions between BhorOBP29 and the five ligands. Furthermore, the site-directed mutagenesis analysis revealed that Leu51 and Met52 residues were indispensable for BhorOBP29-ligands binding. Finally, electroantennogram (EAG) assays confirmed that hexanal, (-)-limonene, and 2-methylbutyraldehyde elicited a concentration-dependent EAG response with a maximum at the concentration of 1/10 v/v. These findings suggest that BhorOBP29 may play a significant role in the perception of host plant volatiles by B. horsfieldi. This study may help to discover novel behavioral regulation and environmentally friendly strategies for controlling B. horsfieldi in the future.