Identification of odorant-binding proteins and functional analysis of antenna-specific BhorOBP28 in Batocera horsfieldi (Hope).

BACKGROUND: The important wood-boring pest Batocera horsfieldi has evolved a sensitive olfactory system to locate host plants. Odorant-binding proteins (OBPs) are thought to play key roles in olfactory recognition. Therefore, exploring the physiological function of OBPs could facilitate a better understanding of insect chemical communications. RESULTS: In this research, 36 BhorOBPs genes were identified via transcriptome sequencing of adults' antennae from B. horsfieldi, and most BhorOBPs were predominantly expressed in chemosensory body parts. Through fluorescence competitive binding and fluorescence quenching assays, the antenna-specific BhorOBP28 was investigated and displayed strong binding affinities forming stable complexes with five volatiles, including (+)-α-Pinene, (+)-Limonene, ß-Pinene, (-)-Limonene, and (+)-Longifolene, which could also elicit conformation changes when they were interacting with BhorOBP28. Batocera horsfieldi females exhibited a preference for (-)-Limonene, and a repellent response to (+)-Longifolene. Feeding dsOBP19 produced by a bacteria-expressed system with a newly constructed vector could lead to the knockdown of BhorOBP28, and could further impair B. horsfieldi attraction to (-)-Limonene and repellent activity of (+)-Longifolene. The analysis of site-directed mutagenesis revealed that Leu7, Leu72, and Phe121 play a vital role in selectively binding properties of BhorOBP28. CONCLUSION: By modeling the molecular mechanism of olfactory recognition, these results demonstrate that BhorOBP28 is involved in the chemoreception of B. horsfieldi. The bacterial-expressed dsRNA delivery system gains new insights into potential population management strategies. Through the olfactory process concluded that discovering novel behavioral regulation and environmentally friendly control options for B. horsfieldi in the future. © 2024 Society of Chemical Industry.

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

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.