Three antenna-specific odorant binding proteins in Protaetia brevitarsis (Coleoptera: Scarabaeoidea) involve in recognition of floral volatiles

Odorant binding proteins (OBPs) play a vital role in the insect olfactory recognition system, as they bind and transport specific semiochemicals to chemosensory receptors for further processing. The agricultural and horticultural pest, white-spotted flower chafer (WSFC), Protaetia brevitarsis (Coleoptera, Scarabaeoidea), has significantly harmed numerous crops and fruits in China. It is hypothesized that WSFCs rely on specific OBPs and chemosensory receptors to identify palatable food sources and optimal oviposition sites. Twenty-three putative OBPs (PbreOBPs) were identified from the WSFC genome in our research. Based on phylogenetic analysis, PbreOBPs exhibited high degree of similarity to those of Holotrichia parallela and Anomala corpulenta. Tissue expression profiles showed that ten PbreOBPs exhibited antenna-biased expression. We recombined and purified three antenna-specific PbreOBPs: PbreOBP8, PbreOBP9, and PbreOBP18. Fluorescence competitive binding assays revealed that they had higher binding affinities to β-ionone, phenethyl salicylate, phenylacetaldehyde, and benzyl benzoate — compounds commonly found in floral volatiles. Additionally, PbreOBP8 showed the ability to bind microbial volatiles, such as 3-octanol, 3-methyl-1-butanol, and 1-octen-3-ol, suggesting a role in locating food or oviposition sites. Forthermore, we also predicted the key acid residues which involved in the binding of three PbreOBPs towards floral and microbial volatiles. The present investigation demonstrated that the antenna-specific PbreOBP8, PbreOBP9 and PbreOBP18 were likely involved in mediating the recognition of floral volatiles. The findings introduce possible avenues for further research into PbreOBPs and provide potential targets for creating olfactory-based control methods for WSFC populations.