Expression Characteristics of Odorant Receptor Gene AcerOR120 and Its Physiological Roles in Mediating Odor...

This study aims to characterize the structural features and spatiotemporal expression patterns of the protein encoded by odorant receptor gene AcerOR120, and to explore its biological functions in olfactory recognition in Apis cerana cerana. Bioinformatic software was used to predict the transmembrane topology, secondary/tertiary structures and conserved domains of the AcerOR120 protein. A neighbor-joining phylogenetic tree was constructed based on homologous sequences within the genus Apis. qRT-PCR was performed to detect the gene expression profiles in antennae of worker bees at 1, 5, 10, 15, 20 and 25 days old, as well as different tissues of foragers. EAG recording was applied to compare the electrophysiological responses of worker antennae to 11 volatile odorants before and after gene silencing via RNA interference. The open reading frame of AcerOR120 is 1203 bp, encoding a 401-amino-acid protein containing seven transmembrane domains with an intracellular N-terminus. Its secondary structure is dominated by α-helices accounting for 82.79%, which matches the typical structural signature of insect odorant receptors. Phylogenetic analysis revealed that AcerOR120 shares high conservation across Apis species. Spatiotemporal expression assays showed that transcript abundance in antennae increased first and then decreased with worker age, reaching the minimum at day 1 and the maximum at day 20. Among tissues of foragers, the highest expression was detected in antennae and thoraxes, followed by heads and legs, while abdomens and wings possessed low expression levels. RNAi silencing significantly reduced overall EAG responses of antennae to all 11 tested odorants, with the most dramatic decreases observed for Geraniol, Decanal, Ocimene and (+)-Dihydrocarvone. AcerOR120 encodes a canonical insect odorant receptor and is highly expressed in forager antennae. It mediates the recognition of multiple floral volatiles and pheromones and is speculated to participate in olfactory-related physiological processes, including nectar source localization and social behavior regulation in A. cerana cerana.