Characterization of the giant panda olfactory receptor repertoire reveals sensory evolution associated with bamboo diet specialization

Abstract Background Olfactory perception mediates key behaviours including foraging and chemical communication in mammals. Olfactory receptors (ORs) constitute the largest G protein-coupled receptor multigene family responsible for detecting volatile odors. The giant panda ( Ailuropoda melanoleuca , Carnivora: Ursidae) has evolved an extreme bamboo-specialized diet yet remains heavily dependent on olfactory cues for food selection and social signalling. Previous OR annotations for giant panda were partial, and expression profiles and potential ligand interactions remain poorly characterised. Results We combined OR gene identification from the giant panda genome, cross-carnivoran comparative genomic analyses, non‑invasive nasal mucus transcriptome sequencing, and in silico molecular docking to characterize the giant panda OR repertoire. Using Genome2OR, we annotated 1397 OR genes (702 functional genes, 695 pseudogenes). Among eight sampled carnivoran species, the giant panda exhibited the highest OR pseudogene proportion, pointing to lineage-specific repertoire shifts linked to dietary specialisation. Most functional ORs belonged to class II and formed large chromosomal clusters. Transcriptomic profiling detected 11 expressed OR genes; OR554 and OR530 showed markedly high transcript abundance. Molecular docking simulations predicted favourable binding affinities of these two receptors to multiple bamboo-derived volatile compounds, nominating candidate receptor-ligand pairs for future experimental validation. Selective-pressure analyses revealed relaxed constraints on giant-panda OR orthologs compared with the other seven sampled carnivoran species. Conclusions Our combined genomic, expression, and docking results suggest that highly expressed giant-panda ORs may participate in recognising plant volatiles relevant to bamboo foraging and habitat sensing. This work provides new insights into the evolution, in-situ expression and putative functional properties of the giant-panda OR repertoire, advancing our understanding of olfactory adaptation in bamboo-specialised mammals.