Functional divergence of bitter taste receptor TAS2R38 in Sulawesi Macaques

Abstract

Bitter taste plays an important role in avoiding ingestion of toxins and resisting bacteria and parasites, which might evolve to reflect species-specific diets during mammalian evolution. Bitter taste receptors (TAS2Rs) mediate the bitter perception in mammals. We investigated the polymorphism of a well-studied bitter taste receptor TAS2R38, protein for the bitter Phenylthiocarbamide (PTC), in four allopatric species (M. hecki (N: 16), M. tonkeana (N: 12), M. nigrescens (N: 11) and M. nigra (N: 15)) of Sulawesi macaques in Sulawesi Island, Indonesia. In most cases, individuals are sensitive to PTC. We observed all individuals of M. hecki are sensitive to PTC while some individuals of M. tonkeana, M. nigra and M. nigrescens showed low sensitive to PTC. Determining TAS2R38 sequence, we found truncated TAS2R38 led to no sensitivity of PTC in M. nigra and M. nigrescens. Functional protein assay showed substitution on three amino acid sites are responsible for low sensitivity in M. tonkeana. Phylogenetic analysis showed TAS2R38 of Sulawesi macaques is derived from M. nemestrina and the low-sensitive allele in M. tonkeana is shared with M. nemestrina. The non-sensitive alleles occurred independently in M. nigra and M. nigrescens after speciation. The low-sensitive alleles in M. tonkeana might express apparently intact TAS2R38 receptor, with low response to PTC. The intact low-sensitive alleles may respond to other bitter compounds. These results revealed species difference on bitter taste; however, whether these differences were resulted from local adaptation need to be studied.