Reduction of bitter taste receptor genes in gibbons

Abstract

Gibbons, lesser apes, are characterized by their evolutionary plasticity of the chromosomal organization (karyotype). It is not well understood if and how this instability affects evolution of multigene families such as bitter taste receptor genes (TAS2Rs). TAS2Rs are spread into multiple chromosomes and are clustered in these chromosomes. The aim of this study is to elucidate the composition of TAS2R gene family across different gibbon species and compare them with other hominoid species to shed light on the influence of chromosomal instability to the gene composition. We examined fourteen individuals from nine gibbon species representing all four genera: Hylobates, Hoolock, Nomascus and Symphalangus. High-throughput targeted capture technology was employed to selectively enrich TAS2Rs, followed by short-read high-depth massive parallel sequencing. We showed that gibbons have 19 to 21 intact TAS2Rs, considerably fewer than 32 intact TAS2Rs estimated to have existed in the common ancestor of hominoids. Expectedly from the chromosomal instability, a gene cluster spanning approximately 125 kb-170kb including five TAS2Rs found in other hominoid species was lost in all gibbon species. This suggests that the region was lost at the common ancestor of all gibbon genera. Gibbons’ unique ecological niche as a swift brachiator may provide gibbons with an ecological superiority even with the reduction of large number of TAS2Rs which are usually required to select non-toxic foods in competition with other animals.