Diversification of Bitter Taste Receptor Gene Family in Western Chimpanzees
Diversification of Bitter Taste Receptor Gene Family in Western Chimpanzees
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DOI：
10.1093/molbev/msq279
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发表时间：
2011-02-01
影响因子：
10.7
通讯作者：
Imai, Hiroo
中科院分区：
文献类型：
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作者：
Sugawara, Tohru;Go, Yasuhiro;Imai, Hiroo
在哺乳动物中，苦味是由T2R基因介导的，T2R基因属于七个跨膜G蛋白偶联受体大家族。由于T2Rs直接参与哺乳动物与它们的饮食来源之间的相互作用，这些基因很可能是为了反映哺乳动物进化过程中物种的特定饮食而进化的。在这里，我们研究了46只西部黑猩猩所有28个假定的功能性黑猩猩T2R基因(CT2R)的序列，以比较黑猩猩的种内变异和已知的所有25个人类功能性T2R基因(HT2R)的变异。西方黑猩猩的功能基因数量因个体而异，大多数黑猩猩比人类多两到三个功能基因。与hT2Rs相似，cT2Rs表现出高度的核苷酸多样性和大量的氨基酸替换。将cT2R基因的核苷酸替换模式与同一个体的5个cT2R假基因和14个常染色体非编码区的核苷酸替换模式进行比较，发现cT2R基因的进化与假定的中性区域的进化几乎相同，Tajima‘s D值轻微但显著为正，表明对这些基因的选择约束放松了，进行了弱平衡选择。这些趋势导致了西部黑猩猩种群和杂合子个体中出现了各种不同的T2Rs等位基因，这些杂合子个体可能有能力品尝更广泛的物质。
In mammals, bitter taste is mediated by T2R genes, which belong to the large family of seven transmembrane G protein coupled receptors. Because T2Rs are directly involved in the interaction between mammals and their dietary sources, it is likely that these genes evolved to reflect species' specific diets during mammalian evolution. Here, we investigated the sequences of all 28 putative functional chimpanzee T2R genes (cT2Rs) in 46 western chimpanzees to compare the intraspecies variations in chimpanzees to those already known for all 25 human functional T2R genes (hT2Rs). The numbers of functional genes varied among individuals in western chimpanzees, and most chimpanzees had two or three more functional genes than humans. Similarly to hT2Rs, cT2Rs showed high nucleotide diversity along with a large number of amino acid substitutions. Comparison of the nucleotide substitution patterns in cT2Rs with those in five cT2R pseudogenes and 14 autosomal intergenic noncoding regions among the same individuals revealed that the evolution of cT2R genes was almost identical to that of putative neutral regions with slight but significantly positive Tajima's D values, suggesting that selective constraint on these genes was relaxed with weak balancing selection. These trends have resulted in the occurrence of various divergent alleles of T2Rs within the western chimpanzee populations and in heterozygous individuals who might have the ability to taste a broader range of substances.