Acceleration of genomic evolution caused by enhanced mutation rate in endocellular symbionts
Acceleration of genomic evolution caused by enhanced mutation rate in endocellular symbionts
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DOI：
10.1073/pnas.192449699
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发表时间：
2002-10-01
影响因子：
11.1
通讯作者：
Nei, M
中科院分区：
文献类型：
--
作者：
Itoh, T;Martin, W;Nei, M
内共生菌在自然界中广泛存在，由于其长期的细胞内生活方式，其基因组经历了还原性进化。在这里，我们比较了两种不同的内共生体，Buchnera和原生生物的全基因组序列，与他们的近亲，研究功能基因的内共生体的进化速率。结果表明，共生体中的氨基酸取代率是其亲属的两倍。在不同功能类别的基因中均匀地观察到这种速率增加，尽管在少数情况下强纯化选择可能抵消了速率增加。我们的数据表明，与目前的观点相反，无论是穆勒的棘轮效应还是轻微有害的突变理论都不能充分解释进化速度的提高。相反，进化速率的提高似乎主要是由于突变率的提高，尽管不能排除净化选择放松的可能性。
Endosymbionts, which are widely observed in nature, have undergone reductive genome evolution because of their long-term intracellular lifestyle. Here we compared the complete genome sequences of two different endosymbionts, Buchnera and a protist mitochondrion, with their close relatives to study the evolutionary rates of functional genes in endosymbionts. The results indicate that the rate of amino acid substitution is two times higher in symbionts than in their relatives. This rate increase was observed uniformly among different functional classes of genes, although strong purifying selection may have counterbalanced the rate increase in a few cases. Our data suggest that, contrary to current views, neither the Muller's ratchet effect nor the slightly deleterious mutation theory sufficiently accounts for the elevated evolutionary rate. Rather, the elevated evolutionary rate appears to be mainly due to enhanced mutation rate, although the possibility of relaxation of purifying selection cannot be ruled out.