Rapidly evolving mitochondrial genome and directional selection in mitochondrial genes in the parasitic wasp Nasonia (Hymenoptera: Pteromalidae)
Rapidly evolving mitochondrial genome and directional selection in mitochondrial genes in the parasitic wasp Nasonia (Hymenoptera: Pteromalidae)
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DOI：
10.1093/molbev/msn159
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发表时间：
2008-10-01
影响因子：
10.7
通讯作者：
Werren, John H.
中科院分区：
文献类型：
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作者：
Oliveira, Deodoro C. S. G.;Raychoudhury, Rhitoban;Werren, John H.
我们对3种寄生蜂（2株）、giraulti Nasonia和longicornis Nasonia)的近完整mtDNA进行了测序，包括全部13个蛋白编码基因和2个rrna，发现了线粒体进化的异常模式。由于多次重排，与其他昆虫的mtDNA相比，纳索尼亚mtDNA具有独特的基因顺序。这些黄蜂的mtdna也显示出核苷酸替代率比核蛋白编码基因快30倍以上，表明在动物线粒体中发现的最高替代率（通常小于10倍）。McDonald and Kreitman检验表明，相对于沉默位点，Nasonia线粒体2个基因atp6和atp8的种内多态性，固定替代位点的种间频率明显高于种内多态性，表明了定向选择。与这一解释一致的是，物种间的Ka/Ks（非同义/同义取代率）比物种内的Ka/Ks高。相比之下，cox1显示出氨基酸序列保守的纯化选择特征，尽管氨基酸取代率仍然高于同类昆虫。线粒体编码的多肽atp6和atp8都出现在电子传递链的F0F1ATP合成酶中。由于这种基本蛋白质的功能障碍严重影响了适应性，我们认为，替换物的加速积累是由于有益的突变，这些突变是补偿由随机遗传漂变或沃尔巴克氏菌在快速进化的纳索尼亚线粒体中固定的轻度有害突变所必需的。我们进一步提出，在一些线粒体基因中相对较高的氨基酸替代率可以由“补偿草案反馈”驱动；轻度有害突变的固定增加导致代偿性突变的选择，代偿性突变导致非重组线粒体基因组中额外有害突变的固定，从而加速氨基酸取代的过程。
We sequenced the nearly complete mtDNA of 3 species of parasitic wasps, Nasonia vitripennis (2 strains), Nasonia giraulti, and Nasonia longicornis, including all 13 protein-coding genes and the 2 rRNAs, and found unusual patterns of mitochondrial evolution. The Nasonia mtDNA has a unique gene order compared with other insect mtDNAs due to multiple rearrangements. The mtDNAs of these wasps also show nucleotide substitution rates over 30 times faster than nuclear protein-coding genes, indicating among the highest substitution rates found in animal mitochondria (normally < 10 times faster). A McDonald and Kreitman test shows that the between-species frequency of fixed replacement sites relative to silent sites is significantly higher compared with within-species polymorphisms in 2 mitochondrial genes of Nasonia, atp6 and atp8, indicating directional selection. Consistent with this interpretation, the Ka/Ks (nonsynonymous/synonymous substitution rates) ratios are higher between species than within species. In contrast, cox1 shows a signature of purifying selection for amino acid sequence conservation, although rates of amino acid substitutions are still higher than for comparable insects. The mitochondrial-encoded polypeptides atp6 and atp8 both occur in F0F1ATP synthase of the electron transport chain. Because malfunction in this fundamental protein severely affects fitness, we suggest that the accelerated accumulation of replacements is due to beneficial mutations necessary to compensate mild-deleterious mutations fixed by random genetic drift or Wolbachia sweeps in the fast evolving mitochondria of Nasonia. We further propose that relatively high rates of amino acid substitution in some mitochondrial genes can be driven by a "Compensation-Draft Feedback"; increased fixation of mildly deleterious mutations results in selection for compensatory mutations, which lead to fixation of additional deleterious mutations in nonrecombining mitochondrial genomes, thus accelerating the process of amino acid substitutions.