Dynamics of reductive genome evolution in mitochondria and obligate intracellular microbes
Dynamics of reductive genome evolution in mitochondria and obligate intracellular microbes
复制标题
DOI：
10.1093/molbev/msl174
复制
发表时间：
2007-02-01
影响因子：
10.7
通讯作者：
dos Santos, Vitor A. P. Martins
中科院分区：
文献类型：
--
作者：
Khachane, Amit N.;Timmis, Kenneth N.;dos Santos, Vitor A. P. Martins
线粒体和专性细胞内微生物的还原进化导致它们的基因组大小和鸟嘌呤+胞嘧啶含量(GC)显著减少。我们证明了原核生物还原进化过程中基因组的收缩遵循指数衰减模式，并提供了一种在进化时间尺度上预测这种衰退程度的方法。我们通过比较基因组学和利用可用的化石证据，通过与已知的线粒体和美洲斑潜蝇基因组减少的估计程度的比较，验证了预测。该模型显示了线粒体祖先如何在融入原真核细胞后不久，以及在真核谱系分裂后的共同分化之前，迅速失去大部分基因组。它还预测，主要的立克次体寄生事件将发生在1.8亿至4.25亿年前(MYA)，考虑到立克次体和线粒体是从共同的甲蛋白细菌祖先进化而来的，这一事件起源于相对较近的进化。这表明立克次体和线粒体的共生事件发生在不同的时间点。此外，我们的模型结果预测，大约在与采采蝇共生的起源时间(50-100MYA)，Wigglesworth glossinidia brevipalpis的祖先很可能是内共生体，从而支持了更早的命题，即目前是母系遗传的初级内共生体，是从次生内共生体进化而来的。
Reductive evolution in mitochondria and obligate intracellular microbes has led to a significant reduction in their genome size and guanine plus cytosine content (GC). We show that genome shrinkage during reductive evolution in prokaryotes follows an exponential decay pattern and provide a method to predict the extent of this decay on an evolutionary timescale. We validated predictions by comparison with estimated extents of genome reduction known to have occurred in mitochondria and Buchnera aphidicola, through comparative genomics and by drawing on available fossil evidences. The model shows how the mitochondrial ancestor would have quickly shed most of its genome, shortly after its incorporation into the protoeukaryotic cell and prior to codivergence subsequent to the split of eukaryotic lineages. It also predicts that the primary rickettsial parasitic event would have occurred between 180 and 425 million years ago (MYA), an event of relatively recent evolutionary origin considering the fact that Rickettsia and mitochondria evolved from a common alphaproteobacterial ancestor. This suggests that the symbiotic events of Rickettsia and mitochondria originated at different time points. Moreover, our model results predict that the ancestor of Wigglesworthia glossinidia brevipalpis, dated around the time of origin of its symbiotic association with the tsetse fly (50-100 MYA), was likely to have been an endosymbiont itself, thus supporting an earlier proposition that Wigglesworthia, which is currently a maternally inherited primary endosymbiont, evolved from a secondary endosymbiont.