The Dispersed Archaeal Eukaryome and the Complex Archaeal Ancestor of Eukaryotes
The Dispersed Archaeal Eukaryome and the Complex Archaeal Ancestor of Eukaryotes
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DOI：
10.1101/cshperspect.a016188
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发表时间：
2014-04-01
影响因子：
7.2
通讯作者：
Yutin, Natalya
中科院分区：
文献类型：
--
作者：
Koonin, Eugene V.;Yutin, Natalya
真核生物基因的祖先集合是由古细菌和细菌起源的基因组成的嵌合体，这要归功于产生线粒体的内共生事件，并且显然早于现存真核生物的最后共同祖先。原线粒体内共生体被确定为α-变形菌。相比之下，真核生物的古生物祖先仍然难以捉摸，尽管越来越多的证据表明它可能属于TACK（Thaumarchaeota，Aigarchaeota，Crenarchaeota，Korarchaeota）超门的深层谱系。最近对古细菌基因组的调查表明，真核生物几个关键功能系统的明显祖先，即古细菌“真核组”的组成部分，例如遍在蛋白信号传导、RNA干扰以及基于肌动蛋白和基于微管蛋白的细胞骨架结构，在不同的古细菌群体中是可以识别的。我们认为，真核生物的古祖先是一个复杂的形式，深深植根于TACK超门，已经拥有一些典型的真核生物的功能，特别是，细胞骨架，也许是一种原始形式的吞噬功能，这将有助于吞噬潜在的共生体。这群被认为是真核生物的物种在灭绝或经历基因组精简之前可能存在了相对较短的时间，导致真核生物的分散。这种情况可能解释了鉴定真核生物的古祖先的困难，尽管可以直接检测到许多真核生物功能系统的明显祖先。
The ancestral set of eukaryotic genes is a chimera composed of genes of archaeal and bacterial origins thanks to the endosymbiosis event that gave rise to the mitochondria and apparently antedated the last common ancestor of the extant eukaryotes. The proto-mitochondrial endosymbiont is confidently identified as an alpha-proteobacterium. In contrast, the archaeal ancestor of eukaryotes remains elusive, although evidence is accumulating that it could have belonged to a deep lineage within the TACK (Thaumarchaeota, Aigarchaeota, Crenarchaeota, Korarchaeota) superphylum of the Archaea. Recent surveys of archaeal genomes show that the apparent ancestors of several key functional systems of eukaryotes, the components of the archaeal "eukaryome," such as ubiquitin signaling, RNA interference, and actin-based and tubulin-based cytoskeleton structures, are identifiable in different archaeal groups. We suggest that the archaeal ancestor of eukaryotes was a complex form, rooted deeply within the TACK superphylum, that already possessed some quintessential eukaryotic features, in particular, a cytoskeleton, and perhaps was capable of a primitive form of phagocytosis that would facilitate the engulfment of potential symbionts. This putative group of Archaea could have existed for a relatively short time before going extinct or undergoing genome streamlining, resulting in the dispersion of the eukaryome. This scenario might explain the difficulty with the identification of the archaeal ancestor of eukaryotes despite the straightforward detection of apparent ancestors to many signature eukaryotic functional systems.