The last universal common ancestor: emergence, constitution and genetic legacy of an elusive forerunner.
The last universal common ancestor: emergence, constitution and genetic legacy of an elusive forerunner.
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DOI：
10.1186/1745-6150-3-29
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发表时间：
2008-07-09
期刊：
影响因子：
5.5
通讯作者：
Labedan B
中科院分区：
文献类型：
--
作者：
Glansdorff N;Xu Y;Labedan B
自从所有生命形式在三个领域（古细菌，细菌，真核生物）的重新分类以来，它们所谓的先驱（最后普遍共同祖先或LUCA）的身份一直是广泛争议的主题：祖传生物或已经复杂的生物，原核生物或原真核生物，嗜热生物或嗜中生物，从简单复制细胞到复杂细胞的长期进展的产物或诞生在摇篮中的“催化封闭”实体？我们对这一主题进行了批判性的调查，并提出了一个设想。LUCA似乎不是一个简单的、原始的、超嗜热的原核生物，而是一个具有RNA基因组的复杂的原真核生物群落，适应广泛的中等温度，遗传冗余，形态和代谢多样化。LUCA的遗传冗余预测，在不同谱系中，同源基因拷贝的丢失是系统发育异常的重要来源，即蛋白质树偏离SSU-rRNA谱系的情况；因此，水平基因转移可能不具有许多人所认为的猖獗特征。检查膜脂表明LUCA具有sn1,2酯脂肪酸脂质，古菌从一开始就通过“热还原”产生了嗜热性，具有一种新型的膜，由sn2,3醚类异戊二烯脂质组成；这一过程没有发生主要的酶再转化。细菌从LUCA通过还原进化产生，一些谱系通过趋同进化进一步获得了极端的嗜热性。这种情况与Forterre提出的RNA到DNA的转化是由不同的病毒入侵引起的假设是一致的。除了反对“复制优先”和“代谢优先”的争论之外，“催化关闭”或“组成遗传”理论的预测论点严重支持卢卡的祖先已经成为复杂的，自我复制的实体，遗传密码在自然选择下产生。生命生来就是复杂的，卢卡展示了这种传统。在通过内共生成熟为适应富氧环境的生物体之前，它就有了嗜中温真核生物的“身体”。大量的迹象表明，这种复杂而异质的实体向“原核”领域古细菌和细菌的还原进化。“原核生物”这个词应该放弃，因为在认识论上是站不住脚的。本文由Anthony Poole， Patrick Forterre和Nicolas Galtier审阅。
Since the reclassification of all life forms in three Domains (Archaea, Bacteria, Eukarya), the identity of their alleged forerunner (Last Universal Common Ancestor or LUCA) has been the subject of extensive controversies: progenote or already complex organism, prokaryote or protoeukaryote, thermophile or mesophile, product of a protracted progression from simple replicators to complex cells or born in the cradle of "catalytically closed" entities? We present a critical survey of the topic and suggest a scenario. LUCA does not appear to have been a simple, primitive, hyperthermophilic prokaryote but rather a complex community of protoeukaryotes with a RNA genome, adapted to a broad range of moderate temperatures, genetically redundant, morphologically and metabolically diverse. LUCA's genetic redundancy predicts loss of paralogous gene copies in divergent lineages to be a significant source of phylogenetic anomalies, i.e. instances where a protein tree departs from the SSU-rRNA genealogy; consequently, horizontal gene transfer may not have the rampant character assumed by many. Examining membrane lipids suggest LUCA had sn1,2 ester fatty acid lipids from which Archaea emerged from the outset as thermophilic by "thermoreduction," with a new type of membrane, composed of sn2,3 ether isoprenoid lipids; this occurred without major enzymatic reconversion. Bacteria emerged by reductive evolution from LUCA and some lineages further acquired extreme thermophily by convergent evolution. This scenario is compatible with the hypothesis that the RNA to DNA transition resulted from different viral invasions as proposed by Forterre. Beyond the controversy opposing "replication first" to metabolism first", the predictive arguments of theories on "catalytic closure" or "compositional heredity" heavily weigh in favour of LUCA's ancestors having emerged as complex, self-replicating entities from which a genetic code arose under natural selection. Life was born complex and the LUCA displayed that heritage. It had the "body "of a mesophilic eukaryote well before maturing by endosymbiosis into an organism adapted to an atmosphere rich in oxygen. Abundant indications suggest reductive evolution of this complex and heterogeneous entity towards the "prokaryotic" Domains Archaea and Bacteria. The word "prokaryote" should be abandoned because epistemologically unsound. This article was reviewed by Anthony Poole, Patrick Forterre, and Nicolas Galtier.
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DOI：
10.1073/pnas.0703522104
发表时间：
2007-06-12
影响因子：
11.1
作者：
Bradford, Justin A.;Dill, Ken A.
通讯作者：
Dill, Ken A.
影响因子：
4.2
作者：
Buford Price, P.
通讯作者：
Buford Price, P.
DOI：
10.1073/pnas.0609592104
发表时间：
2007-05-29
影响因子：
11.1
作者：
Baaske, Philipp;Weinert, Franz M.;Braun, Dieter
通讯作者：
Braun, Dieter
影响因子：
3.9
作者：
Caetano-Anollés, G
通讯作者：
Caetano-Anollés, G
影响因子：
56.9
作者：
Brocks, JJ;Logan, GA;Summons, RE
通讯作者：
Summons, RE