Parallel adaptations to high temperatures in the Archaean eon
Parallel adaptations to high temperatures in the Archaean eon
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DOI：
10.1038/nature07393
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发表时间：
2008-12-18
期刊：
影响因子：
64.8
通讯作者：
Gouy, Manolo
中科院分区：
文献类型：
--
作者：
Boussau, Bastien;Blanquart, Samuel;Gouy, Manolo
从细胞生命的起源和多样性开始的生物化石很少，难以解释（1），因此，研究最后一个普遍共同祖先（LUCA）和三个生命领域的祖先的生态学的替代方法具有重要的科学价值。最近认识到，温度对祖先生物体的影响留下了“遗传足迹”，可以在现存的基因组中发现（2-4）。因此，对复活蛋白的分析预测，细菌祖先是嗜热的，细菌随后适应了较低的温度（3，4）。由于古细菌祖先也被认为是嗜热的（5），LUCA也被粗略地推断为嗜热的。然而，对核糖体RNA的分析支持非超嗜热LUCA的假设（2）。在这里，我们表明，rRNA和蛋白质序列分析与先进的，现实的分子进化模型（6，7）提供独立的支持，两个环境温度相关的阶段，在进化历史的生命之树。在第一个时期，耐热性增加，从嗜温的LUCA嗜热的祖先细菌和真核生物;在第二个时期，它下降。因此，两个世系从LUCA下降，并导致细菌和古细菌的祖先-真核生物收敛适应高温，可能是为了响应早期地球的气候变化（1，8，9），和/或从RNA基因组的过渡帮助LUCA的生物体具有更耐热的DNA基因组（10，11）。这种分析将明显矛盾的结果（2-4）统一为对整个生命树上生态特征进化的连贯描述。
Fossils of organisms dating from the origin and diversification of cellular life are scant and difficult to interpret(1), for this reason alternative means to investigate the ecology of the last universal common ancestor ( LUCA) and of the ancestors of the three domains of life are of great scientific value. It was recently recognized that the effects of temperature on ancestral organisms left 'genetic footprints' that could be uncovered in extant genomes(2-4). Accordingly, analyses of resurrected proteins predicted that the bacterial ancestor was thermophilic and that Bacteria subsequently adapted to lower temperatures(3,4). As the archaeal ancestor is also thought to have been thermophilic(5), the LUCA was parsimoniously inferred as thermophilic too. However, an analysis of ribosomal RNAs supported the hypothesis of a non- hyperthermophilic LUCA(2). Here we show that both rRNA and protein sequences analysed with advanced, realistic models of molecular evolution(6,7) provide independent support for two environmental- temperature-related phases during the evolutionary history of the tree of life. In the first period, thermotolerance increased from a mesophilic LUCA to thermophilic ancestors of Bacteria and of Archaea Eukaryota; in the second period, it decreased. Therefore, the two lineages descending from the LUCA and leading to the ancestors of Bacteria and Archaea - Eukaryota convergently adapted to high temperatures, possibly in response to a climate change of the early Earth(1,8,9), and/or aided by the transition from an RNA genome in the LUCA to organisms with more thermostable DNA genomes(10,11). This analysis unifies apparently contradictory results(2-4) into a coherent depiction of the evolution of an ecological trait over the entire tree of life.