Retroposed elements as archives for the evolutionary history of placental mammals.
Retroposed elements as archives for the evolutionary history of placental mammals.
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复古元素作为胎盘哺乳动物进化史的档案。
DOI：
10.1371/journal.pbio.0040091
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发表时间：
2006-04
期刊：
影响因子：
9.8
通讯作者：
Schmitz J
中科院分区：
文献类型：
--
作者：
Kriegs JO;Churakov G;Kiefmann M;Jordan U;Brosius J;Schmitz J
胎盘哺乳动物（真兽）进化树的重建经历了不同的修订，许多方面仍然存在激烈的争论。最初的基于形态学的等级划分包含了许多错误的分组，这是由于通过类似的选择过程独立进化的特征。分子分析纠正了许多这样的错误分组，胎盘哺乳动物的高级等级最近被组装成四个分支。然而，长时间或快速的进化周期，以及定向突变压力，可以产生分子同源性，缺乏共同祖先的相似特征。相反，逆转录元件随机整合到基因组中，而同一元件独立整合到不同物种的同源位置的概率可以忽略不计。因此，这些元素的存在/缺失分析是分子系统学的一种优越策略。通过计算扫描超过160,000个染色体位点，并明智地从系统发育信息丰富的反转录子中选择用于实验高通量PCR应用，我们恢复了28个清晰，独立的单系标记，最终验证了胎盘哺乳动物进化中最早的分歧。通过考虑祖先多态性的测试，多个长间隔元件和长末端重复元件插入为单系进化分支Boreotheria（与Boreoeutheria同义）、superaprimates（与Euarchontoglires同义）和Laurasiatheria提供了非常重要的证据。更重要的是，两个反位为早期哺乳动物进化的先前情景提供了新的支持，该情景将基础胎盘分化置于Xenarthra和Epitheria之间，后者包括所有剩余的胎盘。由于其几乎无同源性，逆转录子存在/缺失模式的分析避免了其他分子方法的陷阱，并为揭示生物体的进化史提供了快速，明确的手段。作者鉴定并测序了哺乳动物基因组中的逆转录子。这些反转录子的存在和缺失为作者重建胎盘哺乳动物的系统发育历史提供了进化标记。
Reconstruction of the placental mammalian (eutherian) evolutionary tree has undergone diverse revisions, and numerous aspects remain hotly debated. Initial hierarchical divisions based on morphology contained many misgroupings due to features that evolved independently by similar selection processes. Molecular analyses corrected many of these misgroupings and the superordinal hierarchy of placental mammals was recently assembled into four clades. However, long or rapid evolutionary periods, as well as directional mutation pressure, can produce molecular homoplasies, similar characteristics lacking common ancestors. Retroposed elements, by contrast, integrate randomly into genomes with negligible probabilities of the same element integrating independently into orthologous positions in different species. Thus, presence/absence analyses of these elements are a superior strategy for molecular systematics. By computationally scanning more than 160,000 chromosomal loci and judiciously selecting from only phylogenetically informative retroposons for experimental high-throughput PCR applications, we recovered 28 clear, independent monophyly markers that conclusively verify the earliest divergences in placental mammalian evolution. Using tests that take into account ancestral polymorphisms, multiple long interspersed elements and long terminal repeat element insertions provide highly significant evidence for the monophyletic clades Boreotheria (synonymous with Boreoeutheria), Supraprimates (synonymous with Euarchontoglires), and Laurasiatheria. More importantly, two retropositions provide new support for a prior scenario of early mammalian evolution that places the basal placental divergence between Xenarthra and Epitheria, the latter comprising all remaining placentals. Due to its virtually homoplasy-free nature, the analysis of retroposon presence/absence patterns avoids the pitfalls of other molecular methodologies and provides a rapid, unequivocal means for revealing the evolutionary history of organisms. The authors identified and sequenced retroposons in mammalian genomes. The presence and absence of these retroposons provided evolutionary markers from which the authors reconstructed the phylogenetic history of placental mammals.