Insights into Cyclostome Phylogenomics: Pre-2R or Post-2R?
Insights into Cyclostome Phylogenomics: Pre-2R or Post-2R?
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DOI：
10.2108/zsj.25.960
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发表时间：
2008-10-01
影响因子：
0.9
通讯作者：
Kuraku, Shigehiro
中科院分区：
文献类型：
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作者：
Kuraku, Shigehiro
从分子水平上理解从前脊椎动物到脊椎动物的转变的兴趣导致了对现存最早的脊椎动物群体，即盲鳗（Myxiniformes）和七鳃鳗（Petromyzontiformes）的基因组和转录组序列数据的积累。物种系统发育的分子系统发育研究揭示了环口动物的单一性以及盲鳗和七鳃鳗之间的深度分化（超过4亿年）。与此同时，最近的分子系统发育研究揭示了环孔基因组的复杂进化。这包括全基因组复制，至少部分与颌口动物（有颌脊椎动物）共享，以及环口动物谱系特异性的基因组二次修饰，如基因的获得和损失。因此，在基因家族尺度的基因分子系统发育中，需要谨慎区分同源性和类似性，以及在更大规模的分析中，需要谨慎区分非胚性和非胚性基因组特征。在这篇综述中，我们提出了提高这些进化事件可解析性的可能方法，并讨论了环口动物基因组进化的可能情况，特别强调了在环口动物和颌口动物分化之前发生的两轮（2R）基因组复制事件，因此，2R后状态是所有现存脊椎动物的基因组突触性。
Interest in understanding the transition from prevertebrates to vertebrates at the molecular level has resulted in accumulating genomic and transcriptomic sequence data for the earliest groups of extant vertebrates, namely, hagfishes (Myxiniformes) and lampreys (Petromyzontiformes). Molecular phylogenetic studies on species phylogeny have revealed the monophyly of cyclostomes and the deep divergence between hagfishes and lampreys (more than 400 million years). In parallel, recent molecular phylogenetic studies have shed light on the complex evolution of the cyclostome genome. This consists of whole genome duplications, shared at least partly with gnathostomes (jawed vertebrates), and cyclostome lineage-specific secondary modifications of the genome, such as gene gains and losses. Therefore, the analysis of cyclostome genomes requires caution in distinguishing between orthology and paralogy in gene molecular phylogeny at the gene family scale, as well as between apomorphic and plesiomorphic genomic traits in larger-scale analyses. In this review, we propose possible ways of improving the resolvability of these evolutionary events, and discuss probable scenarios for cyclostome genome evolution, with special emphasis on the hypothesis that two-round (2R) genome duplication events occurred before the divergence between cyclostomes and gnathostomes, and therefore that a post-2R state is a genomic synapomorphy for all extant vertebrates.