Genome expansion via lineage splitting and genome reduction in the cicada endosymbiont Hodgkinia
Genome expansion via lineage splitting and genome reduction in the cicada endosymbiont Hodgkinia
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DOI：
10.1073/pnas.1421386112
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发表时间：
2015-08-18
影响因子：
11.1
通讯作者：
McCutcheon, John P.
中科院分区：
文献类型：
--
作者：
Campbell, Matthew A.;Van Leuven, James T.;McCutcheon, John P.
来自线粒体、质体和互利共生内共生细菌的比较基因组学已经表明，细菌在宿主细胞中的稳定建立导致基因组减少。虽然许多高度简化的内共生细菌的基因组在基因内容和基因组结构上是稳定的，但细胞器基因组有时具有显着的结构多样性。以前的研究结果表明，这种细菌的一些谱系已经分裂成两个新的细胞学上不同但遗传上相互依赖的物种。据推测，蝉的长生命周期在一定程度上促成了这种不寻常的谱系分裂事件。在这里，我们通过调查Ca的结构来测试这一假设。Hodgkinia基因组在最长寿的蝉之一，Magicicada tredecim。我们表明，钙。Hodgkinia基因组来自M. Tredecim已分裂成多个新的染色体或基因组，其中至少一些剩余的被分割成离散的细胞。我们还表明，这种谱系分裂过程导致了复杂的Ca。霍奇金氏基因组是1.1 Mb对长度时，考虑在一起，几乎10倍的大小从假设的单基因组祖先。这些结果与细胞器中基因组片段化和扩增的一些例子相平行，尽管引起这些极端基因组不稳定性的机制可能不同。
Comparative genomics from mitochondria, plastids, and mutualistic endosymbiotic bacteria has shown that the stable establishment of a bacterium in a host cell results in genome reduction. Although many highly reduced genomes from endosymbiotic bacteria are stable in gene content and genome structure, organelle genomes are sometimes characterized by dramatic structural diversity. Previous results from Candidatus Hodgkinia cicadicola, an endosymbiont of cicadas, revealed that some lineages of this bacterium had split into two new cytologically distinct yet genetically interdependent species. It was hypothesized that the long life cycle of cicadas in part enabled this unusual lineage-splitting event. Here we test this hypothesis by investigating the structure of the Ca. Hodgkinia genome in one of the longest-lived cicadas, Magicicada tredecim. We show that the Ca. Hodgkinia genome from M. tredecim has fragmented into multiple new chromosomes or genomes, with at least some remaining partitioned into discrete cells. We also show that this lineage-splitting process has resulted in a complex of Ca. Hodgkinia genomes that are 1.1-Mb pairs in length when considered together, an almost 10-fold increase in size from the hypothetical single-genome ancestor. These results parallel some examples of genome fragmentation and expansion in organelles, although the mechanisms that give rise to these extreme genome instabilities are likely different.