Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs
Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs
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DOI：
10.1038/nature11681
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发表时间：
2012-12-06
期刊：
影响因子：
64.8
通讯作者：
Archibald, John M.
中科院分区：
文献类型：
--
作者：
Curtis, Bruce A.;Tanifuji, Goro;Archibald, John M.
隐藻和绿藻是真核藻类通过吞噬而获得光合作用的广泛次生内共生体的过渡形式。与大多数次生质体携带藻类，微型版本的内共生体核（核形物）坚持在隐藻和chlorarachniophytes。为了确定原因，并解决真核生物-真核生物内共生的其他基本问题，我们对隐藻Guillardia theta和绿藻Bigelowiella natans的核基因组进行了测序。两个基因组都有> 21，000个蛋白质基因，并且富含内含子，并且B。natans展示了单细胞生物体前所未有的选择性剪接。系统基因组分析和亚细胞靶向预测揭示了广泛的遗传和生化镶嵌，与宿主和内共生体衍生的基因服务于藻细胞，宿主细胞胞质溶胶，质体和残余的内共生体胞质溶胶的藻类。线粒体到细胞核的基因转移仍然发生在这两种生物中，但质体到细胞核和核形到细胞核的转移没有发生，这解释了为什么一小部分必需基因残留物仍然锁定在每个核形中。
Cryptophyte and chlorarachniophyte algae are transitional forms in the widespread secondary endosymbiotic acquisition of photosynthesis by engulfment of eukaryotic algae. Unlike most secondary plastid-bearing algae, miniaturized versions of the endosymbiont nuclei (nucleomorphs) persist in cryptophytes and chlorarachniophytes. To determine why, and to address other fundamental questions about eukaryote-eukaryote endosymbiosis, we sequenced the nuclear genomes of the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. Both genomes have >21,000 protein genes and are intron rich, and B. natans exhibits unprecedented alternative splicing for a single-celled organism. Phylogenomic analyses and subcellular targeting predictions reveal extensive genetic and biochemical mosaicism, with both host-and endosymbiont-derived genes servicing the mitochondrion, the host cell cytosol, the plastid and the remnant endosymbiont cytosol of both algae. Mitochondrion-to-nucleus gene transfer still occurs in both organisms but plastid-to-nucleus and nucleomorph-to-nucleus transfers do not, which explains why a small residue of essential genes remains locked in each nucleomorph.