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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Genome analysis of the smallest free-living eukaryote Ostreococcus tauri unveils many unique features
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Genome analysis of the smallest free-living eukaryote Ostreococcus tauri unveils many unique features

机译：对最小的自由生存真核生物Ostreococcus tauri的基因组分析揭示了许多独特的功能

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摘要

The green lineage is reportedly 1,500 million years old, evolving shortly after the endosymbiosis event that gave rise to early photosynthetic eukaryotes. In this study, we unveil the complete genome sequence of an ancient member of this lineage, the unicellular green alga Ostreococcus tauri (Prasinophyceae). This cosmopolitan marine primary producer is the world's smallest free-living eukaryote known to date. Features likely reflecting optimization of environmentally relevant pathways, including resource acquisition, unusual photosynthesis apparatus, and genes potentially involved in C-4 photosynthesis, were observed, as was downsizing of many gene families. Overall, the 12.56-Mb nuclear genome has an extremely high gene density, in part because of extensive reduction of intergenic regions and other forms of compaction such as gene fusion. However, the genome is structurally complex. It exhibits previously unobserved levels of heterogeneity for a eukaryote. Two chromosomes differ structurally from the other eighteen. Both have a significantly biased G+C content, and, remarkably, they contain the majority of transposable elements. Many chromosome 2 genes also have unique codon usage and splicing, but phylogenetic analysis and composition do not support alien gene origin. In contrast, most chromosome 19 genes show no similarity to green lineage genes and a large number of them are specialized in cell surface processes. Taken together, the complete genome sequence, unusual features, and downsized gene families, make O. tauri an ideal model system for research on eukaryotic genome evolution, including chromosome specialization and green lineage ancestry.
机译：据报道，这条绿色谱系已有15亿年的历史，发生在共生事件发生后不久，即引起早期光合作用的真核生物的进化。在这项研究中，我们揭示了该谱系古老成员单细胞绿藻Ostreococcus tauri（Prasinophyceae）的完整基因组序列。这个世界性的海洋初级生产者是迄今为止已知的世界上最小的自由生存真核生物。观察到的特征可能反映了与环境有关的途径的最优化，包括资源获取，异常的光合作用机制和可能参与C-4光合作用的基因，以及许多基因家族的缩减。总体而言，12.56-Mb核基因组具有极高的基因密度，部分原因是基因间区域的大量减少和其他形式的紧缩，例如基因融合。然而，基因组在结构上是复杂的。它表现出以前从未观察到的真核生物的异质性水平。两个染色体在结构上不同于其他十八个。两者的G + C含量均存在明显偏差，而且值得注意的是，它们都包含大部分转座因子。许多2号染色体基因也具有独特的密码子用法和剪接，但系统发育分析和组成不支持外来基因起源。相反，大多数19号染色体基因与绿色谱系基因没有相似性，其中许多基因专门用于细胞表面过程。综合起来，完整的基因组序列，不寻常的特征和缩小的基因家族，使得金紫菜（O.tauri）成为研究真核生物基因组进化（包括染色体特化和绿色谱系祖先）的理想模型系统。

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