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Nature:真核生物中原核生物基因的来源

摘要 : 多年来,人们一直假设,真核生物基因组中所见的原核生物基因一定是在一个原核细胞器的内共生之后到达那里的。

 多年来,人们一直假设,真核生物基因组中所见的原核生物基因一定是在一个原核细胞器的内共生之后到达那里的。但最近的证据表明,在真核生物之间以及在原核生物和真核生物之间也存在实质性的横向基因转移。对细菌、古菌和真核生物基因组所做的这项分析,没有发现连续横向基因转移对真核基因内容的演化具有可以检测得到的累积影响的证据。相反,真核生物是在广泛的差异基因(differential gene)丢失之后、在相应于线粒体和质体起源的两次“演化涌入”事件中获得其原核生物基因的。这一历史在复杂细胞的核基因组中留下了内共生的一个巨大印记。

原文链接:

Endosymbiotic origin and differential loss of eukaryotic genes

原文摘要:

Chloroplasts arose from cyanobacteria, mitochondria arose from proteobacteria. Both organelles have conserved their prokaryotic biochemistry, but their genomes are reduced, and most organelle proteins are encoded in the nucleus. Endosymbiotic theory posits that bacterial genes in eukaryotic genomes entered the eukaryotic lineage via organelle ancestors. It predicts episodic influx of prokaryotic genes into the eukaryotic lineage, with acquisition corresponding to endosymbiotic events. Eukaryotic genome sequences, however, increasingly implicate lateral gene transfer, both from prokaryotes to eukaryotes and among eukaryotes, as a source of gene content variation in eukaryotic genomes, which predicts continuous, lineage-specific acquisition of prokaryotic genes in divergent eukaryotic groups. Here we discriminate between these two alternatives by clustering and phylogenetic analysis of eukaryotic gene families having prokaryotic homologues. Our results indicate (1) that gene transfer from bacteria to eukaryotes is episodic, as revealed by gene distributions, and coincides with major evolutionary transitions at the origin of chloroplasts and mitochondria; (2) that gene inheritance in eukaryotes is vertical, as revealed by extensive topological comparison, sparse gene distributions stemming from differential loss; and (3) that continuous, lineage-specific lateral gene transfer, although it sometimes occurs, does not contribute to long-term gene content evolution in eukaryotic genomes.

来源: Nature 浏览次数:107

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