Karlberg O, Canbäck B, Kurland C G, Andersson S G
Department of Molecular Evolution, Uppsala University, 751 24 Uppsala, Sweden.
Yeast. 2000 Sep 30;17(3):170-87. doi: 10.1002/1097-0061(20000930)17:3<170::AID-YEA25>3.0.CO;2-V.
We propose a scheme for the origin of mitochondria based on phylogenetic reconstructions with more than 400 yeast nuclear genes that encode mitochondrial proteins. Half of the yeast mitochondrial proteins have no discernable bacterial homologues, while one-tenth are unequivocally of alpha-proteobacterial origin. These data suggest that the majority of genes encoding yeast mitochondrial proteins are descendants of two different genomic lineages that have evolved in different modes. First, the ancestral free-living alpha-proteobacterium evolved into an endosymbiont of an anaerobic host. Most of the ancestral bacterial genes were lost, but a small fraction of genes supporting bioenergetic and translational processes were retained and eventually transferred to what became the host nuclear genome. In a second, parallel mode, a larger number of novel mitochondrial genes were recruited from the nuclear genome to complement the remaining genes from the bacterial ancestor. These eukaryotic genes, which are primarily involved in transport and regulatory functions, transformed the endosymbiont into an ATP-exporting organelle.
我们基于对400多个编码线粒体蛋白的酵母核基因进行系统发育重建，提出了一种线粒体起源的方案。一半的酵母线粒体蛋白没有可识别的细菌同源物，而十分之一明确起源于α-变形菌。这些数据表明，编码酵母线粒体蛋白的大多数基因是两个以不同模式进化的不同基因组谱系的后代。首先，祖先的自由生活α-变形菌进化成为厌氧宿主的内共生体。大多数祖先细菌基因丢失了，但一小部分支持生物能量和翻译过程的基因被保留下来，并最终转移到后来成为宿主核基因组的部分。在第二种平行模式中，从核基因组中招募了大量新的线粒体基因，以补充来自细菌祖先的其余基因。这些主要参与运输和调节功能的真核基因，将内共生体转变为一个输出ATP的细胞器。
