Gray M W, Burger G, Lang B F
Department of Biochemistry, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada.
Science. 1999 Mar 5;283(5407):1476-81. doi: 10.1126/science.283.5407.1476.
The serial endosymbiosis theory is a favored model for explaining the origin of mitochondria, a defining event in the evolution of eukaryotic cells. As usually described, this theory posits that mitochondria are the direct descendants of a bacterial endosymbiont that became established at an early stage in a nucleus-containing (but amitochondriate) host cell. Gene sequence data strongly support a monophyletic origin of the mitochondrion from a eubacterial ancestor shared with a subgroup of the alpha-Proteobacteria. However, recent studies of unicellular eukaryotes (protists), some of them little known, have provided insights that challenge the traditional serial endosymbiosis-based view of how the eukaryotic cell and its mitochondrion came to be. These data indicate that the mitochondrion arose in a common ancestor of all extant eukaryotes and raise the possibility that this organelle originated at essentially the same time as the nuclear component of the eukaryotic cell rather than in a separate, subsequent event.
连续内共生理论是解释线粒体起源的一个备受青睐的模型，线粒体起源是真核细胞进化中的一个决定性事件。通常所描述的该理论假定，线粒体是一种细菌内共生体的直接后代，这种内共生体在早期存在于一个含有细胞核（但无线粒体）的宿主细胞中。基因序列数据有力地支持了线粒体起源于与α-变形菌亚群共有的真细菌祖先的单系起源。然而，最近对单细胞真核生物（原生生物）的研究，其中一些鲜为人知，提供了一些见解，对基于传统连续内共生的真核细胞及其线粒体如何形成的观点提出了挑战。这些数据表明，线粒体出现在所有现存真核生物的共同祖先中，并增加了这种细胞器与真核细胞的细胞核成分基本同时起源而非在一个单独的后续事件中起源的可能性。
