Department of Biochemistry and Molecular Biology, Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada.
Biosciences University of Exeter, Exeter, United Kingdom.
Mol Biol Evol. 2017 Apr 1;34(4):943-956. doi: 10.1093/molbev/msw298.
Mitochondria are the respiratory organelles of eukaryotes and their evolutionary history is deeply intertwined with that of eukaryotes. The compartmentalization of respiration in mitochondria occurs within cristae, whose evolutionary origin has remained unclear. Recent discoveries, however, have revived the old notion that mitochondrial cristae could have had a pre-endosymbiotic origin. Mitochondrial cristae are likely homologous to the intracytoplasmic membranes (ICMs) used by diverse alphaproteobacteria for harnessing energy. Because the Mitochondrial Contact site and Cristae Organizing System (MICOS) that controls the development of cristae evolved from a simplified version that is phylogenetically restricted to Alphaproteobacteria (alphaMICOS), ICMs most probably transformed into cristae during the endosymbiotic origin of mitochondria. This inference is supported by the sequence and structural similarities between MICOS and alphaMICOS, and the expression pattern and cellular localization of alphaMICOS. Given that cristae and ICMs develop similarly, alphaMICOS likely functions analogously to mitochondrial MICOS by culminating ICM development with the creation of tubular connections and membrane contact sites at the alphaproteobacterial envelope. Mitochondria thus inherited a pre-existing ultrastructure adapted to efficient energy transduction from their alphaproteobacterial ancestors. The widespread nature of purple bacteria among alphaproteobacteria raises the possibility that cristae evolved from photosynthetic ICMs.
线粒体是真核生物的呼吸细胞器，其进化史与真核生物的进化史密切交织在一起。线粒体的呼吸分隔发生在嵴内，但其进化起源仍不清楚。然而，最近的发现重新提出了一个旧观念，即线粒体嵴可能具有前共生起源。线粒体嵴可能与各种α变形菌用于获取能量的胞质内膜（ICM）同源。因为控制嵴发育的线粒体接触位点和嵴组织系统（MICOS）是从一种简化的版本进化而来的，这种简化的版本在系统发育上仅限于α变形菌（alphaMICOS），所以 ICM 很可能在线粒体的内共生起源过程中转化为嵴。这一推断得到了 MICOS 和 alphaMICOS 之间的序列和结构相似性、alphaMICOS 的表达模式和细胞定位的支持。鉴于嵴和 ICM 的发育方式相似，alphaMICOS 很可能通过在α变形菌包膜上形成管状连接和膜接触点，来模拟线粒体 MICOS 的功能，从而完成 ICM 的发育。因此，线粒体从其α变形菌祖先那里继承了一种预先存在的适应于高效能量转导的超微结构。紫细菌在α变形菌中的广泛存在，增加了嵴从光合 ICM 进化而来的可能性。
