An ancestral mitochondrial DNA resembling a eubacterial genome in miniature
An ancestral mitochondrial DNA resembling a eubacterial genome in miniature
复制标题
DOI：
10.1038/387493a0
复制
发表时间：
1997-05-29
期刊：
影响因子：
64.8
通讯作者：
Gray, MW
中科院分区：
文献类型：
--
作者：
Lang, BF;Burger, G;Gray, MW
线粒体是真核细胞中专门负责能量守恒反应的细胞器，由类真细菌内共生体 (1-3) 进化而来，其已知的最近亲是 α-变形菌门的立克次体群 (4,5)。由于表征的线粒体基因组在结构上存在显着差异(3)，因此不可能从中推断出原线粒体基因组的初始形式。这需要鉴定出能更好地反映祖先状态的最低限度来源的线粒体 DNA。在这里，我们描述了淡水原生动物美洲斜纹单胞菌 (Relinomonas americana) 中的这种原始线粒体基因组(6)。该原生生物表现出的超微结构特征使其与 retortamonads(7,8)（一种缺乏线粒体的原生动物群）相结合(8,9)。 R. americana mtDNA（69,034 个碱基对）包含迄今为止在任何 mtDNA 中发现的最大基因集合（97 个），包括 5S 核糖体 RNA 的基因（RNase P 的 RNA 成分）以及至少 18 种以前未知的线粒体编码蛋白。最令人惊讶的是四个基因，指定多亚基、真细菌型 RNA 聚合酶。基因内容的特征以及以前在线粒体基因组中未发现的基因组组织和表达的真细菌特征表明，美洲R. americana mtDNA比迄今为止研究的任何其他mtDNA更类似于祖先原线粒体基因组。
Mitochondria, organelles specialized in energy conservation reactions in eukaryotic cells, have evolved from eubacteria-like endosymbionts(1-3) whose closest known relatives are the rickettsial group of alpha-proteobacteria(4,5). Because characterized mitochondrial genomes vary markedly in structure(3), it has been impossible to infer from them the initial form of the proto-mitochondrial genome. This would require the identification of minimally derived mitochondrial DNAs that better reflect the ancestral state, Here we describe such a primitive mitochondrial genome, in the freshwater protozoon Reclinomonas americana(6). This protist displays ultrastructural characteristics that ally it with the retortamonads(7,8), a protozoan group that lacks mitochondria(8,9). R. americana mtDNA (69,034 base pairs) contains the largest collection of genes (97) so far identified in any mtDNA, including genes for 5S ribosomal RNA, the RNA component of RNase P, and at least 18 proteins not previously known to be encoded in mitochondria, Most surprising are four genes specifying a multisubunit, eubacterial-type RNA polymerase. Features of gene content together with eubacterial characteristics of genome organization and expression not found before in mitochondrial genomes indicate that R. americana mtDNA more closely resembles the ancestral proto-mitochondrial genome than any other mtDNA investigated to date.