Molecular data suggest an early acquisition of the mitochondrion endosymbiont
Molecular data suggest an early acquisition of the mitochondrion endosymbiont
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DOI：
10.1098/rspb.1996.0155
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发表时间：
1996-08-22
影响因子：
4.7
通讯作者：
Embley, TM
中科院分区：
文献类型：
--
作者：
Horner, DS;Hirt, RP;Embley, TM
小亚基核糖体RNA基因组中最深分支的三个真核谱系是无线粒体小孢子虫、后单核虫和副基生虫。其次是裸藻（Euglenozoa）（例如裸藻（Euglena）和锥虫（Trypanosoma））或Percolozoa，它们是第一个含有裸藻的真核生物。为了调查的假设，甚至更早的时间内共生的寄生虫，我们已经扩增了部分cpn-60编码区的parabasalid阴道毛滴虫和第一个这样的序列percolozoan，福氏耐格里。预测的蛋白质序列的分析揭示了高度的序列相似性（大于或等于40%）与选择的公布的细菌和线粒体的CPN-60的两个类群。这两个序列恢复在一个强烈支持的单系群，否则定义的线粒体序列，系统地与α-变形菌群集。这些结果为T.迷走细胞曾经包含产生线粒体的内共生体，并表明这种共生可能发生在毛滴虫谱系从主要的真核生物主干分化之前。这也使得发表的假设，即毛滴虫氢化酶体可能代表一个生化修饰的蛋白质是可行的。分析了N. Fowleri cpn-60不支持这样的假设，即含毛滴虫的Percolozoa代表cpn-60树中比毛滴虫或锥虫更早的分支。
The three deepest branching eucaryotic lineages in small subunit ribosomal RNA phylogenies are the amitochondriate Microspora, Metamonada and Parabasala. They are followed by either the Euglenozoa (e.g. Euglena and Trypanosoma) or the Percolozoa as the first mitochondria-containing eucaryotes. To investigate the hypothesis of an even earlier timing of the mitochondrion endosymbiosis we have amplified a partial cpn-60 coding region from the parabasalid Trichomonas vaginalis and the first such sequence from a percolozoan, Naegleria fowleri. Analysis of predicted protein sequences reveals a high degree of sequence similarity (greater than or equal to 40%) with a selection of published bacterial and mitochondrial cpn-60s for both taxa. Both sequences were recovered within a strongly supported monophyletic group, otherwise defined by mitochondrial sequences, which systematically clustered with alpha-proteobacteria. These results provide compelling evidence that the ancestor of T. vaginalis once contained the endosymbiont which gave rise to mitochondria, and suggest that this symbiosis probably occurred before the Trichomonas lineage diverged from the main eukaryote trunk. It also makes feasible the published hypothesis that the Trichomonas hydrogenosome might represent a biochemically modified mitochondrion. Analysis of the N. fowleri cpn-60 did not support the hypothesis that the mitochondrion-containing Percolozoa represent an earlier branch in the cpn-60 tree than Trichomonas or Trypanosoma.