Harada Ryo, Shiratori Takashi, Yabuki Akinori, Inagaki Yuji, Roger Andrew J, Kamikawa Ryoma
Department of Biochemistry and Molecular Biology, Institute for Comparative Genomics, Dalhousie University, Halifax, Nova Scotia, Canada.
Institute of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
J Eukaryot Microbiol. 2025 May-Jun;72(3):e70012. doi: 10.1111/jeu.70012.
Mitochondria of eukaryotic cells are direct descendants of an endosymbiotic bacterium related to Alphaproteobacteria. These organelles retain their own genomes, which are highly reduced and divergent when compared to those of their bacterial relatives. To better understand the trajectory of mitochondrial genome evolution from the last eukaryotic common ancestor (LECA) to extant species, mitochondrial genome sequences from phylogenetically diverse lineages of eukaryotes-particularly protists-are essential. For this reason, we focused on the mitochondrial genomes of Ancyromonadida, an independent and understudied protist lineage in the eukaryote tree of life. Here we report the mitochondrial genomes from three Ancyromonadida: Ancyromonas sigmoides, Nutomonas longa, and Fabomonas tropica. Our analyses reveal that these mitochondrial genomes are circularly mapping molecules with inverted repeats that carry genes. This inverted repeat structure has been observed in other mitochondrial genomes but is patchily distributed over the tree of eukaryotes. Ancyromonad mitochondrial genomes possess several protein-coding genes, which have not been detected from any other mitochondrial genomes of eukaryotes sequenced to date, thereby extending the known mitochondrial gene repertoire of ancestral eukaryotes, including LECA. These findings significantly expand our understanding of mitochondrial genome diversity across eukaryotes, shedding light on the early phases of mitochondrial genome evolution.
真核细胞的线粒体是与α-变形菌相关的内共生细菌的直接后代。这些细胞器保留了自己的基因组，与它们的细菌亲属的基因组相比，这些基因组高度简化且存在差异。为了更好地理解线粒体基因组从最后的真核生物共同祖先（LECA）到现存物种的进化轨迹，来自系统发育上不同的真核生物谱系——特别是原生生物——的线粒体基因组序列至关重要。出于这个原因，我们专注于锚定单胞虫纲的线粒体基因组，这是真核生物生命之树中一个独立且研究不足的原生生物谱系。在这里，我们报告了三种锚定单胞虫纲生物的线粒体基因组：西格玛锚定单胞虫、长形营养单胞虫和热带法博单胞虫。我们的分析表明，这些线粒体基因组是带有携带基因的反向重复序列的环状图谱分子。这种反向重复结构在其他线粒体基因组中也有观察到，但在真核生物树中分布不均。锚定单胞虫线粒体基因组拥有几个蛋白质编码基因，这些基因在迄今为止测序的任何其他真核生物线粒体基因组中都未被检测到，从而扩展了包括LECA在内的祖先真核生物已知的线粒体基因库。这些发现显著扩展了我们对真核生物线粒体基因组多样性的理解，为线粒体基因组进化的早期阶段提供了线索。
