Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.
Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia 30602, USA.
Genome Res. 2021 May;31(5):852-865. doi: 10.1101/gr.266403.120. Epub 2021 Apr 27.
Mitochondrial genome content and structure vary widely across the eukaryotic tree of life, with protists displaying extreme examples. Apicomplexan and dinoflagellate protists have evolved highly reduced mitochondrial genome sequences, mtDNA, consisting of only three cytochrome genes and fragmented rRNA genes. Here, we report the independent evolution of fragmented cytochrome genes in and related tissue coccidia and evolution of a novel genome architecture consisting minimally of 21 sequence blocks (SBs) totaling 5.9 kb that exist as nonrandom concatemers. Single-molecule Nanopore reads consisting entirely of SBs ranging from 0.1 to 23.6 kb reveal both whole and fragmented cytochrome genes. Full-length cytochrome transcripts including a divergent are detected. The topology of the mitochondrial genome remains an enigma. Analysis of a point mutation reveals that homoplasmy of SBs is maintained. Tissue coccidia are important pathogens of man and animals, and the mitochondrion represents an important therapeutic target. The mtDNA sequence has been elucidated, but a definitive genome architecture remains elusive.
线粒体基因组的内容和结构在真核生物的生命之树上差异很大，原生动物表现出极端的例子。顶复门和甲藻原生动物的线粒体基因组序列高度简化，仅由三个细胞色素基因和碎片化的 rRNA 基因组成。在这里，我们报告了 和相关组织球虫中碎片化细胞色素基因的独立进化，以及一种由 21 个序列块（SBs）组成的最小基因组结构的进化，这些 SBs 总长达 5.9kb，以非随机串联体的形式存在。完全由 0.1 到 23.6kb 的 SB 组成的单分子纳米孔读数揭示了完整和碎片化的细胞色素基因。包括一个分歧的 在内的全长细胞色素转录本被检测到。线粒体基因组的拓扑结构仍然是一个谜。对一个 点突变的分析表明，SBs 的同型合子性得以维持。组织球虫是人类和动物的重要病原体，线粒体是一个重要的治疗靶点。线粒体 DNA 序列已经阐明，但明确的基因组结构仍然难以捉摸。
