AUTHOR=Nishimura Yuki , Kume Keitaro , Sonehara Keito , Tanifuji Goro , Shiratori Takashi , Ishida Ken-ichiro , Hashimoto Tetsuo , Inagaki Yuji , Ohkuma Moriya 

TITLE=Mitochondrial Genomes of Hemiarma marina and Leucocryptos marina Revised the Evolution of Cytochrome c Maturation in Cryptista

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2020.00140

DOI=10.3389/fevo.2020.00140

ISSN=2296-701X

ABSTRACT=<p>Two evolutionarily distinct systems for cytochrome <italic>c</italic> maturation in mitochondria—Systems I and III—have been found among diverse aerobic eukaryotes. System I requires a set of proteins including mitochondrion-encoded CcmA, CcmB, CcmC, and CcmF (or a subset of the four proteins). On the other hand, System III is operated exclusively by nucleus-encoded proteins. The two systems are mutually exclusive among eukaryotes except a single organism possessing both. Recent advances in understanding both diversity and phylogeny of eukaryotes united cryptophytes, goniomonads, <italic>Hemiarma marina</italic>, kathablepharids and <italic>Palpitomonas bilix</italic> into one of the major taxonomic assemblages in eukaryotes (Cryptista). Among the lineages/species in Cryptista, the mitochondrial genomes (mtDNAs) have been completed for multiple cryptophytes, a goniomonad and <italic>P. bilix</italic>, and <italic>ccm</italic> genes were found solely in the <italic>P. bilix</italic> mtDNA. Nevertheless, we have been unsure whether <italic>H. marina</italic> and/or kathablepharids use System I for cytochrome <italic>c</italic> maturation, as no mtDNA was available for either of the two cryptist members. In this study, we determined the complete sequences of the mtDNAs of <italic>H. marina</italic> and a kathablepharid <italic>Leucocryptos marina</italic>, and found <italic>ccmA, ccmC</italic>, and <italic>ccmF</italic> in the former genome. Curiously, the <italic>ccm</italic> genes found in the <italic>H. marina</italic> mtDNA showed no phylogenetic affinity to the <italic>P. bilix</italic> homologs, unfavoring vertical inheritance of the <italic>ccm</italic> genes in the mtDNA evolution in Cryptista. Finally, we propose revised scenarios for the evolution of cytochrome <italic>c</italic> maturation systems in Cryptista by incorporating the mtDNA data obtained in this study.</p>