title: Metabolic Capacity of Mitochondrion-related Organelles in the Free-living Anaerobic Stramenopile Cantina marsupialis.
abstract: Functionally and morphologically degenerate mitochondria, so-called mitochondrion-related organelles (MROs), are frequently found in eukaryotes inhabiting hypoxic or anoxic environments. In the last decade, MROs have been discovered from a phylogenetically broad range of eukaryotic lineages and these organelles have been revealed to possess diverse metabolic capacities. In this study, the biochemical characteristics of an MRO in the free-living anaerobic protist Cantina marsupialis, which represents an independent lineage in stramenopiles, were inferred based on RNA-seq data. We found transcripts for proteins known to function in one form of MROs, the hydrogenosome, such as pyruvate:ferredoxin oxidoreductase, iron-hydrogenase, acetate:succinate CoA-transferase, and succinyl-CoA synthase, along with transcripts for acetyl-CoA synthetase (ADP-forming). These proteins possess putative mitochondrial targeting signals at their N-termini, suggesting dual ATP generation systems through anaerobic pyruvate metabolism in Cantina MROs. In addition, MROs in Cantina were also shown to share several features with canonical mitochondria, including amino acid metabolism and an "incomplete" tricarboxylic acid cycle. Transcripts for all four subunits of complex II (CII) of the electron transport chain were detected, while there was no evidence for the presence of complexes I, III, IV, or F1Fo ATPase. Cantina MRO biochemistry challenges the categories of mitochondrial organelles recently proposed.
authors.affiliation: Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo, Japan; Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Noguchi
authors.affiliation: Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shimamura
authors.affiliation: Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan.
authors.forename: Takuro
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Euki
authors.initials: E
authors.lastname: Yazaki
authors.affiliation: Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Yabuki
authors.affiliation: Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Hashimoto
authors.affiliation: Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Inagaki
authors.affiliation: Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo, Japan; Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan.
authors.forename: Katsunori
authors.initials: K
authors.lastname: Fujikura
authors.affiliation: Graduate School of Marine Science and Technology, Tokyo University of Marine Science and Technology, Minato-ku, Tokyo, Japan; Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan. Electronic address: takishitak@jamstec.go.jp.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Takishita
mesh_terms: D008928:Mitochondria / Q000378:metabolism*; D010802:Phylogeny; D017423:Sequence Analysis, RNA; D058009:Stramenopiles / Q000235:genetics / Q000378:metabolism*
keywords: Anoxic; hydrogenosomes; mitochondria; stramenopiles.