title: Lateral transfer of tetrahymanol-synthesizing genes has allowed multiple diverse eukaryote lineages to independently adapt to environments without oxygen.
abstract: Sterols are key components of eukaryotic cellular membranes that are synthesized by multi-enzyme pathways that require molecular oxygen. Because prokaryotes fundamentally lack sterols, it is unclear how the vast diversity of bacterivorous eukaryotes that inhabit hypoxic environments obtain, or synthesize, sterols. Here we show that tetrahymanol, a triterpenoid that does not require molecular oxygen for its biosynthesis, likely functions as a surrogate of sterol in eukaryotes inhabiting oxygen-poor environments. Genes encoding the tetrahymanol synthesizing enzyme squalene-tetrahymanol cyclase were found from several phylogenetically diverged eukaryotes that live in oxygen-poor environments and appear to have been laterally transferred among such eukaryotes.
authors.affiliation: Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, 237-0061, Japan. takishitak@jamstec.go.jp
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Takishita
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Chikaraishi
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Leger
authors.forename: Eunsoo
authors.initials: E
authors.lastname: Kim
authors.forename: Akinori
authors.initials: A
authors.lastname: Yabuki
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Roger
mesh_terms: D000220:Adaptation, Biological; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D002462:Cell Membrane / Q000737:chemistry; D056890:Eukaryota / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D008401:Gas Chromatography-Mass Spectrometry; D022761:Gene Transfer, Horizontal; D008055:Lipids / Q000032:analysis / Q000737:chemistry / Q000235:genetics; D008190:Lyases / Q000235:genetics; D010100:Oxygen / Q000737:chemistry; D010587:Phagocytosis; D010802:Phylogeny; D016415:Sequence Alignment; D013045:Species Specificity; D014315:Triterpenes / Q000737:chemistry*
chemical_list: D008055:Lipids; D014315:Triterpenes; C100046:tetrahymanol; D008190:Lyases; C022651:squalene cyclase; D010100:Oxygen