title: Molecular characterization of iron-containing superoxide dismutases in the heterotrophic dinoflagellate Crypthecodinium cohnii.
abstract: Superoxide dismutases (SODs) are a family of antioxidant enzymes that catalyse the degradation of toxic superoxide radicals in obligate and facultative aerobic organisms. Here, we report the presence of a multi-copy gene family encoding SODs in the heterotrophic dinoflagellate Crypthecodinium cohnii. All the genes identified (sod1 to sod17) have been cloned and sequenced, and shown to encode potentially functional dimeric iron-containing SOD isozymes. Our data revealed a considerable molecular heterogeneity of this enzyme in C. cohnii at both genomic and transcriptional levels. The C. cohnii SOD1, overexpressed in Escherichia coli, was active and its structure obtained by homology modeling using X-ray crystal structures of homologues exhibited the typical fold of dimeric FeSODs. Phylogenetic studies including 110 other dimeric FeSODs and closely related cambialistic dimeric SOD sequences showed that the C. cohnii SODs form a monophyletic group and have all been acquired by the same event of horizontal gene transfer. It also revealed a dichotomy within the C. cohnii SOD sequences that could be explained by an ancestral sod gene duplication followed by subsequent gene duplications within each of the two groups. Enzyme assays of SOD activity indicated the presence of two FeSOD activities in C. cohnii cell lysate whereas MnSOD and Cu/ZnSOD were not detected. These activities contrasted with the SOD repertoire previously characterized in photosynthetic dinoflagellates. To explain these differences, a hypothetical evolutionary scenario is proposed that suggests gains and losses of sod genes in dinoflagellates.
authors.affiliation: Institut Pasteur de Lille, Université Lille 2, 59019 Lille cedex, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Dufernez
authors.forename: Evelyne
authors.initials: E
authors.lastname: Derelle
authors.forename: Christophe
authors.initials: C
authors.lastname: Noël
authors.forename: Giovanna
authors.initials: G
authors.lastname: Sanciu
authors.forename: Cléa
authors.initials: C
authors.lastname: Mantini
authors.forename: Daniel
authors.initials: D
authors.lastname: Dive
authors.forename: Marie-Odile
authors.initials: MO
authors.lastname: Soyer-Gobillard
authors.forename: Monique
authors.initials: M
authors.lastname: Capron
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Pierce
authors.forename: René
authors.initials: R
authors.lastname: Wintjens
authors.forename: Delphine
authors.initials: D
authors.lastname: Guillebault
authors.forename: Eric
authors.initials: E
authors.lastname: Viscogliosi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000460:Chlorophyta / Q000145:classification / Q000201:enzymology / Q000235:genetics; D003001:Cloning, Molecular; D004141:Dinoflagellida / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D052836:Heterotrophic Processes; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010944:Plants / Q000145:classification / Q000201:enzymology / Q000235:genetics; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D015800:Protozoan Proteins; D013482:Superoxide Dismutase