THE ROLE AND EVOLUTION OF SUPEROXIDE DISMUTASES IN ALGAE

Authors

  • Felisa Wolfe-Simon,

    1. Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, New Jersey 08901, USA
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  • Daniel Grzebyk,

    1. Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, New Jersey 08901, USA
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  • Oscar Schofield,

    1. Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, New Jersey 08901, USA
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  • Paul G. Falkowski

    1. Environmental Biophysics and Molecular Ecology Program, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, New Jersey 08901, USA; and Department of Geological Science, Rutgers University, Wright Geological Laboratory, 610 Taylor Road, Piscataway, New Jersey 08854, USA
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  • 1Received 3 September 2004. Accepted 15 March 2005.

Abstract

Superoxide dismutases (SOD) catalyze the disproportionation of the potentially destructive superoxide anion radical (O2•−, a byproduct of aerobic metabolism) to molecular oxygen and hydrogen peroxide: 2O2•−+2H+→H2O2+O2. Based on metal cofactors, four known metalloforms of SOD enzymes have been identified: they contain either Fe, Mn, Cu and Zn, or Ni. Orthologs of all metalloforms are present in oxygenic photoautotrophs. The expression of SOD is highly regulated, with specific metalloforms playing an inducible protective role for specific cellular compartments. The various metalloforms of SOD are not distributed equally within either cyanobacteria or eukaryotic algae. Typically, cyanobacteria contain either an NiSOD alone or combinations of Mn and Ni or Fe and Mn metalloforms (CuZn is rare among the cyanobacteria). The bacillariophytes and rhodophytes retain an active MnSOD, whereas the chlorophytes, haptophytes, and embryophytes have either FeSOD or multiple combinations of Fe, Mn, and CuZnSODs. The NiSOD is a relatively novel SOD and has been generally excluded from evolutionary analyses. In both cyanobacteria and chlorophyte algae, the FeSOD metalloform appears to be associated with PSI, where its primary role is most likely to deactivate reactive oxygen produced by the Mehler reaction. The CuZnSOD also appears to be associated with the plastid but is phylogenetically more restricted in its distribution. In eukaryotic algae, SODs are all nuclear encoded and, based on nucleotide sequence, protein structures, and phylogenetic distributions, appear to have unique evolutionary histories arising from the lateral gene transfer of three distinct genes to the nucleus after the endosymbiotic acquisition of mitochondria and plastids. The varied phylogenetic histories and subcellular localizations suggest significantly different selection on these SOD metalloforms after the endosymbiont organelle-to-host gene transfer.

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