| SS4.02 Ecology and Physiology of Marine Organisms: Insights from Genes, Genomes, and Proteomes |
| Wolfe, F, L, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, USA, wolfe@imcs.rutgers.edu |
| Schofield, O, M, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, USA, oscar@imcs.rutgers.edu |
| Falkowski, P, G, Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, USA, falko@imcs.rutgers.edu |
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| THE DIVERSE MOLECULAR EVOLUTION OF IRON AND MANGANESE SUPEROXIDE DISMUTASES IN OXYGENIC PHOTOAUTOTROPHS |
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| The evolution of oxygenic photosynthesis is coupled to a highly conserved set of protective enzymes that defend cells from reactive oxygen species. The metalloenzyme superoxide dismutase (SOD) is the most prevalent and comes in several forms distinguished by the biogeochemically significant metal cofactor (Fe, Mn, Cu, Ni) present. We employed a maximum likelihood approach using both DNA and amino acid data to investigate the evolutionary relationships between SODs. Although the iron (Fe) and manganese (Mn) forms are homologous whole sequence maximum likelihood analyses suggest they evolved under different selective pressures. These phylogenetic trees indicate that MnSODs of eukaryotic and prokaryotic phytoplankton group together and share a common origin with the major FeSOD clade whereas their true FeSODs have different recent ancestors. Furthermore, the primary sequence can be divided into two domains, the N and C-terminals, which exhibit different divergence patterns. Although its position is presently unclear, root placement is critical to understanding which SOD form evolved first. Our data suggest that understanding the timing of diversification between these genes elucidates information about the local redox conditions under which they evolved. |
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