title: Roles for heme-copper oxidases in extreme high-light and oxidative stress response in the cyanobacterium Synechococcus sp. PCC 7002.
abstract: The ctaCIDIEI and ctaCIIDIIEII gene clusters that encode heme-copper cytochrome oxidases have been characterized in the marine cyanobacterium Synechococcus sp. PCC 7002 and the inactivation of ctaDI was shown to affect high-light adaptation. In this study, Synechococcus sp. PCC 7002 wild-type, ctaDI, ctaDII, and ctaDI-ctaDII double mutants were grown under extreme high-light and oxidative stress to further assess the roles of cytochrome oxidases in cyanobacteria. Cells of the ctaDI mutant strain barely grew under extreme high-light illumination of 4.5 mE m(-2) s(-1), suggesting that CtaDI is required for high-light acclimation in Synechococcus sp. PCC 7002. The ctaDI-ctaDII double mutant cells unexpectedly tolerated extreme high-light intensity, indicating that the disruption of ctaDII gene suppresses the high-light sensitivity phenotype of the ctaDI single mutant. The ctaDII mutant cells also exhibited higher tolerance to the oxidative stress compound, methyl viologen, in the growth media. The ctaDII mutant and the ctaDI-ctaDII double mutant cells had approximately twofold higher levels of superoxide dismutase (SOD) activity, indicating that the disruption of ctaDII gene increased the capacity to decompose active oxygen species. These results suggest that the CtaII cytochrome oxidase may be involved with the oxidative stress response, including the control of SOD expression.
authors.affiliation: Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY, 13210-2726, USA. ctnomura@esf.edu
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Nomura
authors.forename: Toshio
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
mesh_terms: D001426:Bacterial Proteins; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000458:Cyanobacteria / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D010269:Paraquat / Q000494:pharmacology; D010544:Peroxidases / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002734:Chlorophyll; D006418:Heme; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D010544:Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; C024748:copper oxidase; D010269:Paraquat; D010100:Oxygen