Nomura Christopher T, Sakamoto Toshio, Bryant Donald A
Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY, 13210-2726, USA.
Arch Microbiol. 2006 Jun;185(6):471-9. doi: 10.1007/s00203-006-0107-7. Epub 2006 Apr 27.
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.
编码血红素-铜细胞色素氧化酶的ctaCIDIEI和ctaCIIDIIEII基因簇已在海洋蓝藻聚球藻属PCC 7002中得到表征，并且已证明ctaDI的失活会影响高光适应。在本研究中，聚球藻属PCC 7002野生型、ctaDI、ctaDII和ctaDI-ctaDII双突变体在极端高光和氧化应激条件下生长，以进一步评估细胞色素氧化酶在蓝藻中的作用。ctaDI突变株的细胞在4.5 mE m(-2) s(-1)的极端高光照射下几乎无法生长，这表明CtaDI是聚球藻属PCC 7002中高光适应所必需的。ctaDI-ctaDII双突变体细胞出人意料地耐受极端高光强度，这表明ctaDII基因的破坏抑制了ctaDI单突变体的高光敏感表型。ctaDII突变体细胞在生长培养基中对氧化应激化合物甲基紫精也表现出更高的耐受性。ctaDII突变体和ctaDI-ctaDII双突变体细胞的超氧化物歧化酶（SOD）活性水平大约高出两倍，这表明ctaDII基因的破坏增加了分解活性氧的能力。这些结果表明，CtaII细胞色素氧化酶可能参与氧化应激反应，包括对SOD表达的控制。
