Group 2 Sigma Factors are Central Regulators of Oxidative Stress Acclimation in Cyanobacteria
Group 2 Sigma Factors are Central Regulators of Oxidative Stress Acclimation in Cyanobacteria
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DOI：
10.1093/pcp/pcy221
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发表时间：
2019-02-01
影响因子：
4.9
通讯作者：
Tyystjarvi, Taina
中科院分区：
文献类型：
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作者：
Hakkila, Kaisa;Valev, Dimitar;Tyystjarvi, Taina
蓝藻聚囊藻（synnechocystis sp. PCC 6803）适应次优环境时，RNA聚合酶（RNAP）的调控因子根据环境线索调节基因表达。在这里，我们展示了非必需的2组西格玛因子在氧化应激反应中的核心作用。缺少所有2组sigma因子的细胞不能适应化学诱导的单线态氧、超氧化物或H2O2胁迫，并且在强光下失去色素。SigB和SigD是氧化应激中的主要sigma因子，而SigC和SigE仅起次要作用。SigD因子在强光、单线态氧和H2O2胁迫下表达上调，δ sigBCE菌株中SigD因子的过量表达导致δ sigBCE细胞在这些胁迫条件下具有较好的生长能力。超氧化物不诱导SigD因子的产生，但适度诱导SigB和SigC因子的产生。δ sigBDE中单独的SigB因子在超氧胁迫下支持的生长速度几乎与对照菌株中完全补充的sigma因子一样快，但过量使用与平稳相相关的SigC因子会导致δ sigBDE在超氧胁迫下生长停滞。在H2O2胁迫下，功能性RNAP的急剧减少限制了细胞的转录能力，这解释了蓝藻对H2O2敏感的原因。H2O2胁迫下，RNAP-SigB和RNAP-SigD全酶的形成显著增强，且仅含SigB （δ sigCDE）或SigD （δ sigBCE）的细胞在H2O2胁迫下表现出较好的生长。
Regulatory sigma factors of the RNA polymerase (RNAP) adjust gene expression according to environmental cues when the cyanobacterium Synechocystis sp. PCC 6803 acclimates to suboptimal conditions. Here we show central roles of the non-essential group 2 sigma factors in oxidative stress responses. Cells missing all group 2 sigma factors fail to acclimate to chemically induced singlet oxygen, superoxide or H2O2 stresses, and lose pigments in high light. SigB and SigD are the major sigma factors in oxidative stress, whereas SigC and SigE play only minor roles. The SigD factor is up-regulated in high light, singlet oxygen and H2O2 stresses, and overproduction of the SigD factor in the Delta sigBCE strain leads to superior growth of Delta sigBCE cells in those stress conditions. Superoxide does not induce the production of the SigD factor but instead SigB and SigC factors are moderately induced. The SigB factor alone in Delta sigCDE can support almost as fast growth in superoxide stress as the full complement of sigma factors in the control strain, but an overdose of the stationary phase-related SigC factor causes growth arrest of Delta sigBDE in superoxide stress. A drastic decrease of the functional RNAP limits the transcription capacity of the cells in H2O2 stress, which explains why cyanobacteria are sensitive to H2O2. Formation of RNAP-SigB and RNAP-SigD holoenzymes is highly enhanced in H2O2 stress, and cells containing only SigB (Delta sigCDE) or SigD (Delta sigBCE) show superior growth in H2O2 stress.