RpoHII Activates Oxidative-Stress Defense Systems and Is Controlled by RpoE in the Singlet Oxygen-Dependent Response in Rhodobacter sphaeroides
RpoHII Activates Oxidative-Stress Defense Systems and Is Controlled by RpoE in the Singlet Oxygen-Dependent Response in Rhodobacter sphaeroides
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DOI：
10.1128/jb.00925-08
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发表时间：
2009-01-01
影响因子：
3.2
通讯作者：
Klug, Gabriele
中科院分区：
文献类型：
--
作者：
Nuss, Aaron M.;Glaeser, Jens;Klug, Gabriele
光合生物需要防御系统来抵抗由产生高活性单线态氧（O-1(2)）引起的光氧化应激。在这里，我们表明替代sigma因子RpoH（II）是重要防御因子的表达所必需的，RpoH（II）的缺失导致球形红杆菌对暴露于O-1(2)和甲基乙二醛的敏感性增加。编码RpoH（II）的基因受RpoE控制，从而构成一个sigma因子级联。我们提供了第一个体内研究，确定了由RpoH（II）型sigma因子控制的基因，该因子广泛分布于α变形菌中。RpoH（II）依赖基因编码氧化应激防御系统，包括用于甲基乙二醛降解、过氧化物解毒、O-1(2)清除、氧化还原和铁稳态的蛋白质。我们的实验表明，依赖谷胱甘肽（GSH）的机制参与光合细菌对光氧化应激的防御。因此，我们得出结论，生物防御光氧化应激的关键系统强烈依赖于谷胱甘肽，并且在圆叶参中被RpoH（II）特异性识别。
Photosynthetic organisms need defense systems against photooxidative stress caused by the generation of highly reactive singlet oxygen (O-1(2)). Here we show that the alternative sigma factor RpoH(II) is required for the expression of important defense factors and that deletion of rpoH(II) leads to increased sensitivity against exposure to O-1(2) and methylglyoxal in Rhodobacter sphaeroides. The gene encoding RpoH(II) is controlled by RpoE, and thereby a sigma factor cascade is constituted. We provide the first in vivo study that identifies genes controlled by an RpoH(II)-type sigma factor, which is widely distributed in the Alphaproteobacteria. RpoH(II)-dependent genes encode oxidative-stress defense systems, including proteins for the degradation of methylglyoxal, detoxification of peroxides, O-1(2) scavenging, and redox and iron homeostasis. Our experiments indicate that glutathione (GSH)-dependent mechanisms are involved in the defense against photooxidative stress in photosynthetic bacteria. Therefore, we conclude that systems pivotal for the organism's defense against photooxidative stress are strongly dependent on GSH and are specifically recognized by RpoH(II) in R. sphaeroides.