The Pseudomonas stutzeri-Specific Regulatory Noncoding RNA NfiS Targets katB mRNA Encoding a Catalase Essential for Optimal Oxidative Resistance and Nitrogenase Activity

文献类型： 外文期刊

第一作者： Zhang, Hongyang

作者： Zhang, Hongyang;Zhan, Yuhua;Yan, Yongliang;Liu, Yichao;Hu, Guihua;Wang, Shanshan;Yang, Hua;Qiu, Xuemeng;Liu, Yaqun;Li, Jiang;Lu, Wei;Lin, Min;Elmerich, Claudine

作者机构：

关键词： H2O2; NfiS; Pseudomonas stutzeri A1501; katB mRNA; nitrogen fixation; oxidative stress response; regulatory ncRNA

期刊名称：JOURNAL OF BACTERIOLOGY （ 影响因子：3.49； 五年影响因子：3.534 ）

ISSN： 0021-9193

年卷期： 2019 年 201 卷 19 期

页码：

收录情况： SCI

摘要： Pseudornonas stutzeri A1501 is a versatile nitrogen-fixing bacterium capable of living in diverse environments and coping with various oxidative stresses. NfiS, a regulatory noncoding RNA (ncRNA) involved in the control of nitrogen fixation in A1501, was previously shown to be required for optimal resistance to H2O2 ; however, the precise role of NfiS and the target genes involved in the oxidative stress response is entirely unknown. In this work, we systematically investigated the NfiS-based mechanisms underlying the response of this bacterium to H2O2 at the cellular and molecular levels. A mutant strain carrying a deletion of nfiS showed significant downregulation of oxidative stress response genes, especially kora, a catalase gene, and oxyR, an essential regulator for transcription of catalase genes. Secondary structure prediction revealed two binding sites in NfiS for katB mRNA. Complementation experiments using truncated nfiS genes showed that each of two sites is functional, but not sufficient, for NfiS-mediated regulation of oxidative stress resistance and nitrogenase activities. Microscale thermophoresis assays further indicated direct base pairing between katB mRNA and NfiS at both sites 1 and 2, thus enhancing the half-life of the transcript. We also demonstrated that katB expression is dependent on OxyR and that both OxyR and KatB are essential for optimal oxidative stress resistance and nitrogenase activities. H2O2 at low concentrations was detoxified by KatB, leaving O-2 as a by-product to support nitrogen fixation under O-2 insufficient conditions. Moreover, our data suggest that the direct interaction between NfiS and katB mRNA is a conserved and widespread mechanism among P. stutzeri strains. IMPORTANCE Protection against oxygen damage is crucial for survival of nitrogenfixing bacteria due to the extreme oxygen sensitivity of nitrogenase. This work exemplifies how the small ncRNA NfiS coordinates oxidative stress response and nitrogen fixation via base pairing with katB mRNA and nifK mRNA. Hence, NfiS acts as a molecular link to coordinate the expression of genes involved in oxidative stress response and nitrogen fixation. Our study provides the first insight into the biological functions of NfiS in oxidative stress regulation and adds a new regulation level to the mechanisms that contribute to the oxygen protection of the MoFe nitrogenase.

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