The SskA and SrrA response regulators are implicated in oxidative stress responses of hyphae and asexual spores in the phosphorelay signaling network of Aspergillus nidulans
The SskA and SrrA response regulators are implicated in oxidative stress responses of hyphae and asexual spores in the phosphorelay signaling network of Aspergillus nidulans
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DOI：
10.1271/bbb.60665
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发表时间：
2007-04-01
影响因子：
1.6
通讯作者：
Mizuno, Takeshi
中科院分区：
文献类型：
--
作者：
Hagiwara, Daisuke;Asano, Yoshihiro;Mizuno, Takeshi
组氨酸-天冬氨酸（His-Asp）磷酸化（或双组分）系统是一种常见的信号转导机制，涉及原核生物和真核生物对环境刺激的各种细胞反应。对于一种模式丝状真菌——细粒曲霉（Aspergillus nidulans），在本研究中，我们首先编制了完整的His-Asp磷接力组分列表，包括15个his -激酶（HK）基因，4个反应调节基因。（RR），而含组氨酸的磷酸转移中间体（HPt）只有1个。对于这些RR基因，构建一组缺失突变体，为每个基因创建一个空等位基因。当对这些突变菌株在菌丝生长和无性孢子发育的各种条件下进行检测时，其中两个（指定为Delta sskA和Delta srrA）表现出对氧化应激（特别是过氧化氢）超敏的显着表型。在这方面，在两个突变体中，植物期特异性catB过氧化氢酶基因的表达严重受损。此外，Delta sskA的分生孢子不仅对H2O2敏感，而且对异常低（4℃）和异常高（50℃）的处理也敏感，导致萌发效率降低。在这方面，Delta sskA的分生孢子中，不仅是无性发育的catA过氧化氢酶基因，而且还有一组编码合成某些耐胁迫相容溶质（如海藻糖和甘油）的酶的基因都明显下调。这些结果共同表明了涉及SskA和SrrA反应调节因子的His-Asp磷接力信号网络的生理重要性。
Histidine-to-Aspartate (His-Asp) phosphorelay (or two-component) systems are common signal transduction mechanisms implicated in a wide variety of cellular responses to environmental stimuli in both prokaryotes and eukaryotes. For a model filamentous fungi, Aspergillus nidulans, in this study we first compiled a complete list of His-Asp phosphorelay components, including 15 genes for His-kinase (HK), four genes for response regulator. (RR), and only one for histidine-containing phosphotransfer intermediate (HPt). For these RR genes, a set of deletion mutants was constructed so as to create a null allele for each. When examined these mutant strains under various conditions stressful for hyphal growth and asexual spore development, two of them (designated Delta sskA and Delta srrA) showed a marked phenotype of hypersensitivity to oxidative stresses (particularly, to hydrogen peroxide). In this respect, expression of the vegetative-stage specific catB catalase gene was severely impaired in both mutants. Furthermore, conidia from Delta sskA were hypersensitive not only to treatment with H2O2, but also to treatment at aberrantly low (4 degrees C) and high (50 degrees C) temperatures, resulting in reduced germination efficiency. In this respect, not only the catA catalase gene specific for asexual development, but also a set of genes encoding the enzymes for synthesis of certain stress tolerant compatible solutes, such as trehalose and glycerol, were markedly downregulated in conidia from Delta sskA. These results together are indicative of the physiological importance of the His-Asp phosphorelay signaling network involving the SskA and SrrA response regulators.