Roles of the cyanobacterial isiABC operon in protection from oxidative and heat stresses
Roles of the cyanobacterial isiABC operon in protection from oxidative and heat stresses
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DOI：
10.1111/j.1399-3054.2006.00781.x
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发表时间：
2006-11-01
影响因子：
6.4
通讯作者：
Nakamoto, Hitoshi
中科院分区：
文献类型：
--
作者：
Kojima, Kouji;Suzuki-Maenaka, Toyoko;Nakamoto, Hitoshi
编码CP 43 '和黄素氧还蛋白的isiAB操纵子的表达在氧化或热应激条件以及铁限制条件下被诱导。本研究的目的是阐明他们的作用，获得耐受细胞对氧化或热应激与使用isiA中断和isiB缺失突变体的集胞藻PCC 6803。在前一个突变体中，isiA信使RNA被截短，isiB转录被完全废除。北方印迹分析表明，一个开放的阅读框sll 0249位于直接下游的isiB与isiAB在铁限制条件下共转录。因此，我们将该基因命名为isiC，并构建了isiC缺失突变体，以测试isiA和isiB破坏对isiC表达的极性影响。所有的突变体是高度敏感的氧化应激引起的甲基紫精的存在下，指示的操纵子，特别是isiC，在氧化应激下的重要作用。isiA突变体比其它突变体更易受亚致死热胁迫的影响。致死温度处理后的存活率的测定证实了isiA基因在热应激管理中的重要作用。我们发现，光照条件后立即致死温度处理有很大的影响野生型和isiA突变株的存活率。我们认为IsiA和IsiB可能在优化光能供应以避免细胞损伤以及在热应激后恢复过程中利用光能方面发挥作用。
The expression of the isiAB operon, which encodes CP43' and flavodoxin, is induced under oxidative- or heat-stress conditions as well as iron-limited conditions. The aim of this study is to elucidate their roles for acquisition of tolerance by cells against oxidative or heat stress with using the isiA interruption and the isiB deletion mutants of Synechocystis sp. PCC 6803. In the former mutant, the isiA messenger RNA was truncated and the isiB transcription was totally abolished. Northern blot analysis indicated that an open reading frame sll0249 located immediate downstream of isiB is cotranscribed with isiAB under iron-limited conditions. Thus, we designated the gene as isiC and constructed an isiC deletion mutant to test polar effects of the isiA and isiB disruptions on the isiC expression. All the mutants were highly sensitive to oxidative stress caused by the presence of methyl viologen, indicating an essential role of the operon, especially isiC, under oxidative stress. The isiA mutant was much more susceptible to the sublethal heat stress than the other mutants. Determination of the survival rate after a lethal temperature treatment confirmed the essential role of the isiA gene for the thermal stress management. We found that light conditions immediately after the lethal temperature treatment have a great effect on the survival rate of the wild-type and the isiA mutant strains. We suggest that IsiA and IsiB may play a role in optimizing the light energy supply to avoid cellular damage and utilizing the light energy in the post-heat-stress recovery process.