Lee Yunho, Peña-Llopis Samuel, Kang Yoon-Suk, Shin Hyeon-Dong, Demple Bruce, Madsen Eugene L, Jeon Che Ok, Park Woojun
Division of Environmental Science and Ecological Engineering, Korea University, Anam-Dong 5Ga, Seungbuk-Ku, Seoul 136-701, Republic of Korea.
Biochem Biophys Res Commun. 2006 Jan 27;339(4):1246-54. doi: 10.1016/j.bbrc.2005.11.135.
The ferredoxin-NADP+ reductase (fpr) participates in cellular defense against oxidative damage. The fpr expression in Pseudomonas putida KT2440 is induced by oxidative and osmotic stresses. FinR, a LysR-type transcriptional factor near the fpr gene in the P. putida KT2440 genome, is required for induction of the fpr under both conditions. We have shown that the fpr and finR gene products can counteract the effects of oxidative and osmotic stresses. Interestingly, FinR-independent expression occurs either during a long period of incubation with paraquat or with high concentrations of oxidative stress agent. This result indicates that there may be additional regulators present in the P. putida KT2440 genome. In contrast to in vivo expression kinetics of fpr from the plant pathogen, Pseudomonas syringae, the fpr gene from P. putida KT2440 exhibited unusually prolonged expression after oxidative stress. Transcriptional fusion and Northern blot analysis studies indicated that the FinR is negatively autoregulated. Expression of the fpr promoter was higher in minimal media than in rich media during exponential phase growth. Consistent with this result, the fpr and finR mutants had a long lag phase in minimal media in contrast to wild-type growth characteristics. Antioxidants such as ascorbate could increase the growth rate of all tested strains in minimal media. This result confirmed that P. putida KT2440 experienced more oxidative stress during exponential growth in minimal media than in rich media. Endogenous promoter activity of the fpr gene is much higher during exponential growth than during stationary growth. These findings demonstrate new relationships between fpr, finR, and the physiology of oxidative stress in P. putida KT2440.
铁氧化还原蛋白-NADP⁺还原酶（fpr）参与细胞对氧化损伤的防御。恶臭假单胞菌KT2440中的fpr表达受氧化应激和渗透应激诱导。FinR是恶臭假单胞菌KT2440基因组中fpr基因附近的一种LysR型转录因子，在这两种条件下诱导fpr表达均需要该因子。我们已经表明，fpr和finR基因产物可以抵消氧化应激和渗透应激的影响。有趣的是，在与百草枯长时间孵育期间或使用高浓度氧化应激剂时会出现不依赖FinR的表达。这一结果表明，恶臭假单胞菌KT2440基因组中可能存在其他调节因子。与植物病原体丁香假单胞菌中fpr的体内表达动力学不同，恶臭假单胞菌KT2440的fpr基因在氧化应激后表现出异常延长的表达。转录融合和Northern印迹分析研究表明，FinR存在负自调控。在指数生长期，fpr启动子在基本培养基中的表达高于丰富培养基。与该结果一致，与野生型生长特性相比，fpr和finR突变体在基本培养基中有较长的延迟期。抗氧化剂如抗坏血酸可以提高所有测试菌株在基本培养基中的生长速率。这一结果证实，恶臭假单胞菌KT2440在基本培养基中指数生长期间比在丰富培养基中经历更多的氧化应激。fpr基因的内源性启动子活性在指数生长期比稳定期高得多。这些发现揭示了恶臭假单胞菌KT2440中fpr、finR与氧化应激生理之间的新关系。
