The ECF sigma factor σT is involved in osmotic and oxidative stress responses in Caulobacter crescentus
The ECF sigma factor σT is involved in osmotic and oxidative stress responses in Caulobacter crescentus
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DOI：
10.1111/j.1365-2958.2007.06005.x
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发表时间：
2007-12-01
影响因子：
3.6
通讯作者：
Gomes, Suely L.
中科院分区：
文献类型：
--
作者：
Alvarez-Martinez, Cristina E.;Lourenco, Rogerio F.;Gomes, Suely L.
ECF亚家族的Sigma因子是细菌应激反应的重要调节因子。对新月形茎杆菌基因组序列的分析表明，存在13个ECF（外胞浆功能）亚家族成员，表明这些调节因子在新月形茎杆菌生理中起重要作用。本文描述了两个高度相似的新月形香菇ECF因子sigma(U)和sigma(T)的特征。相应的基因在正常生长条件下不是必需的，缺少sigma(U)并不影响细菌对环境胁迫的抵抗力。然而，缺少sigma(T)会显著影响月牙菇细胞在渗透和氧化应激中的生存能力。通过对sigT和sigU上游区域的转录融合，我们证明了这两个基因都以依赖于sigma(T)的方式被渗透胁迫诱导。sigU和sigT转录起始位点的测定揭示了一个相同的启动子基序，这是典型的ecf依赖性启动子。转录组分析揭示了sigma(T)调控的40个可能成员，包括sigU和sigR，编码另一个ECF亚家族成员，以及参与一般应激反应和细胞包膜功能的基因。其中20个基因在其上游区域表现出sigT/sigU启动子基序。我们的数据表明sigma(T)在月牙草不同的胁迫反应中起作用。
Sigma factors of the ECF subfamily are important regulators of stress responses in bacteria. Analysis of Caulobacter crescentus genome sequence has indicated the presence of 13 members of the ECF (extracytoplasmic function) subfamily, suggesting that these regulators play an important role in C. crescentus physiology. This work describes the characterization of two highly similar C. crescentus ECF sigma factors, sigma(U) and sigma(T). The corresponding genes are not essential under normal growth conditions and absence of sigma(U) does not impair bacterial resistance to the environmental stresses tested. However, absence of sigma(T) significantly affects the ability of C. crescentus cells to survive osmotic and oxidative stress. Using transcription fusions to sigT and sigU upstream regions we demonstrate that both genes are induced by osmotic stress in a sigma(T)-dependent manner. Determination of sigU and sigT transcription start sites revealed an identical promoter motif, typical of ECF-dependent promoters. Transcriptome analysis revealed 40 putative members of the sigma(T) regulon, including sigU and sigR, encoding another ECF subfamily member, and genes involved in general stress responses and cell envelope functions. Twenty of those genes exhibit the sigT/sigU promoter motif in their upstream regions. Our data indicate a role of sigma(T) in distinct stress responses in C. crescentus.