Global transcriptional response of Caulobacter crescentus to iron availability.
Global transcriptional response of Caulobacter crescentus to iron availability.
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DOI：
10.1186/1471-2164-14-549
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发表时间：
2013-08-13
期刊：
影响因子：
4.4
通讯作者：
Marques MV
中科院分区：
文献类型：
--
作者：
da Silva Neto JF;Lourenço RF;Marques MV
在变形菌的α亚类中，铁稳态由不同的铁响应调节剂控制。新月柄杆菌（Caulobacter crescentus）是一种重要的淡水α-变形菌，它利用铁吸收抑制因子（Fur）来实现这一目的。铁的有效性对C. crescentus转录组和涉及的调控网络的整体前景仍然未知。在这项工作中，我们报告的铁响应和毛皮调控基因的鉴定C。crescentus使用基于微阵列的全球转录分析。我们确定了42个基因，强烈上调突变的毛皮和铁限制条件。其中，有参与铁吸收的基因（四个TonB依赖性受体基因簇和feoAB），核黄素生物合成和编码假设蛋白质的基因。这些基因中的大多数与预测的Fur结合位点相关，暗示它们是Fur介导的抑制的直接靶点。这些数据通过β-半乳糖苷酶和EMSA测定法对编码推定转运蛋白的两个操纵子进行验证。考虑到27个基因被毛突变和低铁条件下下调，毛作为正调节因子的作用也是显而易见的。正如预期的那样，这一组包括许多参与能量代谢的基因，主要是铁使用酶。令人惊讶的是，该组中还包括TonB依赖性受体基因和基因fixK，fixT和ftrB编码缺氧期间生长所需的氧信号传导网络。生物信息学分析表明，Fur的正调控主要是间接的。除了Fur modulon，铁限制改变了113个基因的表达，包括诱导参与Fe-S簇组装，氧化应激和热休克反应的基因，以及抑制氨基酸代谢，趋化性和运动性的基因。使用全局转录方法，我们确定了C。新月形铁兴奋剂。许多铁响应基因直接或间接受Fur基因控制。铁限制刺激子与其他调节系统重叠，如RpoH和FixK调节子。总之，我们的研究结果表明，C。crescentus对铁限制的作用不仅涉及增加铁获取系统的转录和减少铁利用蛋白的产生，而且还包括新的基因和调控机制。
In the alpha subclass of proteobacteria iron homeostasis is controlled by diverse iron responsive regulators. Caulobacter crescentus, an important freshwater α-proteobacterium, uses the ferric uptake repressor (Fur) for such purpose. However, the impact of the iron availability on the C. crescentus transcriptome and an overall perspective of the regulatory networks involved remain unknown. In this work we report the identification of iron-responsive and Fur-regulated genes in C. crescentus using microarray-based global transcriptional analyses. We identified 42 genes that were strongly upregulated both by mutation of fur and by iron limitation condition. Among them, there are genes involved in iron uptake (four TonB-dependent receptor gene clusters, and feoAB), riboflavin biosynthesis and genes encoding hypothetical proteins. Most of these genes are associated with predicted Fur binding sites, implicating them as direct targets of Fur-mediated repression. These data were validated by β-galactosidase and EMSA assays for two operons encoding putative transporters. The role of Fur as a positive regulator is also evident, given that 27 genes were downregulated both by mutation of fur and under low-iron condition. As expected, this group includes many genes involved in energy metabolism, mostly iron-using enzymes. Surprisingly, included in this group are also TonB-dependent receptors genes and the genes fixK, fixT and ftrB encoding an oxygen signaling network required for growth during hypoxia. Bioinformatics analyses suggest that positive regulation by Fur is mainly indirect. In addition to the Fur modulon, iron limitation altered expression of 113 more genes, including induction of genes involved in Fe-S cluster assembly, oxidative stress and heat shock response, as well as repression of genes implicated in amino acid metabolism, chemotaxis and motility. Using a global transcriptional approach, we determined the C. crescentus iron stimulon. Many but not all of iron responsive genes were directly or indirectly controlled by Fur. The iron limitation stimulon overlaps with other regulatory systems, such as the RpoH and FixK regulons. Altogether, our results showed that adaptation of C. crescentus to iron limitation not only involves increasing the transcription of iron-acquisition systems and decreasing the production of iron-using proteins, but also includes novel genes and regulatory mechanisms.