Transcriptome analysis reveals response regulator SO2426-mediated gene expression in Shewanella oneidensis MR-1 under chromate challenge.
Transcriptome analysis reveals response regulator SO2426-mediated gene expression in Shewanella oneidensis MR-1 under chromate challenge.
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DOI：
10.1186/1471-2164-9-395
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发表时间：
2008-08-21
期刊：
影响因子：
4.4
通讯作者：
Thompson DK
中科院分区：
文献类型：
--
作者：
Chourey K;Wei W;Wan XF;Thompson DK
希瓦氏菌MR-1具有不同的金属离子还原能力，因此作为生物修复剂具有潜在的实用性。然而，对重金属胁迫下细胞反应的分子组成和调控机制的认识仍然不完整。在以前的工作中，S。oneidensis so2426基因，注释为DNA结合反应调节因子，被证明在转录和蛋白质水平上对急性铬酸盐[Cr（VI）]攻击具有特异性反应。为了描述SO2426的细胞功能及其对金属应激反应的贡献，我们将遗传和生理方法与全基因组筛选包括SO2426调节子的靶基因候选物相结合。失活so2426的框内删除导致增强的铬酸盐敏感性和能力降低，以消除细胞外铬（VI）相对于亲本菌株。时间分辨微阵列分析用于比较野生型和SO2426缺陷突变体S.在铬酸盐暴露的条件下，在Δso2426突变体中，总共有841个基因（占阵列基因组的18%）在6个时间点条件中的至少一个条件下上调或下调至少两倍。时间转录谱的层次聚类分析鉴定了由随时间表现出显著下调表达（p < 0.05）的协同调节基因组成的独特聚类（n = 46）。这些基因中有13个编码与转运和结合功能相关的蛋白质，特别是那些参与铁转运和体内平衡的蛋白质（例如，铁载体生物合成酶、TonB依赖性受体和铁储存蛋白铁蛋白）。一个保守的假设操纵子（so 1188-so 1189-so 1190），以前确定为一个潜在的目标，毛皮介导的镇压，以及一个假定的双环霉素抗性基因（so2280）和阳离子外排家族蛋白基因（so2045）也被阻遏在so2426缺失突变体。此外，包括cpxR同源物在内的四个调控基因的时间表达谱在染色质挑战突变体中受到干扰。我们的研究结果表明，以前未被认识到的功能作用的反应调节SO2426在铁载体介导的铁的收购，铁存储和其他阳离子转运机制所需的基因的激活。SO2426的调节功能在分子水平上参与了铁稳态与S. oneidensis。
Shewanella oneidensis MR-1 exhibits diverse metal ion-reducing capabilities and thus is of potential utility as a bioremediation agent. Knowledge of the molecular components and regulatory mechanisms dictating cellular responses to heavy metal stress, however, remains incomplete. In a previous work, the S. oneidensis so2426 gene, annotated as a DNA-binding response regulator, was demonstrated to be specifically responsive at both the transcript and protein levels to acute chromate [Cr(VI)] challenge. To delineate the cellular function of SO2426 and its contribution to metal stress response, we integrated genetic and physiological approaches with a genome-wide screen for target gene candidates comprising the SO2426 regulon. Inactivation of so2426 by an in-frame deletion resulted in enhanced chromate sensitivity and a reduced capacity to remove extracellular Cr(VI) relative to the parental strain. Time-resolved microarray analysis was used to compare transcriptomic profiles of wild-type and SO2426-deficient mutant S. oneidensis under conditions of chromate exposure. In total, 841 genes (18% of the arrayed genome) were up- or downregulated at least twofold in the Δso2426 mutant for at least one of six time-point conditions. Hierarchical cluster analysis of temporal transcriptional profiles identified a distinct cluster (n = 46) comprised of co-ordinately regulated genes exhibiting significant downregulated expression (p < 0.05) over time. Thirteen of these genes encoded proteins associated with transport and binding functions, particularly those involved in Fe transport and homeostasis (e.g., siderophore biosynthetic enzymes, TonB-dependent receptors, and the iron-storage protein ferritin). A conserved hypothetical operon (so1188-so1189-so1190), previously identified as a potential target of Fur-mediated repression, as well as a putative bicyclomycin resistance gene (so2280) and cation efflux family protein gene (so2045) also were repressed in the so2426 deletion mutant. Furthermore, the temporal expression profiles of four regulatory genes including a cpxR homolog were perturbed in the chromate-challenged mutant. Our findings suggest a previously unrecognized functional role for the response regulator SO2426 in the activation of genes required for siderophore-mediated Fe acquisition, Fe storage, and other cation transport mechanisms. SO2426 regulatory function is involved at a fundamental molecular level in the linkage between Fe homeostasis and the cellular response to chromate-induced stress in S. oneidensis.
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