The Sinorhizobium meliloti SyrM Regulon: Effects on Global Gene Expression Are Mediated by syrA and nodD3
The Sinorhizobium meliloti SyrM Regulon: Effects on Global Gene Expression Are Mediated by syrA and nodD3
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DOI：
10.1128/jb.02626-14
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发表时间：
2015-05-01
影响因子：
3.2
通讯作者：
Long, Sharon R.
中科院分区：
文献类型：
--
作者：
Barnett, Melanie J.;Long, Sharon R.
在苜蓿中华根瘤菌（Sinorhizobium meliloti）中，三种NodD转录调节因子激活细菌生长调节（nod）基因的表达。NodD 1和NodD 2需要植物化合物来激活nod基因。NodD 3蛋白不需要外源化合物来激活nod基因表达;相反，另一种转录调节因子SyrM激活NodD 3表达。此外，NodD 3还能激活CD 4 M的表达。SyrM还激活另一个基因的表达，当过度表达时，它会导致胞外多糖产量的急剧增加。在以前的研究中，我们确定了超过200个基因的表达改变，在菌株中过表达CD 10 D3。在这项工作中，我们定义了过表达CIMM或CIMA的菌株的转录组。SyrM、SyrD 3和SyrA过表达转录组具有相似的基因表达变化;分析表明，SyrD 3和SyrA是SyrM直接激活的唯一靶标。我们提出，大多数的基因表达变化时观察到的NodD 3过表达是由于NodD 3激活的NodM的表达，这反过来又刺激SyrM激活的NodA的表达。随后SyrA丰度的增加导致基因表达的广泛变化，最有可能是由ChvI-ExoS-ExoR调节回路介导的。
In Sinorhizobium meliloti, three NodD transcriptional regulators activate bacterial nodulation (nod) gene expression. NodD1 and NodD2 require plant compounds to activate nod genes. The NodD3 protein does not require exogenous compounds to activate nod gene expression; instead, another transcriptional regulator, SyrM, activates nodD3 expression. In addition, NodD3 can activate syrM expression. SyrM also activates expression of another gene, syrA, which when overexpressed causes a dramatic increase in exopolysaccharide production. In a previous study, we identified more than 200 genes with altered expression in a strain overexpressing nodD3. In this work, we define the transcriptomes of strains overexpressing syrM or syrA. The syrM, nodD3, and syrA overexpression transcriptomes share similar gene expression changes; analyses imply that nodD3 and syrA are the only targets directly activated by SyrM. We propose that most of the gene expression changes observed when nodD3 is overexpressed are due to NodD3 activation of syrM expression, which in turn stimulates SyrM activation of syrA expression. The subsequent increase in SyrA abundance results in broad changes in gene expression, most likely mediated by the ChvI-ExoS-ExoR regulatory circuit.