Regulatory network controlling extracellular proteins in Erwinia carotovora subsp carotovora:: FlhDC, the master regulator of flagellar genes, activates rsmB regulatory RNA production by affecting gacA and hexA (lrhA) expression
Regulatory network controlling extracellular proteins in Erwinia carotovora subsp carotovora:: FlhDC, the master regulator of flagellar genes, activates rsmB regulatory RNA production by affecting gacA and hexA (lrhA) expression
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DOI：
10.1128/jb.01828-07
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Chatterjee, Arun K.
中科院分区：
文献类型：
--
作者：
Cui, Yaya;Chatterjee, Asita;Chatterjee, Arun K.
胡萝卜软腐欧文氏菌亚种胡萝卜素产生一系列细胞外蛋白（即外蛋白），包括植物细胞壁降解酶和 Harpin（一种负责引发过敏反应的效应子）。外蛋白基因受到群体感应信号、N-酰基高丝氨酸内酯、植物信号、各种转录因子/调节因子（GacS/A、ExpR1、ExpR2、KdgR、RpoS、HexA 和 RsmQ）以及转录后调节因子（RsmA、rsmB RNA）的共同调节。rsmB RNA 的产生受到 GacS/A（一种二元组分）的正调节。系统，并受到 HexA（菊欧文氏菌中的 PecT；大肠杆菌中的 LrhA [LysR 同源物 A]）和 RsmC（一种假定的转录接头）的负调节，而游离 RsmA（一种 RNA 结合蛋白）会促进外蛋白基因 mRNA 的衰变，而 RsmA 与 rsmB RNA 的结合会中和 RsmA 效应。发现与大肠杆菌 flhDC 操纵子具有强同源性的基因座也控制细胞外酶的产生，转座子插入 FlhDC(-) 突变体产生非常低水平的果胶酸裂合酶、多聚半乳糖醛酸酶、蛋白酶和胡萝卜软腐菌 Harpin 亚种 (Harpin(Ecc))，并且其植物毒力严重减弱，这些外蛋白的产生得到恢复。序列分析和转录分析表明，E. carotovora subsp. 的 flhD 操纵子与其他肠杆菌一样，由 flhD 和 flhC 组成。 互补分析表明，调节作用需要 flhD 和 flhC 产物的功能。此处提供的数据表明，FlhDC 正向调节 gacA、rsmC 和 fliA。有证据表明，FlhDC 通过对 hexA 和 gacA 的累积作用来控制细胞外蛋白质的产生，FlhDC(-) 突变体中 GacA 水平的降低和 HexA 水平的升高负责抑制 rsmB RNA 的产生，这是一种有利于游离 RsmA 积累的条件。 rsmB(+) DNA 证实 FlhDC 缺陷的负面影响是通过 RsmA 发挥的。FlhDC 介导的 fliA 调节与 E. carotovora subsp. 的外蛋白产生无关。胡萝卜科。
Erwinia carotovora subsp. carotovora produces an array of extracellular proteins (i.e., exoproteins), including plant cell wall-degrading enzymes and Harpin, an effector responsible for eliciting hypersensitive reaction. Exoprotein genes are coregulated by the quorum-sensing signal, N-acyl homoserine lactone, plant signals, an assortment of transcriptional factors/regulators (GacS/A, ExpR1, ExpR2, KdgR, RpoS, HexA, and RsmQ and posttranscriptional regulators (RsmA, rsmB RNA). rsmB RNA production is positively regulated by GacS/A, a two-component system, and negatively regulated by HexA (PecT in Erwinia chrysanthemi; LrhA [LysR homolog A] in Escherichia coli) and RsmC, a putative transcriptional adaptor. While free RsmA, an RNA-binding protein, promotes decay of mRNAs of exoprotein genes, binding of RsmA with rsmB RNA neutralizes the RsmA effect. In the course of studies of GacA regulation, we discovered that a locus bearing strong homology to the flhDC operon of E. coli also controls extracellular enzyme production. A transposon insertion FlhDC(-) mutant produces very low levels of pectate lyase, polygalacturonase, cellulase, protease, and E. carotovora subsp. carotovora Harpin (Harpin(Ecc)) and is severely attenuated in its plant virulence. The production of these exoproteins is restored in the mutant carrying an FlhDC(+) plasmid. Sequence analysis and transcript assays disclosed that the flhD operon of E. carotovora subsp. carotovora, like those of other enterobacteria, consists of flhD and flhC. Complementation analysis revealed that the regulatory effect requires functions of both flhD and flhC products. The data presented here show that FlhDC positively regulates gacA, rsmC, and fliA and negatively regulates hexA (lrhA). Evidence shows that FlhDC controls extracellular protein production through cumulative effects on hexA and gacA. Reduced levels of GacA and elevated levels of HexA in the FlhDC(-) mutant are responsible for the inhibition of rsmB RNA production, a condition conducive to the accumulation of free RsmA. Indeed, studies with an RsmA(-) FlhDC(-) double mutant and multiple copies of rsmB(+) DNA establish that the negative effect of FlhDC deficiency is exerted via RsmA. The FlhDC-mediated regulation of fliA has no bearing on exoprotein production in E. carotovora subsp. carotovora. Our observations for the first time establish a regulatory connection between FlhDC, HexA, GacA, and rsmB RNA in the context of the exoprotein production and virulence of E. carotovora subsp. carotovora.