SoxR-dependent response to oxidative stress and virulence of Erwinia chrysanthemi:: the key role of SufC, an orphan ABC ATPase
SoxR-dependent response to oxidative stress and virulence of Erwinia chrysanthemi:: the key role of SufC, an orphan ABC ATPase
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DOI：
10.1046/j.1365-2958.2001.02288.x
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发表时间：
2001-02-01
影响因子：
3.6
通讯作者：
Barras, F
中科院分区：
文献类型：
--
作者：
Nachin, L;El Hassouni, M;Barras, F
菊欧文氏菌会引起多种植物的软腐病。除了植物细胞壁降解酶的解聚活性之外，铁的获取和对氧化应激的抵抗力也极大地促进了这种病原体的毒力。在这里，我们研究了最初被认为编码新毒力因子的 pin10 基因座。序列分析揭示了与大肠杆菌sufA、sufB、sufC、sufD、sufS和sufE基因同源的6个开放阅读框。序列相似性搜索预测 (i) SufA、SufB、SufD、SufS 和 SufE 蛋白参与铁代谢，并可能参与 Fe-S 簇组装； (ii) SufC 是 ABC 转运蛋白的 ATP 酶。逆转录聚合酶链式反应程序表明，sufABCDSE 基因构成操纵子，发现 sufB::uidA 融合体的表达在缺铁生长条件下被诱导，并受到铁敏感 Fur 阻遏物的抑制。六个 suf 基因中的每一个都通过插入产生非极性突变的盒而失活。通过对铁激活抗生素链黑素的敏感性增加来评估，sufA、sufS、sufC、sufS 和 sufE 突变体的细胞内铁水平高于野生型。此外，sufC 和 sufD 失活导致对百草枯的敏感性增加。毒力测试表明，sufA 和 sufC 突变体引起菊苣叶浸渍的能力降低，而功能性的 sufC 基因对于细菌引起紫花苜蓿的系统入侵是必需的。通过反向遗传使大肠杆菌 sufC 同源物失活。发现这种突变可以改变 soxS 基因表达的 soxR 依赖性诱导。我们讨论了 SufC 是一种多功能 ATP 酶的可能性，它可以与其他 Suf 蛋白结合形成 Fe-S 簇组装机器，或与染色体其他位置编码的膜蛋白结合形成 Fe-S ABC 输出蛋白。总的来说，这些结果强调了菊花感染早期阶段铁代谢与氧化应激之间联系的重要性。
Erwinia chrysanthemi causes soft-rot disease in a great variety of plants. In addition to the depolymerizing activity of plant cell wall-degrading enzymes, iron acquisition and resistance to oxidative stress contribute greatly to the virulence of this pathogen. Here, we studied the pin10 locus originally thought to encode new virulence factors. The sequence analysis revealed six open reading frames that were homologous to the Escherichia coli sufA, sufB, sufC, sufD, sufS and sufE genes. Sequence similarity searching predicted that (i) SufA, SufB, SufD, SufS and SufE proteins are involved in iron metabolism and possibly in Fe-S cluster assembly; and (ii) SufC is an ATPase of an ABC transporter. The reverse transcription-polymerase chain reaction procedure showed that the sufABCDSE genes constitute an operon, Expression of a sufB::uidA fusion was found to be induced in iron-deficient growth conditions and to be repressed by the iron-sensing Fur repressor. Each of the six suf genes was inactivated by the insertion of a cassette generating a non-polar mutation. The intracellular iron level in the sufA, sufS, sufC, sufS and sufE mutants was higher than in the wild type, as assessed by increased sensitivity to the iron-activated antibiotic streptonigrin. In addition, inactivation of sufC and sufD led to increased sensitivity to paraquat. Virulence tests showed that sufA and sufC mutants exhibited reduced ability to cause maceration of chicory leaves, whereas a functional sufC gene was necessary for the bacteria to cause systemic invasion of Saintpaulia ionantha. The E. coli sufC homologue was inactivated by reverse genetic. This mutation was found to modify the soxR-dependent Induction of soxS gene expression. We discuss the possibility that SufC is a versatile ATPase that can associate either with the other Suf proteins to form a Fe-S cluster-assembling machinery or with membrane proteins encoded elsewhere in the chromosome to form an Fe-S ABC exporter. Overall, these results stress the importance of the connection between iron metabolism and oxidative stress during the early steps of infection by E. chrysanthemi.