Ralstonia solanacearum iron scavenging by the siderophore staphyloferrin B is controlled by PhcA, the global virulence regulator
Ralstonia solanacearum iron scavenging by the siderophore staphyloferrin B is controlled by PhcA, the global virulence regulator
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DOI：
10.1128/jb.186.23.7896-7904.2004
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发表时间：
2004-12-01
影响因子：
3.2
通讯作者：
Denny, TP
中科院分区：
文献类型：
--
作者：
Bhatt, G;Denny, TP
PhcA是植物病原菌青枯菌（Ralstonia solanacearum）中激活多个毒力基因表达的转录调节因子。相对于它们的野生型父母，phcA突变体过度产生铁清除活性检测与Chrome天青S铁载体检测介质。转座子诱变菌株AW 1-PC（phcA 1）产生菌株GB 6，其为铁载体阴性但保留弱的铁清除活性。在GB 6中失活的ssd基因编码一种类似于IV组氨基酸脱羧酶的蛋白质，其转录被铁（III）和PhcA抑制。SSD是推定操纵子中的末端基因，该操纵子似乎也编码三个铁载体合成酶亚基、一个完整的膜输出蛋白和三个在铁载体产生中没有明显作用的基因。在耐金属罗尔斯通氏菌和金黄色葡萄球菌的基因组中发现了同源操纵子，这两种菌都产生聚羧酸铁载体葡萄球菌铁蛋白B。比较了红曲霉培养上清中铁载体的含量。青枯菌R. metallidurans和巨大芽孢杆菌（Bacillusmegaterium）的铁载体利用率测定、薄层色谱和质谱分析表明，R.青枯菌产生葡萄铁蛋白B，而不是以前报道的青枯菌。失活的野生型AW 1背景中的ssd导致突变体几乎不能清除铁，但通常有毒的番茄植物。AW 1在番茄木质部汁液中培养时不产生铁载体活性，表明番茄中的铁载体主要定位在根际。青枯菌在发病过程中是铁充足的。
PhcA is a transcriptional regulator that activates expression of multiple virulence genes in the plant pathogen Ralstonia solanacearum. Relative to their wild-type parents, phcA mutants overproduced iron-scavenging activity detected with chrome azurol S siderophore detection medium. Transposon mutagenesis of strain AW1-PC (phcA1) generated strain GB6, which was siderophore negative but retained weak iron-scavenging activity. The ssd gene inactivated in GB6 encodes a protein similar to group IV amino acid decarboxylases, and its transcription was repressed by iron(III) and PhcA. ssd is the terminal gene in a putative operon that also appears to encode three siderophore synthetase subunits, a integral membrane exporter, and three genes with no obvious role in siderophore production. A homologous operon was found in the genomes of Ralstonia metallidurans and Staphylococcus aureus, both of which produce the polycarboxylate siderophore staphyloferrin B. Comparison of the siderophores present in culture supernatants of R. solanacearum, R. metallidurans, and Bacillus megaterium using chemical tests, a siderophore utilization bioassay, thin-layer chromatography, and mass spectroscopy indicated that R. solanacearum produces staphyloferrin B rather than schizokinen as was reported previously. Inactivation of ssd in a wild-type AW1 background resulted in a mutant almost incapable of scavenging iron but normally virulent on tomato plants. AW1 did not produce siderophore activity when cultured in tomato xylem sap, suggesting that the main location in tomato for R. solanacearum during pathogenesis is iron replete.