Research Institute of Molecular Genetics, Kochi University, Nankoku, Kochi, Japan.
FEMS Microbiol Lett. 2011 Apr;317(1):75-82. doi: 10.1111/j.1574-6968.2011.02213.x. Epub 2011 Feb 7.
The genes in the hrp regulon encode the proteins composing type III secretion system in Ralstonia solanacearum. The hrp regulon is positively controlled by HrpB, and hrpB expression is activated by both HrpG and PrhG. We have identified three genes, prhK, prhL, and prhM, which positively control the hrp regulon in strain OE1-1. These genes are likely to form an operon, and this operon is well conserved in the genera Ralstonia and Burkholderia. This indicates that the operon is not specific to the plant pathogens. Mutations in each of these three genes abolished hrpB and prhG expression. prhK, prhL, and prhM mutant strains lost pathogenicity toward tomato completely, and they were less virulent toward tobacco. PrhK and PrhL share sequence similarity with allophanate hydrolase and PrhM with LamB. This suggests that the three gene products are not transcriptional regulators in the strict sense, but regulate hrp regulon indirectly. This novel class of virulence-related genes will mark the beginning of new findings regarding the overall infection mode of R. solanacearum.
hrp 调控子中的基因编码组成雷尔氏菌属植物病原菌Ⅲ型分泌系统的蛋白质。hrp 调控子受 HrpB 正向调控，而 HrpB 的表达受 HrpG 和 PrhG 激活。我们已经鉴定了三个基因，prhK、prhL 和 prhM，它们在 OE1-1 菌株中正向调控 hrp 调控子。这些基因可能形成一个操纵子，并且这个操纵子在雷尔氏菌属和伯克霍尔德氏菌属中高度保守。这表明该操纵子不是植物病原菌所特有的。这些基因中的每一个突变都消除了 hrpB 和 prhG 的表达。prhK、prhL 和 prhM 突变株完全丧失了对番茄的致病性，对烟草的毒力也降低。PrhK 和 PrhL 与异肽酶和 PrhM 与 LamB 具有序列相似性。这表明这三个基因产物不是严格意义上的转录调控因子，而是间接调节 hrp 调控子。这一类新的与毒力相关的基因将标志着关于雷尔氏菌属植物病原菌整体感染模式的新发现的开始。
