Identification of novel Ralstonia solanacearum type III effector proteins through translocation analysis of hrpB-regulated gene products
Identification of novel Ralstonia solanacearum type III effector proteins through translocation analysis of hrpB-regulated gene products
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DOI：
10.1099/mic.0.027763-0
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发表时间：
2009-07-01
期刊：
影响因子：
2.8
通讯作者：
Tamura, Naoyuki
中科院分区：
文献类型：
--
作者：
Mukaihara, Takafumi;Tamura, Naoyuki
辣根过氧化物酶III型分泌系统（TTSS）是茄枯菌（Ralstonia solanacearum）对寄主植物致病性的关键。Hrp TTSS是一种特殊的分泌系统，它将毒力蛋白，即所谓的III型效应蛋白注入植物细胞。在龙葵中，Hrp ttss相关基因的表达受一种arac型转录激活因子HrpB的调控。我们鉴定了30个hrpb调控的hpx （hrpb依赖表达）基因和3个已知的hrpb调控基因popA、popB和popC作为葡萄球菌RS1000的候选效应基因。在这项研究中，我们新克隆了11个候选效应基因，这些基因与已知的番茄红霉RS1000的hpx基因具有同源性。利用Cya报告系统，我们通过Hrp TTSS研究了这44个基因产物在植物细胞中的易位，并鉴定了34个效应蛋白。其中包括由四个以上成员组成的三个效应家族，即Hpx4、Hpx30和GALA家族。Hpx30家族效应蛋白的大小在2200- 2500aa之间，是动植物致病菌中最大的一类效应蛋白。该家族的成员包含12-18个新的42 aa基序的串联重复序列，称为SKWP重复序列。
The Hrp type III secretion system (TTSS) is essential for the pathogenicity of Ralstonia solanacearum on host plants. Hrp TTSS is a specialized secretion system that injects virulence proteins, the so-called type III effector proteins, into plant cells. In R. solanacearum, the expression of Hrp TTSS-related genes is regulated by an AraC-type transcriptional activator, HrpB. We have identified 30 hrpB-regulated hpx (hrpB-dependent expression) genes and three well-known hrpB-regulated genes, popA, popB and popC, as candidate effector genes in R. solanacearum strain RS1000. In this study, we newly cloned 11 additional candidate effector genes that share homology with known hpx genes from R. solanacearum RS1000. Using a Cya reporter system, we investigated the translocation of these 44 gene products into plant cells via the Hrp TTSS and identified 34 effector proteins. These include three effector families composed of more than four members, namely the Hpx4, Hpx30 and GALA families. The Hpx30 family effectors are 2200-2500 aa in size and appear to be the largest class of effector proteins among animal- and plant-pathogenic bacteria. Members of this family contain 12-18 tandem repeats of a novel 42 aa motif, designated SKWP repeats.