Inventory and functional analysis of the large Hrp regulon in Ralstonia solanacearum:: identification of novel effector proteins translocated to plant host cells through the type III secretion system
Inventory and functional analysis of the large Hrp regulon in Ralstonia solanacearum:: identification of novel effector proteins translocated to plant host cells through the type III secretion system
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DOI：
10.1111/j.1365-2958.2004.04118.x
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发表时间：
2004-07-01
影响因子：
3.6
通讯作者：
Genin, S
中科院分区：
文献类型：
--
作者：
Cunnac, S;Occhialini, A;Genin, S
青枯雷尔氏菌菌株GMI1000在广泛的宿主植物（包括大多数茄科和拟南芥）上引起疾病的能力取决于由调节基因hrpB激活的基因。HrpB控制III型分泌系统（TTSS）的表达和通过该途径转运的致病性效应物。为了建立属于Hrp调节子的TTSS依赖性效应子的完整库并开始其功能分析，我们开发了一种快速插入诱变方法，该方法用于监测71个候选基因的表达并破坏其中的56个。该分析共获得了48个新的hrpB调控基因。利用百日咳博德特氏菌钙调素依赖性腺苷酸环化酶报告基因融合系统，我们提供了直接的生化证据，五个R。青枯菌效应蛋白通过TTSS易位到植物宿主细胞中。在这些新的TTSS效应子中，RipA和RipG都属于多基因家族，RipG定义了一类新的富含亮氨酸重复序列的携带蛋白。这些多基因家族的成员受到差异调节，由以hrpB依赖或hrpB非依赖方式表达的基因组成。致病性试验的56个突变株在两种宿主植物表明，有两个例外，在个别效应突变没有影响的毒力，遗传和功能冗余的可能后果。这种HrpB调控基因的大库，包括> 20个可能的TTSS效应基因，在其他细菌物种中没有对应物，代表了对R的全基因组理解的重要一步。青枯菌毒力
The ability of Ralstonia solanacearum strain GMI1000 to cause disease on a wide range of host plants (including most Solanaceae and Arabidopsis thaliana) depends on genes activated by the regulatory gene hrpB. HrpB controls the expression of the type III secretion system (TTSS) and pathogenicity effectors transiting through this pathway. In order to establish the complete repertoire of TTSS-dependent effectors belonging to the Hrp regulon and to start their functional analysis, we developed a rapid method for insertional mutagenesis, which was used to monitor the expression of 71 candidate genes and disrupt 56 of them. This analysis yielded a total of 48 novel hrpB-regulated genes. Using the Bordetella pertussis calmodulin-dependent adenylate cyclase reporter fusion system, we provide direct biochemical evidence that five R. solanacearum effector proteins are translocated into plant host cells through the TTSS. Among these novel TTSS effectors, RipA and RipG both belong to multigenic families, RipG defining a novel class of leucine-rich-repeats harbouring proteins. The members of these multigenic families are differentially regulated, being composed of genes expressed in either an hrpB-dependent or an hrpB-independent manner. Pathogenicity assays of the 56 mutant strains on two host plants indicate that, with two exceptions, mutations in individual effectors have no effect on virulence, a probable consequence of genetic and functional redundancy. This large repertoire of HrpB-regulated genes, which comprises > 20 probable TTSS effector genes with no counterparts in other bacterial species, represents an important step towards a full-genome understanding of R. solanacearum virulence.