Grimm C, Aufsatz W, Panopoulos N J
Institute of Botany, University of Vienna, Austria.
Mol Microbiol. 1995 Jan;15(1):155-65. doi: 10.1111/j.1365-2958.1995.tb02230.x.
The right part of the hrp cluster of Pseudomonas syringae pv. phaseolicola contains two regulatory genes, the previously described hrpS gene and an adjacent locus, hrpR. In this study we determined the sequence of hrpR and analysed the functional organization of the two genes. HrpR and HrpS show high sequence similarities to each other and to other response regulators of the two-component regulatory system. This has recently also been described for the hrpRS system of the closely related pathogen Pseudomonas syringae pv. syringae. The results of our genetic analyses strongly indicate that hrpS expression is regulated by the hrpR gene product. DNA-protein binding studies and site-directed mutagenesis of the hrpR sequence provided further evidence that HrpR activates hrpS transcription by binding to an activator site. This HrpR binding site was mapped in a fragment which is located 378-609 nucleotides upstream of the hrpS transcription start site. The hrpS transcription start site maps 179 nucleotides upstream of the initiation codon ATG, as determined by primer extension analysis, and is preceded by a typical -12/-24 promoter motif.
菜豆假单胞菌的hrp基因簇右侧部分包含两个调控基因，即先前描述的hrpS基因和一个相邻位点hrpR。在本研究中，我们测定了hrpR的序列，并分析了这两个基因的功能组织。HrpR和HrpS彼此之间以及与双组分调控系统的其他应答调控因子具有高度的序列相似性。最近，在密切相关的病原菌丁香假单胞菌丁香致病变种的hrpRS系统中也有类似描述。我们的遗传分析结果强烈表明，hrpS的表达受hrpR基因产物的调控。DNA-蛋白质结合研究以及hrpR序列的定点诱变提供了进一步的证据，表明HrpR通过与激活位点结合来激活hrpS转录。该HrpR结合位点定位于hrpS转录起始位点上游378-609个核苷酸的片段中。通过引物延伸分析确定，hrpS转录起始位点位于起始密码子ATG上游179个核苷酸处，并且在其之前有一个典型的-12/-24启动子基序。
