Mansfield J, Jenner C, Hockenhull R, Bennett M A, Stewart R
Biological Sciences Department, Wye College, University of London, Ashford, Kent, U.K.
Mol Plant Microbe Interact. 1994 Nov-Dec;7(6):726-39. doi: 10.1094/mpmi-7-0726.
The avirulence gene matching the R2 gene for resistance to halo-blight disease in Phaseolus was cloned and sequenced from race 4 strain 1302A of Pseudomonas syringae pv. phaseolicola. The predicted 41-kDa AvrPphE protein is hydrophilic, has no features that indicate function, and no similarity to other protein sequences. The promoter region of avrPphE contains a "harp box" motif. The gene was expressed more strongly in minimal than in nutrient-rich media. Lower concentrations of the phytoalexin phaseollin accumulated in tissue undergoing the hypersensitive reaction (HR) determined by avrPphE than by avrPphB. Homologs of avrPphE were detected in strains representing eight races of P. s. pv. phaseolicola including those virulent on cultivars with the R2 resistance gene, and in P. s. pv. tabaci but not in P. cichorii or P. s. pvs. coronafaciens, glycinea, maculicola, pisi, or syringae. Disruption of avrPphE prevented induction of the HR but did not appear to affect basic pathogenicity. Transposon mutagenesis and DNA sequencing showed that avrPphE was linked to hrpY a hrp locus identified at the left end of the hrp gene cluster. Sequence analysis showed that the region linked to avrPphE was very similar to DNA containing hrp genes from P. s. pv. syringae including hrpJ, hrpL, and hrpK.
从菜豆丁香假单胞菌菜豆致病变种的4号小种1302A菌株中克隆并测序了与菜豆抗晕疫病的R2基因匹配的无毒基因。预测的41 kDa AvrPphE蛋白具有亲水性，没有表明功能的特征，且与其他蛋白质序列没有相似性。avrPphE的启动子区域包含一个“harp box”基序。该基因在基本培养基中的表达比在营养丰富的培养基中更强。在由avrPphE决定的过敏反应（HR）组织中积累的植物抗毒素菜豆素浓度低于由avrPphB决定的情况。在代表菜豆丁香假单胞菌八个小种的菌株中检测到了avrPphE的同源物，包括那些对具有R2抗性基因的品种有毒性的菌株，以及在烟草丁香假单胞菌中，但在菊苣假单胞菌或丁香假单胞菌的其他致病变种（如菜豆晕斑病菌、大豆疫霉、黄斑病菌、豌豆疫霉或丁香疫霉）中未检测到。avrPphE的破坏阻止了HR的诱导，但似乎不影响基本致病性。转座子诱变和DNA测序表明，avrPphE与hrpY连锁，hrpY是在hrp基因簇左端鉴定出的一个hrp位点。序列分析表明，与avrPphE连锁的区域与包含来自丁香假单胞菌菜豆致病变种的hrp基因（包括hrpJ、hrpL和hrpK）的DNA非常相似。
