Frederick R D, Chiu J, Bennetzen J L, Handa A K
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
Mol Plant Microbe Interact. 1997 Apr;10(3):407-15. doi: 10.1094/MPMI.1997.10.3.407.
A mutant of Erwinia carotovora subsp. carotovora, AH2552, created by a Mud1 insertion was found to be reduced in plant pathogenicity and deficient in extracellular protease and cellulase activity, although it produced normal levels of pectate lyase and polygalacturonase. A cosmid clone, pEC462, was isolated from a wild-type E. carotovora subsp. carotovora DNA library that concomitantly restored pathogenicity and protease and cellulase activities of AH2552 to wild-type levels when present in trans. The genetic locus that was disrupted in AH2552 by insertion of Mud1 has been designated rpfA, for regulator of pathogenicity factors. Sequencing of the rpfA region identified an open reading frame of 2,787 bp, and the predicted 929-amino acid polypeptide shared high identity with several two-component sensor-regulator proteins: BarA from Escherichia coli, ApdA from Pseudomonas fluorescens, PheN from P. tolaasii, RepA from P. viridiflava, LemA from P. syringae pv. syringae, and RpfC from Xanthomonas campestris pv. campestris. The RpfA locus described in this study encodes a putative sensor kinase protein that is involved in both extracellular protease and cellulase production and the pathogenicity of E. carotovora subsp. carotovora on potato tubers.
通过Mud1插入构建的胡萝卜软腐欧文氏菌胡萝卜软腐亚种突变体AH2552，其植物致病性降低，胞外蛋白酶和纤维素酶活性缺失，不过其果胶酸裂解酶和多聚半乳糖醛酸酶水平正常。从野生型胡萝卜软腐欧文氏菌胡萝卜软腐亚种DNA文库中分离出一个黏粒克隆pEC462，当它以反式存在时，可将AH2552的致病性、蛋白酶和纤维素酶活性恢复到野生型水平。在AH2552中因Mud1插入而被破坏的基因座被命名为rpfA，即致病因子调节基因。rpfA区域的测序鉴定出一个2787 bp的开放阅读框，预测的929个氨基酸的多肽与几种双组分传感调节蛋白具有高度同源性：大肠杆菌的BarA、荧光假单胞菌的ApdA、托拉斯假单胞菌的PheN、绿黄假单胞菌的RepA、丁香假单胞菌丁香致病变种的LemA以及野油菜黄单胞菌野油菜致病变种的RpfC。本研究中描述的RpfA基因座编码一种假定的传感激酶蛋白，它参与胡萝卜软腐欧文氏菌胡萝卜软腐亚种胞外蛋白酶和纤维素酶的产生以及对马铃薯块茎的致病性。
