Pierson L S, Keppenne V D, Wood D W
Department of Plant Pathology, University of Arizona, Tucson 85721.
J Bacteriol. 1994 Jul;176(13):3966-74. doi: 10.1128/jb.176.13.3966-3974.1994.
We have identified a gene that acts in trans to activate the expression of the phenazine biosynthetic genes in the biological control organism Pseudomonas aureofaciens 30-84. This gene, phzR (phenazine regulator), is located upstream of and divergently transcribed from the phenazine biosynthetic genes. Thus, the phenazine biosynthetic locus consists of at least two divergently transcribed operons. A functional phzR gene is required for phenazine production. The nucleotide sequence of phzR revealed an open reading frame of 723 nucleotides encoding a protein of ca. 27 kDa. The predicted amino acid sequence of PhzR has homology with other bacterial positive transcriptional activators, including LasR of Pseudomonas aeruginosa, LuxR of Vibrio fischerii, and TraR of Agrobacterium tumefaciens. The addition of cell-free supernatants from late-exponential-phase cultures of strain 30-84 resulted in expression of a genomic phzB:lacZ reporter strain at a lower cell density than normal, indicating the possible presence of an autoinducer. These results indicate that PhzR is a member of a two-component sensor-regulator family with known or predicted carboxy-terminal DNA-binding domains which regulates gene expression in response to environmental and cell density signals.
我们已鉴定出一个基因，它以反式作用激活生防菌金色假单胞菌30 - 84中吩嗪生物合成基因的表达。这个基因，即phzR（吩嗪调节基因），位于吩嗪生物合成基因的上游，且与其转录方向相反。因此，吩嗪生物合成基因座至少由两个转录方向相反的操纵子组成。吩嗪的产生需要一个有功能的phzR基因。phzR的核苷酸序列显示有一个723个核苷酸的开放阅读框，编码一个约27 kDa的蛋白质。预测的PhzR氨基酸序列与其他细菌的正向转录激活因子具有同源性，包括铜绿假单胞菌的LasR、费氏弧菌的LuxR和根癌土壤杆菌的TraR。添加来自30 - 84菌株指数生长后期培养物的无细胞上清液，导致基因组phzB:lacZ报告菌株在比正常情况更低的细胞密度下表达，这表明可能存在一种自诱导物。这些结果表明，PhzR是一个双组分传感调节家族的成员，该家族具有已知或预测的羧基末端DNA结合结构域，可响应环境和细胞密度信号调节基因表达。
