Shi Mingqi, Li Yaqian, Wang Yi, Huang Jiaofang, Huang Xianqing, Xu Yuquan
College of Life Science, Shanghai Jiaotong University, Shanghai 200240, China.
Wei Sheng Wu Xue Bao. 2009 Oct;49(10):1306-16.
The regulatory function investigation of two component system gacS/gacA on two phz gene clusters expression and quorum sensing system (QS) in Pseudomonas. sp. M18.
The two phz gene clusters were sequenced and the expressional features by GacA were analyzed using RT-PCR and phzA-lacZ transcriptional fusions, the regulation of GacA over QS system was studied also in P. sp. M18.
Two phenazine sturctural clusters, namely, phzA1-G1 and phzA2-G2 in P. sp. M18 shared 99% identities with those in P. aeruginosa PAO1. However, in the non-coding region downstream the phzA2-G2, P. sp. M18 has a three-144 bp-repeat sequence which does not exist in P. aeruginosa PAO1. PhzA1-G1 expressed at a higher level than phzA2-G2 in the wide type M18 strain. GacA functioned differently over these two phz gene clusters but negatively regulating the two clusters expression at the whole level, which was opposite to that in P. aeruginosa PAO1. The inactivation of gacA gene can reduce rhlI expression while has no effect on lasI expression, indicating that the phz gene expression regulated by GacA via QS was a minor part and the major phz expression was regulated by GacA through an unknown pathway instead of QS in P. sp. M18.
The different regulation of GacA activity on secondary metabolites and QS in P. sp. M18 and P. aeruginosa PAO1 may be the results imposed by the environmental selective pressure during evolution pathway.
研究双组分系统gacS/gacA对假单胞菌属M18中两个吩嗪合成酶基因簇（phz）表达及群体感应系统（QS）的调控作用。
对两个phz基因簇进行测序，采用RT-PCR和phzA-lacZ转录融合技术分析GacA的表达特征，并在假单胞菌属M18中研究GacA对QS系统的调控。
假单胞菌属M18中的两个吩嗪结构基因簇phzA1-G1和phzA2-G2与铜绿假单胞菌PAO1中的相应基因簇具有99%的同源性。然而，在phzA2-G2下游的非编码区，假单胞菌属M18有一个144 bp的三重复序列，而铜绿假单胞菌PAO1中不存在该序列。在野生型M18菌株中，PhzA1-G1的表达水平高于PhzA2-G2。GacA对这两个phz基因簇的作用不同，但在整体水平上负调控这两个基因簇的表达，这与铜绿假单胞菌PAO1中的情况相反。gacA基因的失活可降低rhlI的表达，但对lasI的表达无影响，表明在假单胞菌属M18中，GacA通过QS对phz基因表达的调控作用较小，phz的主要表达是由GacA通过未知途径而非QS调控的。
GacA活性对假单胞菌属M18和铜绿假单胞菌PAO1中次生代谢产物和QS的不同调控可能是进化过程中环境选择压力作用的结果。
