GacA对假单胞菌株M18两个phz基因簇和菌群传感的调控

Regulation of GacA on two phz gene clusters and quorum sensing in Pseudomonas sp. M18

摘要:

摘要:【目的】假单胞菌株M18（Pseudomonas sp. M18）是从甜瓜根际土壤中分离获得的一株对多种植物病原菌具有显著拮抗作用的菌株，在菌群传感（quorum sensing）系统的调控下，能分泌吩嗪-1-羧酸（PCA）以及多种吩嗪（phz）类衍生物的抗真菌物质。全局性因子GacA是M18菌株吩嗪类物质的合成与菌群传感系统的重要调控因子，本文将就GacA对上述两者的调控做进一步研究。【方法】PCR基因扩增和测序研究M18菌株中PCA合成基因簇，运用RT-PCR及构建phzA-lacZ转录融合手段

Abstract:

Abstract: [Objective] The regulatory function investigation of two component system gacS/gacA on two phz gene clusters expression and quorum sensing system (QS) in Pseu-domonas. sp. M18. [Methods] The two phz gene clusters were sequenced and the expres-sional features by GacA were analyzed using RT-PCR and phzA-lacZ transcriptional fu-sions, the regulation of GacA over QS system was studied also in P. sp. M18. [Results] 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. [Conclusion] 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.