荧光假单胞杆菌2P24中生防相关调控基因gacS的克隆和功能分析  

Cloning and functional characterization of the gacS gene of the biocontrol strain Pseuodomonas fluorescens 2P24

作　　者：魏海雷[1] 张力群[1] 

机构地区：[1]中国农业大学植物病理系,北京100094

出　　处：《微生物学报》2005年第3期368-372,共5页Acta Microbiologica Sinica

基　　金：国家自然科学基金 ( 3 0 10 0 12 0 ;3 0 3 70 95 2 );国家"863计划"( 2 0 0 3AA2 41170 )~~

摘　　要：荧光假单胞杆菌2P2 4菌株分离自小麦全蚀病自然衰退土壤,可产生多种次生抗菌物质,对一些作物土传病害具有较好的防治能力。通过PCR介导的方法从荧光假单胞杆菌2P2 4的基因组文库中克隆到调控基因gacS。序列分析发现,该基因长度为2 75 4bp ,编码917个氨基酸的肽链。此肽链与Pseudomonaschlororaphis双因子组分之一的感受激酶GacS相似性达91% ,与P .fluorescensCHA0的GacS相似性为89%。与野生菌株2P2 4相比,gacS基因的缺失突变体完全丧失产生抗菌代谢物2 ,4_二乙酰基间苯三酚、氢氰酸、蛋白酶的能力。拮抗试验中,gacS缺失突变体丧失对小麦全蚀病菌的拮抗作用,温室生物测定显示gacS的缺失突变体对小麦全蚀病的生防能力大幅下降。但是gacS基因的互补突变体能够恢复产生抗菌次生代谢物的能力,且重新获得拮抗能力和生防能力。由此证明GacS是生防菌株2P2 4中一个控制生防因子并影响生防效果的重要调控元件。Pseudomonasfluorescens 2P24, a biocontrol agent for soil_borne diseases has been isolated from the wheat take_all decline soil, and was characterized with efficient production of antifungal compounds. In this study, thegacSgene was cloned by PCR from theP. fluorescens 2P24 genomic library. Nucleotide sequencing indicated that thegacS gene contains 2754 bp, and is predicted to encode a peptide of 917 amino acids with molecular mass of 101 kD. The deduced amino acid sequence shares 91% identity to that of the sensor kinase GacS ofP. chlororaphis and 89% identity to GacS ofP. fluorescens CHA0. Further research revealed that thegacS_knock_out mutant was unable to produce antifungal metabolites, such as 2,4_DAPG, HCN and proteinase. Moreover, it lost the ability to inhibit the growth ofGaeumannomyces graminis in Petri dish and to control the development of wheat take_all disease in greenhouse. The complemented strain containing a plasmid_bearinggacS gene could restore all of the lost phenotypes. The results indicated that GacS in an important regulatory factor and directly controls the synthesis of key biocontrol factors and the biocontrol efficacy ofP. fluorescens 2P24.

关 键 词：荧光假单胞杆菌 生物防治 双因子调控系统 gacS基因 

分 类 号：S476.1[农业科学—农业昆虫与害虫防治]