Improving biocontrol activity of Pseudomonas fluorescens through chromosomal inte-gration of 2,4-diacetylphloro-glucinol biosynthesis genes

Antibiotic 2,4-diacetylphloroglucinol (2,4- DAPG) produced by Pseudomonas fluorescens CPF-10 and 2P24 is a principal factor enabling bacteria to suppress plant diseases caused by soilborne pathogens. In this study, a 2,4-DAPG biosynthesis locus phlACBDE cloned from strain CPF-10 was assembled into a mini-Tn5 transposon and in- troduced into the chromosome of P. fluorescens P32 (2,4- DAPG?), CPF-10 and 2P24 to construct the 2,4-DAPG over- producing derivatives P32-38, CPF10-9 and 2P24-48, respec- tively. All the transgenic strains showed an enhanced anti- biosis capacity against plant microbial pathogens in vitro and two strains, P32-38 and CPF10-9, provided significantly bet- ter protection against wheat take-all disease caused by Gae- umannomyces graminis var. tritici and tomato bacterial wilt caused by Ralstonia solanacearum in greenhouse. Compared to their parental strains, the 2,4-DAPG overproducing de- rivatives colonized to the same extent on the wheat tips in the autoclaved soil, but developed larger populations in natural soil. These results indicated that production of antibiotics 2,4- DAPG by biological control pseudomonads can contribute not only to their disease suppression capacities but also to the ecological competence in the resident microflora. Our re- search also suggests that it is a realistic approach to improve biocontrol capacity of P. fluorescens through the genetic modification of its antibiotic 2,4-DAPG production.

Antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) produced by Pseudomonasfluorescens CPF-10 and 2P24 is a principal factor enabling bacteria to suppress plant diseasescaused by soiiborne pathogens. In this study, a 2,4-BAPG biosynthesis locus phlACBDE cloned fromstrain CPF-10 was assembled into a mini-Tn5 transposon and introduced into the chromosome of P.fluorescens P32 (2,4-DAPG'), CPF-10 and 2P24 to construct the 2,4-DAPG overproducing derivativesP32-38, CPF10-9 and 2P24-48, respectively. All the transgenic strains showed an enhanced antibiosiscapacity against plant microbial pathogens in vitro and two strains, P32-38 and CPF10-9, providedsignificantly better protection against wheat take-all disease caused by Gae-umannomyces graminisvar. tritici and tomato bacterial wilt caused by Ralstonia solanacearum in greenhouse. Compared totheir parental strains, the 2,4-DAPG overproducing derivatives colonized to the same extent on thewheat tips in the autoclaved soil, but developed larger populations in natural soil. These resultsindicated that production of antibiotics 2,4-DAPG by biological control pseudomonads can contributenot only to their disease suppression capacities but also to the ecological competence in theresident microflora. Our research also suggests that it is a realistic approach to improvebiocontrol capacity of P. fluorescens through the genetic modification of its antibiotic 2,4-DAPGproduction.