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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 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, respecively-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, providing significant 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.