Improving biocontrol activity ofPseudomonas fluorescens through chromosomal integration of 2,4-diacetylphloroglucinol biosynthesis genes

Antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) produced byPseudomonas 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 locusphlACBDE cloned from strain CPF-10 was assembled into a mini-Tn5 transposon and introduced into the chromosome ofP. fluorescens P32 (2,4-DAPG“), CPF-10 and 2P24 to construct the 2,4-DAPG overproducing derivatives P32-38, CPF10-–9 and 2P24–48, respectively. All the transgenic strains showed an enhanced antibiosis capacity against plant microbial pathogensin vitro and two strains, P32–38 and CPF10–9, provided significantly better protection against wheat take-all disease caused byGaeumannomyces graminis var.tritici and tomato bacterial wilt caused byRalstonia solanacearum in greenhouse. Compared to their parental strains, the 2,4-DAPG overproducing derivatives 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 research also suggests that it is a realistic approach to improve biocontrol capacity ofP. fluorescens through the genetic modification of its antibiotic 2,4-DAPG production.