The Study On Transcription Regulator PhlH Modulates 2,4-diacetylphloroglucinol Degradation In Pseudomonas Fluorescens

Certain strains of biocontrol Pseudomonas fluorescens produce the secondary metabolite 2,4-diacetylphloroglucinol(2,4-DAPG)to antagonize the soil-borne phytopathogens in the rhizosphere and the gene cluster termed phlACBDEFGH involves in the biosynthesis of this compound.However,little is known about the physiological function and regulation mechanism of the TetR family regulator PhlH.Here,we found that phlH in Pseudomonas fluorescens 2P24 represses the expression of the phlG gene encoding the 2,4-DAPG hydrolase by binding to a sequence motif overlapping with the-35 site recognized by ?70 factors.Through biochemical screening we identified the end product 2,4-DAPG and its biosynthetic intermediate monoacetylphloroglucinol(MAPG)can act as signaling molecules to modulate the binding of PhlH to the target sequence,leading to the de-repressed expression of PhlG.Comparison of 2,4-DAPG production between the ?phlH,?phlG and ?phlHG mutants confirms that phlH and phlG impose negative feedback regulation over 2,4-DAPG biosynthesis.Taken together,our data suggests that by monitoring and down-tuning in situ levels of 2,4-DAPG,the phlHG genes could dynamically modulate the metabolic loads attributed to 2,4-DAPG production and potentially contribute to the rhizosphere adaptation.