IntroductionPseudomonas fluorescens2P24 was isolated from soil of natural decay associated with wheat take-all and it can effectively control soil-borne diseases caused by a variety of plant pathogens. 2,4-diacetylphloroglucinol (2,4-DAPG), is produced byP. fluorescens2P24 and plays an important role in the prevention and control of plant diseases. To understand the resistant mechanism, in this study, we conducted experiments to explore the regulation role ofrpoZin the synthesis of the antibiotic 2,4-DAPG and regulation of QS system.MethodsA random mini-Tn5 mutagenesis procedure was used to screen regulators forphlAtranscription in stain PM901, which containing a phlA∷lacZ transcriptional fusion reporter plasmid. We identified 12 insertion mutants could significantly changephlAgene expression. By analyzing the amino acid sequences of the interrupted gene, we obtained a mutant strain Aa4-29 destroyed therpoZgene, which encodes the omiga subunit. We constructed the plasmid ofrpoZmutant (pBBR-△rpoZ) transformed into competent cells ofP. fluorescens2P24 by electro-transformation assay. The strains ofP. fluorescens2P24/pBBR, 2P24-△rpoZ/pBBR, 2P24-△rpoZ/pBBR-rpoZ were used to evaluate the regulation role ofrpoZin 2,4-DAPG production and quorum sensing system.ResultsAccording to β-galactosidase activity, we found thatrpoZpositively regulated the expression ofphlA(a synthesis gene of 2,4-DAPG) andPcoI(a synthesis gene of PcoI/PcoR QS signal system) at the transcriptional level. The production of 2,4-DAPG antibiotic and signal molecule AHL was influenced byrpoZ. Further,rpoZwas involved in regulatingrsmAexpression.RpoZalso has a certain regulatory effect onrpoStranscription, but no effect on the transcription ofphlF,emhABCandemhR. According to the biocontrol assay,P. fluorescens2P24 strains withrpoZshowed obvious antagonism ability against theRhizoctonia solaniin cotton, while the mutant strain ofrpoZlost the biocontrol effect.RpoZhad a significant effect on the swimming and biofilm formation inP. fluorescens2P24.ConclusionOur data showed thatrpoZwas an important regulator of QS system, 2,4-DAPG inP. fluorescens2P24. This may imply thatP. fluorescens 2P24has evolved different regulatory features to adapt to different environmental threats.