regulates 2,4-DAPG production and quorum sensing system in 2P24.

Introduction: 2P24 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 by 2P24 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 of in the synthesis of the antibiotic 2,4-DAPG and regulation of QS system.

Methods: A random mini-Tn5 mutagenesis procedure was used to screen regulators for transcription in stain PM901, which containing a phlA∷lacZ transcriptional fusion reporter plasmid. We identified 12 insertion mutants could significantly change gene expression. By analyzing the amino acid sequences of the interrupted gene, we obtained a mutant strain Aa4-29 destroyed the gene, which encodes the omiga subunit. We constructed the plasmid of mutant (pBBR-△rpoZ) transformed into competent cells of 2P24 by electro-transformation assay. The strains of 2P24/pBBR, 2P24-△rpoZ/pBBR, 2P24-△rpoZ/pBBR-rpoZ were used to evaluate the regulation role of in 2,4-DAPG production and quorum sensing system.

Results: According to β-galactosidase activity, we found that positively regulated the expression of (a synthesis gene of 2,4-DAPG) and (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 by . Further, was involved in regulating expression. also has a certain regulatory effect on transcription, but no effect on the transcription of , and . According to the biocontrol assay, 2P24 strains with showed obvious antagonism ability against the in cotton, while the mutant strain of lost the biocontrol effect. had a significant effect on the swimming and biofilm formation in 2P24.

Conclusion: Our data showed that was an important regulator of QS system, 2,4-DAPG in 2P24. This may imply that has evolved different regulatory features to adapt to different environmental threats.