Effect of the hfq gene on 2,4-diacetylphloroglucinol production and the PcoI/PcoR quorum-sensing system in Pseudomonas fluorescens 2P24

Abstract

Pseudomonas fluorescens 2P24 is an effective biological control agent of a number of soilborne plant diseases caused by pathogenic microorganisms. Among a range of secondary metabolites produced by strain 2P24, the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) is the major determinant of its disease-suppressive capacity. In this study, we performed random mutagenesis using mini-Tn5 in order to screen for the transcriptional regulators of the phlA gene, a biosynthase gene responsible for 2,4-DAPG production. The mutant PMphlA23 with significantly decreased phlA gene expression was identified from approximately 10,000 insertion colonies. The protein sequence of the interrupted gene has 84% identity to Hfq, a key regulator important for stress resistance and virulence in Pseudomonas aeruginosa. Genetic inactivation of hfq resulted in decreased expression of phlA and reduced production of 2,4-DAPG. Furthermore, the hfq gene was also required for the expression of pcoI, a synthase gene for the LuxI-type quorum-sensing signaling molecule N-acyl-homoserine lactone. Additionally, the hfq mutation drastically reduced biofilm formation and impaired the colonization ability of strain 2P24 on wheat rhizospheres. Based on these results, we propose that Hfq functions as an important regulatory element in the complex network controlling environmental adaption in P. fluorescens 2P24.

Multiple-Level Regulation of 2,4-Diacetylphloroglucinol Production by the Sigma Regulator PsrA in Pseudomonas fluorescens 2P24

“…2B). To test the influence of PsrA on the phlA transcription, p970Gm-phlAp [46] carrying a phlA-lacZ transcriptional fusion was transformed into the psrA mutant and its parental strain 2P24. When the cultures were in the stationary phase, expression of phlA increased about 3-fold in the psrA mutant compared to that of strain 2P24 (Fig.…”

“…Each of these cis -acting regions was inserted as a Bam HI or a Bgl II fragment into pRG970Gm [46] to place them upstream of a promoterless lacZ gene. Plasmid p970Gm-rsmZMp was constructed by PCR amplification using primer pair rsmZMp and RsmZ-P3361 and inserted into pRG970Gm as a Bam HI fragment.…”

Mechanisms of post-transcriptional gene regulation in bacterial biofilms

“…The effects of hfq mutation in these pathogens are not only restricted to the biofilm production; they often exhibit pleiotropic phenotypes, including defects in quorum sensing, motility, antibiotic susceptibility, growth rate, stress tolerance, and virulence (Hammer and Bassler, 2007; Kint et al, 2010; Wu et al, 2010; Liu et al, 2011; Monteiro et al, 2012; Roscetto et al, 2012; Zeng et al, 2013). …”

Effect of Biocontrol Agent Pseudomonas fluorescens 2P24 on Soil Fungal Community in Cucumber Rhizosphere Using T-RFLP and DGGE

“…The root colonization and biocontrol mechanism of it have been studied [23]–[25] and it has been commercialized. However, the potential effect of P. fluorescens 2P24 on agricultural soil fungal community is still unknown, as it is important to address the displacements of indigenous microorganisms by inoculates and assess the potential effects on soil microcosm [26].…”