Role of Vfr in the regulation of antifungal compound production by Pseudomonas fluorescens FD6

Abstract

Pseudomonas fluorescens FD6 has been shown to possess many beneficial traits involved in the biocontrol of fungal plant pathogens, such as Botrytis cinerea and Monilinia fructicola. Vfr (virulence factor regulator) a highly conserved global regulator of gram-negative bacteria, such as the human pathogen Pseudomonas aeruginosa, is required for the expression of many important virulence traits. The role of Vfr in the regulation of biocontrol traits, such as the production of antibiotics to control fungal pathogens by antagonistic bacteria, has not been elucidated. This study investigated the effect of a vfr mutant derived from P. fluorescens FD6 to better understand the regulation of some important biocontrol traits associated with the bacterium. Biochemical studies indicated that the production of the antibiotics 2,4-diacetylphloroglucinol, pyrrolnitrin and pyoluteorin, was markedly enhanced in the vfr mutant. The vfr mutation also increased biofilm production, swimming motility and the expression of exopolysaccharide-associated gene (pelA, pslA and pslB) transcripts, but reduced protease production. Wheat rhizosphere and root tip colonization by the vfr mutant was higher than that by the wild type at 7 and 21days after inoculation. These findings demonstrate that Vfr modulates the expression of several key traits and the production of important antibiotics involved in the biocontrol potential of P. fluorescens FD6.

vfr, A Global Regulatory Gene, is Required for Pyrrolnitrin but not for Phenazine-1-carboxylic Acid Biosynthesis in Pseudomonas chlororaphis G05

“…In general, Vfr is not only related tightly to the pathogenicity of some bacteria, but also plays a critical role in their infection. In one other previous study, it was reported Vfr in P. fluorescens had a negative regulation on the biosynthesis of secondary antifungal metabolites, such as pyrrolnitrin, PLT, and DAPG ( Zhang et al, 2016 ). Knockout of the vfr gene brought increased production of antifungal compounds.…”

“…In P. chlororaphis PA23, ANR and PtrA were identified to mediate pyrrolnitrin production ( Nandi et al, 2016 ; Shah et al, 2016 ). In P. fluorescens FD6, RetS and Vfr were reported to regulate pyrrolnitrin biosynthesis ( Zhang et al, 2015 , 2016 ). In P. chlororaphis O6, RpoS and GacS deficiency could change the production of pyrrolnitrin ( Oh et al, 2013 ; Park et al, 2018 ).…”

In vitro study of biocontrol potential of rhizospheric Pseudomonas aeruginosa against Fusarium oxysporum f. sp. cucumerinum

“…Examples of antifungal and secondary metabolites produced by Pseudomonas spp. include phenazines (Hu et al 2014), 2,4-diacetylphoroglucinol (Zhang et al 2016), pyoluteorin (Wu et al 2011), pyrrolnitrin (Zhang et al 2016), cyclic lipopeptides (Michelsen et al 2015), siderophores (Sulochana et al 2014), volatile compounds (Mannaa et al 2017), hydrolytic enzymes (Solanki et al 2014), and so on. Fluorescent pseudomonads, for example, Pseudomonas aeruginosa (Fatima and Anjum 2017), Pseudomonas putida (Yu and Lee 2015), and Pseudomonas fluorescens (Zhang et al 2016), are well-known to protect plants from fungal infections.…”

Construction of a β-galactosidase-gene-based fusion is convenient for screening candidate genes involved in regulation of pyrrolnitrin biosynthesis in <i>Pseudomonas chlororaphis</i> G05

“…Although some regulators, such as the GacS/GacA system, the Quorum Sensing system, ANR, Vfr, and RpoS, were identified in certain Pseudomonas spp. to mediate pyrrolnitrin biosynthesis positively or negatively (Selin et al, 2010(Selin et al, , 2012(Selin et al, , 2014Haas and Keel, 2003;Nandi et al, 2016;Oh et al, 2013;Zhang et al, 2016), we still do not know much about the regulatory pathway of pyrrolnitrin biosynthesis in detail.…”