The Gac/Rsm Signaling Pathway of a Biocontrol Bacterium, Pseudomonas chlororaphis O6

Abstract

Pseudomonas chlororaphis O6, isolated from the roots of dryland, field-grown commercial wheat in the USA, enhances plant health and therefore it is used in agriculture as a biofertilizer and biocontrol agent. The metabolites produced by this pseudomonad stimulate plant growth through direct antagonism of pathogens and by inducing systemic resistance in the plant. Studies upon P. chlororaphis O6 identify the pathways through which defined bacterial metabolites generate protection against pathogenic microbes, insects, and nematodes. P. chlororaphis O6 also triggers plant resistance to drought and salinity stresses. The beneficial determinants are produced from bacterial cells as they form biofilms during root colonization. Molecular control these processes in P. chlororaphis O6 involves the global regulatory Gac/Rsm signaling cascade with cross-talk between other global regulatory pathways. The Gac/Rsm regulon allows for coordinate phasing of expression of the genes that encode these beneficial traits among a community of cells. This review provides insights on the Gac/Rsm regulon in expression of beneficial traits of the P. chlororaphis O6 which can contribute to help yield enhancement and quality in agricultural production.

Biocontrol Efficacy of Formulated Pseudomonas chlororaphis O6 against Plant Diseases and Root-Knot Nematodes

“…1 ). This result confirmed our previous findings that P. chlororaphis O6 bacterial cultures had biocontrol activity when used directly or indirectly against these tomato diseases ( Anderson et al, 2017 ; Anderson and Kim, 2018 ; Oh et al, 2013 ; Park et al, 2011 ).…”

Proteomic Analysis of the GacA Response Regulator in Pseudomonas chlororaphis O6

“…Production of an extracellular protease (data not shown) was also reduced by the mutation whereas siderophore was overproduced, as observed with a gacS mutant. These phenotypes were similar to those of the gacS mutant of P. chlororaphis O6 (Anderson et al, 2017;Kang et al, 2004Kang et al, , 2007Kim et al, 2014aKim et al, , 2014bKim et al, , 2014cOh et al, 2013a;Park et al, 2018;Ryu et al, 2007). These findings indicate that GacA is a functional regulator for these traits, working through regulation by GacS (Kim and Anderson, 2018).…”

“…In P. chlororaphis G5, swimming and indole acetic acid production were decreased, but there was increased biofilm in biofilm formation and survival under oxidative stresses in gacS mutant (Li et al, 2015). In contrast, for P. chlororaphis O6 the gacS mutation increases swimming and swarming, and indole acetic acid formation (Anderson et al, 2017; Microbial strains and growth conditions. Bacteria were stored at -80°C in 25% glycerol.…”

Bacterial species recognized for the first time for its biocontrol activity against fire blight (Erwinia amylovora)

“…It also increased the growth of this plant seedlings in greenhouse vegetable production systems (Nakkeeran et al 2006). Moreover, the strain O6 of P. chlororaphis, isolated from the roots of dryland, field-grown commercial wheat, enhances plant health and therefore it is used in agriculture as a biofertilizer and biocontrol agent (Anderson et al 2017). On the other hand strain SR1 of P. chlororaphis subsp.…”