Pseudomonas simiae WCS417: star track of a model beneficial rhizobacterium

Abstract

Background Since the 1980s, numerous mutualistic Pseudomonas spp. strains have been used in studies on the biology of plant growth-promoting rhizobacteria (PGPR) and their interactions with host plants. In 1988, a strain from the Pseudomonas fluorescens group, WCS417, was isolated from lesions of wheat roots growing in a take-all disease-suppressive soil. In subsequent trials, WCS417 limited the build-up of take-all disease in field-grown wheat and significantly increased wheat yield. In 1991, WCS417 was featured in one of the first landmark studies on rhizobacteria-induced systemic resistance (ISR), in which it was shown to confer systemic immunity in carnation (Dianthus caryophyllus) against Fusarium wilt. The discovery that WCS417 conferred systemic immunity in the model plant species Arabidopsis thaliana in 1996 incited intensive research on the molecular mechanisms by which PGPR promote plant growth and induce broad-spectrum disease resistance in plants. Since then, the strain name appeared in over 750 studies on beneficial plant-microbe interactions. Scope In this review, we will highlight key discoveries in plant-microbe interactions research that have emerged from over 30 years of research featuring WCS417 as a model rhizobacterial strain. WCS417 was instrumental in improving our understanding of the microbial determinants that are involved in root colonization and the establishment of mutually beneficial interactions with the host plant. The model strain also provided novel insight into the molecular mechanisms of plant growth promotion and the onset and expression of rhizobacteria-ISR. More recently, WCS417 has been featured in studies on host immune evasion during root colonization, and chemical communication in the rhizosphere during root microbiome assembly. Conclusions Numerous studies on the modes of action of WCS417 have provided major conceptual advances in our understanding of how free-living mutualists colonize the rhizosphere, modulate plant immunity, and promote plant growth. The concepts may prove useful in our understanding of the molecular mechanisms involved in other binary plant-beneficial microbe interactions, and in more complex microbial community contexts, such as the root microbiome.

Deciphering the Bacillus amyloliquefaciens B9601-Y2 as a Potential Antagonist of Tobacco Leaf Mildew Pathogen During Flue-Curing

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Rapid evolution of bacterial mutualism in the plant rhizosphere

“…To investigate effects of the ancestor and evolved strains of P. protegens CHA0 on expression of MYB72, we applied a GUS histochemical staining assay to the 30 selected isolates (Table S2). MYB72 is a transcription factor involved in production of the coumarin scopoletin in Arabidopsis roots and specific rhizobacteria can upregulate expression of MYB72 in the roots 66 . Scopoletin is an ironmobilizing phenolic compound with selective antimicrobial activity 22 .…”

Genome-Based Characterization of Plant-Associated Rhodococcus qingshengii RL1 Reveals Stress Tolerance and Plant–Microbe Interaction Traits

“…Cha2324a_16 and the ACC utilizing strain Variovorax sp. M92526_27 isolated from wheat roots (this study), the nitrogen-fixing and IAA producing Herbaspirillum frisingense GSF30 DSM 1328 ( Kirchhof et al, 2001 ), the nitrogen-fixing Azospirillum brasilense Sp7 DSM 1690 ( Tarrand et al, 1978 ; Hartmann and Hurek, 1988 ), the biofilm-producing Pseudomonas simiae WCS417r ( Pieterse et al, 2020 ) and the non-biofilm-producing Escherichia coli DH5α ( Anton and Raleigh, 2016 ). Strains were cultivated in liquid nutrient broth (NB, Roth, Germany) (beef extract 3 g/l, gelatin peptone 5 g/l) or solid nutrient agar (with 1.7% agar) with pH 6.8, unless further specified, at 28°C at 180 rpm.…”