Adaptation of <i>Pseudomonas fluorescens</i> to the plant rhizosphere

Rainey, Paul B.

doi:10.1046/j.1462-2920.1999.00040.x

Cited by 341 publications

(354 citation statements)

References 74 publications

(86 reference statements)

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“…The reasons for these effects are unknown. Previously, Rainey (29) has shown that genes involved in type III secretion in P. fluorescens SBW25 are induced in the sugarbeet rhizosphere. In our experiments, genes encoding translocation proteins involved in type III secretion (pscR, pscQ, and pscP) showed a complex pattern of regulation in response to the root exudates.…”

Section: Resultsmentioning

confidence: 99%

“…In vivo expression technology is now established as a method of analyzing bacterial gene expression in the rhizosphere as an approach for the identification of genes involved in microbe-plant interactions (22,23,29,35). One clear advantage of in vivo expression technology is that investigations are carried out in the appropriate environment in the organism of interest; there is no extrapolation from in vitro model systems.…”

Section: Evaluation and Comparison With Other Techniques To Study Rhizo-mentioning

confidence: 99%

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Transcriptome profiling of bacterial responses to root exudates identifies genes involved in microbe-plant interactions

Mark

Dow

Kiely

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

224

166

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Molecules exuded by plant roots are thought to act as signals to influence the ability of microbial strains to colonize the roots and to survive in the rhizosphere. Differential bacterial responses to signals from different plant species may mediate the selection of specific rhizosphere populations. Very little, however, is known about the effects of plant exudates on patterns of bacterial gene expression. Here, we have tested the concept that plant root exudates modulate expression of bacterial genes involved in establishing microbe-plant interactions. We have examined the influence on the Pseudomonas aeruginosa PA01 transcriptome of exudates from two varieties of sugarbeet that select for genetically distinct pseudomonad populations in the rhizosphere. The response to the two exudates showed only a partial overlap; the majority of those genes with altered expression was regulated in response to only one of the two exudates. Genes with altered expression included those with functions previously implicated in microbe-plant interactions, such as aspects of metabolism, chemotaxis and type III secretion, and a subset with putative or unknown function. Use of a panel of mutants with targeted disruptions allowed us to identify previously uncharacterized genes with roles in the competitive ability of P. aeruginosa in the rhizosphere within this subset. No genes with host-specific effects were identified. Homologues of the genes identified occur in the genomes of both beneficial and pathogenic root-associated bacteria, suggesting that this strategy may help to elucidate molecular interactions that are important for biocontrol, plant growth promotion, and plant pathogenesis.Pseudomonas ͉ Rhizosphere colonization

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Section: Resultsmentioning

confidence: 99%

Section: Evaluation and Comparison With Other Techniques To Study Rhizo-mentioning

confidence: 99%

Transcriptome profiling of bacterial responses to root exudates identifies genes involved in microbe-plant interactions

Mark

Dow

Kiely

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

224

166

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“…The gtsB synonymous mutations (A15A and G38G) were individually introduced into SBW25 using a previously described allelic exchange method involving the pUIC3 vector 32,33 . PCR fragments containing the mutations and 1-kb of flanking sequence on each side were amplified using primers 4845-BglII-F and 4845-AvrII-R from chromosomal DNA isolated from the evolved bacteria.…”

Section: Methodsmentioning

confidence: 99%

Adaptive synonymous mutations in an experimentally evolved Pseudomonas fluorescens population

2014

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Conventional wisdom holds that synonymous mutations, nucleotide changes that do not alter the encoded amino acid, have no detectable effect on phenotype or fitness. However, a growing body of evidence from both comparative and experimental studies suggests otherwise. Synonymous mutations have been shown to impact gene expression, protein folding and fitness, however, direct evidence that they can be positively selected, and so contribute to adaptation, is lacking. Here we report the recovery of two beneficial synonymous single base pair changes that arose spontaneously and independently in an experimentally evolved population of Pseudomonas fluorescens. We show experimentally that these mutations increase fitness by an amount comparable to non-synonymous mutations and that the fitness increases stem from increased gene expression. These results provide unequivocal evidence that synonymous mutations can drive adaptive evolution and suggest that this class of mutation may be underappreciated as a cause of adaptation and evolutionary dynamics.

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“…The rhizosphere is a complex environment that supports a large and metabolically active microbial population, several orders of magnitude higher than the non-rhizospheric soil. Many bacterial genes and traits have been shown to be involved in plant-root colonization (Lugtenberg & Dekkers, 1999;Rainey, 1999;Lugtenberg et al, 2001). However, not only colonization but also the pseudomonads' ability to compete with the indigenous microbial population are essential to improve their biotechnological applications in the rhizosphere environment.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Pseudomonas fluorescens F113 genes implicated in flagellar filament synthesis and their role in competitive root colonization

et al. 2004

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The ability of plant-associated micro-organisms to colonize and compete in the rhizosphere is specially relevant for the biotechnological application of micro-organisms as inoculants. Pseudomonads are one of the best root colonizers and they are widely used in plant-pathogen biocontrol and in soil bioremediation. This study analyses the motility mechanism of the well-known biocontrol strain Pseudomonas fluorescens F113. A 6?5 kb region involved in the flagellar filament synthesis, containing the fliC, flaG, fliD, fliS, fliT and fleQ genes and part of the fleS gene, was sequenced and mutants in this region were made. Several non-motile mutants affected in the fliC, fliS and fleQ genes, and a fliT mutant with reduced motility properties, were obtained. These mutants were completely displaced from the root tip when competing with the wild-type F113 strain, indicating that the wild-type motility properties are necessary for competitive root colonization. A mutant affected in the flaG gene had longer flagella, but the same motility and colonization properties as the wild-type. However, in rich medium or in the absence of iron limitation, it showed a higher motility, suggesting the possibility of improving competitive root colonization by manipulating the motility processes. INTRODUCTIONThe study of rhizosphere colonization by micro-organisms is crucial for the efficient application of bacteria as inoculants, both in agricultural and in environmental biotechnology processes. Pseudomonas spp. can colonize the roots of a wide range of plants (Simons et al., 1996;Naseby & Lynch, 1998;Villacieros et al., 2003), being one of the best root colonizers, and are used as a model in root-colonization studies (Bloemberg et al., 2000; Chin-a-Woeng et al., 2000). The rhizosphere is a complex environment that supports a large and metabolically active microbial population, several orders of magnitude higher than the non-rhizospheric soil. Many bacterial genes and traits have been shown to be involved in plant-root colonization (Lugtenberg & Dekkers, 1999;Rainey, 1999;Lugtenberg et al., 2001). However, not only colonization but also the pseudomonads' ability to compete with the indigenous microbial population are essential to improve their biotechnological applications in the rhizosphere environment.The soil-borne fluorescent pseudomonads are used as biocontrol inoculants because of their ability to produce some antifungal metabolites (Dowling & O'Gara, 1994;Walsh et al., 2001). Other applications of pseudomonads include soil biofertilization and rhizoremediation (Ramos et al., 1991; Brazil et al., 1995; Höflich et al., 1995;Yee et al., 1998).The strain Pseudomonas fluorescens F113 was isolated from the sugarbeet rhizosphere and it is used as a biocontrol agent against the fungal pathogen Pythium ultimum, which causes damping-off disease in sugarbeet seedlings. The biocontrol abilities of this strain are due mainly to the production of the antifungal metabolite DAPG (2,4-diacetylphloroglucinol) (Shanahan et al., 1992). P. fluorescens ...

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Adaptation of Pseudomonas fluorescens to the plant rhizosphere

Cited by 341 publications

References 74 publications

Transcriptome profiling of bacterial responses to root exudates identifies genes involved in microbe-plant interactions

Transcriptome profiling of bacterial responses to root exudates identifies genes involved in microbe-plant interactions

Adaptive synonymous mutations in an experimentally evolved Pseudomonas fluorescens population

Analysis of Pseudomonas fluorescens F113 genes implicated in flagellar filament synthesis and their role in competitive root colonization

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