Faculty Opinions recommendation of Fusaric acid-producing strains of Fusarium oxysporum alter 2,4-diacetylphloroglucinol biosynthetic gene expression in Pseudomonas fluorescens CHA0 in vitro and in the rhizosphere of wheat.

2003 ◽  
Author(s):  
Ben Lugtenberg
Keyword(s):  
Gene Expression ◽  
Fusarium Oxysporum ◽  
Pseudomonas Fluorescens ◽  
Fusaric Acid ◽  
Biosynthetic Gene ◽  
Biosynthetic Gene Expression

scholarly journals Fusaric Acid-Producing Strains of Fusarium oxysporum Alter 2,4-Diacetylphloroglucinol Biosynthetic Gene Expression in Pseudomonas fluorescens CHA0 In Vitro and in the Rhizosphere of Wheat

2002 ◽  
Vol 68 (5) ◽  
pp. 2229-2235 ◽  
Author(s):  
Regina Notz ◽  
Monika Maurhofer ◽  
Helen Dubach ◽  
Dieter Haas ◽  
Geneviève Défago
Keyword(s):  
Fusarium Oxysporum ◽  
Pseudomonas Fluorescens ◽  
Culture Media ◽  
Fusaric Acid ◽  
Strongly Correlated ◽  
Wheat Rhizosphere ◽  
Key Factor ◽  
In The Wild ◽  
Biocontrol Strain

ABSTRACT The phytotoxic pathogenicity factor fusaric acid (FA) represses the production of 2,4-diacetylphloroglucinol (DAPG), a key factor in the antimicrobial activity of the biocontrol strain Pseudomonas fluorescens CHA0. FA production by 12 Fusarium oxysporum strains varied substantially. We measured the effect of FA production on expression of the phlACBDE biosynthetic operon of strain CHA0 in culture media and in the wheat rhizosphere by using a translational phlA′-′lacZ fusion. Only FA-producing F. oxysporum strains could suppress DAPG production in strain CHA0, and the FA concentration was strongly correlated with the degree of phlA repression. The repressing effect of FA on phlA′-′lacZ expression was abolished in a mutant that lacked the DAPG pathway-specific repressor PhlF. One FA-producing strain (798) and one nonproducing strain (242) of F. oxysporum were tested for their influence on phlA expression in CHA0 in the rhizosphere of wheat in a gnotobiotic system containing a sand and clay mineral-based artificial soil. F. oxysporum strain 798 (FA+) repressed phlA expression in CHA0 significantly, whereas strain 242 (FA−) did not. In the phlF mutant CHA638, phlA expression was not altered by the presence of either F. oxysporum strain 242 or 798. phlA expression levels were seven to eight times higher in strain CHA638 than in the wild-type CHA0, indicating that PhlF limits phlA expression in the wheat rhizosphere.

scholarly journals Role of Chemotaxis Toward Fusaric Acid in Colonization of Hyphae of Fusarium oxysporum f. sp. radicis-lycopersici by Pseudomonas fluorescens WCS365

2004 ◽  
Vol 17 (11) ◽  
pp. 1185-1191 ◽  
Author(s):  
Sandra de Weert ◽  
Irene Kuiper ◽  
Ellen L. Lagendijk ◽  
Gerda E. M. Lamers ◽  
Ben J. J. Lugtenberg
Keyword(s):  
Fusarium Oxysporum ◽  
Pseudomonas Fluorescens ◽  
Fusaric Acid ◽  
Chemotactic Response ◽  
Phytopathogenic Fungus ◽  
Root Tips ◽  
Tomato Root ◽  
Vitro Assay

Pseudomonas fluorescens WCS365 is an excellent competitive colonizer of tomato root tips after bacterization of seed or seedlings. The strain controls tomato foot and root rot (TFRR) caused by the phytopathogenic fungus Fusarium oxysporum f. sp. radicis-lycopersici. Under biocontrol conditions, fungal hyphae were shown to be colonized by WCS365 bacteria. Because chemotaxis is required for root colonization by WCS365 cells, we studied whether chemotaxis also is required for hyphae colonization. To that end, an in vitro assay was developed to study hyphae colonization by bacteria. The results indicated that cells of the cheA mutant FAJ2060 colonize hyphae less efficiently than cells of wild-type strain WCS365, when single strains were analyzed as well as when both strains were applied together. Cells of WCS365 show a chemotactic response toward the spent growth medium of F. oxysporum f. sp. radicis-lycopersici, but those of its cheA mutant, FAJ2060, did not. Fusaric acid, a secondary metabolite secreted by Fusarium strains, appeared to be an excellent chemo-attractant. Supernatant fluids of a number of Fusarium strains secreting different levels of fusaric acid were tested as chemo-attractants. A positive correlation was found between chemo-attractant activity and fusaric acid level. No chemotactic response was observed toward the low fusaric acid-producer FO242. Nevertheless, the hyphae of FO242 still were colonized by WCS365, suggesting that other metabolites also play a role in this process. The possible function of hyphae colonization for the bacterium is discussed.

scholarly journals Impaired sucrose-induction mutants reveal the modulation of sugar-induced starch biosynthetic gene expression by abscisic acid signalling

2001 ◽  
Vol 26 (4) ◽  
pp. 421-433 ◽  
Author(s):  
Fred Rook ◽  
Fiona Corke ◽  
Roderick Card ◽  
Georg Munz ◽  
Caroline Smith ◽  
...  
Keyword(s):  
Gene Expression ◽  
Abscisic Acid ◽  
Biosynthetic Gene ◽  
Sucrose Induction ◽  
Biosynthetic Gene Expression

scholarly journals Defense Responses of Fusarium oxysporum to 2,4-Diacetylphloroglucinol, a Broad-Spectrum Antibiotic Produced by Pseudomonas fluorescens

2004 ◽  
Vol 17 (11) ◽  
pp. 1201-1211 ◽  
Author(s):  
Alexander Schouten ◽  
Grardy van den Berg ◽  
Véronique Edel-Hermann ◽  
Christian Steinberg ◽  
Nadine Gautheron ◽  
...  
Keyword(s):  
Fusarium Oxysporum ◽  
Pseudomonas Fluorescens ◽  
Broad Spectrum ◽  
Acid Production ◽  
Fusaric Acid ◽  
Geographic Origin ◽  
Intergenic Spacer ◽  
Pathogenic Fungi ◽  
Defense Responses ◽  
Broad Spectrum Antibiotic

A collection of 76 plant-pathogenic and 41 saprophytic Fusarium oxysporum strains was screened for sensitivity to 2,4-diacetylphloroglucinol (2,4-DAPG), a broad-spectrum antibiotic produced by multiple strains of antagonistic Pseudomonas fluorescens. Approximately 17% of the F. oxysporum strains were relatively tolerant to high 2,4-DAPG concentrations. Tolerance to 2,4-DAPG did not correlate with the geographic origin of the strains, formae speciales, intergenic spacer (IGS) group, or fusaric acid production levels. Biochemical analysis showed that 18 of 20 tolerant F. oxysporum strains were capable of metabolizing 2,4-DAPG. For two tolerant strains, analysis by mass spectrometry indicated that deacetylation of 2,4-DAPG to the less fungitoxic derivatives monoacetylphloroglucinol and phloroglucinol is among the initial mechanisms of 2,4-DAPG degradation. Production of fusaric acid, a known inhibitor of 2,4-DAPG biosynthesis in P. fluorescens, differed considerably among both 2,4-DAPG-sensitive and -tolerant F. oxysporum strains, indicating that fusaric acid production may be as important for 2,4-DAPG-sensitive as for -tolerant F. oxysporum strains. Whether 2,4-DAPG triggers fusaric acid production was studied for six F. oxysporum strains; 2,4-DAPG had no significant effect on fusaric acid production in four strains. In two strains, however, sublethal concentrations of 2,4-DAPG either enhanced or significantly decreased fusaric acid production. The implications of 2,4-DAPG degradation, the distribution of this trait within F. oxysporum and other plant-pathogenic fungi, and the consequences for the efficacy of biological control are discussed.

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