Defense responses of Fusarium oxysporum to 2,4-Diacetylphloroglucinol, a broad-spectrum antibiotic produced by Pseudomonas fluorescens

A. Schouten, G. van den Berg, V. Edel-Hermann, C. Steinberg, N. Gautheron, C. Alabouvette, C.H. de Vos, P. Lemanceau, J.M. Raaijmakers

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Abstract

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 E 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 E 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 E oxysporum strains, indicating that fusaric acid production may be as important for 2,4-DAPG-sensitive as for -tolerant E oxysporum strains. Whether 2,4-DAPG triggers fusaric acid production was studied for six E 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 E oxysporum and other plant-pathogenic fungi, and the consequences for the efficacy of biological control are discussed.
Original languageEnglish
Pages (from-to)1201-1211
JournalMolecular Plant-Microbe Interactions
Volume17
Issue number11
DOIs
Publication statusPublished - 2004

Keywords

  • genetic diversity
  • abc transporters
  • take-all
  • biocontrol
  • resistance
  • populations
  • biosynthesis
  • sensitivity
  • strains
  • tomato

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