title: Induced systemic resistance in Arabidopsis thaliana against Pseudomonas syringae pv. tomato by 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens.
abstract: Pseudomonas fluorescens strains that produce the polyketide antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) are among the most effective rhizobacteria that suppress root and crown rots, wilts, and damping-off diseases of a variety of crops, and they play a key role in the natural suppressiveness of some soils to certain soilborne pathogens. Root colonization by 2,4-DAPG-producing P. fluorescens strains Pf-5 (genotype A), Q2-87 (genotype B), Q8r1-96 (genotype D), and HT5-1 (genotype N) produced induced systemic resistance (ISR) in Arabidopsis thaliana accession Col-0 against bacterial speck caused by P. syringae pv. tomato. The ISR-eliciting activity of the four bacterial genotypes was similar, and all genotypes were equivalent in activity to the well-characterized strain P. fluorescens WCS417r. The 2,4-DAPG biosynthetic locus consists of the genes phlHGF and phlACBDE. phlD or phlBC mutants of Q2-87 (2,4-DAPG minus) were significantly reduced in ISR activity, and genetic complementation of the mutants restored ISR activity back to wild-type levels. A phlF regulatory mutant (overproducer of 2,4-DAPG) had ISR activity equivalent to the wild-type Q2-87. Introduction of DAPG into soil at concentrations of 10 to 250 μM 4 days before challenge inoculation induced resistance equivalent to or better than the bacteria. Strain Q2-87 induced resistance on transgenic NahG plants but not on npr1-1, jar1, and etr1 Arabidopsis mutants. These results indicate that the antibiotic 2,4-DAPG is a major determinant of ISR in 2,4-DAPG-producing P. fluorescens, that the genotype of the strain does not affect its ISR activity, and that the activity induced by these bacteria operates through the ethylene- and jasmonic acid-dependent signal transduction pathway.
authors.affiliation: United States Department of Agriculture–Agricultural Research Service, Root Disease and Biological Control Research Unit, Pullman, WA 99164-6430, USA. wellerd@wsu.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Weller
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Mavrodi
authors.forename: Johan A
authors.initials: JA
authors.lastname: van Pelt
authors.forename: Corné M J
authors.initials: CM
authors.lastname: Pieterse
authors.forename: Leendert C
authors.initials: LC
authors.lastname: van Loon
authors.forename: Peter A H M
authors.initials: PA
authors.lastname: Bakker
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics; D005816:Genetic Complementation Test; D005838:Genotype; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D057865:Plant Immunity; D018515:Plant Leaves / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D018517:Plant Roots / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D011551:Pseudomonas fluorescens / Q000502:physiology*; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D011956:Receptors, Cell Surface / Q000235:genetics; D015398:Signal Transduction; D010453:Peptide Synthases
chemical_list: D000900:Anti-Bacterial Agents; D029681:Arabidopsis Proteins; D009713:Nucleotidyltransferases; D010696:Phloroglucinol; D011956:Receptors, Cell Surface; C494590:ETR1 protein, Arabidopsis; C105496:NPR1 protein, Arabidopsis; C059817:2,4-diacetylphloroglucinol; C412831:AT2G46370 protein, Arabidopsis; D010453:Peptide Synthases