title: Plants respond to pathogen infection by enhancing the antifungal gene expression of root-associated bacteria.
abstract: Plant health and fitness widely depend on interactions with soil microorganisms. Some bacteria such as pseudomonads can inhibit pathogens by producing antibiotics, and controlling these bacteria could help improve plant fitness. In the present study, we tested whether plants induce changes in the antifungal activity of root-associated bacteria as a response to root pathogens. We grew barley plants in a split-root system with one side of the root system challenged by the pathogen Pythium ultimum and the other side inoculated with the biocontrol strain Pseudomonas fluorescens CHA0. We used reporter genes to follow the expression of ribosomal RNA indicative of the metabolic state and of the gene phlA, required for production of 2,4-diacetylphloroglucinol, a key component of antifungal activity. Infection increased the expression of the antifungal gene phlA. No contact with the pathogen was required, indicating that barley influenced gene expression by the bacteria in a systemic way. This effect relied on increased exudation of diffusible molecules increasing phlA expression, suggesting that communication with rhizosphere bacteria is part of the pathogen response of plants. Tripartite interactions among plants, pathogens, and bacteria appear as a novel determinant of plant response to root pathogens.
authors.affiliation: Georg-August University, Gottingen, Germany. ajousse@gwdg.de
authors.forename: Alexandre
authors.initials: A
authors.lastname: Jousset
authors.forename: Laurène
authors.initials: L
authors.lastname: Rochat
authors.forename: Arnaud
authors.initials: A
authors.lastname: Lanoue
authors.forename: Michael
authors.initials: M
authors.lastname: Bonkowski
authors.forename: Christoph
authors.initials: C
authors.lastname: Keel
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheu
mesh_terms: D000935:Antifungal Agents / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism; D005650:Fumarates / Q000378:metabolism; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D020459:Genes, rRNA; D001467:Hordeum / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D010572:Pest Control, Biological; D010696:Phloroglucinol / Q000031:analogs & derivatives / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000469:parasitology; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D011422:Propionates; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism*; D011775:Pythium / Q000472:pathogenicity*; D058441:Rhizosphere; D013045:Species Specificity; D014641:Vanillic Acid / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D003373:Coumaric Acids; D005650:Fumarates; D011422:Propionates; C032005:fumaric acid; C059817:2,4-diacetylphloroglucinol; D010696:Phloroglucinol; D014641:Vanillic Acid; C495469:p-coumaric acid