title: Dickeya dadantii pectic enzymes necessary for virulence are also responsible for activation of the Arabidopsis thaliana innate immune system.
abstract: Soft-rot diseases of plants attributed to Dickeya dadantii result from lysis of the plant cell wall caused by pectic enzymes released by the bacterial cell by a type II secretion system (T2SS). Arabidopsis thaliana can express several lines of defence against this bacterium. We employed bacterial mutants with defective envelope structures or secreted proteins to examine early plant defence reactions. We focused on the production of AtrbohD-dependent reactive oxygen species (ROS), callose deposition and cell death as indicators of these reactions. We observed a significant reduction in ROS and callose formation with a bacterial mutant in which genes encoding five pectate lyases (Pels) were disrupted. Treatment of plant leaves with bacterial culture filtrates containing Pels resulted in ROS and callose production, and both reactions were dependent on a functional AtrbohD gene. ROS and callose were produced in response to treatment with a cellular fraction of a T2SS-negative mutant grown in a Pels-inducing medium. Finally, ROS and callose were produced in leaves treated with purified Pels that had also been shown to induce the expression of jasmonic acid-dependent defence genes. Pel catalytic activity is required for the induction of ROS accumulation. In contrast, cell death observed in leaves infected with the wild-type strain appeared to be independent of a functional AtrbohD gene. It was also independent of the bacterial production of pectic enzymes and the type III secretion system (T3SS). In conclusion, the work presented here shows that D. dadantii is recognized by the A. thaliana innate immune system through the action of pectic enzymes secreted by bacteria at the site of infection. This recognition leads to AtrbohD-dependent ROS and callose accumulation, but not cell death.
authors.affiliation: Laboratoire Interactions Plantes-Pathogènes, Institut National de la Recherche Agronomique/AgroParisTech/Université Pierre et Marie Curie, 16 rue Claude Bernard 75231, Cedex 05 Paris, France.|lnstitut Jean-Pierre Bourgin, UMR1318 Institut National de la Recherche Agronomique, AgroParisTech, ERL3559 Centre National de la Recherche Scientifique, Université Paris-Saclay, RD10, 78026, Versailles Cedex, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Expert
authors.affiliation: Laboratoire Interactions Plantes-Pathogènes, Institut National de la Recherche Agronomique/AgroParisTech/Université Pierre et Marie Curie, 16 rue Claude Bernard 75231, Cedex 05 Paris, France.
authors.forename: Oriane
authors.initials: O
authors.lastname: Patrit
authors.affiliation: Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France; INSA-Lyon, F-69621 Villeurbanne, France; CNRS UMR5240 Microbiologie, Adaptation et Pathogénie, F-69622 Villeurbanne, France.
authors.forename: Vladimir E
authors.initials: VE
authors.lastname: Shevchik
authors.affiliation: Laboratoire Interactions Plantes-Pathogènes, Institut National de la Recherche Agronomique/AgroParisTech/Université Pierre et Marie Curie, 16 rue Claude Bernard 75231, Cedex 05 Paris, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Perino
authors.affiliation: Laboratoire Interactions Plantes-Pathogènes, Institut National de la Recherche Agronomique/AgroParisTech/Université Pierre et Marie Curie, 16 rue Claude Bernard 75231, Cedex 05 Paris, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Boucher
authors.affiliation: Bases of Infectious Diseases, CNRS, UMR 5086, F-69367, Lyon Cedex 07, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Creze
authors.affiliation: lnstitut Jean-Pierre Bourgin, UMR1318 Institut National de la Recherche Agronomique, AgroParisTech, ERL3559 Centre National de la Recherche Scientifique, Université Paris-Saclay, RD10, 78026, Versailles Cedex, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Wenes
authors.affiliation: lnstitut Jean-Pierre Bourgin, UMR1318 Institut National de la Recherche Agronomique, AgroParisTech, ERL3559 Centre National de la Recherche Scientifique, Université Paris-Saclay, RD10, 78026, Versailles Cedex, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Fagard
mesh_terms: D017360:Arabidopsis / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D020563:Gammaproteobacteria / Q000201:enzymology*; D005936:Glucans / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology; D009844:Oligosaccharides / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D000069296:Type III Secretion Systems / Q000378:metabolism; D014774:Virulence / Q000235:genetics / Q000502:physiology
chemical_list: D005936:Glucans; D009844:Oligosaccharides; D017382:Reactive Oxygen Species; D000069296:Type III Secretion Systems; C412763:oligogalacturonic acid; C048306:callose; D011133:Polysaccharide-Lyases; C023911:pectate lyase
keywords: Arabidopsis; Dickeya; innate immunity; oligogalacturonides; pectate lyases