title: Modulation of defense responses of Malus spp. during compatible and incompatible interactions with Erwinia amylovora.
abstract: Erwinia amylovora is the causal agent of fire blight, a disease affecting members of subfamily Maloideae. In order to analyze mechanisms leading to compatible or incompatible interactions, early plant molecular events were investigated in two genotypes of Malus with contrasting susceptibility to fire blight, after confrontation with either E. amylovora or the incompatible tobacco pathogen Pseudomonas syringae pv. tabaci. Many defense mechanisms, including generation of an oxidative burst and accumulation of pathogenesis-related proteins, were elicited in both resistant and susceptible genotypes by the two pathogens at similar rates and according to an equivalent time course. This elicitation was linked with the functional hypersensitive reaction and pathogenicity (hrp) cluster of E. amylovora, because an hrp secretion mutant did not induce such responses. However, a delayed induction of several genes of various branch pathways of the phenylpropanoid metabolism was recorded in tissues of the susceptible genotype challenged with the wild-type strain of E. amylovora, whereas these genes were quickly induced in every other plant-bacteria interaction, including interactions with the hrp secretion mutant. This suggests the existence of hrp-independent elicitors of defense in the fire blight pathogen as well as hrp-dependant mechanisms of suppression of these nonspecific inductions.
authors.affiliation: Unité d'Amélioration des Espèces Fruitières et Ornementales, INRA, Beaucouzé, France.
authors.forename: Jean-Stéphane
authors.initials: JS
authors.lastname: Venisse
authors.forename: Mickaël
authors.initials: M
authors.lastname: Malnoy
authors.forename: Mohamed
authors.initials: M
authors.lastname: Faize
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Paulin
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Brisset
mesh_terms: D029681:Arabidopsis Proteins; D060387:Ascorbate Peroxidases; D002688:Chitinases / Q000235:genetics / Q000378:metabolism; D044644:Endo-1,3(4)-beta-Glucanase; D004885:Erwinia / Q000254:growth & development*; D035264:Flowers / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D018506:Gene Expression Regulation, Plant; D005980:Glutathione Reductase / Q000235:genetics / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate / Q000235:genetics; D027845:Malus / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D010100:Oxygen / Q000378:metabolism; D009195:Peroxidase / Q000235:genetics / Q000378:metabolism; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D018520:Plant Shoots / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D013481:Superoxides / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D013481:Superoxides; D010544:Peroxidases; D060387:Ascorbate Peroxidases; D009195:Peroxidase; D005980:Glutathione Reductase; D006026:Glycoside Hydrolases; D002688:Chitinases; D044644:Endo-1,3(4)-beta-Glucanase; D010100:Oxygen