title: DspA/E, a type III effector essential for Erwinia amylovora pathogenicity and growth in planta, induces cell death in host apple and nonhost tobacco plants.
abstract: Erwinia amylovora is responsible for fire blight, a necrotic disease of apples and pears. E. amylovora relies on a type III secretion system (TTSS) to induce disease on hosts and hypersensitive response (HR) on nonhost plants. The DspA/E protein is essential for E. amylovora pathogenicity and is secreted via the TTSS in vitro. DspA/E belongs to a type III effector family that is conserved in several phytopathogenic bacteria. In E. amylovora, DspA/E has been implicated in the generation of an oxidative stress during disease and the suppression of callose deposition. We investigated the fate of DspA/E in planta. DspA/E delivered artificially to apple or tobacco cells by agroinfection induced necrotic symptoms, indicating that DspA/E was probably injected via the TTSS. We confirmed that DspA/E acts as a major cell-death inducer during disease and HR, because the dspA/E mutant is severely impaired in its ability to induce electrolyte leakage in apple and tobacco leaves. Expression of the defense marker gene PR1 was delayed when dspA/E was transiently expressed in tobacco, suggesting that DspA/E-mediated necrosis may be associated with an alteration of defense responses.
authors.affiliation: Laboratoire des Interactions Plantes-Pathogènes, UMR217 INRA/INA-PG/Université Paris VI, 16 rue Claude Bernard, 75231 Paris Cedex 05, France.
authors.forename: Tristan
authors.initials: T
authors.lastname: Boureau
authors.forename: Hayat
authors.initials: H
authors.lastname: ElMaarouf-Bouteau
authors.forename: Amélie
authors.initials: A
authors.lastname: Garnier
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Brisset
authors.forename: Claude
authors.initials: C
authors.lastname: Perino
authors.forename: Igor
authors.initials: I
authors.lastname: Pucheu
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Barny
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D016923:Cell Death; D044084:Erwinia amylovora / Q000254:growth & development* / Q000472:pathogenicity*; D015870:Gene Expression; D027845:Malus / Q000166:cytology / Q000382:microbiology*; D009154:Mutation / Q000235:genetics; D009336:Necrosis; D010802:Phylogeny; D010935:Plant Diseases; D018515:Plant Leaves / Q000166:cytology / Q000648:ultrastructure; D010940:Plant Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium; D016415:Sequence Alignment; D013997:Time Factors; D014026:Nicotiana / Q000166:cytology / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; C110611:DspA protein, Erwinia amylovora; D010940:Plant Proteins; D012333:RNA, Messenger; C053376:pathogenesis-related proteins, plant