title: The downy mildew effector proteins ATR1 and ATR13 promote disease susceptibility in Arabidopsis thaliana.
abstract: The downy mildew (Hyaloperonospora parasitica) effector proteins ATR1 and ATR13 trigger RPP1-Nd/WsB- and RPP13-Nd-dependent resistance, respectively, in Arabidopsis thaliana. To better understand the functions of these effectors during compatible and incompatible interactions of H. parasitica isolates on Arabidopsis accessions, we developed a novel delivery system using Pseudomonas syringae type III secretion via fusions of ATRs to the N terminus of the P. syringae effector protein, AvrRPS4. ATR1 and ATR13 both triggered the hypersensitive response (HR) and resistance to bacterial pathogens in Arabidopsis carrying RPP1-Nd/WsB or RPP13-Nd, respectively, when delivered from P. syringae pv tomato (Pst) DC3000. In addition, multiple alleles of ATR1 and ATR13 confer enhanced virulence to Pst DC3000 on susceptible Arabidopsis accessions. We conclude that ATR1 and ATR13 positively contribute to pathogen virulence inside host cells. Two ATR13 alleles suppressed bacterial PAMP (for Pathogen-Associated Molecular Patterns)-triggered callose deposition in susceptible Arabidopsis when delivered by DC3000 DeltaCEL mutants. Furthermore, expression of another allele of ATR13 in plant cells suppressed PAMP-triggered reactive oxygen species production in addition to callose deposition. Intriguingly, although Wassilewskija (Ws-0) is highly susceptible to H. parasitica isolate Emco5, ATR13Emco5 when delivered by Pst DC3000 triggered localized immunity, including HR, on Ws-0. We suggest that an additional H. parasitica Emco5 effector might suppress ATR13-triggered immunity.
authors.affiliation: Sainsbury Laboratory, John Ines Centre, Norwich NR4 7UH, United Kingdom.
authors.forename: Kee Hoon
authors.initials: KH
authors.lastname: Sohn
authors.forename: Rita
authors.initials: R
authors.lastname: Lei
authors.forename: Adnane
authors.initials: A
authors.lastname: Nemri
authors.forename: Jonathan D G
authors.initials: JD
authors.lastname: Jones
mesh_terms: D000483:Alleles; D020816:Amino Acid Motifs / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D018506:Gene Expression Regulation, Plant; D005936:Glucans / Q000378:metabolism; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D016133:Polymerase Chain Reaction; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics* / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity; D017382:Reactive Oxygen Species / Q000378:metabolism; D014774:Virulence / Q000235:genetics
chemical_list: C511988:ATR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; C098294:AvrRps4 protein, Pseudomonas syringae; D001426:Bacterial Proteins; D005936:Glucans; D020598:Proto-Oncogene Proteins c-myb; D017382:Reactive Oxygen Species; C420919:avrRpt2 protein, Pseudomonas syringae; C048306:callose