title: Immunomodulation by the Pseudomonas syringae HopZ type III effector family in Arabidopsis.
abstract: Pseudomonas syringae employs a type III secretion system to inject 20-30 different type III effector (T3SE) proteins into plant host cells. A major role of T3SEs is to suppress plant immune responses and promote bacterial infection. The YopJ/HopZ acetyltransferases are a superfamily of T3SEs found in both plant and animal pathogenic bacteria. In P. syringae, this superfamily includes the evolutionarily diverse HopZ1, HopZ2 and HopZ3 alleles. To investigate the roles of the HopZ family in immunomodulation, we generated dexamethasone-inducible T3SE transgenic lines of Arabidopsis for HopZ family members and characterized them for immune suppression phenotypes. We show that all of the HopZ family members can actively suppress various facets of Arabidopsis immunity in a catalytic residue-dependent manner. HopZ family members can differentially suppress the activation of mitogen-activated protein (MAP) kinase cascades or the production of reactive oxygen species, whereas all members can promote the growth of non-virulent P. syringae. Localization studies show that four of the HopZ family members containing predicted myristoylation sites are localized to the vicinity of the plasma membrane while HopZ3 which lacks the myristoylation site is at least partially nuclear localized, suggesting diversification of immunosuppressive mechanisms. Overall, we demonstrate that despite significant evolutionary diversification, all HopZ family members can suppress immunity in Arabidopsis.
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada; Plant Gene Expression Center, United States Department of Agriculture, Albany, California, United States of America; Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America.
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Lewis
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Mike
authors.initials: M
authors.lastname: Wilton
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: G Adam
authors.initials: GA
authors.lastname: Mott
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Wenwan
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America.
authors.forename: Jana A
authors.initials: JA
authors.lastname: Hassan
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada; Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada.
authors.forename: David S
authors.initials: DS
authors.lastname: Guttman
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada; Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Darrell
authors.initials: D
authors.lastname: Desveaux
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D001426:Bacterial Proteins / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D055162:Biocatalysis; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D060467:Disease Resistance / Q000276:immunology; D004789:Enzyme Activation; D056747:Immunomodulation; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D010935:Plant Diseases / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000382:microbiology; D030821:Plants, Genetically Modified; D044224:Pseudomonas syringae / Q000276:immunology*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; D017382:Reactive Oxygen Species; D020928:Mitogen-Activated Protein Kinases; D003545:Cysteine