title: Genomic screens identify a new phytobacterial microbe-associated molecular pattern and the cognate Arabidopsis receptor-like kinase that mediates its immune elicitation.
abstract: BACKGROUND
  The recognition of microbe-associated molecular patterns during infection is central to the mounting of an effective immune response. In spite of their importance, it remains difficult to identify these molecules and the host receptors required for their perception, ultimately limiting our understanding of the role of these molecules in the evolution of host-pathogen relationships.
  
  
  RESULTS
  We employ a comparative genomics screen to identify six new immune eliciting peptides from the phytopathogenic bacterium Pseudomonas syringae. We then perform a reverse genetic screen to identify Arabidopsis thaliana leucine-rich repeat receptor-like kinases required for the recognition of these elicitors. We test the six elicitors on 187 receptor-like kinase knock-down insertion lines using a high-throughput peroxidase-based immune assay and identify multiple lines that show decreased immune responses to specific peptides. From this primary screen data, we focused on the interaction between the xup25 peptide from a bacterial xanthine/uracil permease and the Arabidopsis receptor-like kinase xanthine/uracil permease sensing 1; a family XII protein closely related to two well-characterized receptor-like kinases. We show that xup25 treatment increases pathogenesis-related gene induction, callose deposition, seedling growth inhibition, and resistance to virulent bacteria, all in a xanthine/uracil permease sensing 1-dependent manner. Finally, we show that this kinase-like receptor can bind the xup25 peptide directly. These results identify xup25 as a P. syringae microbe-associated molecular pattern and xanthine/uracil permease sensing 1 as a receptor-like kinase that detects the xup25 epitope to activate immune responses.
  
  
  CONCLUSIONS
  The present study demonstrates an efficient method to identify immune elicitors and the plant receptors responsible for their perception. Further exploration of these molecules will increase our understanding of plant-pathogen interactions and the basis for host specificity.
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada.
authors.forename: G Adam
authors.initials: GA
authors.lastname: Mott
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada.
authors.forename: Shalabh
authors.initials: S
authors.lastname: Thakur
authors.affiliation: Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr Bohr Gasse 3, Vienna, 1030, Austria.
authors.forename: Elwira
authors.initials: E
authors.lastname: Smakowska
authors.affiliation: Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Pauline W
authors.initials: PW
authors.lastname: Wang
authors.affiliation: Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr Bohr Gasse 3, Vienna, 1030, Austria.
authors.forename: Youssef
authors.initials: Y
authors.lastname: Belkhadir
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada. darrell.desveaux@utoronto.ca.|Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada. darrell.desveaux@utoronto.ca.
authors.forename: Darrell
authors.initials: D
authors.lastname: Desveaux
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada. david.guttman@utoronto.ca.|Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada. david.guttman@utoronto.ca.
authors.forename: David S
authors.initials: DS
authors.lastname: Guttman
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling / Q000379:methods; D018745:Genome, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics*; D057865:Plant Immunity / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D044224:Pseudomonas syringae / Q000235:genetics / Q000472:pathogenicity; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D011956:Receptors, Cell Surface; D011494:Protein Kinases