title: Plant pattern-recognition receptor FLS2 is directed for degradation by the bacterial ubiquitin ligase AvrPtoB.
abstract: BACKGROUND
  An important layer of active defense in plant immunity is the detection of pathogen-associated molecular patterns (PAMPs) mediated by cell-surface receptors. For the establishment of disease, pathogens depend on the ability to overcome PAMP perception and disable plant signaling pathways activated in response to PAMPs. Pattern recognition receptors (PRRs) are therefore prime targets for pathogen effectors. FLS2, its coreceptor BAK1, and EFR encode receptor-like kinases that play a role in immunity against bacterial pathogens.
  
  
  RESULTS
  Here, we report that virulence of Pseudomonas syringae pv tomato DC3000 (PtoDC3000) in Arabidopsis is enhanced through the action of its effector AvrPtoB, which promotes degradation of FLS2. We show that AvrPtoB, through its N terminus, associates with FLS2 and BAK1, of which interaction with FLS2 is enhanced by flg22 activation. In vitro, AvrPtoB is active as an E3 ligase to catalyze polyubiquitination of the kinase domain of FLS2, a process confirmed in planta. Full enhancement of PtoDC3000 virulence appears to require the E3 ligase activity of AvrPtoB.
  
  
  CONCLUSIONS
  AvrPtoB, initially identified through its activation of hypersensitive resistance in tomato cultivars expressing the Pto kinase, is composed of at least two functional domains: the N terminus is responsible for interaction with Pto, and the C terminus carries an E3 ligase activity. Based on our findings, we propose that both domains of AvrPtoB act together to support the virulence of PtoDC3000 in Arabidopsis through their ability to eliminate FLS2 from the cell periphery, and probably also other PAMP sensors that are constitutively expressed or induced after pathogen challenge.
authors.affiliation: Max-Planck-Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Cologne, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Göhre
authors.forename: Thomas
authors.initials: T
authors.lastname: Spallek
authors.forename: Heidrun
authors.initials: H
authors.lastname: Häweker
authors.forename: Sophia
authors.initials: S
authors.lastname: Mersmann
authors.forename: Tobias
authors.initials: T
authors.lastname: Mentzel
authors.forename: Thomas
authors.initials: T
authors.lastname: Boller
authors.forename: Marta
authors.initials: M
authors.lastname: de Torres
authors.forename: John W
authors.initials: JW
authors.lastname: Mansfield
authors.forename: Silke
authors.initials: S
authors.lastname: Robatzek
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000382:microbiology; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D044224:Pseudomonas syringae / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D015398:Signal Transduction; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D025801:Ubiquitin; C081695:avrPto protein, Pseudomonas syringae; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis