title: A novel Arabidopsis CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1) mutant with enhanced pathogen-induced cell death and altered receptor processing.
abstract: Plants detect pathogens by sensing microbe-associated molecular patterns (MAMPs) through pattern recognition receptors. Pattern recognition receptor complexes also have roles in cell death control, but the underlying mechanisms are poorly understood. Here, we report isolation of cerk1-4, a novel mutant allele of the Arabidopsis chitin receptor CERK1 with enhanced defense responses. We identified cerk1-4 in a forward genetic screen with barley powdery mildew and consequently characterized it by pathogen assays, mutant crosses and analysis of defense pathways. CERK1 and CERK1-4 proteins were analyzed biochemically. The cerk1-4 mutation causes an amino acid exchange in the CERK1 ectodomain. Mutant plants maintain chitin signaling capacity but exhibit hyper-inducible salicylic acid concentrations and deregulated cell death upon pathogen challenge. In contrast to chitin signaling, the cerk1-4 phenotype does not require kinase activity and is conferred by the N-terminal part of the receptor. CERK1 undergoes ectodomain shedding, a well-known process in animal cell surface proteins. Wild-type plants contain the full-length CERK1 receptor protein as well as a soluble form of the CERK1 ectodomain, whereas cerk1-4 plants lack the N-terminal shedding product. Our work suggests that CERK1 may have a chitin-independent role in cell death control and is the first report of ectodomain shedding in plants.
authors.affiliation: Department of Plant Cell Biology, Albrecht von Haller Institute, Georg August University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany; The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK.
authors.forename: Elena K
authors.initials: EK
authors.lastname: Petutschnig
authors.forename: Marnie
authors.initials: M
authors.lastname: Stolze
authors.forename: Ulrike
authors.initials: U
authors.lastname: Lipka
authors.forename: Michaela
authors.initials: M
authors.lastname: Kopischke
authors.forename: Juliane
authors.initials: J
authors.lastname: Horlacher
authors.forename: Oliver
authors.initials: O
authors.lastname: Valerius
authors.forename: Wilfried
authors.initials: W
authors.lastname: Rozhon
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Gust
authors.forename: Birgit
authors.initials: B
authors.lastname: Kemmerling
authors.forename: Brigitte
authors.initials: B
authors.lastname: Poppenberger
authors.forename: Gerhard H
authors.initials: GH
authors.lastname: Braus
authors.forename: Thorsten
authors.initials: T
authors.lastname: Nürnberger
authors.forename: Volker
authors.initials: V
authors.lastname: Lipka
mesh_terms: D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001203:Ascomycota / Q000472:pathogenicity; D016923:Cell Death / Q000187:drug effects; D002686:Chitin / Q000378:metabolism; D054884:Host-Pathogen Interactions; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D002686:Chitin; C525882:CERK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D020156:Salicylic Acid
keywords: Arabidopsis; CHITIN ELICITOR RECEPTOR KINASE 1 (CERK1); cell death; ectodomain shedding; lysin motif receptor-like kinase (LysM-RLK); pattern recognition receptor (PRR); powdery mildew; receptor processing