title: The calcium-dependent protein kinase CPK28 buffers plant immunity and regulates BIK1 turnover.
abstract: Plant perception of pathogen-associated molecular patterns (PAMPs) triggers a phosphorylation relay leading to PAMP-triggered immunity (PTI). Despite increasing knowledge of PTI signaling, how immune homeostasis is maintained remains largely unknown. Here we describe a forward-genetic screen to identify loci involved in PTI and characterize the Arabidopsis calcium-dependent protein kinase CPK28 as a negative regulator of immune signaling. Genetic analyses demonstrate that CPK28 attenuates PAMP-triggered immune responses and antibacterial immunity. CPK28 interacts with and phosphorylates the plasma-membrane-associated cytoplasmic kinase BIK1, an important convergent substrate of multiple pattern recognition receptor (PRR) complexes. We find that BIK1 is rate limiting in PTI signaling and that it is continuously turned over to maintain cellular homeostasis. We further show that CPK28 contributes to BIK1 turnover. Our results suggest a negative regulatory mechanism that continually buffers immune signaling by controlling the turnover of this key signaling kinase.
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Monaghan
authors.affiliation: Department of Plant Biochemistry, Dahlem Centre of Plant Sciences, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Matschi
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Oluwaseyi
authors.initials: O
authors.lastname: Shorinola
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Hanna
authors.initials: H
authors.lastname: Rovenich
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Matei
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Cécile
authors.initials: C
authors.lastname: Segonzac
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Frederikke Gro
authors.initials: FG
authors.lastname: Malinovsky
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: John P
authors.initials: JP
authors.lastname: Rathjen
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK.
authors.forename: Dan
authors.initials: D
authors.lastname: MacLean
authors.affiliation: Department of Plant Biochemistry, Dahlem Centre of Plant Sciences, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Romeis
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, UK. Electronic address: cyril.zipfel@tsl.ac.uk.
authors.forename: Cyril
authors.initials: C
authors.lastname: Zipfel
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000276:immunology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D056426:Genetic Loci; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010935:Plant Diseases / Q000276:immunology; D057865:Plant Immunity / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D029681:Arabidopsis Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C509522:BIK1 protein, Arabidopsis