title: Microbe-associated molecular pattern-induced calcium signaling requires the receptor-like cytoplasmic kinases, PBL1 and BIK1.
abstract: BACKGROUND
  Plant perception of conserved microbe-derived or damage-derived molecules (so-called microbe- or damage-associated molecular patterns, MAMPs or DAMPs, respectively) triggers cellular signaling cascades to initiate counteracting defence responses. Using MAMP-induced rise in cellular calcium levels as one of the earliest biochemical readouts, we initiated a genetic screen for components involved in early MAMP signaling in Arabidopsis thaliana.
  
  
  RESULTS
  We characterized here the "changed calcium elevation 5" (cce5) mutant, where five allelic cce5 mutants were isolated. They all show reduced calcium levels after elicitation with peptides representing bacteria-derived MAMPs (flg22 and elf18) and endogenous DAMP (AtPep1), but a normal response to chitin octamers. Mapping, sequencing of the mutated locus and complementation studies revealed CCE5 to encode the receptor-like cytoplasmic kinase (RLCK), avrPphB sensitive 1-like 1 (PBL1). Kinase activities of PBL1 derived from three of the cce5 alleles are abrogated in vivo. Validation with T-DNA mutants revealed that, besides PBL1, another RLCK, Botrytis-induced kinase 1 (BIK1), is also required for MAMP/DAMP-induced calcium elevations.
  
  
  CONCLUSIONS
  Hence, PBL1 and BIK1 (but not two related RLCKs, PBS1 and PBL2) are required for MAMP/DAMP-induced calcium signaling. It remains to be investigated if the many other RLCKs encoded in the Arabidopsis genome affect early calcium signal transduction - perhaps in dependence on the type of MAMP/DAMP ligands. A future challenge would be to identify the substrates of these various RLCKs, in order to elucidate their signaling role between the receptor complexes at the plasma membrane and downstream cellular signaling components.
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. ranf@wzw.tum.de.|Phytopathology, Center of Life and Food Sciences Weihenstephan, Technische Universität München, Emil-Ramann-Str. 2, Freising, Weihenstephan, D-85350, Germany. ranf@wzw.tum.de.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ranf
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. leschen@ipb-halle.de.
authors.forename: Lennart
authors.initials: L
authors.lastname: Eschen-Lippold
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. Katja.Froehlich@gmx.de.
authors.forename: Katja
authors.initials: K
authors.lastname: Fröhlich
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. Lore.Westphal@ipb-halle.de.
authors.forename: Lore
authors.initials: L
authors.lastname: Westphal
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. dscheel@ipb-halle.de.
authors.forename: Dierk
authors.initials: D
authors.lastname: Scheel
authors.affiliation: Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle/Saale, D-06120, Germany. jlee@ipb-halle.de.
authors.forename: Justin
authors.initials: J
authors.lastname: Lee
mesh_terms: D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000276:immunology; D020013:Calcium Signaling / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; C500179:avrPphB protein, Pseudomonas syringae; C000599849:PBL1 protein, Arabidopsis; D011494:Protein Kinases; C463660:BAK1 protein, Arabidopsis; C509522:BIK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases