title: Constitutively active mitogen-activated protein kinase versions reveal functions of Arabidopsis MPK4 in pathogen defense signaling.
abstract: Plant mitogen-activated protein kinases (MAPKs) are involved in important processes, including stress signaling and development. In a functional yeast screen, we identified mutations that render Arabidopsis thaliana MAPKs constitutively active (CA). Importantly, CA-MAPKs maintain their specificity toward known activators and substrates. As a proof-of-concept, Arabidopsis MAPK4 (MPK4) function in plant immunity was investigated. In agreement with the phenotype of mpk4 mutants, CA-MPK4 plants were compromised in pathogen-induced salicylic acid accumulation and disease resistance. MPK4 activity was found to negatively regulate pathogen-associated molecular pattern-induced reactive oxygen species production but had no impact on callose deposition, indicating that CA-MPK4 allows discriminating between processes regulated by MPK4 activity from processes indirectly affected by mpk4 mutation. Finally, MPK4 activity was also found to compromise effector-triggered immunity conditioned by the Toll Interleukin-1 Receptor-nucleotide binding (NB)-Leu-rich repeat (LRR) receptors RPS4 and RPP4 but not by the coiled coil-NB-LRR receptors RPM1 and RPS2. Overall, these data reveal important insights on how MPK4 regulates plant defenses and establishes that CA-MAPKs offer a powerful tool to analyze the function of plant MAPK pathways.
authors.affiliation: Unité de Recherche en Génomique Végétale, Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/Université Evry Val d'Essone, 91000 Evry, France.
authors.forename: Souha
authors.initials: S
authors.lastname: Berriri
authors.forename: Ana Victoria
authors.initials: AV
authors.lastname: Garcia
authors.forename: Nicolas
authors.initials: N
authors.lastname: Frei dit Frey
authors.forename: Wilfried
authors.initials: W
authors.lastname: Rozhon
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Pateyron
authors.forename: Nathalie
authors.initials: N
authors.lastname: Leonhardt
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Montillet
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Leung
authors.forename: Heribert
authors.initials: H
authors.lastname: Hirt
authors.forename: Jean
authors.initials: J
authors.lastname: Colcombet
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000276:immunology / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D060467:Disease Resistance / Q000235:genetics; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D057865:Plant Immunity / Q000235:genetics*; D044224:Pseudomonas syringae / Q000276:immunology; D017382:Reactive Oxygen Species / Q000378:metabolism; D020156:Salicylic Acid / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; C436292:AtMPK4 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020156:Salicylic Acid