title: The NLR protein SUMM2 senses the disruption of an immune signaling MAP kinase cascade via CRCK3.
abstract: MAP kinase signaling is an integral part of plant immunity. Disruption of the MEKK1-MKK1/2-MPK4 kinase cascade results in constitutive immune responses mediated by the NLR protein SUMM2, but the molecular mechanism is so far poorly characterized. Here, we report that SUMM2 monitors a substrate protein of MPK4, CALMODULIN-BINDING RECEPTOR-LIKE CYTOPLASMIC KINASE 3 (CRCK3). Similar to SUMM2, CRCK3 was isolated from a suppressor screen of mkk1 mkk2 and is required for the autoimmunity phenotypes in mekk1, mkk1 mkk2, and mpk4 mutants. In wild-type plants, CRCK3 is mostly phosphorylated. MPK4 interacts with CRCK3 and can phosphorylate CRCK3 in vitro In mpk4 mutant plants, phosphorylation of CRCK3 is substantially reduced, suggesting that MPK4 phosphorylates CRCK3 in vivo Further, CRCK3 associates with SUMM2 in planta, suggesting SUMM2 senses the disruption of the MEKK1-MKK1/2-MPK4 kinase cascade through CRCK3. Our study suggests that a MAP kinase substrate is used as a guardee or decoy for monitoring the integrity of MAP kinase signaling.
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Zhibin
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: National Institute of Biological Sciences, Beijing, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Huang
authors.affiliation: National Institute of Biological Sciences, Beijing, China.
authors.forename: Minghui
authors.initials: M
authors.lastname: Gao
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Qing
authors.initials: Q
authors.lastname: Kong
authors.affiliation: Department of Botany, University of British Columbia, Vancouver, BC, Canada yuelin.zhang@ubc.ca.
authors.forename: Yuelin
authors.identifier: 0000-0002-3480-5478
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D015551:Autoimmunity; D015870:Gene Expression; D005838:Genotype; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D000070576:NLR Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D013379:Substrate Specificity
chemical_list: D000070576:NLR Proteins; D010940:Plant Proteins; D020928:Mitogen-Activated Protein Kinases
keywords: CRCK3; MAP kinase cascade; MPK4; SUMM2; plant immunity