title: Arabidopsis MAKR5 is a positive effector of BAM3-dependent CLE45 signaling.
abstract: Receptor kinases convey diverse environmental and developmental inputs by sensing extracellular ligands. In plants, one group of receptor-like kinases (RLKs) is characterized by extracellular leucine-rich repeat (LRR) domains, which interact with various ligands that include the plant hormone brassinosteroid and peptides of the CLAVATA3/EMBRYO SURROUNDING REGION (CLE) type. For instance, the CLE45 peptide requires the LRR-RLK BARELY ANY MERISTEM 3 (BAM3) to prevent protophloem formation in Arabidopsis root meristems. Here, we show that other proposed CLE45 receptors, the two redundantly acting LRR-RLKs STERILITY-REGULATING KINASE MEMBER 1 (SKM1) and SKM2 (which perceive CLE45 in the context of pollen tube elongation), cannot substitute for BAM3 in the root. Moreover, we identify MEMBRANE-ASSOCIATED KINASE REGULATOR 5 (MAKR5) as a post-transcriptionally regulated amplifier of the CLE45 signal that acts downstream of BAM3. MAKR5 belongs to a small protein family whose prototypical member, BRI1 KINASE INHIBITOR 1, is an essentially negative regulator of brassinosteroid signaling. By contrast, MAKR5 is a positive effector of CLE45 signaling, revealing an unexpected diversity in the conceptual roles of MAKR genes in different signaling pathways.
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Yeon Hee
authors.initials: YH
authors.lastname: Kang
authors.affiliation: Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland christian.hardtke@unil.ch.
authors.forename: Christian S
authors.identifier: 0000-0003-3203-1058
authors.initials: CS
authors.lastname: Hardtke
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008565:Membrane Proteins / Q000378:metabolism*; D010641:Phenotype; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; C581881:CLE45 protein, Arabidopsis; D008565:Membrane Proteins; C581880:BAM3 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases
keywords: CLE peptide; SKM1; SKM2; protophloem; receptor‐like kinase