title: Cytokinin signaling stabilizes the response activator ARR1.
abstract: The cytokinins play essential roles in the development and environmental responses of higher plants. Cytokinin signaling leads to the phosphorylation-dependent activation of two classes of Arabidopsis response regulators (RRs): the type-B RR (RRB) transcriptional activators that promote the expression of cytokinin response genes and the type-A RRs (RRAs) that are encoded by primary cytokinin response genes and function as response inhibitors. We show that cytokinin signaling increases the abundance of ARR1, a ubiquitously expressed RRB, by preventing its degradation by the 26S proteasome. We also show that the RRAs act to suppress ARR1 accumulation, thus providing an explanation for their inhibitory action in cytokinin signaling. Collectively, our results reveal an additional regulatory mechanism in the cytokinin response pathway that involves the cytokinin-dependent stability control of a major RRB response activator.
authors.affiliation: Plant Physiology, Biochemistry, Molecular Biology Program, Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA.
authors.forename: Jasmina
authors.initials: J
authors.lastname: Kurepa
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Jan A
authors.initials: JA
authors.lastname: Smalle
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D010641:Phenotype; D018517:Plant Roots; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D036226:Seedlings / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C117138:ARR1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease
keywords: 26S proteasome; ARR1; Arabidopsis thaliana; cytokinin signaling; protein degradation