title: Type B response regulators of Arabidopsis play key roles in cytokinin signaling and plant development.
abstract: The type B Arabidopsis Response Regulators (ARRs) of Arabidopsis thaliana are transcription factors that act as positive regulators in the two-component cytokinin signaling pathway. We employed a mutant-based approach to perform a detailed characterization of the roles of ARR1, ARR10, and ARR12 in plant growth and development. The most pronounced phenotype was found in the arr1-3 arr10-5 arr12-1 triple loss-of-function mutant, which showed almost complete insensitivity to high levels of exogenously applied cytokinins. The triple mutant exhibited reduced stature due to decreased cell division in the shoot, enhanced seed size, increased sensitivity to light, altered chlorophyll and anthocyanin concentrations, and an aborted primary root with protoxylem but no metaxylem. Microarray analysis revealed that expression of the majority of cytokinin-regulated genes requires the function of ARR1, ARR10, and ARR12. Characterization of double mutants revealed differing contributions of the type B ARRs to mutant phenotypes. Our results support a model in which cytokinin regulates a wide array of downstream responses through the action of a multistep phosphorelay that culminates in transcriptional regulation by ARR1, ARR10, and ARR12.
authors: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors: Rebecca D
authors: RD
authors: Argyros
authors: Dennis E
authors: DE
authors: Mathews
authors: Yi-Hsuan
authors: YH
authors: Chiang
authors: Christine M
authors: CM
authors: Palmer
authors: Derek M
authors: DM
authors: Thibault
authors: Naomi
authors: N
authors: Etheridge
authors: D Aaron
authors: DA
authors: Argyros
authors: Michael G
authors: MG
authors: Mason
authors: Joseph J
authors: JJ
authors: Kieber
authors: G Eric
authors: GE
authors: Schaller
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003583:Cytokinins / Q000378:metabolism* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008957:Models, Genetic; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: C117138:ARR1 protein, Arabidopsis; C469257:ARR10 protein, Arabidopsis; C519632:ARR12 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D004268:DNA-Binding Proteins; D014157:Transcription Factors