Type B response regulators of Arabidopsis play key roles in cytokinin signaling and plant development

Plant Cell. 2008 Aug;20(8):2102-16. doi: 10.1105/tpc.108.059584. Epub 2008 Aug 22.


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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Cytokinins / metabolism*
  • Cytokinins / physiology
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant
  • Hypocotyl / genetics
  • Hypocotyl / growth & development
  • Hypocotyl / metabolism
  • Models, Genetic
  • Plant Roots / genetics
  • Plant Roots / growth & development
  • Plant Roots / metabolism
  • Plant Shoots / genetics
  • Plant Shoots / growth & development
  • Plant Shoots / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / genetics
  • Signal Transduction / physiology*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology


  • ARR1 protein, Arabidopsis
  • ARR10 protein, Arabidopsis
  • ARR12 protein, Arabidopsis
  • Arabidopsis Proteins
  • Cytokinins
  • DNA-Binding Proteins
  • Transcription Factors