Phosphorylation of Arabidopsis response regulator 7 (ARR7) at the putative phospho-accepting site is required for ARR7 to act as a negative regulator of cytokinin signaling.
Cytokinins are plant hormones that regulate diverse aspects of plant growth and development. Arabidopsis cytokinin signal transduction utilizes a multi-step two-component signaling (TCS) system by histidyl-aspartidyl phosphorelays. We here show that phosphorylation of ARR7, an A-type response regulator that acts as a negative regulator of cytokinin signaling, is required for its function in plants. Phosphorylation of ARR7 is inhibited in vitro by mutation in a putative phospho-accepting Asp residue into an Asn residue (ARR7(D85N)). While ectopic expression of ARR7 decreases root-growth inhibition, callus formation, and cytokinin-inducible gene expression, overexpression of ARR7 ( D85N ) at the similar level does not generate these phenotypes. ARR7(D85N) is localized to the nucleus and the half-life of this mutant protein is similar to that of ARR7 in Arabidopsis mesophyll protoplasts. These results suggest that the phosphorylation of ARR7 is necessary for ARR7-mediated cytokinin response.
Lee
Dong Ju
DJ
Department of Plant Biotechnology, Agricultural Plant Stress Research Center, Biotechnology Research Institute, Chonnam National University, Buk-Gu, Gwangju 500-757, South Korea.
Kim
Sunmi
S
Ha
Young-Min
YM
Kim
Jungmook
J
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development; D017434:Protein Structure, Tertiary; D011523:Protoplasts / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
C507238:ARR7 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D001224:Aspartic Acid; D010770:Phosphotransferases