期刊
PLANTA
卷 227, 期 3, 页码 577-587出版社
SPRINGER
DOI: 10.1007/s00425-007-0640-x
关键词
Arabidopsis; cytokinins; phosphorelay; protoplast; response regulator; two-component
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.
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