This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 19/12/3901    most recent tpc.107.052662v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by To, J. P.C. Articles by Kieber, J. J. Search for Related Content PubMed PubMed Citation Articles by To, J. P.C. Articles by Kieber, J. J. Agricola Articles by To, J. P.C. Articles by Kieber, J. J.

Cytokinin Regulates Type-A Arabidopsis Response Regulator Activity and Protein Stability via Two-Component Phosphorelay^[W]

^a Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280
^b Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755

³ Address correspondence to jkieber{at}unc.edu.

The plant hormone cytokinin regulates many aspects of growth and development. Cytokinin signaling involves His kinase receptors that perceive cytokinin and transmit the signal via a multistep phosphorelay similar to bacterial two-component signaling systems. The final targets of this phosphorelay are a set of Arabidopsis thaliana Response Regulator (ARR) proteins containing a receiver domain with a conserved Asp phosphorylation site. One class of these, the type-A ARRs, are negative regulators of cytokinin signaling that are rapidly transcriptionally upregulated in response to cytokinin. In this study, we tested the role of phosphorylation in type-A ARR function. Our results indicate that phosphorylation of the receiver domain is required for type-A ARR function and suggest that negative regulation of cytokinin signaling by the type-A ARRs most likely involves phosphorylation-dependent interactions. Furthermore, we show that a subset of the type-A ARR proteins are stabilized in response to cytokinin in part via phosphorylation. These studies shed light on the mechanism by which type-A ARRs act to negatively regulate cytokinin signaling and reveal a novel mechanism by which cytokinin controls type-A ARR function.