title: A tobacco calcium-dependent protein kinase, CDPK1, regulates the transcription factor REPRESSION OF SHOOT GROWTH in response to gibberellins.
abstract: The homeostasis of gibberellins (GAs) is maintained by negative feedback in plants. REPRESSION OF SHOOT GROWTH (RSG) is a tobacco (Nicotiana tabacum) transcriptional activator that has been suggested to play a role in GA feedback by the regulation of GA biosynthetic enzymes. The 14-3-3 signaling proteins negatively regulate RSG by sequestering it in the cytoplasm in response to GAs. The phosphorylation on Ser-114 of RSG is essential for 14-3-3 binding of RSG. Here, we identified tobacco Ca(2+)-dependent protein kinase (CDPK1) as an RSG kinase that promotes 14-3-3 binding to RSG by phosphorylation of Ser-114 of RSG. CDPK1 interacts with RSG in a Ca(2+)-dependent manner in vivo and in vitro and specifically phosphorylates Ser-114 of RSG. Inhibition of CDPK repressed the GA-induced phosphorylation of Ser-114 of RSG and the GA-induced nuclear export of RSG. Overexpression of CDPK1 inhibited the feedback regulation of a GA 20-oxidase gene and resulted in sensitization to the GA biosynthetic inhibitor. Our results suggest that CDPK1 decodes the Ca(2+) signal produced by GAs and regulates the intracellular localization of RSG.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Sarahmi
authors.initials: S
authors.lastname: Ishida
authors.forename: Takashi
authors.initials: T
authors.lastname: Yuasa
authors.forename: Masaru
authors.initials: M
authors.lastname: Nakata
authors.forename: Yohsuke
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism* / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D005875:Gibberellins / Q000494:pharmacology*; D015151:Immunoblotting; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D002135:Calcium-Binding Proteins; D005875:Gibberellins; D010940:Plant Proteins; D011494:Protein Kinases