Involvement of 14-3-3 signaling protein binding in the functional regulation of the transcriptional activator REPRESSION OF SHOOT GROWTH by gibberellins.
REPRESSION OF SHOOT GROWTH (RSG) is a tobacco (Nicotiana tabacum) transcriptional activator with a basic Leu zipper domain that regulates endogenous amounts of gibberellins (GAs) by the control of a GA biosynthetic enzyme. The 14-3-3 signaling proteins have been suggested to suppress RSG by sequestering it in the cytoplasm. Here, we show that RSG phosphorylation on Ser-114 is important for 14-3-3 binding. We found that GA levels regulate the intracellular localization of RSG. RSG translocated into the nucleus in response to a reduction in GA levels. GA treatment could reverse this nuclear accumulation. The GA-induced disappearance of RSG-green fluorescent protein from the nucleus did not depend on protein degradation. By contrast, the mutant RSG (S114A) that could not bind to 14-3-3 continued to be localized predominantly in the nucleus after GA application. Analysis of the mRNA levels of GA biosynthetic genes showed that the feedback regulation of the GA 20-oxidase gene was inhibited in transgenic plants expressing a dominant negative form of RSG. Our results suggest that RSG is negatively modulated by GAs by 14-3-3 binding and might be involved in GA homeostasis.
Ishida
Sarahmi
S
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Fukazawa
Jutarou
J
Yuasa
Takashi
T
Takahashi
Yohsuke
Y
D048948:14-3-3 Proteins / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D005875:Gibberellins / Q000502:physiology*; D008969:Molecular Sequence Data; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000378:metabolism; D014026:Nicotiana / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*
D048948:14-3-3 Proteins; D005875:Gibberellins; D015534:Trans-Activators; D012694:Serine