Abstract
RSG is a bZIP transcriptional activator, which regulates shoot growth by controlling GA level. Suppression of RSG resulted in severe dwarfism. We have demonstrated 1) RSG interacts with 14-3-3 proteins, which are broadly conserved regulatory factors in eukaryotes, through phosphorylated serine-114(pS114) in RSG; 2) Binding with 14-3-3 inhibits nuclear localization of RSG; 3) RSG is not statically sequestered in the cytoplasm by 14-3-3, but dynamically shuttling between nucleus and cytoplasm; 4) endogenous level of GA regulates function of RSG by control of intracellular localization; 5) GA promotes nuclear export of RSG by 14-3-3 binding of RSG through phosphorylation of S114 of RSG, when GA negative feedback regulation occurred. We identified NtCDPK1 as an RSG kinase that specifically phosphorylates S114 of RSG. Then, commitment of NtCDPK1 to the regulation of the transcriptional activator RSG in the signaling of GA feedback regulation was examined.
