Abstract
RSG is a transcriptional activator that regulates endogenous amounts of GAs through the control of a GA biosynthetic enzyme. Functional repression of RSG reduced endogenous amounts of GAs and severely inhibited the process of cell elongation of stems, resulting in a dwarf phenotype. The 14-3-3 signaling proteins have been shown to bind to RSG through phosphorylated Ser-114 and suppress RSG by sequestering it in the cytoplasm. The intracellular localization of RSG is regulated by GA levels. We have identified calcium-dependent protein kinase (CDPK) as a protein kinase that specifically phosphorylates Ser-114 of RSG. We found that 14-3-3 proteins bind to CDPK as well as RSG. To know the binding domain of CDPK to RSG and 14-3-3, we performed pull-down assay. Furthermore, we examined the effects of overexpression of CDPK on the feedback regulation of the GA 20-oxidase gene in the transgenic plants.
