Abstract
As a sessile organism, plants have acquired developmental plasticity during their evolution to integrate their endogenous program for morphogenesis with ever-fluctuating environment through out their life cycle. We focus upon flexible elongation growth as a plant's innate competence for adaptation to environment and try to unravel mechanism of GA-feedback regulation, which comprehends the process of biogenesis and the cascade of signal transduction of hormones, in molecular terms.
We have succeeded to demonstrate that signals of endogenous level of GA are transmitted to a transcriptional activator RSG dominating transcription of genes encoding GA-biosynthetic enzymes via one of calcium-dependent protein kinase, CDPK1. CDPK1 is received phosphorylation by elevation of level of endogenous GA. To elucidate the function of phosphorylation of CDPK1 in transduction of GA signal, we tried to determine the site(s) of GA-induced phosphorylation in vivo. Furthermore CDPK1 was revealed to be phosphorylated by itself with in vitro phosphorylation assay. Two sites of autophosphorylation, S259 and S429 were determined.
