Abstract
RSG is a bZIP transcriptional activator that regulates endogenous amounts of gibberellins. The endogenous level of GA decreased in the transgenic tobacco expressed of dominant negative form of RSG (dnRSG). The transgenic tobacco exhibited dwarf phenotypes.We investigated the expression levels of six GA biosynthetic genes. RSG regulates GA biosynthesis through the transcriptional control of ent -kaurene oxidase gene.
dnRSG inhibits the feedback regulation of the GA20-oxidase (Ntc12) gene. GAs regulates intracellular localization of RSG. To search where is necessary to feedback regulation in Ntc12 promoter, we produced transgenic tobacco that GUS gene fused to Ntc12 promoter. We identified a cis element that is important of GA feedback regulation. RSG binds this element directly. The point mutation of this element in Ntc12 promoter is disrupting the feedback regulation. These results indicate that RSG regulates feedback regulation of GA in Ntc12 promoter.
