Abstract
Gibberellins (GAs) are phytohormones that regulate many aspects of plant development. RSG is a tabacco transcriptional activator with a bZIP domain that is involved in the regulation of endogenous amounts of GAs. The functional repression of RSG reduced endogenous amounts of GAs and inhibited feedback regulation of NtGA20ox1. ChIP studies demonstrated that RSG binds to the promoter of NtGA20ox1 in vivo when endogenous amount of GAs is decreased. We found that RSG is regulated by NTCDPK1 and 14-3-3; however, the relationship to DELLA proteins that play a key role in GA signaling was unknown.
In this study, we studied the role of AtRSG, Arabidopsis ortholog of RSG, in the transcriptional regulation of GA-biosynthetic enzyme genes. Transient assay showed that AtGA20ox1 is activated by AtRSG. Furthermore, we investigated possible involvement of nuclear GA signaling repressor, DELLA proteins in the transcriptional regulation of GA-biosynthetic enzyme genes by AtRSG.
