Abstract
Because gibberellin(GA) regulates various aspect of plant growth, endogenous amount of GA and its signal transduction must be regulated appropriately. Gibberellin 3-oxidase, GA3ox catalyzes a final step of biosynthesis of active GA and might be a crtical point to control endogenous amount of active GA. Arabidopsis containes four deduced GA3oxes. One of them, AtGA3ox1 is under negative feedback regulation at transcription. To elucidate molecular mechanism of this regulation, we carried promoter deletion assay using AtGA3ox1 promoter and found 50 bp cis region necessary for feedback regulation. Minimal promoter fused with this region gained feedback responsibility. Novel AT-hook trans factor was obtained by one hybrid screening using this region. This AT-hook protein behaved as a transcriptional activator and dimereized in yeast. We demonstrated that AT-hook protein binds to the cis region specifically by gel shift assay and determined the sequence necessary for AT-hook protein binding to AtGA3ox1 promoter.
