Abstract
Gibberellin affects a lot of phases of plant development such as germination, stem elongation and flowering. Thus its biosynthesis and signal transduction must be controlled strictly. We are interested in GA3oxidases, which directly catalyze production of active gibberellins, and the expression of some of them is under GA negative feedback regulation. Analysis of this feedback regulation of GA3oxidase may uncover the mechanism regulating the amount of endogenous gibberellin. We already have shown by promoter deletion assay that the region between 1000 bp and 800 bp of AtGA3ox1 promoter is necessary for GA negative feedback regulation. By further deletion of this region, the 50 bp region within this 200 bp was shown to be necessary for GA negative feedback regulation. Yeast one-hybrid screening using this region identified a DNA binding protein, which contained an AT-hook motif and novel domain. More detailed analysis is under way.
