Effects of shoot-applied gibberellin/gibberellin-biosynthesis inhibitors on root growth and expression of gibberellin biosynthesis genes in Arabidopsis thaliana

Abstract

To elucidate the involvement of gibberellin (GA) in the growth regulation of Arabidopsis roots, effects of shoot-applied GA and GA-biosynthesis inhibitors on the root were examined. Applying GA to the shoot of Arabidopsis slightly enhanced the primary root elongation. Treating shoots with uniconazole, a GA biosynthesis inhibitor, also resulted in enhancement of primary root elongation, while shoots treated with uniconazole were stunted and bolting was delayed. Analysis of the expression of GA3ox and GA20ox confirmed the up-regulation of these genes in roots following the inhibitor application to shoots. The results suggest that the inhibition of GA-biosynthesis enhances the production of bioactive GAs in roots and promotes root elongation.