Feedback regulation of GA5 expression and metabolic engineering of gibberellin levels in Arabidopsis
1999
Xu, Y.L. | Li, L. | Gage, D.A. | Zeevaart, J.A.D.
The gibberellin (GA) 20-oxidase encoded by the GA5 gene of Arabidopsis directs GA biosynthesis to active GAs, whereas that encoded by the P16 gene of pumpkin endosperm leads to biosynthesis of inactive GAs. Negative feedback regulation of GA5 expression was demonstrated in stems of Arabidopsis by bioactive GAs but not by inactive GA. In transgenic Arabidopsis plants overexpressing P16, there was a severe reduction in the amounts of C(20)-GA intermediates, accumulation of large amounts of inactive GA(25) and GA(17), a reduction in GA(4) content, and a small increase in GA(1). However, due to feedback regulation, expression of GA5 and GA4, the gene coding for the subsequent 3beta-hydroxylase, was greatly increased to compensate for the effects of the P16 transgene. Consequently, stem height was only slightly reduced in the transgenic plants.
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