Gibberellin biosynthesis: metabolic evidence for three steps in the early 13-hydroxylation pathway of rice

Abstract

[ 14C 4]GA 53, [ 14C 4]GA 44, and [ 2H 2 / 14C 4]GA 19 were injected separately into seedlings of rice ( Oryza sativa) using a dwarf mutant ( d 35) that has low levels of endogenous gibberellins (GAs). After 8 h incubation, the shoots were extracted and the labeled metabolites were identified by full-scan gas chromatography–mass spectrometry (GC–MS) and Kovats retention indices (KRIs). Our results document the metabolic sequence, GA 53→GA 44→GA 19→GA 20 and the presence of endogenous GA 53, GA 44, GA 19, GA 20 and GA 1. Previous metabolic studies have shown the presence of the step, GA 20→GA 1 in rice. Taken together, the data establish in vegetative shoots of rice the presence of the early 13-hydroxylation pathway, a pathway that originates from GA 12 and leads to bio-active GA 1.