Characterization of Endogenous Gibberellins and Molecular Cloning of a Putative Gibberellin 3-Oxidase Gene in Bunching Onion

To clarify the role of gibberellin (GA) in the growth of bunching onion (Allium fistulosum), identification of endogenous GAs and expression analysis of a putative gibberellin 3-oxidase (AfGA3ox1) were conducted. GA(1), GA(3), GA(4), GA(9), GA(20), and GA(34) were identified with levels of GA(4) and GA(9) being higher than those of GA(1), GA(3), and GA(20). The young seedlings were clearly elongated by exogenous GA(4) treatment but not by GA(3). These results indicate that the 13-non-hydroxylation pathway of GA biosynthesis may be predominant in shoots with GA(4) playing an important role in the growth of bunching onion. Expression of AfGA3ox1 was higher in leaf sheaths than leaf blades during vegetative growth. In reproductive organs, expression of AfGA3ox1 was higher at early and middle development stages in the stalks but was detected at a late development stage in the umbels. AfGA3ox1 was mapped on chromosome 7A from shallot, a bunching onion-related species.