The Gibberellin 20-Oxidase of Gibberella fujikuroi Is a

The genes for gibberellin (GA) biosynthesis are clus-tered in the fungus Gibberella fujikuroi. In addition to genes encoding a GA-specific geranylgeranyl diphos-phate synthase and a bifunctional ent-copalyl diphos-phate/ent-kaurene synthase, the cluster contains four cytochrome P450 monooxygenase genes (P450-1,-2,-3,-4). Recently it was shown that P450-4 and P450-1 encode multifunctional enzymes catalyzing the three oxidation steps from ent-kaurene to ent-kaurenoic acid and the four oxidation steps from ent-kaurenoic acid to GA14, respectively. Here we describe the functional analysis of the P450-2 gene by gene disruption and by expressing the gene in a mutant that lacks the entire GA biosynthe-sis gene cluster. Mutants in which P450-2 is inactivated by the insertion of a large piece of DNA accumulated GA14 and lacked biosynthetically more advanced metab