Gibberellin biosynthetic pathway in Gibberella fujikuroi: Evidence for a gene cluster

Differential screening of a Gibberella fujikuroi cDNA library was used to s uccessfully clone and identify genes involved in the pathway of gibberellin biosynthesis, Several cDNA clones that hybridized preferentially to a cDNA probe prepared from mycelium induced for gibberellin production were isola ted and characterized, The deduced amino acid sequences of two (identical) clones contained the conserved heme-binding motif of cytochrome P450 monoox ygenases (FXXGXXXCXG), One of these cDNA fragments was used as a homologous probe for the screening of a genomic library, A hybridizing 6.7-kb genomic Sail fragment was cloned into pUC19, The sequencing of this clone revealed that a second cytochrome P450 monooxygenase gene was closely linked to the first one, Since at least four cytochrome P450 monooxygenase-catalyzed ste ps are involved in the synthesis of gibberellins, chromosome walking was pe rformed to find a further gene of this family or other genes involved in gi bberellin pathway. Next to the two P450 monooxygenase genes, a putative ger anylgeranyl diphosphate synthase gene, the copalyl diphosphate synthase gen e, which is the first specific gene of the gibberellin pathway, and a third P450 monooxygenase gene were identified, These results suggest that at lea st some of the genes involved in the biosynthesis of gibberellins are close ly linked in a gene cluster in G. fujikuroi, as has been recently found for other "dispensable" pathways in fungi, (C) 1998 Academic Press.