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Rojas MC, Hedden P, Gaskin P, Tudzynski B: The P450-1 gene of Gibberella fujikuroi encodes a multifunctional enzyme in gibberellin biosynthesis. Proc Natl Acad Sci U S A. 2001 May 8;98(10):5838-43. Epub 2001 Apr 24.
Recent studies have shown that the genes of the gibberellin (GA) biosynthesis pathway in the fungus Gibberella fujikuroi are organized in a cluster of at least seven genes. P450-1 is one of four cytochrome P450 monooxygenase genes in this cluster. Disruption of the P450-1 gene in the GA-producing wild-type strain IMI 58289 led to total loss of GA production. Analysis of the P450-1-disrupted mutants indicated that GA biosynthesis was blocked immediately after ent-kaurenoic acid. The function of the P450-1 gene product was investigated further by inserting the gene into mutants of G. fujikuroi that lack the entire GA gene cluster; the gene was highly expressed under GA production conditions in the absence of the other GA-biosynthesis genes. Cultures of transformants containing P450-1 converted ent-[(14) C] kaurenoic acid efficiently into [(14) C] GA (14), indicating that P450-1 catalyzes four sequential steps in the GA-biosynthetic pathway: 7beta-hydroxylation, contraction of ring B by oxidation at C-6, 3beta-hydroxylation, and oxidation at C-7. The GA precursors ent-7alpha-hydroxy [(14) C] kaurenoic acid, [(14) C] GA (12)-aldehyde, and [(14) C] GA (12) were also converted to [(14) C] GA (14). In addition, there is an indication that P450-1 may also be involved in the formation of the kaurenolides and fujenoic acids, which are by-products of GA biosynthesis in G. fujikuroi. Thus, P450-1 displays remarkable multifunctionality and may be responsible for the formation of 12 products. |
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