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Applied and Environmental Microbiology, August 2001, p. 3514-3522, Vol. 67, No. 8
Westfälische Wilhelms-Universität
Münster, Institut für Botanik, Schloßgarten 3, D-48149
Münster, Germany,1 and
IACR-Long Ashton Research Station, Department of Agricultural
Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF,
United Kingdom2
Received 28 February 2001/Accepted 23 May 2001
At least five genes of the gibberellin (GA) biosynthesis pathway
are clustered on chromosome 4 of Gibberella fujikuroi;
these genes encode the bifunctional ent-copalyl diphosphate
synthase/ent-kaurene synthase, a GA-specific geranylgeranyl
diphosphate synthase, and three cytochrome P450 monooxygenases. We now
describe a fourth cytochrome P450 monooxygenase gene
(P450-4). Gas chromatography-mass spectrometry analysis of
extracts of mycelia and culture fluid of a P450-4 knockout
mutant identified ent-kaurene as the only intermediate of
the GA pathway. Incubations with radiolabeled precursors showed that
the metabolism of ent-kaurene, ent-kaurenol, and ent-kaurenal was blocked in the transformants, whereas
ent-kaurenoic acid was metabolized efficiently to
GA4. The GA-deficient mutant strain SG139, which lacks the
30-kb GA biosynthesis gene cluster, converted ent-kaurene
to ent-kaurenoic acid after transformation with
P450-4. The B1-41a mutant, described as blocked between
ent-kaurenal and ent-kaurenoic acid, was fully
complemented by P450-4. There is a single nucleotide
difference between the sequence of the B1-41a and wild-type
P450-4 alleles at the 3' consensus sequence of intron 2 in
the mutant, resulting in reduced levels of active protein due to a
splicing defect in the mutant. These data suggest that
P450-4 encodes a multifunctional ent-kaurene
oxidase catalyzing all three oxidation steps between
ent-kaurene and ent-kaurenoic acid.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.8.3514-3522.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
The P450-4 Gene of Gibberella
fujikuroi Encodes ent-Kaurene Oxidase in the
Gibberellin Biosynthesis Pathway
*
Corresponding author. Mailing address:
Westfälische Wilhelms-Universität Münster, Institut
für Botanik, Schloßgarten 3, D-48149 Münster, Germany.
Phone: (49) 251.832-24801. Fax: (49)251.8323823. E-mail:
Bettina.Tudzynski{at}uni-muenster.de.
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