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Applied and Environmental Microbiology, September 2008, p. 5325-5339, Vol. 74, No. 17
0099-2240/08/$08.00+0 doi:10.1128/AEM.00694-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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Westfälische Wilhelms-Universität Münster, Institut für Botanik, Schlossgarten 3, 48149 Münster, Germany,1 Laboratorio de Bioorgánica, Departamento de Química, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile,2 Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, United Kingdom3
Received 25 March 2008/ Accepted 14 June 2008
Gibberellins (GAs) are tetracyclic diterpenoid phytohormones that were first identified as secondary metabolites of the fungus Fusarium fujikuroi (teleomorph, Gibberella fujikuroi). GAs were also found in the cassava pathogen Sphaceloma manihoticola, but the spectrum of GAs differed from that in F. fujikuroi. In contrast to F. fujikuroi, the GA biosynthetic pathway has not been studied in detail in S. manihoticola, and none of the GA biosynthetic genes have been cloned from the species. Here, we present the identification of the GA biosynthetic gene cluster from S. manihoticola consisting of five genes encoding a bifunctional ent-copalyl/ent-kaurene synthase (CPS/KS), a pathway-specific geranylgeranyl diphosphate synthase (GGS2), and three cytochrome P450 monooxygenases. The functions of all of the genes were analyzed either by a gene replacement approach or by complementing the corresponding F. fujikuroi mutants. The cluster organization and gene functions are similar to those in F. fujikuroi. However, the two border genes in the Fusarium cluster encoding the GA4 desaturase (DES) and the 13-hydroxylase (P450-3) are absent in the S. manihoticola GA gene cluster, consistent with the spectrum of GAs produced by this fungus. The close similarity between the two GA gene clusters, the identical gene functions, and the conserved intron positions suggest a common evolutionary origin despite the distant relatedness of the two fungi.
Published ahead of print on 20 June 2008.
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