Evidence for a gene cluster involving trichothecene-pathway biosynthetic genes in Fusarium sporotrichioides.
Two overlapping cosmid clones (Cos1-1 and Cos9-1) carrying the Tox5 gene were isolated from a library of F. sporotrichioides strain NRRL 3299 genomic DNA. These cosmids were used to transform three T-2 toxin-deficient mutants that are blocked at different steps in the trichothecene pathway. Both cosmids restored T-2 toxin production to Tox3-1- or Tox4-1- mutants but neither restored T-2 toxin production to a Tox1-2- mutant. The production of T-2 toxin by the complemented Tox3-1- and Tox4-1- mutants, as well as the production of diacetoxycirpenol by the cosmid-transformed Tox1-2- mutant, were 2- to 10-fold higher than in strain NRRL 3299. In addition, those transformants carrying Cos9-1 produced significantly higher levels of trichothecenes than transformants carrying Cos1-1. Two different DNA fragments (FSC13-9 and FSC14-5), representing the region of overlap between the cosmid clones, were isolated. These fragments specifically complemented either the Tox3-1- mutant (FSC14-5) or the Tox4-1- mutant (FSC13-9). The trichothecene-production phenotype of these transformants was similar to NRRL 3299. These results suggest that two or more genes involved in the biosynthesis of trichothecenes are closely linked to Tox5.
Hohn
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Mycotoxin Research Unit, USDA/ARS, National Center for Agricultural Utilization Research, Peoria, IL 61604.
McCormick
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SP
Desjardins
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AE
D003001:Cloning, Molecular; D005670:Fusarium / Q000235:genetics*; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D005810:Multigene Family; D009154:Mutation; D015183:Restriction Mapping; D013605:T-2 Toxin / Q000096:biosynthesis / Q000235:genetics; D014170:Transformation, Genetic; D014255:Trichothecenes / Q000096:biosynthesis*
D014255:Trichothecenes; D013605:T-2 Toxin