Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 30, 1994
Publication Date: N/A
Interpretive Summary: The mold Fusarium is a common contaminant of small grains. Several species of Fusarium produce toxins called trichothecenes which can be harmful to human and animal health. We are investigating genes involved in trichothecene production using a Fusarium species. We have identified a gene that controls trichothecene production. When this gene is rendered nonfunctional it prevents other trichothecene genes from functioning properly. Understanding how trichothecene production is controlled will be useful in developing new strategies for controlling trichothecene contamination of food and feed products.
Technical Abstract: In Fusarium sporotrichioides, several genes required for biosynthesis of the trichothecene, T-2 toxin, are closely linked. Further characterization of this gene cluster has revealed a gene, Tri6, that specifies a 217 amino acid protein with unusual Cys2His2 zinc finger motifs. The levels of Tri6 mRNA show a pattern of expression similar to trichothecene pathway genes. Analysis of Tri6 transcripts indicated that transcription is initiated at multiple sites within two regions 62 bp apart. Disruption of Tri6 resulted in a mutant that did not produce T-2 toxin but that accumulated low levels of the trichothecene precursor, trichodiene. The Tri6- mutant was unable to convert several trichothecene pathway intermediates to T-2 toxin indicating that at least six pathway enzymes are not expressed in the mutant. In addition, the transcription of the two pathway genes, Tri4 and Tri5, was shown to be greatly reduced in the Tri6- mutant relative to the wild type. A mobility shift DNA binding assay, employing TRI6 expressed in Escherichia coli, revealed that the Tri6 gene product binds within a 209 bp region of the Tri4 promoter. The product of Tri6 was also found to function as a transcriptional activator in yeast when fused to the DNA binding region of GAL4. These results indicate that Tri6 encodes a protein involved in the transcriptional regulation of trichothecene pathway genes in F. sporotrichioides.