TRI6 ENCODES AN UNUSUAL ZINC-FINGER PROTEIN INVOLVED IN REGULATION OFTRICHOTHECENE BIOSYNTHESIS IN FUSARIUM SPOROTRICHIOIDES

In fusarium sporotrichioides, several genes required for biosynthesis of the trichothecene mycotoxin T-2 toxin are closely linked. Further c haracterization of this gene cluster has revealed a gene, Tri6, that s pecifies a 217-amino-acid protein with regions similar to Cys(2)His(2) zinc finger proteins. Temporal expression of Tri6 is similar to that of trichothecene biosynthetic pathway genes. Analysis of Tri6 transcri pts indicated that transcription is initiated in two regions and that within each region there may be at least four initiation sites. Disrup tion of Tri6 resulted in a mutant that did not produce trichothecenes but that did accumulate low levels of the trichothecene precursor tric hodiene. The Tri6 mutant was unable to convert six trichothecene biosy nthetic intermediates to T-2 toxin, and transcription of two biosynthe tic genes, Tri4 and Tri5, was greatly reduced in the mutant relative t o the wild type. In addition, the product of Tri6 functioned as a tran scriptional activator in Saccharomyces cerevisiae when fused to the DN A binding region of GAL4. These results indicate that Tri6 encodes a p rotein involved in the transcriptional regulation of trichothecene bio synthetic genes in F. sporotrichioides.