A novel regulatory gene, Tri10, controls trichothecene toxin production and gene expression

We report here the characterization of Tri10, a novel regulatory gene withi n the trichothecene gene cluster. Comparison of Tri10 genomic and mRNA sequ ences revealed that removal of a single 77-bp intron provided a 1,260-bp op en reading frame, encoding a 420-amino-acid protein. Disruption of Tri10 in Fusarium sporotrichioides abolished T-2 toxin production and dramatically decreased the transcript accumulation for four trichothecene genes (Tri4, T ri5, Tri6, and Tri101) and an apparent farnesyl pyrophosphate synthetase (F pps) gene. Conversely, homologous integration of a disruption vector by a s ingle upstream crossover event significantly increased T-2 toxin production and elevated the transcript accumulation of the trichothecene genes and Fp ps. Further analysis revealed that disruption of Tri10, and to a greater ex tent the disruption of Tri6, increased sensitivity to T-2 toxin under certa in growth conditions. Although Tri10 is conserved in Fusarium graminearum a nd Fusarium sambucinum and clearly plays a central role in regulating trich othecene gene expression, it does not show any significant matches to prote ins of known or predicted function or to motifs except a single transmembra ne domain. We suggest a model in which Tri10 acts upstream of the cluster-e ncoded transcription factor TRI6 and is necessary for full expression of bo th the other trichothecene genes and the genes for the primary metabolic pa thway that precedes the trichothecene biosynthetic pathway, as well as for wild-type levels of trichothecene self-protection. We further suggest the p resence of a regulatory loop where Tri6 is not required for the transcripti on of Tri10 but is required to limit the expression of Tri10.