Submitted to: Phytochemical Society of North America Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 13, 2003
Publication Date: N/A
Technical Abstract: Fusarium graminearum, the causative agent of wheat scab, is an international problem due to economic losses to the agricultural industry and because of food safety concerns resulting from mycotoxin contamination. Mycotoxin synthesis is coordinated by the tri6 gene which encodes a transcription factor. In order to better understand the regulation of tri6 gene expression and mycotoxin synthesis, we have employed the method of 5'-RACE to map the limits of the bidirectional promoter within the tri4/tri6 intergenic region of Fusarium graminearum strain GZ3639. We conclude that this bidirectional promoter consists of 892 nucleotides, mapping from -109 to -1000 nucleotides 5' of the tri4 translational start codon. We analyzed the DNA sequence of this bidirectional promoter and the analogous sequence from 41 other Fusarium strains for transcription factor binding sites. Our analysis of the 42 strains reveals 21 to 30 transcription factor binding sites, specific to 14 different transcription factors. The transcription factor binding site that is most commonly represented in each strain is specific to the Nit2 transcription factor. The Nit2/Area family of transcription factors upregulate genes involved in the utilization of secondary nitrogen sources when primary nitrogen sources become limiting. This nitrogen regulatory circuit is known as nitrogen metabolite repression. We hypothesize that the nit2 sites within the Fusarium graminearum tri4/tri6 bidirectional promoter function to bring tri4 and tri6 gene expression, and mycotoxin biosynthesis under nitrogen metabolite repression control.