Abstract
The central region of the trichothecene gene cluster contains two pathway and two regulatory genes (four Tri genes) that are necessary for forming the trichothecene skeleton. One of these genes, Tri4, encodes a multifunctional cytochrome P 450 monooxygenase, and the expression of this gene is highly induced under trichothecene-inducing conditions. Apart from this gene cluster, Tri101 occurs as a single non-cluster gene, and the product of this gene contributes to the function of self-protection in Fusarium graminearum. The promoter activity of these Tri genes was compared with that of TEF1α (a highly expressed translation elongation factor 1-alpha) gene under toxin-inducing conditions by using the β-glucuronidase (GUS) gene as a reporter. The Tri101 promoter- and TEF1α promoter-reporter fusions integrated at the end of the gene cluster showed activities that were similar to those of the original loci with respect to the timing and the level of GUS protein accumulation. However, as opposed to the normal pattern of Tri4 transcription from the original locus, no GUS activity was detected when the Tri4 promoter was placed at the end of the gene cluster. Thus, we can conclude that the position of the promoter in the gene cluster is important for native transcriptional regulation of Tri4 in trichothecene biosynthesis.
