|Jurgenson, J - UN NO IA, CEDAR FALLS, IA|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 9, 2002
Publication Date: N/A
Technical Abstract: Many of the genes involved in the trichothecene biosynthetic pathway have now been identified within a 29 kb section of DNA. Within this cluster are 3 genes (Tri4, Tri11, and Tri13) encoding P450 oxygenases, a gene (Tri5) encoding sesquiterpene cyclase, a gene encoding an esterase (Tri8), two acetyltransferase genes (Tri3 and Tri7), a transport pump gene (Tri12), and two regulatory genes (Tri6 and Tri10). One gene encoding an acetyltransferase, Tri101, is not located within the cluster. However, not all of these genes are functional in every Fusarium species. The Fusarium toxins can be divided into two groups based on the substitution of the A ring. Fusarium sporotrichioides produces A-type trichothecenes, such as T-2 toxin or 4,15-diacetoxyscirpenol while F. graminearum produces B-type trichothecenes, such as deoxynivalenol (DON), that have a carbonyl at C-8. These differences in side groups are due, at least, to the nonfunctional Tri7 and Tri13 in B-type trichothecene producers. In the search for the remaining trichothecene genes, the use of an EST library from a toxin overproducing strain carrying an altered Tri10, has identified Tri16, a gene believed to be involved with trichothecene biosynthesis. We isolated and cloned this gene from F. sporotrichioides, then formed disruption vectors through insertional disruption and truncated disruption. Insertional disruption vectors produced only single cross-over events when the vector was transformed into the host protoplasts thus producing a transformant with both a disrupted as well as an intact copy of the gene. Transformants carrying the truncated disruption vector were selected and tested by PCR and Southern hybridization for disruption events and analyzed for toxin production. Disruption of Tri16 does not affect toxin production. Northern analyses suggest that Tri16 is regulated like a secondary metabolite as it is turned on in later cultures like several of the other toxin biosynthetic genes. Tri16 is physically located on linkage group 2 whereas the main trichothecene cluster is on linkage group 1. Even though Tri16 is found in the EST library, these studies show that Tri16 is not necessary for toxin production.