Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 11, 2001
Publication Date: N/A
Technical Abstract: The elucidation of the biochemical pathway of trichothecene production by Fusarium species has been the focus of our laboratory for a number of years. The complex pathway begins with the sesquiterpene hydrocarbon trichodiene and consists of multiple oxygenation, cyclization, and esterification steps. As is found in a number of other organisms that produce toxic/antibiotic compounds, many of the genes involved in the pathway of trichothecene production in Fusarium are located within a gene cluster. Identified genes within this cluster are two genes encoding P450 oxygenases (TRI11 and TRI4), a sesquiterpene cyclase (TRI5), two acetyltransferases (TRI3 and TRI7), a pump (TRI12), and a gene for transcriptional regulation (TRI6). We have now identified the function of TRI8, a gene located adjacent to TRI7. To determine the function of TRI8, we disrupted the gene in both F. graminearum and F. sporotrichioides, transformed the parental strains, and analyzed transformants. Gene disruption was confirmed by PCR analysis as well as Southern hybridizations. The culture filtrate of F. graminearum mutants produced by genetic disruption of TRI8 accumulated three C-3 acetylated compounds not normally seen in filtrates of the parent strain. We also conducted whole-cell and cell-free feeding experiments using acetylated trichothecenes. The wild-type parental converted the compounds into the deacetylated form whereas the disruptant mutants did not. Heterologous expression of TRI8 and TRI12 in yeast resulted in a strain that could remove the C-3 acetyl group from a number of trichothecenes. Based on this evidence, we have identified that TRI8 encodes an esterase that removes the C-3 acetyl group of F. sporotrichioides and F. graminearum trichothecenes.