A genetic and biochemical approach to study trichothecene diversity in Fusarium sporotrichioides and Fusarium graminearum

The trichothecenes T-2 toxin and deoxynivalenol (DON) are natural fungal pr oducts that are toxic to both animals and plants. Their importance in the p athogenicity of Fusarium spp, on crop plants has inspired efforts to unders tand the genetic and biochemical mechanisms leading to trichothecene synthe sis. In order to better understand T-2 toxin biosynthesis by Fusarium sporo trichioides and DON biosynthesis by F. graminearum, we compared the nucleot ide sequence of the 23-kb core trichothecene gene cluster from each organis m. This comparative genetic analysis allowed us to predict proteins encoded by two trichothecene genes, TRI9 and TRI10, that had not previously been d escribed from either Fusarium species. Differences in gene structure also w ere correlated with differences in the types of trichothecenes that the two species produce, Gene disruption experiments showed that F. sporotrichioid es TRI7 (FsTRI7) is required for acetylation of the oxygen on C-4 of T-2 to xin, Sequence analysis indicated that F. graminearum TRI7 (FgTRI7) is nonfu nctional. This is consistent with the fact that the FgTRI7 product is not r equired for DON synthesis in F. graminearum because C-4 is not oxygenated.