ARS | Publication request: Genetic basis for the 3-ADON and 15-ADON Trichothecene chemotypes in Fusarium

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 9, 2010
Publication Date: December 9, 2010
Citation: Alexander, N.J., Mccormick, S.P., Proctor, R. 2010. Genetic basis for the 3-ADON and 15-ADON Trichothecene chemotypes in Fusarium. Meeting Abstract.

Technical Abstract: Fungi in the Fusarium graminearum species complex (FGSC) and the related species F. cerealis (synonym F. crookwellense) and F. culmorum can cause Fusarium head blight (FHB) of wheat, barley, and other small cereal grain crops worldwide and contaminate grain with trichothecene mycotoxins. In general, Fusarium species that cause FHB exhibit three trichothecene production phenotypes (chemotypes): nivalenol (NIV) production, 3-acetyldeoxynivalenol (3-ADON) production, or 15-acetyldeoxynivalenol (15-ADON) production. The genetic basis for the NIV versus 3-ADON/15ADON chemotypes has been demonstrated previously. However, until now, the genetic basis for the 3-ADON and 15ADON chemotypes has not been identified. Two genes, TRI3 and TRI8, have been proposed to affect 3-ADON and 15-ADON production based on functional analysis of the genes in 15-ADON strains of the FHB pathogen F. graminearum sensu stricto and in F. sporotrichioides, which produces another type of trichothecene, T-2 toxin. The analyses indicate that TRI3 encodes an enzyme that catalyzes acetylation of trichothecenes at carbon atom 15 (C-15) and that TRI8 encodes an enzyme that deacetylases trichothecenes at C-3. Here, we identified consistent DNA sequence differences in the coding region of the trichothecene biosynthetic gene TRI8 in 3-ADON and 15-ADON strains. Functional analyses of the TRI8 enzyme (Tri8), including gene disruption, cell-free feeding, yeast expression, and fungal transgenic expression, revealed that Tri8 from 3-ADON strains catalyzes deacetylation of the trichothecene biosynthetic intermediate 3,15-diacetyldeoxynivalenol at C-15 to yield 3-ADON, whereas Tri8 from 15-ADON strains catalyzes deacetylation of 3,15-diacetyldeoxynivalenol at carbon 3 to yield 15-ADON. In contrast, the function of TRI3 was the same in NIV, 3-ADON and 15-ADON strains, and the function of TRI8 was the same in NIV strains as it was in 15-ADON strains. Together, our data indicate that differential activity of Tri8 determines the 3-ADON and 15-ADON chemotypes in Fusarium.