Isolation and characterization of Tri3, a gene encoding 15-O-acetyltransferase from Fusarium sporotrichioides.

An acetyltransferase gene (Tri3) was isolated from Fusarium sporotrichioides by complementation of a previously identified Tri3- mutant and shown to be closely linked to three other trichothecene biosynthetic pathway genes. Comparison of the Tri3 sequence with its cDNA revealed the presence of four introns. The Tri3 cDNA contains a 1,539-bp open reading frame that encodes a protein with a molecular mass of 57,418 Da. Regulation of Tri3 transcription in liquid cultures appeared identical to that of other trichothecene pathway genes. Disruption of the Tri3 gene resulted in the accumulation of deacetylated calonectrins rather than T-2 toxin. The results of whole-cell feeding experiments with Tri3- strains suggested that 15-O-acetylation is blocked. Cell-free feeding experiments confirmed that Tri3- strains are able to acetylate a trichothecene C-3 hydroxyl group but are unable to acetylate a trichothecene C-15 hydroxyl group. Our results show that Tri3 encodes an acetyltransferase that converts 15-decalonectrin to calonectrin.