THE MYSTERY OF THE TRICHOTHECENE 3-O-ACETYLTRANSFERASE GENE - ANALYSIS OF THE REGION AROUND TRI101 AND CHARACTERIZATION OF ITS HOMOLOG FROMFUSARIUM-SPOROTRICHIOIDES

The trichothecene 3-O-acetyltransferase gene, Tr101, plays a pivotal r ole for the well-being of the type B trichothecene producer Fusarium g raminearum. We have analyzed the cosmids containing Tri101 and found t hat this resistance gene is not in the biosynthetic gene cluster repor ted so far. It mas located between the UTP-ammonia ligase gene and the phosphate permease gene which are not related to trichothecene biosyn thesis, These two 'house-keeping' genes were also linked in Fusarium s pecies that do not produce trichothecenes. The result suggests that th e isolated occurrence of Tri101 is attributed to horizontal gene trans fer and not to the reciprocal translocation of the chromosome containi ng the gene cluster. Interestingly, 3-O-acetylation mas not always a p rimary self-defensive strategy for all the t-type trichothecene produc ers; i,e. the type A trichothecene producer Fusarium sporotrichioides did not acetylate T-2 toxin in vivo although the fungus possessed a fu nctional 3-O-acetyltransferase gene. Thus Tri101 appears to be a defen se option which the producers have independently acquired in addition to their original resistance mechanisms. (C) 1998 Federation of Europe an Biochemical Societies.