title: Fusarium Tri8 encodes a trichothecene C-3 esterase.
abstract: Mutant strains of Fusarium graminearum Z3639 produced by disruption of Tri8 were altered in their ability to biosynthesize 15-acetyldeoxynivalenol and instead accumulated 3,15-diacetyldeoxynivalenol, 7,8-dihydroxycalonectrin, and calonectrin. Fusarium sporotrichioides NRRL3299 Tri8 mutant strains accumulated 3-acetyl T-2 toxin, 3-acetyl neosolaniol, and 3,4,15-triacetoxyscirpenol rather than T-2 toxin, neosolaniol, and 4,15-diacetoxyscirpenol. The accumulation of these C-3-acetylated compounds suggests that Tri8 encodes an esterase responsible for deacetylation at C-3. This gene function was confirmed by cell-free enzyme assays and feeding experiments with yeast expressing Tri8. Previous studies have shown that Tri101 encodes a C-3 transacetylase that acts as a self-protection or resistance factor during biosynthesis and that the presence of a free C-3 hydroxyl group is a key component of Fusarium trichothecene phytotoxicity. Since Tri8 encodes the esterase that removes the C-3 protecting group, it may be considered a toxicity factor.
authors.affiliation: Mycotoxin Research Unit, USDA/ARS, National Center for Agricultural Utilization Research, Peoria, Illinois 61604-3902, USA. mccormsp@mail.ncaur.usda.gov
authors.forename: Susan P
authors.initials: SP
authors.lastname: McCormick
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Alexander
mesh_terms: D002474:Cell-Free System; D004950:Esterases / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D005670:Fusarium / Q000201:enzymology*; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014255:Trichothecenes / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D014255:Trichothecenes; D004950:Esterases