Immunochemical studies of an esterase from Fusarium sporotrichioides

Cardoza

et al. 2018

J. Agric. Food Chem.

Trichothecenes are sesquiterpenoid toxins produced by multiple fungi, including plant pathogens, entomopathogens, and saprotrophs. Most of these fungi have the acyltransferase-encoding gene tri18. Even though its function has not been determined, tri18 is predicted to be involved in trichothecene biosynthesis because of its pattern of expression and its location near other trichothecene biosynthetic genes. Here, molecular genetic, precursor feeding, and analytical chemistry experiments indicate that in the saprotroph Trichoderma arundinaceum the tri18-encoded acyltransferase (TRI18) and a previously characterized acyltransferase (TRI3) are required for conversion of the trichothecene biosynthetic intermediate trichodermol to harzianum A, an antifungal trichothecene analog with an octa-2,4,6-trienedioyl acyl group. On the basis of the results, we propose that TRI3 catalyzes trichothecene 4-O-acetylation, and subsequently, TRI18 catalyzes replacement of the resulting acetyl group with octa-2,4,6-trienedioyl to form harzianum A. Thus, the findings provide evidence for a previously unrecognized two-step acylation process during trichothecene biosynthesis in T. arundinaceum and possibly other fungi.

Section: ■ Results and Discussionmentioning

confidence: 99%

Requirement of Two Acyltransferases for 4-O-Acylation during Biosynthesis of Harzianum A, an Antifungal Trichothecene Produced by Trichoderma arundinaceum

Lindo

Cardoza

et al. 2018

J. Agric. Food Chem.

“…In cultures of mutants that accumulate trichothecenes with a C-3 acetyl group, e.g., 15-decalonectrin or isotrichodermin, these acetylated compounds are slowly deacetylated. Four esterases that may remove acetyl groups from various positions of the trichothecene skeleton are known (23). Kimura et al (14) reported that there was no conversion to an acetylated product when T-2 toxin was added to F. sporotrichioides cultures, although crude extracts of recombinant TRI101 from Escherichia coli and from F. graminearum cultures both could convert T-2 toxin to 3-acetyl T-2 toxin.…”

Section: Discussionmentioning

confidence: 99%

Disruption of TRI101 , the Gene Encoding Trichothecene 3- O -Acetyltransferase, from Fusarium sporotrichioides

Alexander

Trapp

et al. 1999

Appl Environ Microbiol

106

We screened a Fusarium sporotrichioides NRRL 3299 cDNA expression library in a toxin-sensitive Saccharomyces cerevisiae strain lacking a functional PDR5 gene. Fourteen yeast transformants were identified as resistant to the trichothecene 4,15-diacetoxyscirpenol, and each carried a cDNA encoding the trichothecene 3-O-acetyltransferase that is theF. sporotrichioides homolog of the Fusarium graminearum TRI101 gene. Mutants of F. sporotrichioides NRRL 3299 produced by disruption ofTRI101 were altered in their abilities to synthesize T-2 toxin and accumulated isotrichodermol and small amounts of 3,15-didecalonectrin and 3-decalonectrin, trichothecenes that are not observed in cultures of the parent strain. Our results indicate that TRI101 converts isotrichodermol to isotrichodermin and is required for the biosynthesis of T-2 toxin.

“…sporotrichioides esterases were partially purified and characterized by Park and Chu (19,20). The esterase isozyme III, which had primarily C-3 esterase activity when assayed by conversion of 3-acetyl T-2 toxin to T-2 toxin, is a possible product of Tri8.…”

Section: Discussionmentioning

confidence: 99%

Fusarium Tri8 Encodes a Trichothecene C-3 Esterase

Alexander

2002

Appl Environ Microbiol

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.