Fusarium Tri8 encodes a trichothecene C-3 esterase

Area of Science:

• Mycology
• Plant Pathology
• Biochemistry

Background:

• Fusarium species produce trichothecene mycotoxins, which are significant plant pathogens.
• Trichothecene biosynthesis involves complex enzymatic pathways, including acetylation and deacetylation steps.
• The Tri8 gene's role in Fusarium trichothecene biosynthesis has been previously unclear.

Purpose of the Study:

• To elucidate the function of the Tri8 gene in Fusarium trichothecene biosynthesis.
• To investigate the impact of Tri8 disruption on the accumulation of specific trichothecene derivatives.
• To determine if Tri8 encodes a deacetylation enzyme and its role in fungal phytotoxicity.

Main Methods:

• Generating Tri8 mutant strains of Fusarium graminearum and Fusarium sporotrichioides.
• Analyzing the trichothecene profiles of wild-type and mutant strains using chromatography and mass spectrometry.
• Conducting cell-free enzyme assays and yeast expression experiments to confirm gene function.

Main Results:

• Tri8 disruption in F. graminearum led to accumulation of 3,15-diacetyldeoxynivalenol and other C-3 acetylated compounds instead of 15-acetyldeoxynivalenol.
• Tri8 mutants of F. sporotrichioides accumulated 3-acetyl T-2 toxin and related compounds, differing from wild-type profiles.
• Enzyme assays and yeast feeding experiments confirmed Tri8 encodes an esterase that deacetylates the C-3 position.

Conclusions:

• The Tri8 gene encodes a C-3 esterase responsible for deacetylation in Fusarium trichothecene biosynthesis.
• The C-3 acetyl group, removed by Tri8, appears to be a protective group, and its removal by Tri8 may contribute to phytotoxicity.
• Tri8 functions in opposition to Tri101 (a transacetylase), collectively regulating trichothecene structure and potential toxicity.