Biological detoxification of the mycotoxin deoxynivalenol and its use in genetically engineered crops and feed additives |
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Authors: | Petr Karlovsky |
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Institution: | (1) Molecular Phytopathology and Mycotoxin Research, University Goettingen, Grisebachstrasse 6, 37077, Goettingen, Germany |
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Abstract: | Deoxynivalenol (DON) is the major mycotoxin produced by Fusarium fungi in grains. Food and feed contaminated with DON pose a health risk to humans and livestock. The risk can be reduced
by enzymatic detoxification. Complete mineralization of DON by microbial cultures has rarely been observed and the activities
turned out to be unstable. The detoxification of DON by reactions targeting its epoxide group or hydroxyl on carbon 3 is more
feasible. Microbial strains that de-epoxidize DON under anaerobic conditions have been isolated from animal digestive system.
Feed additives claimed to de-epoxidize trichothecenes enzymatically are on the market but their efficacy has been disputed.
A new detoxification pathway leading to 3-oxo-DON and 3-epi-DON was discovered in taxonomically unrelated soil bacteria from
three continents; the enzymes involved remain to be identified. Arabidopsis, tobacco, wheat, barley, and rice were engineered to acetylate DON on carbon 3. In wheat expressing DON acetylation activity,
the increase in resistance against Fusarium head blight was only moderate. The Tri101 gene from Fusarium sporotrichioides was used; Fusarium graminearum enzyme which possesses higher activity towards DON would presumably be a better choice. Glycosylation of trichothecenes occurs
in plants, contributing to the resistance of wheat to F. graminearum infection. Marker-assisted selection based on the trichothecene-3-O-glucosyltransferase gene can be used in breeding for
resistance. Fungal acetyltransferases and plant glucosyltransferases targeting carbon 3 of trichothecenes remain promising
candidates for engineering resistance against Fusarium head blight. Bacterial enzymes catalyzing oxidation, epimerization, and less likely de-epoxidation of DON may extend this
list in future. |
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