EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
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SESSION 4: GENETICS OF HOSTS – PLANT RESISTANCE TO FUSARIUM,<br />
VARIETY DEVELOPMENT<br />
In planta inactivation <strong>of</strong> Fusarium mycotoxins<br />
M. P. Kovalsky-Paris 1 , W. Schweiger 1 , G. Wiesenberger 1 , J. A. Torres-<br />
Acosta 1 , H. Michlmayr 1 , S. Newmister 2 , M. Lemmens 1 , A. Malachova 1 , S.<br />
Shin 3 , G. Muehlbauer 3 , T. Weigl-Pollack 4 , P. Fruhmann 4 , H. Mikula 4 , C.<br />
Hametner 4 , B. Kluger 1 , R. Schuhmacher 1 , R. Krska 1 , J. Fröhlich 4 , I. Rayment 2 ,<br />
F. Berthiller 1 , G. Adam 1<br />
1 University <strong>of</strong> Natural Resources and Life Sciences, Vienna (BOKU), Konrad Lorenz Str, 20 + 24, A<br />
3430 Tulln Austria; 2 University <strong>of</strong> Wisconsin, Madison, WI 53706-1544, USA; 3 University <strong>of</strong> Minnesota,<br />
St. Paul, MN 55108-6026, USA; 4 University <strong>of</strong> Technology, Institute <strong>of</strong> Applied Synthetic Chemistry,<br />
A-1060 Vienna, Austria.<br />
E-mail: gerhard.adam@boku.ac.at<br />
Secondary metabolites <strong>of</strong> plant pathogens are suspected to play a role as<br />
virulence factors, but in many cases their mode <strong>of</strong> action is unknown. We could<br />
demonstrate that Hsp90 is the plant target for the (estrogenic) Fusarium<br />
mycotoxin zearalenone. ZON is efficiently glycosylated in various plants. We<br />
identified a barley UDP-glucosyltransferase (UGT) which produces a mixture <strong>of</strong><br />
the known ZON-4-glucoside and the novel ZON-2-glucoside. In contrast to ZON<br />
and beta-zearalenol their glycosylated forms are not able to inhibit Hsp90 ATPase<br />
activity. DON is known to be required for fungal spread in wheat. It is inactivated<br />
in planta by formation <strong>of</strong> a glucoside, which is no longer able to interact with the<br />
ribosomal target. We characterized candidate UGTs from barley, Brachypodium,<br />
Sorghum, rice and wheat by heterologous expression in yeast. Some genes<br />
encode enzymes with the ability to detoxify DON, NIV and other trichothecenes.<br />
Surprisingly, the detoxification capability and substrate specificity towards<br />
different toxins was quite different in highly similar genes, which are typically<br />
encoded in clusters <strong>of</strong> variable gene number in the different genomes. The<br />
Brachypodium genome seemingly has the capacity to encode more than 150<br />
functional UGTs. One rice UGT gene could be expressed in E. coli with a<br />
solubility tag. The availability <strong>of</strong> affinity purified active enzyme now allows efficient<br />
enzymatic production <strong>of</strong> DON-3-O-glucoside, and also <strong>of</strong> still uncharacterized<br />
glucosides <strong>of</strong> 15-ADON, nivalenol, fusarenone X and HT-2 toxin. They should<br />
become valuable reference substances to study metabolism <strong>of</strong> mycotoxins in<br />
various plants. Recently a novel detoxification mechanism for DON was<br />
demonstrated, the formation <strong>of</strong> glutathione adducts and processing products<br />
(Kluger et al., 2012). Chemically synthesized S-methyl-DON (SMD) which is<br />
presumably generated in planta from DON-cysteine by cysteine-S-conjugatebeta-lyase<br />
and methylation was 12-fold less toxic than DON, suggesting that<br />
formation <strong>of</strong> bulky glutathione adducts is a detoxification reaction.<br />
Keywords: detoxification, glucoside, glutathione, conjugation<br />
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