Trakia Journal of Sciences, Vol. 7, No. 2, 2009 18 Trakia Journal of Sciences, Vol.7, No. 2, pp 18-27, 2009 Copyright © 2009 Trakia University Available online at: http://www.uni-sz.bg ISSN 1313-7050 (print) ISSN 1313-3551 (online) Original Contribution TRANSFORMED TOBACCO EXPRESSING ScAYT1 DETOXIFIES DEOXYNIVALENOL IN EXTRACT OF dsRNA AND CURED ISOLATES OF Fusarium graminearum S. Shahbazi 1 , A. Alizadeh 1 , A. Mousavi 2 , N. Safaie 1 , F. Sanjarian 2 , P. Aminian 1 1 Plant Pathology Department, Faculty of Agriculture, Tarbiat Modares University, P. O. Box 14155-336, Tehran, Iran; 2 National Institute of Genetic Engineering and Biotechnology, P. O. Box 14155-6343, Tehran, Iran ABSTRACT Fusarium head blight (FHB), has been the most destructive disease of wheat, and producing the mycotoxin deoxynivalenol (DON), a protein synthesis inhibitor, which is harmful to humans and livestock. Previous studies have indicated that over-expression of yeast acetyl transferase gene (ScAYT1) encoding a 3-OH trichothecene acetyl transferase that converts DON to a less toxic acetylated form, leads to suppression of the DON sensitivity. In this study, we tested whether over-expression in tobacco transgenic plants can also increase toxin resistance. Thus, we introduced AYT1 into the model tobacco plants through Agrobacterium-mediated transformation in an attempt to detoxify DON. In vitro tests with extraction of normal and dsRNA carrying isolates of F. graminearum and 10 ppm of DON indicated variable resistance levels in transgenic plants and formation of 3AcDON upon DON treatment was confirmed by TLC method. Key Words: Fusarium head blight, Detoxification, DON, 3ADON, ScAYT1, In vitro screening, TLC INTRODUCTION Gibberella zeae (Schwein.) Petch (anamorph: Fusarium graminearum Schwabe) is an important pathogen of cereal crops, and causes head and seedling blight of small grains, such as wheat and barley (1)1 Available options of managing FHB include use of fungicides, cultural practices, resistant cultivars and biological agents (2). Resistance mechanisms involved in wheat to FHB are not well understood, but quantitative trait loci associated with resistance have been identified (3). Resistance to FHB is classified into five types and resistance to mycotoxin accumulation is one of them. However, no wheat cultivar is completely resistant to FHB (4). Head blight is a disease of contaminated grains; it is a mycotoxin, such as 8-ketotrichothecene (including * Correspondence to: Naser Safaie, Plant Pathology Department, Faculty of Agriculture, Tarbiat Modares University, Iran; Tel.: + 98 2144194911; Fax: + 98.2144196524; E-mail address: nsafaie47@yahoo.com deoxynivalenol (DON), nivalenol (NIV), as well as an oestrogenic mycotoxin, zearalenone (5). Trichothecene mycotoxins such as deoxynivalenol are potent protein synthesis inhibitors for eukaryotic organisms. Trichothecene biosynthesis genes are localised in a gene cluster, and include those encoding trichodiene synthetase (Tri5) (6), P450 oxygenases (Tri4 and Tri11) (7, 8), a cytochrome P450 monooxygenase required for oxygenation of position C-8(Tri1) (9), acetyl transferase (Tri3) (10), a toxin efflux pump (Tri12) (11), and two regulatory genes, Tri6 (12) and Tri10 (13). Tri7 controls C-4 acetylation but is a non-functional pseudo gene in F. graminearum strains that produce DONs that lack C-4 hydroxyl or acetoxy groups (14) and Tri8 encodes an esterase responsible for removal of the C-3 acetyl group from trichothecenes as a final step in biosynthesis (15). Other studies indicate that Tri16 encodes a C-8 acetyl transferase and establishes the presence of a second trichothecene gene cluster (16). Another acetyl transferase (Tri101) is unlinked to the cluster, and encodes the trichothecene C-3 acetyltransferase (17).