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Appl. Environ. Microbiol. doi:10.1128/AEM.01077-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Reduced Contamination by the Fusarium Mycotoxin Zearalenone in Maize Kernels through Genetic Modification with a Detoxification Gene

Plant & Microbial Metabolic Engineering Research Unit and Laboratory for Remediation Research, Discovery Research Institute (DRI) and Plant Science Center (PSC1), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, Environmental Molecular Biology Laboratory, Discovery Research Institute (DRI), RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, and Life Science Research Institute, Kumiai Chemical Industry Co., Ltd., Tamari 276, Kakegawa, Shizuoka 436-0011, Japan

^* To whom correspondence should be addressed. Email: mkimura{at}riken.jp.

	Abstract

Maize is subject to ear rot caused by toxigenic Aspergillus and Fusarium species, resulting in contamination with aflatoxins, fumonisins, trichothecenes, and zearalenone (ZEN). The latter two mycotoxins are produced by the cereal pathogen Fusarium graminearum. A transgenic detoxification system for the elimination of ZEN was previously developed using a egfp::zhd101 gene (gfzhd101), encoding an enhanced green fluorescent protein fused to a ZEN-degrading enzyme. In this study, we produced a transgenic maize line expressing an intact copy of gfzhd101 and examined the feasibility of transgene-mediated detoxification in the kernels. ZEN-degrading activity has been detected in transgenic kernels during seed maturation (for a period of 6 weeks after pollination). The level of detoxification activity was unaltered after an additional storage period of 16 weeks at 6 ^oC. When the seeds were artificially contaminated by immersing in the ZEN solution for 48 h at 28 ^oC, the total amount of the mycotoxin in the transgenic seeds was uniformly reduced to less than one tenth of that in the wild type. The ZEN in the transgenic maize kernels was also efficiently decontaminated under conditions with lower water activity (a_w) and temperature; e.g., 16.9 µg of ZEN was removed per gram of seed within 48 h at a_w = 0.90 at 20 ^oC. F. graminearum infection assays demonstrated an absence of ZEN in the transgenic maize seeds while the wild-type accumulated the mycotoxin in the kernels under the same conditions. Transgene-mediated detoxification may offer a simple solution to the problems of mycotoxin contamination in maize.