| Summary: | <p>Abstract</p> <p>Background</p> <p>It has become increasingly evident that dietary Se plays a significant role in reducing the incidence of lung, colorectal and prostate cancer in humans. Different forms of Se vary in their chemopreventative efficacy, with <it>Se</it>-methylselenocysteine being one of the most potent. Interestingly, the Se accumulating plant <it>Astragalus bisulcatus </it>(Two-grooved poison vetch) contains up to 0.6% of its shoot dry weight as <it>Se</it>-methylselenocysteine. The ability of this Se accumulator to biosynthesize <it>Se</it>-methylselenocysteine provides a critical metabolic shunt that prevents selenocysteine and selenomethionine from entering the protein biosynthetic machinery. Such a metabolic shunt has been proposed to be vital for Se tolerance in <it>A. bisulcatus</it>. Utilization of this mechanism in other plants may provide a possible avenue for the genetic engineering of Se tolerance in plants ideally suited for the phytoremediation of Se contaminated land. Here, we describe the overexpression of a selenocysteine methyltransferase from <it>A. bisulcatus </it>to engineer <it>Se</it>-methylselenocysteine metabolism in the Se non-accumulator <it>Arabidopsis thaliana </it>(Thale cress).</p> <p>Results</p> <p>By over producing the <it>A. bisulcatus </it>enzyme selenocysteine methyltransferase in <it>A. thaliana</it>, we have introduced a novel biosynthetic ability that allows the non-accumulator to accumulate <it>Se</it>-methylselenocysteine and γ-glutamylmethylselenocysteine in shoots. The biosynthesis of <it>Se</it>-methylselenocysteine in <it>A. thaliana </it>also confers significantly increased selenite tolerance and foliar Se accumulation.</p> <p>Conclusion</p> <p>These results demonstrate the feasibility of developing transgenic plant-based production of <it>Se</it>-methylselenocysteine, as well as bioengineering selenite resistance in plants. Selenite resistance is the first step in engineering plants that are resistant to selenate, the predominant form of Se in the environment.</p>
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