Production of Se-methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase

• Published in: BMC plant biology Vol. 4; no. 1; p. 1
• Main Authors: Ellis, Danielle R, Sors, Thomas G, Brunk, Dennis G, Albrecht, Carrie, Orser, Cindy, Lahner, Brett, Wood, Karl V, Harris, Hugh H, Pickering, Ingrid J, Salt, David E
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 28.01.2004; BioMed Central; BMC
• Subjects: Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Astragalus bisulcatus; Astragalus Plant - enzymology; Chromatography, High Pressure Liquid; Cysteine - analogs & derivatives; Cysteine - biosynthesis; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Mass Spectrometry - methods; Methyltransferases - genetics; Methyltransferases - metabolism; Organoselenium Compounds; Plant Shoots - drug effects; Plant Shoots - genetics; Plant Shoots - metabolism; Plants, Genetically Modified; Selenium - analysis; Selenium - pharmacology; Selenocysteine - analogs & derivatives; Sodium Selenite - pharmacology
• ISSN: 1471-2229; 1471-2229
• DOI: 10.1186/1471-2229-4-1

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 Se-methylselenocysteine being one of the most potent. Interestingly, the Se accumulating plant Astragalus bisulcatus (Two-grooved poison vetch) contains up to 0.6% of its shoot dry weight as Se-methylselenocysteine. The ability of this Se accumulator to biosynthesize Se-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 A. bisulcatus. 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 A. bisulcatus to engineer Se-methylselenocysteine metabolism in the Se non-accumulator Arabidopsis thaliana (Thale cress). By over producing the A. bisulcatus enzyme selenocysteine methyltransferase in A. thaliana, we have introduced a novel biosynthetic ability that allows the non-accumulator to accumulate Se-methylselenocysteine and gamma-glutamylmethylselenocysteine in shoots. The biosynthesis of Se-methylselenocysteine in A. thaliana also confers significantly increased selenite tolerance and foliar Se accumulation. These results demonstrate the feasibility of developing transgenic plant-based production of Se-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.