This Article Full Text Full Text (PDF) All Versions of this Article: 138/1/409    most recent pp.104.056549v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Plant Physiol. Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via ISI Web of Science (17) Citing Articles via Google Scholar Google Scholar Articles by Lyi, S. M. Articles by Li, L. Search for Related Content PubMed PubMed Citation Articles by Lyi, S. M. Articles by Li, L. Agricola Articles by Lyi, S. M. Articles by Li, L.

BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Molecular and Biochemical Characterization of the Selenocysteine Se-Methyltransferase Gene and Se-Methylselenocysteine Synthesis in Broccoli

United States Department of Agriculture Agricultural Research Service, Plant, Soil and Nutrition Laboratory, Cornell University, Ithaca, New York 14853

Selenium (Se) plays an indispensable role in human nutrition and has been implicated to have important health benefits, including being a cancer preventative agent. While different forms of Se vary in their anticarcinogenic efficacy, Se-methylselenocysteine (SeMSC) has been demonstrated to be one of the most effective chemopreventative compounds. Broccoli (Brassica oleracea var. italica) is known for its ability to accumulate high levels of Se with the majority of the selenoamino acids in the form of Se-methylselenocysteine. Therefore, it serves as a good model to study the regulation of SeMSC accumulation in plants. A cDNA encoding selenocysteine Se-methyltransferase, the key enzyme responsible for SeMSC formation, was cloned from broccoli using a homocysteine S-methyltransferase gene probe from Arabidopsis (Arabidopsis thaliana). This clone, designated as BoSMT, was functionally expressed in Escherichia coli, and its identity was confirmed by its substrate specificity in the methylation of selenocysteine. The BoSMT gene represents a single copy sequence in the broccoli genome. Examination of BoSMT gene expression and SeMSC accumulation in response to selenate, selenite, and sulfate treatments showed that the BoSMT transcript and SeMSC synthesis were significantly up-regulated in plants exposed to selenate but were low in plants supplied with selenite. Simultaneous treatment of selenate with selenite significantly reduced SeMSC production. In addition, high levels of sulfate suppressed selenate uptake, resulting in a dramatic reduction of BoSMT mRNA level and SeMSC accumulation. Our results reveal that SeMSC accumulation closely correlated with the BoSMT gene expression and the total Se status in tissues and provide important information for maximizing the SeMSC production in this beneficial vegetable plant.

^* Corresponding author; e-mail ll37{at}cornell.edu; fax 1–607–255–1132.

Received November 19, 2004; returned for revision January 24, 2005; accepted February 3, 2005.

Related articles in Plant Physiol.:

On the Inside

Peter V. Minorsky
Plant Physiol. 2005 138: 78-79. [Full Text]  

This article has been cited by other articles:

				J. Qin, B. P. Rosen, Y. Zhang, G. Wang, S. Franke, and C. Rensing Arsenic detoxification and evolution of trimethylarsine gas by a microbial arsenite S-adenosylmethionine methyltransferase PNAS, February 14, 2006; 103(7): 2075 - 2080. [Abstract] [Full Text] [PDF]