ARS | Publication request: The effects of Selenocysteine Se-Methyltransferase on Selenium metabolism in Broccoli

Submitted to: Plant Physiology
Publication Type: Abstract Only
Publication Acceptance Date: January 2, 2007
Publication Date: January 16, 2007
Citation: Zhou, X., Lyi, M., Heller, L., Rutzke, M., Welch, R.M., Kochian, L.V., Li, L. 2007. The effects of Selenocysteine Se-Methyltransferase on Selenium metabolism in Broccoli [abstract]. Plant Physiology. p. 113.

Technical Abstract: Selenium (Se) plays an indispensable role in human nutrition and has suggested to have important health benefits, including as a cancer preventative agent. Se-methylselenocysteine, a monomethylated form of Se, has been shown to be one of the most effective chemopreventative compounds. Broccoli is known for its ability to accumulate high levels of Se-methylselenocysteine. Thus, it is a good model to study the regulation of Se-methylselenocysteine accumulation in plants. A cDNA encoding selenocysteine Se-methyltransferase (BoSMT), the key enzyme responsible for Se-methylselenocysteine formation, was previously cloned from broccoli. To produce broccoli with altered level of Se-methylselenocysteine and to gain a better understanding of Se metabolism in plants, we have generated BoSMT RNAi and 35S:BoSMT overexpressing transgenic lines. As expected, the BoSMT RNAi lines with had low levels of BoSMT mRNA contained reduced amounts of Se-methylselenocysteine accumulation. Surprisingly, we found that overexpression of BoSMT did not result in significantly elevated levels of Se-methylselenocysteine accumulation, indicating that Se-methylselenocysteine may be further metabolized into other Se compounds. The results obtained will shed more light on the metabolism of Se in broccoli, which will be critical for developing strategies to improve the anticarcinogenic efficacy of broccoli plant through engineering of the Se metabolic pathway.