Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2006
Publication Date: 7/5/2006
Citation: Zhou, X., Lyi, S., Heller, L., Rutzke, M., Welch, R.M., Kochian, L.V., Li, L. 2006. The effects of selenocysteine se-methyltransferase on selenium metabolism in transgenic broccoli [abstract]. American Society of Plant Biologists Annual Meeting. p. 226.
Technical Abstract: Selenium (Se) plays an indispensable role in human nutrition and has been implicated to have important health benefits, including being 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 in the form of Se-methylselenocysteine. Thus, it provides 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 (Plant Physiology, 138:409, 1995). 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 showing low levels of BoSMT mRNA contained reduced amounts of Se-methylselenocysteine accumulation. Surprisingly, our preliminary results revealed that overexpression of BoSMT in broccoli did not result in significantly elevated levels of Se-methylselenocysteine accumulation, indicating that Se-methylselenocysteine may be further metabolized into other Se compounds. Detailed characterization of BoSMT RNAi and overexpressing lines, such as quantification of volatile Se compounds and analysis of Se speciation, are being carried out. 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.