TRANSGENIC INDIAN MUSTARD OVEREXPRESSING SELENOCYSTEINE LYASE, SELENOCYSTEINE METHYLTRANSFERASE, OR METHIONINE METHYLTRANSFERASE EXHIBIT ENHANCED POTENTIAL FOR SELENIUM PHPYTOREMEDIATION UNDER FIELD CONDITIONS.

Authors: Banuelos, Gary; LEDUC, D - UC BERKELEY; PILON-SMITS, E - COLORADO STATE UNIV.

Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2006
Publication Date: 8/10/2007
Citation: Banuelos, G.S., Leduc, D.L., Pilon-Smits, E.A. 2007. Transgenic Indian Mustard Overexpressing Selenocysteine Lyase, Selenocysteine Methyltransferase, or Methionine Methyltransferase Exhibit Enhanced Potential for Selenium Phytoremediation Under Field Conditions. Journal of Environmental Science and Technology. 41:599-605.

Interpretive Summary: Use of phytoremediation as a technology for the cleanup of selenium is limited by the slow rate of biological processes involved. There is a need to develop plants that can remove Se from soil at much faster rates than are presently available. Genetic engineering offers an exciting and innovative approach for increasing the efficiency of phytoremediation. Most work in this area has only been evaluated under growth chamber and greenhouse conditions. In this regard, three different transgenic lines of Indian mustard were produced and tested under field conditions for their ability to accumulate selenium (Se) from Se-and boron-contaminated saline sediment during spring and fall. For both growing seasons the different lines of Indian mustard accumulated more selenium, especially in the Fall, then the untransformed Indian mustard after almost 8 weeks in the field. These results are significant because this is only the second scientific report showing that plants genetically engineered for phytoremediation can successfully accumulate more Se than untransformed plants under field conditions.

Technical Abstract: The effective use of phytoremediation of Se as a clean-up technology could be enhanced by improving the ability of plants to accumulate Se. In this regar, three transgenic Indican mustard (Brassica juncea (L.) Czern.) lines were tested under field conditions for their ability to accumulate selenium (Se) from Se- and boron-contaminated saline sediment. The transgenic lines overexpress genes encoding the enzymes selenocysteine lyzse (cpSL), selenocysteine methyltransferase (SMT), and methionine methyltransferase (MMT), respectively. In a Spring planting, spSL, SMT, and wildtype plants (WT) were compared, while SMT, MMT, and WT were compared in a Fall planting. In the Spring planting, shoots of the cpSL transgenic plants accumulated 2-fold more Se (p <0.01), had 1.8 times higher leaf Se concentrations (p < 0.01), and grew better on contaminated soil than WT. The SMT plants had a 1.7-fold higher leaf Se concentration than WT (p <0.05). In the Fall planting, the SMT transgenics accumulated 1.6-fold more Se in their shoots than WT (p < 0.01) with Se concentrations being higher in both leaves and stems. MMT plants were less effective than the other transgenics; nevertheless, they did exhibit ~2-fold higher Se bioaccumulation ratios in stems than WT. These results support the view that cpSL and SMT, and, to a lesser extent, MMT transgenic lines can significantly enhance the ability of Indian mustard for Se phytoremediation under field conditions. Moreover, this is only the second report showing that Indian mustard plants genetically engineered for Se phytoremediation can successfully accumulate more Se than untransformed mustard plants under field contitions.