Poster: Phytoremediation

Abs # 987: Manipulation of Plant Selenium Metabolism for Environmental Cleanup: Biotechnology Meets Bioremediation

Presenter:	Pilon-Smits, Elizabeth A, epsmits@lamar.colostate.edu
Authors	Pilon-Smits, Elizabeth A (A)   Garifullina, Gulnara F (A)   Abdel-Ghany, Salah  (A)   van Huysen, Tiffany  (A)   Lindblom, Stormy Dawn  (A)   Tufan, Hale  (A)   Pilon, Marinus  (A)
Affiliations:	(A): Colorado State University, Biology Department

In order to obtain insight into the mechanisms by which plants metabolize selenium (Se) and to create plants with enhanced capacity for environmental cleanup, several enzymes thought to play a role in Se metabolism were expressed in Brassica juncea or Arabidopsis thaliana. Selenium, a trace element that is toxic at higher levels, is thought to be metabolized by the sulfate assimilation pathway. Previously it was found that overexpression of ATP sulfurylase, the key enzyme of the pathway, enhances selenate reduction, Se accumulation, and Se-tolerance. These results, obtained in a hydroponic setup, were confirmed in a recent phytoremediation pot experiment, where the APS transgenics accumulated 3-fold more Se from environmental Se-rich soil compared to wildtype B. juncea. Overexpression of the enzyme cystathionine gamma synthase, the key enzyme for the conversion of selenocysteine (SeCys) to volatile dimethylselenide, resulted in 3-fold higher Se volatilization, reduced Se accumulation and enhanced Se tolerance. Also, introduction of a mammalian SeCys lyase, capable of converting SeCys to less toxic elemental Se, resulted in 2-fold enhanced Se accumulation, and either enhanced or reduced Se tolerance, depending on the intracellular location of the enzyme. Interestingly, during these studies an A. thaliana homolog of the mammalian SeCys lyase was discovered (AtCpNifS) and shown to be of vital importance for Se tolerance. Together these results demonstrate the involvement of the S assimilation pathway in Se metabolism, and the relative importance of the various enzymes tested for Se tolerance, accumulation and volatilization. The obtained transgenics show promise for use in environmental cleanup, which is of significance since Se pollution is a serious problem worldwide.