Exploring the selenium phytoremediation potential of transgenic Indian mustard overexpressing ATP sulfurylase or cystathionine-gamma-synthase

Indian mustard (Brassica juncea) plants overexpressing ATP sulfurylase (APS transgenics) were previously shown to have higher shoot selenium (Se) levels and enhanced Se tolerance compared to wild type when supplied with selenate in a hydroponic system. Other transgenic Indian mustard overexpressing cystathionine-gamma-synthase (CGS) showed a higher Se volatilization rate, lower shoot Se levels, and higher Se tolerance than wild type, also in hydroponic studies. In the present study, these APS and CGS transgenics were evaluated for their capacity to accumulate Se from soil that is naturally rich in Se. Wildtype Indian mustard and the Se hyperaccumulator Stanleya pinnata were included for comparison. After 10 weeks on Se soil, the APS transgenics contained 2.5-fold higher shoot Se levels than wild-type Indian mustard, similar to those of S. pinnata. The CGS transgenics contained 40% lower shoot Se levels than wild type. Shoot biomass was comparable for all Indian mustard types and higher than that of S. pinnata. These results obtained with these transgenics on soil are in agreement with those obtained earlier using hydroponics. The significance of these findings is that they are the first report on the performance of transgenic plants on Se in soil and show the potential of genetic engineering for phytoremediation.