Bioremediation and Biodegradation Analysis of Transgenic Indian Mustard Plants for Phytoremediation of Metal-Contaminated Mine Tailings

tion of the site was included for comparison. The ECS and GS trans- genics accumulated significantly (P 0.05) more metal in their shoot stabilization and accumulation (Salt et al., 1998). Phyto- than wild-type (WT) Indian mustard, while the APS plants did not. stabilization of metals may employ plants to reduce Of the six metals tested, the ECS and GS transgenics accumulated leaching, runoff, and erosion via stabilization of soil by 1.5-fold more Cd, and 1.5- to 2-fold more Zn, compared with wild- plant roots, or metals may be transformed to less toxic type Indian mustard. Furthermore, the ECS transgenics accumulated forms (Berti and Cunningham, 2000). Accumulation of 2.4- to 3-fold more Cr, Cu, and Pb, relative to WT. The grass mixture metals in shoot tissue, followed by harvesting of shoot accumulated significantly less metal than Indian mustard: approxi- biomass, is called phytoextraction (Blaylock and Huang, mately 2-fold less Cd, Cu, Mn, and Zn, and 5.7-fold less Pb than WT 2000). The harvested plant material may be used for non- Indian mustard. All transgenics removed significantly more metal from food purposes; alternatively, it can be ashed followed the soil compared with WT Indian mustard or an unplanted control. by recycling of the metals or disposal in a landfill (Cha- While WT did not remove more metal than the unplanted control for any of the metals tested, all three types of transgenics significantly ney et al., 2000). These various metal phytoremediation reduced the soil metal concentration, and removed between 6% (Zn) technologies are already being used effectively (Salt et and 25% (Cd) of the soil metal. This study is the first to demonstrate al., 1998; Blaylock, 2000). enhanced phytoextraction potential of transgenic plants using polluted To further enhance the efficiency of metal phytore- environmental soil. The results confirm the importance of metal- mediation, the following strategies may be used: (i) new binding peptides for plant metal accumulation and show that results suitable plant species may be identified in screening from hydroponic systems have value as an indicator for phytoremedia- studies, (ii) agronomic practices may be optimized for tion potential. maximal biomass production and metal uptake (Chaney et al., 2000), and (iii) selected species may be further bred for the desired property, via classical breeding or