Increased cadmium tolerance and accumulation by plants expressing bacterial arsenate reductase

Cadmium (Cd) is a major environmental pollutant that poses a serious threat to natural ecosystems. However, most initial attempts to engineer phytoremediation of Cd have not succeeded in developing sufficient Cd tolerance for vigorous plant growth. We found that the bacterial arsenate reductase gene (arsC ) provided Cd(II) resistance to Escherichia coli . When ArsC is overexpressed in tobacco (Nicotiana tabacum ) and Arabidopsis thaliana , both transgenic plant species showed significantly greater Cd tolerance than wild-type controls. At 50, 75, and 100 mum concentrations of Cd (II), the ArsC expressing transgenic lines grew bigger with broader leaves and longer roots than wild-type controls, which were stunted, turned yellow, flowered early, and often died. At the various Cd(II) concentrations, ArsC transgenic plants attained f. wt 2-3-fold higher than the wild-type plants and had roots significantly longer than wild-type plants. These transgenic plants also contained 30-50% higher Cd concentrations than wild-type plants. It is likely that the arsC gene directs Cd tolerance via the electrochemical reduction of Cd(II) to Cd(0).