The heavy metals cadmium and lead are both serious environmental contaminants that are listed among the top ten hazards by the Agency for Toxic Substances and Disease Registry (U.S. Department of Health and Human Services) based on their toxicity and prevalence in the environment. For example, lead contamination is widespread due to the ubiquitious use of lead based paints until 1978. Even recently, the USEPA estimated that 12 million homes have lead in their yards at levels exceeding the new 400 ppm standard for play areas, while 4.7 million homes exceed the new 1,200 ppm standard for the rest of the yard. Traditional means of remediation, excavation and removal of the contaminated soils, is not feasible for such a large area, but phytoremediation, or the use of plants to take up contaminants, can provide an alternative, cost-effective, method. ? ? While plants have been identified that can tolerate high levels of toxic metals in their environment, many of these plants are unsuitable for phytoremediation based on the low amounts of biomass they produce or their limited growing range. To improve the potential for phytoremediation of metals such as lead and cadmium, the laboratory of Dr. Julian Schroeder at the University of California, San Diego, has identified two candidate genes that have been demonstrated to increase metal tolerance and accumulation in plants. The first gene, 3-ECS encodes the key enzyme in the synthesis of glutathione, an essential component in metal tolerance and the oxidative stress response. The second gene, YCF1, encodes an ABC transporter that transports glutathione metal complexes into the vacuole, sequestering the metals there and reducing cellular toxicity of the metals. These two genes will be stacked together in a single plant to test the hypothesis that they will act synergistically together and provide significantly increased tolerance. The potential of the transgenic plant for phytoremediation will be demonstrated with soil collected from contaminated sites, followed in Phase II with a field trial at one of these sites. Toxic metals such as cadmium and lead are consistently classified as among the top environmental hazards by the Environmental Protection Agency and U.S. Department of Health and Human Services, but traditional remediation methods are too expensive to address the widespread contamination. This SBIR project will develop enhanced plants that can accumulate greater levels of cadmium and lead than naturally occurring plants, allowing for removal of the metals from contaminated soil or water. These plants could lead to novel remediation technologies with reduced environmental impact than traditional solutions. ? ? ?
