Creation and Propagation of Cottonwood for the Commercial Phytoremediation of Mercury

Mercury pollution affects the health of human and wildlife populations, but few ecologically sound or cost-effective remedies to mercury contamination of soil and water have been proposed. There is a strong demand for environmentally friendly and inexpensive alternatives to excavation and removal of mercury-contaminated soil and sediment. Applied PhytoGenetics, Inc. (APGEN), in collaboration with Subcontractor Principal Investigator Richard Meagher, has developed a genetics-based phytoremediation strategy as just such an alternative, using plants to extract, detoxify, and sequester (EDS) heavy metal pollutants. The EDS strategy for mercury began with model plants and recently has been extended to a variety of larger plants for field testing. These modified plants all thrive on mercury concentrations in soil or water that kill parent plants. Eastern cottonwood, Populus deltoides, grows rapidly in a variety of growth conditions, including riverbanks and floodplains. Cottonwood engineered to express the MerB and MerA enzymes efficiently detoxify methylmercury and ionic mercury, respectively. Methylmercury presents the most serious threat of all mercury compounds, due to both its extreme toxicity and efficient biomagnification in aquatic ecosystems. Recently, the Meagher Laboratory has shown that model plants overexpressing certain metal-binding peptides (MBPs) become extremely resistant to mercury. MBP-expressing cottonwood plants are being constructed and examined for mercury hyperaccumulation. APGEN plans to commercialize cottonwood plants that detoxify various mercury species and hyperaccumulate ionic mercury above ground. Completing several objectives will lead to: (1) the propagation of cottonwood lines that stably express MerB, MerA, and MBP; (2) demonstration that these cottonwood plants detoxify mercury species and accumulate mercury above ground; (3) a marketing and commercialization strategy for the phytoremediation of mercury; and (4) plans for the phytoremediation of two large mercury-contaminated Superfund sites. This research ultimately will lead to the development of a novel, innovative, cost-effective method for the in situ treatment of mercury and methylmercury