Arsenic contamination in the food chain is a global health problem and causes damage to most human organs. A significant need exists to develop approaches for addressing environmental arsenic. The long term goal is to develop a plant-based phytoremediation approach for contaminated land that is cost-effective and ecologically friendly as an alternative to conventional remediation methods. The objective of this study is to develop a genetics-based phytoremediation strategy for arsenic uptake, translocation, detoxification, and hyperaccumulation into the fast-growing, high biomass, non-food crop Crambe abyssinica. Nanosulfur will be utilized to modulate the bioavailability and phytoextraction of As from soil and to increase the storage capacity via enhanced sulfur assimilation. The engineered Crambe will be evaluated for removing arsenic from the soil in laboratory, greenhouse, and field conditions. Our central hypothesis is that organ-specific expression of genes, which control the transport, oxidation state, and binding of As, can be tuned to yield efficient extraction and hyperaccumulation into above-ground plant tissues. To test our hypothesis, we propose the following specific aims. 1) Genetically engineer Crambe abyssinica lines for co-expressing bacterial ArsC, gECS, and AtABCC1 and RNAi suppression of endogenous arsenate reductase CaACR2; 2) Evaluate the engineered Crambe lines for metal(loids) tolerance and accumulation; 3) Synthesize and apply nanosulfur to modulate the bioavailability, phytoextraction, and accumulation of toxic metal(loids); and 4) Conduct a pilot field study of engineered Crambe lines for phytoextraction on a contaminated site. After initial screening in tissue culture media supplemented with metals, the best performing quadruple gene stacked (ArcS+gECS+AtABCC1+CaACR2Ri) Crambe lines with wild type controls will be tested using contaminated soils with arsenic as well as co-contaminants in greenhouse. A pilot field-scale study will then be carried out at a site contaminated with arsenic. The soil will be extensively characterized, and analysis for metal content and arsenic speciation will be determined using ICP/MS, HPLC- ICP/MS as well as XANES (X-ray Absorption Near-Edge Spectroscopy). Last, soil amendments with engineered nanosulfur will be used to evaluate the impacts on soil structure and contaminant availability and phytoextraction. Nanosulfur will also be foliarly applied to plants to increase the metal storage capacity via enhanced sulfur assimilation. The expected outcome of this project is a mechanistic understanding of the biogeochemical and plant processes of arsenic remediation that connects key soil characteristics with the efficiency of phytoextraction and hyperaccumulation of arsenic. The results will have an immediate and important positive impact because the knowledge generated from this study will enable efficient and effective phytoremediation approaches to minimize or remove arsenic contamination in the food chain and enhance public health.
s The overall goal of this project is to utilize hypothesis driven experimentation to elucidate key mechanistic processes governing the phytoextraction of arsenic from soil, transport, detoxification and sequestration into above ground biomass. Detailed investigations will focus on biogeochemical processes in the soil that impact contaminant availability to plant roots and also on critical biological limitations and physiological processes that can enable sustained and significant contaminant phytoextraction and hyperaccumulation. This ?bottom-up? focus on mechanisms at and within the abiotic-biotic interface will enable the optimization of plant-based remedial strategies for arsenic and facilitate the development of future analogous platforms for additional contaminants.
