Baoshan Xing - US grants

The productivity of an ecosystem depends on the recycling of nutrients through the process of decomposition. Decomposition is primarily governed by climate and the chemical composition of plant litter. Traditionally, decomposition rates have been estimated using concentrations of carbon, nitrogen and lignin in the litter. However, the structural characteristics of many hard-to-degrade compounds (biopolymers), including lignins, tannins and cuticular matrices, can dictate overall decomposition rates. The climate in which plants grow can strongly influence the structural properties of these compounds. Climate change thus has the potential to alter decomposition both directly, by changing temperature and moisture, and also indirectly, by changing the structural attributes of biopolymers in plant litter, in ways that are not factored into traditional nutrient cycling models. This project has three long-term goals. The first goal is to learn how growing season temperature and moisture availability affect the diversity and chemical properties of biopolymers that govern decomposition of plant litter. The second goal is to understand how environmental conditions interact with the chemical composition of litter to affect decomposition and nutrient cycling. The third goal is to develop and test models of decomposition that incorporate new knowledge of the roles of climate and biopolymer properties. The investigators will test these hypotheses using six plant species from the Boston-Area Climate Experiment, which exposes patches of old fields with tree seedlings to twelve possible future climates.
Results from this project will improve predictions of carbon and nitrogen cycling in a changing climate. The results will have application beyond soil nutrient dynamics, as tannins are relevant to food quality (as antioxidants), fodder quality and herbivory (as deterrents). The project will provide undergraduates with opportunities for creative inquiry and a new course offering, and will develop a summer course for in-service K-12 teachers and non-formal educators. The project also will provide learning and research experiences to high school students and students from the minority college in the state through the South Carolina Life program.

Project Summary: 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.