Date of Award

12-2007

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plants, Soils, and Insects

Major Professor

C. Neal Stewart, Jr.

Committee Members

Albrecht von Arnim, Janice Zale, Michael E. Essington

Abstract

This dissertation is a compilation of four studies that were conducted in the laboratory of Dr. C. Neal Stewart, Jr. at the University of Tennessee, Knoxville. The first study describes an investigation into arsenate metabolism in Arabidopsis thaliana using microarray technology. The second study summarizes progress made to date towards the development of an As-specific phytosensor, or a plant genetically engineered to detect the presence of As in the environment. The third study describes efforts towards genetic transformation of Pteris cretica and Pteris vittata, both As-hyperaccumulating ferns that have been recently demonstrated as effective in the removal of As from contaminated areas. This paper demonstrates the development of a modified tissue culture protocol that was effective in callus generation from both Pteris vittata and Pteris cretica gametophytes as well as regeneration of plantlets from that callus. Attempts towards genetic transformation were made via biolistic bombardment and Agrobacterium-mediated transient expression using leaf infiltration. Optimization of the Pteris tissue culture protocol will facilitate continued efforts towards the genetic transformation of this unique plant, thereby enabling means of more effectively exploring the underlying mechanisms of As hyperaccumulation. The final study reports a field-scale investigation of plant metal uptake at a local contaminated site in Knoxville, TN. The Smokey Mountain Smelters Site is an abandoned secondary aluminum smelter where waste product from the smelting process (slag) was illegally dumped in large piles over much of the property. Interestingly, wild vegetation was found growing on the slag piles without any obvious symptoms of toxicity. Therefore, a study was conducted to quantify the v metal uptake of these plants, characterize the metal profile of the slag material, and investigate the capacity of Pteris cretica in extracting arsenic from slag on-site. As a result, these studies have provided new insights into arsenate metabolism in plants, and generated many testable hypotheses to enhance our understanding of plant genetic responses to metal stress. The following introduction serves to provide a background on phytoremediation, arsenic, and plant responses to the toxic metalloid.

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