UC San Diego

Cadmium (Cd) is a toxic heavy metal and its remediation from contaminated soil is a matter of public health. Current remediation technologies are expensive and inefficient, and there is interest in the development of alternative strategies such as phytoextraction. In order to use plants to remove Cd from the soil, it must be taken up by the plant and efficiently translocated and stored in harvestable tissue. Thiol peptides such as glutathione (GSH) and phytochelatins (PCs) are known to chelate and sequester Cd intracellularly and evidence has suggested that PCs may also be invoved in the long-distance translocation of Cd. Their role in detoxification, translocation and sequestration of Cd makes thiol-peptides of interest for the development of Cd phytoextraction technologies. In this thesis, the phloem and xylem saps of Brassica napus were analyzed and it was determined that the phloem is the major vascular system for the thiol- mediated translocation of Cd. Manipulation of PC-Cd transporters may facilitate Cd phytoextraction, however no plant PC-Cd transporters have yet been identified. In the second part of this thesis, a method for the screening and characterization of plant PC-Cd transporters is presented and validated with a known yeast PC-Cd transporter. In the third part of this thesis, a strategy is presented for how thiol-Cd transporters might be used to increase the retention of Cd in harvestable tissue. While this approach does not appear to have been successful, alternative approaches are also proposed