Understanding Plant Signaling Response to and Accumulation of Heavy Metals and Arsenic
Arsenic, lead, and cadmium are among the EPA’s highest priority hazardous substances for research and remediation. These toxic elements are high priorities due to extensive soil and water contamination, and extreme impact on human health, including increased cancer rates, liver disease, respiratory disorders, and learning disabilities. As part of my dissertation work I have investigated heavy metal and metalloid uptake, movement, accumulation, and signaling responses in plants at three different levels. First, I pursued a basic science project using a forward genetic screen to identify new components in the heavy metal and arsenic transcriptional response network. I identified At4g10930 and At4g13575 as likely genes to contain the causative mutation in a mutant Arabidopsis line that displayed a constitutive cadmium response (crc1), and identified a candidate region and 25 candidate mutations for a super-response to cadmium (src1) mutant. In a more translational research project, I generated transgenic Arabidopsis expressing known heavy metal and arsenic detoxification machinery driven by a root specific promoter. These transgenic Arabidopsis lines may provide a proof of concept for manipulating spatial sequestration of heavy metals and arsenic in order to minimize contamination of aerial, often edible, tissues in crops. We are also working to generate transgenic rice utilizing the same concept to minimize heavy metal and metalloid storage in the grain. Lastly, I worked on a community outreach project monitoring heavy metal and arsenic accumulation in food plants grown at a community garden in Southeastern San Diego in collaboration with Dr. Keith Pezzoli, the head of the Community Engagement and Research Translation Cores (CEC/RTC) of the UCSD Superfund. As part of this project longitudinal tracking of heavy metal and arsenic accumulation was done in edible and non-edible fruit tree tissue. Lead accumulation was found in leaf tissue of several fruit trees, however no detectable accumulation was found in fruit samples. Additionally, heavy metals and arsenic accumulation in a number of ground grown plant samples, which led to the incorporation of raised beds at the Ocean View Growing Grounds, mitigating this potential exposure risk.