Tracy Punshon

Tracy Punshon, Ph.D.

Research Assistant Professor
Department of Biological Sciences
Dartmouth College
Hanover, NH, 03755
Tel: 603-646-1037
E-mail: Tracy.Punshon@Dartmouth.Edu

Areas of Expertise: Elemental imaging

Research: Dr. Punshon's research uses synchrotron x-ray fluorescence microspectroscopy (SXRF) and x-ray absorption spectroscopy (XAS) to help characterize the function of genes involved in metal and metalloid transport in plants. She works closely with molecular geneticists to provide elemental images that help in the functional characterization of genes.

Synchrotron x-ray fluorescence microspectroscopy is a technique which allows the distribution and abundance of multiple elements within biological tissues to be imaged non-destructively, often without the need for intrusive sample preparation and sectioning. She began using SXRF and collaborating with beam line scientist Antonio Lanzirotti at beamline X26A of the National Synchrotron Light Source in 2000. She was investigating the impact of metal and radionuclide contamination on plants, and found a metal signature in the annual rings of willows growing on a former radiological settling basin. In a subsequent paper she used XAS to investigate the speciation of nickel in the annual rings.

She joined the Guerinot lab in 2005, where research was underway on the characterization of VIT1 (Vacuolar Iron Transporter1) in Arabidopsis; a gene highly expressed in the seed. Other lines of evidence suggested VIT1 was involved in loading Fe in to the vacuole, but deletion did not change the volume-averaged concentration of Fe in the seed. By collecting three dimensional images of the Fe fluorescence in wild type and knock out mutants they have been able to image directly the influence of VIT1. This gene acts in the cells of the embryonic vasculature (in the radicle; the pericycle) to load the vacuole with Fe, presumably in preparation for germination.

Dr. Punshon brings her expertise to the research team studying Arsenic Uptake, Transport and Accumulation in Plants, as they search for and characterize genes involved in arsenic transportation to the grain in rice plants, using molecular genetics, ionomics, SXRF, XAS mapping and various other speciation techniques offered by our Trace Element Analysis Core to understand arsenic homeostasis in rice.