Poster: Heavy Metals

Abs # 99: Gene Expression Changes in Arabidopsis thaliana Exposed to Low Levels of Copper

Presenter:	Campbell, Michael A, mac17@psu.edu
Authors	Campbell, Michael A (A)   Feile, Melissa S (A)
Affiliations:	(A): Penn State Erie

Low levels of heavy metal contamination are a persisting problem, especially in the regions of the great lakes water shed. Presque Isle Bay located on the south shore of Lake Erie, is contaminated with low levels of lead, nickel, zinc, and copper. At specific sites within the bay, soil levels exceed the Probable Effect Concentrations (PEC) for lead, nickel, zinc, and copper. However, the biological response of plants to the PEC-levels for these metals is not known. In order to examine the PEC-level effect of copper on plants, we grew Arabidopsis thaliana on soil supplemented with copper to a final concentration of 175mg/kg. Total RNA was isolated and hybridized to an A. thaliana Gene Chip microarray (Affymetrix). The copper treated plants exhibited 20 up-regulated and 4 down-regulated mRNA sequences out of the 8000+ genes on the microarray chip. Each experiment was replicated twice and transcripts demonstrating a +/- 1.1 fold change were selected for further analysis. A specific mRNA, encoded by the metal regulated peptide (MRP1), was increased by over 2-fold after exposure to copper. Transcript levels of MRP1 were measured in plants exposed to other heavy metals. Quantitative real-time PCR analysis demonstrated that MRP1 exhibits a 2-fold increase in expression in comparison to ACT2 and GAPDH when plants were grown in PEC-levels of lead, nickel, and copper. MRP1 encodes for a 52 amino acid polypeptide with no significant similarity or identity to any previously characterized gene product. We have isolated a unique transcript whose expression level is altered by the presence of heavy metals.