Analysis of gene expression in red maple (Acer rubrum) and trembling aspen (Populus tremuloides) populations from a mining region.

The Greater Sudbury Region has been known as one of the most ecologically disturbed areas in Canada for the past century. Plant adaptation to environmental stressors often results in modifications in gene expression at the transcriptional level. The main objective of the present study was to compare the expression of genes associated with nickel resistance in Acer rubrum and Populus tremuloides growing in areas contaminated and uncontaminated with metals. Primers targeting Nramps4, Nas 3, At2G, MRP4 and alpha-tubulin genes were used to amplify cDNA of both species. The expression of the At2G gene, was 2× and 9× higher in P. tremuloides than in A. rubrum for St. Charles (uncontaminated site) and Kelly Lake (metal contaminated site), respectively. There was a much smaller difference between the two species for the Nramps 4 gene as its expression was 2.5× and 3× higher in P. tremuloides compared to A. rubrum from St. Charles and Kelly Lake, respectively. The same trend was observed for the MRP4 gene whose expression was 2× and 14× higher in P. tremuloides than in A. rubrum from St. Charles and Kelly Lake, respectively. For the Nas 3 gene, the expression was similar in both sites. This gene was upregulated 11× and 10× in P. tremuloides compared to A. rubrum in samples from St. Charles and Kelly Lake, respectively. In general, no significant difference was observed between the metal contaminated and uncontaminated sites for gene expression. In depth analysis revealed that AT2G and MRP4 genes were significantly down regulated in A. rubrum from the metal contaminated sites compared to those from uncontaminated areas, but environmental factors driving this differential gene expression couldn't be established.