Nickel and copper translocation in Pinus resinosa (red pine) and their effects on the expression of genes associated with nickel and copper resistance

Abstract

Metals are required in plant tissues at small concentrations for several physiological processes; however, excess metal can cause toxicity. The City of Greater Sudbury Region (CGS) has a rich mining history that has resulted in contaminating emissions that damaged surrounding ecosystems. The main objectives were to 1) investigate metal accumulation and translocation in Pinus spp., 2) evaluate the effects of different concentrations of nickel and copper on P. resinosa genotypes, and 3) determine the effects of different concentrations of nickel and copper on gene expression in Pinus resinosa. Soil, roots, and shoots of P. resinosa were sampled in the CGS. Additionally, seedlings were treated with different concentrations of nickel nitrate and copper sulphate and corresponding salt controls in growth chamber screening tests. P. resinosa accumulate nickel and copper in roots and shoots. Susceptibility to nickel exposure increased with seedling age. Resistance to copper on the other hand increased in old genotypes. The expression of genes associated with nickel resistance including 1-aminocyclopropane-1-carboxylic acid deaminase (ACC deaminase), glutathione-Stransferase (GST), High-affinity Ni transporter (NiCoT or AT2G16800), natural resistance-associated macrophage protein 3 (NRAMP3) and Serine acetyltransferase (SAT) were analyzed using qPCR. Each gene was downregulated in genotypes treated with the 1,600 mg/kg nickel, while GST expression was increased six folds compared to the water control. The expression of MRP4 and RAN1 genes associated with copper resistance was also investigated. Only the lowest concentrations (13 mg/kg) of copper ions suppressed the expression of these genes while higher concentrations had no effects. This research suggests that P. resinosa is in general resistant to nickel and copper contaminants. Nickel and copper ions affect gene expression, even at low concentrations.