Copper induces a downregulation of the Multidrug resistance protein 4 (MRP4) and Copper-transporting ATPase-RAN1 (RAN1) genes in red pine (Pinus resinosa) at low concentrations

Copper is required in plant tissues at small concentrations for several physiological processes; however, excess metal can cause toxicity. The main objectives of this study were to (1) evaluate Pinus resinosa resistance to different concentrations of copper, and (2) assess changes induced by copper ions on gene expression. The targeted genes include the Multidrug resistance protein 4 (MRP4) and Copper-transporting ATPase-RAN1 (RAN1). P. resinosa seedlings were treated with different concentrations of copper sulphate and corresponding salt controls in growth chamber screening tests. These concentrations include 13, 130 mg and 1300 mg of copper per 1 kg of dry soil. Potassium sulfate and water were used as controls. The expression of MRP4 and RANI genes was assessed using RT-qPCR. All the genotypes tested were resistant to copper. There was a significant suppression of the MRP4 and RANI genes at the lowest concentration of copper (13 mg/kg) in comparison to the water control. Further increases in the copper concentrations (130 mg /kg and 1300 mg/kg) did not induce any significant change in gene expression. Overall, this study showed that P. resinosa is in general resistant to copper contaminants. However, copper ions affect gene expression, even at low concentrations.