Differential Gene Transcription in Red Oak (Quercus rubra) Genotypes Resistant to Copper Toxicity

Toxicity of metals is a major abiotic stressor of plants. Copper (Cu) is one of the most abundant metals in soils from the Greater Sudbury Region (GSR) due to its mining history. Recent studies have described several transporters and chelating proteins involved in copper resistance. Quercus rubra (Red Oak) is a common species that grows in metal contaminated soils in Northern Ontario (Canada). The main objectives of this study were1) to evaluate the toxicity of copper to Q. rubrum plants and 2) assess the level of transcriptionof genes associated with copper resistance (RAN1, MT2b and MRP4). Q. rubra seedlings were grown in growth chambers and treated with copper at different doses. Total RNA was extracted from leaves and amplified by RT-qPCR. All the plants tested were resistant to Cu even at high concentrations of 1312 mg of Cu per kg of dry soil since no damage associated with Cu toxicity was observed after 14 days of treatment. RAN1 transporter and the chelating protein MT2b were significantly downregulated (p≤0.05) at high doses of 656 mg and 1312 mg of copper per kg of dry soil compared to water control. The transcription of MRP4 was significantly increased in the presence of copper at a concentration of 1312 mg/kg. No gene demonstrated differential transcription in samples treated with a low dose of 130 mg of copper/kg of dry soil that is equivalent to the bioavailable amount of copper under natural conditions in the Greater Sudbury Region.