Response of Trembling Aspen (Populus tremuloides) to Nickel Toxicity: Analysis of Gene Expression.

Long term exposure to toxic levels of nickel (Ni) and other heavy metals can lead to some woody plant species like trembling aspen (Populus tremuloides) to develop metal resistant populations. It has been reported recently that P. tremuloides accumulates nickel in leaves. Mechanisms of heavy metal resistance as well as genes associated with Ni tolerance in trembling aspen (Populus tremuloides) are unknown. Candidate genes for Ni resistance have been identified from model plant organisms. The main objectives of the present study were to 1) assess the level of nickel toxicity in P. tremuloides and 2) identify genes associated with Ni resistance and their expression levels at different doses of Ni treatments. Six month old P. tremuloides seedlings were treated with varying doses of nickel (150 mg / kg, 800 mg / kg, and 1,600 mg/kg) in greenhouse screening tests. Nickel resistant and susceptible plants were identified. Six candidate genes for nickel resistance in non-model plants were targeted for this study. Their expression in P. tremuloides under different conditions will be discussed.