Effects of nickel toxicity on seed germination and expression of genes associated with nickel resistance in Populus tremuloides

Abstract

Although Nickel is an essential nutrient for plant growth in low concentrations, its excessive amounts in soil above threshold values can result in toxicity. The main objectives of the present research were to determine the effects of different doses of nickel on a) trembling aspen (Populus tremuloides) seed germination and b) gene expression. This study revealed that nickel in agarose media even at a low dose inhibits seed germination. In soil however, only the highest dose of 1, 600 mg of Ni per 1 kg of soil has detrimental effects on germination of P. tremuloides seeds. P. tremuloides seedlings were resistant to 150 mg /kg, 400 mg /kg, and 800 mg /kg of Ni doses in growth chamber screening tests. At high Ni dose of 1, 600 mg /kg, differential responses were observed as Ni- resistant, moderately resistant, and susceptible genotypes were identified. Expression of the AT2G16800 gene was repressed with increasing nickel concentration and this effect was most significant at the 800 mg/kg Ni dose. Surprisingly, the study also revealed that the higher concentration of potassium nitrate without nickel (800 mg/kg and 1, 600 mg/kg) induced a significant upregulation of the NAS3 and NRAMP4 genes.