Abstract
Vegetable crops grown on a high nickel-contaminated soil often show toxic symptoms, due to the over-accumulation of nickel. However, we have limited information on the molecular mechanism of nickel uptake, and this prevents to create an effective solution. This time we proposed a hypothesis that excess nickel was miss-transported by the transporters of other heavy metals, and examined the possibility of excess nickel uptake via uptake system of iron, which is a primary micro essential nutrient, in root of Arabidopsis thaliana. Plant samples were cultured hydroponically under two iron condition (0 or 50 μM Fe(III)-EDTA), then exposed to 25 μM NiCl2. As a result, iron-unsupplemented samples showed visible nickel phytotoxic symptoms and increased their nickel concentration 70% higher than those of iron-supplemented. Next we examined nickel transport activity of IRT1, a high-affinity iron transporter in root, using yeast-expression system. The strain expressing IRT1 was more sensitive to nickel, and showed 2-fold higher nickel accumulation compared to control. These results suggested that nickel is transported via IRT1 iron uptake system of root under excess nickel condition.
