Functional analyses of TaHMA2, a P1B‐type ATPase in wheat

Summary Currently, there are few studies concerning the function of heavy metal ATP ase 2 ( HMA 2), particularly in monocotyledons, and the potential application of this protein in biofortification and phytoremediation. Thus, we isolated and characterized the T a HMA 2 gene from wheat ( T riticum aestivum L .). Our results indicate that T a HMA 2 is localized to the plasma membrane and stably expressed, except in the nodes, which showed relatively high expression. Zinc/cadmium ( Z n/ C d) resistance was observed in T a HMA 2 ‐transformed yeast. The over‐expression of T a HMA 2 increased the elongation and decreased the seed‐setting rate in rice ( O ryza sativa L .), but not A rabidopsis thaliana , tobacco ( N icotiana tabacum L .) or wheat. T a HMA 2 over‐expression also improved root‐shoot Z n/ C d translocation, especially in rice. The seeds of transgenic rice and wheat, not tobacco, showed decreased Z n concentrations. The Z n concentration was decreased in all parts of the transgenic rice seeds, but was decreased only in the ventral endosperm of wheat, which showed an increased Z n concentration in the embryo and aleurone. The over‐expression of T a HMA 2 improved plant tolerance under moderate Z n stress and Z n deficiency, but Z n and C d resistance decreased under high levels of Z n and C d stress, respectively. The C d concentration in transgenic rice seedlings was dramatically increased under Z n deficiency. Thus, over‐expression of T a HMA 2 showed a more obvious phenotype in monocotyledons than in dicotyledons. These findings provide important information for T a HMA 2, and more efforts should be made in the future to characterize the reduced Z n concentration in T a HMA 2 transgenic grains and the diversity of T a HMA 2 substrate specificity.