Transgenic tobacco plants expressing a P1B-ATPase gene from Populus tomentosa Carr. (PtoHMA5) demonstrate improved cadmium transport

Heavy metal ATPase (HMA) plays an important role in phytoremediation via long-distance transportation from root to shoot. In this report, we identified a heavy metal ATPase gene, PtoHMA5, from Populus tomentosa Carr. Its encoded peptide consists of 967 amino acids and has eight trans-membrane motifs inside. Tobacco plants were transformed with this gene via Agrobacterium tumefaciens-mediated method. After exposure to 50 mg/LCdCl2 for 10 d, the transgenic lines displayed higher cadmium accumulation in leaves than did the wild-type plants with an absolute increase of 25.04%, while the transfer coefficient increased by 16.01%-43.25%. Physiological testing including assessment of relative electrolytic leakage (REL), malondialdehyde (MDA) content, and chlorophyll content revealed that the transgenic lines were seriously affected when compared with the wild-type plants. In summary, PtoHMA5 is really involved in cadmium transport from root to shoot but is not associated with the removal of cadmium toxicity.