Expression of the Phytochelatin Synthase TaPCS1 in Transgenic Aspen, Insight into the Problems and Qualities in Phytoremediation of Pb

The response of Populus tremula x tremuloides cv. Etrepole transgenic lines expressing the phytochelatin synthase TaPCS1 for Pb tolerance and accumulation was studied. In a hydroponic experiment, the concentrations of Pb in plants did not differ significantly between any of the transgenic lines assayed and the wild type (wt) plants, with any of the Pb solutions tested. However, total biomass and Pb accumulation were significantly higher in transgenic lines (PTa3, PTa5, PTa10) than in the control (wt) line when the plants were grown in solutions containing 0.75 and 1.5 mM Pb. The PTa3 and PTa5 lines accumulated 1.7 times more Pb than the wt plants. A concentration of 3.0 mM Pb was found to be toxic for both transgenic and wt plants. Biomass production was higher in transgenic lines PTa3 and PTa5 than in the wt plants growing in M4 mining soil, accumulating more Pb and Zn than in the wt plants. When the plant material was grown in soil M15, none of the parameters differed significantly between the transgenic and wt plants. The different response in soils M4 and M15 indicated that the physicochemical properties of the soil play a determinant role in the phytoremediation potential.