Homolog of Human placenta-specific gene 8, PcPLAC8-10, enhances cadmium uptake by Populus roots

Cadmium (Cd) pollution of soil occurs worldwide. Phytoremediation is an effective approach for cleaning up Cd polluted soil. Fast growing Populus species with high Cd uptake capacities are desirable for phytoremediation. Thus, it is important to elucidate the molecular functions of genes involved in Cd uptake by poplars. In this study, PcPLAC8–10, a homolog of Human placenta-specific gene 8 (PLAC8) implicated in Cd transport was functionally characterized in Populus × canescens. PcPLAC8–10 was transcriptionally induced in Cd-treated roots and it encoded a plasma membrane-localized transporter. PcPLAC8–10 exhibited Cd uptake activity when expressed in yeast cells. No difference in growth was observed between wild type (WT) and PcPLAC8–10-overexpressing poplars. PcPLAC8–10-overexpressing poplars exhibited increases in net Cd2+ influxes by 192% and Cd accumulation by 57% in the roots. However, similar reductions in biomass were found in WT and transgenic poplars when exposed to Cd. The complete motif of CCXXXXCPC in PcPLAC8–10 was essential for its Cd transport activity. These results suggest that PcPLAC8–10 is a plasma membrane-localized transporter responsible for Cd uptake in the roots and the complete CCXXXXCPC motif of PcPLAC8–10 plays a key role in its Cd transport activity in poplars.