Increased accumulation of cadmium and lead under Ca and Fe deficiency in Typha latifolia: A study of two pore channel (TPC1) gene responses

Knowledge of the uptake mechanisms, storage and tolerance to heavy metals by plants is required for improving the phytoremediation process. Nevertheless, the transport mechanisms that determine the internalization of toxic metals, such as Pb and Cd, in plants remain not well understood. We investigated the influence of the Ca, Fe and Zn status on the uptake of divalent cations (Cd²⁺ and Pb²⁺) in cattail (Typha latifolia). The plants (n=3) were exposed to nutrient solutions of Ca, Fe and Zn with Cd or Pb. The cattail plants growing under Ca-deficiency conditions removed and accumulated more Cd and Pb in their tissues; however, this effect was more evident in the case of Cd. The iron status only affected the uptake of Pb, whereas Zn had no evident effect on heavy metal uptake. These results indicate a competition between the divalent cations in the nutrient solution for the uptake mechanisms. To study the mechanistic basis for this response, a Ca²⁺-channel gene TlTPC1 encoding a putative membrane protein was cloned from cattail. The expression of TlTPC1 in the roots of plants growing in solutions containing Cd or Pb increased similarly to that observed in plants growing in solutions with Ca. Additionally, the results showed high correlation coefficients between the differential expression of TlTPC1 and the concentration of Ca, Cd and Pb in the solutions.