Expression of New Pteris vittata Phosphate Transporter PvPht1;4 Reduces Arsenic Translocation from the Roots to Shoots in Tobacco Plants.

Arsenic-hyperaccumulator Pteris vittata is efficient in As uptake, probably through phosphate transporters (Pht). Here, for the first time, we cloned a new PvPht1;4 gene from P. vittata and investigated its role in arsenate (AsV) uptake and transport in yeast and transgenic tobacco plants. Based on qRT-PCR, PvPht1;4 was abundantly expressed in P. vittata fronds and roots, with its transcripts in the roots being induced by both P deficiency and As exposure. PvPht1;4 was localized to the plasma membrane, which complemented a yeast-mutant defective in P uptake and showed higher P transport affinity than PvPht1;3. Under AsV exposure, PvPht1;4 yeast transformants showed comparable tolerance as PvPht1;3, but higher As accumulation than PvPht1;2 transformants, indicating that PvPht1;4 had considerable AsV and P transport activity. However, in soil and hydroponic experiments, PvPht1;4 expressing tobacco lines accumulated 26-44% and 37-55% lower As in the shoots than WT plants, with lower root-to-shoot As translocation. In the roots of PvPht1;4 lines, higher glutathione (GSH) contents and expression levels of GSH synthetase gene NtGSH2 corroborated with better AsIII complexation and detoxification. In addition, the transcripts of As-GSH transporter NtABCC1 in PvPht1;4 lines were up-regulated. The data suggested that PvPht1;4 lines probably detoxified As by complexing As with GSH, which was stored in root vacuoles, thereby reducing As translocation in transgenic tobacco. Given its strong AsV transport capacity, expression of PvPht1;4 provides a new molecular approach to reduce As-accumulation in plant shoots.