Overexpression of TtNRAMP6 enhances the accumulation of Cd in Arabidopsis

The uptake and translocation of non-essential heavy metals in plant are always through metal transporters for essential micronutrient transport, such as NRAMP (Natural Resistance-Associated Macrophage Protein). NRAMPs from different species exhibit different biological functions, although their sequences are highly identical. In the present study, a NRAMP6 was isolated from Ailanmai (Triticum turgidum L. ssp. turgidum). TtNRAMP6, localized on chromosome 3B, was mainly expressed in roots, followed by other tissues varied with different growth stages. At the seedling stage, TtNRAMP6 was significantly regulated by Cd stress in roots, but not by the deficiency of Zn, Fe or Mg. Subcellular localization analysis indicated that TtNRAMP6 encoded a plasma membrane protein. Expressing-TtNRAMP6 significantly enhanced the Cd concentration in yeast, and increased the Cd sensitivity. Meanwhile, overexpression of TtNRAMP6 also increased the Cd concentration in roots, stems, leaves and the whole plant of Arabidopsis, which indicated that overexpression of TtNRAMP6 enhanced the Cd accumulation. Thus, genetic manipulation of TtNRAMP6 may reduce the uptake of Cd from external solution to wheat, finally protecting the safety of wheat food.