Wheat ZIP3-2A encodes a metal transporter for Cd influx

Cadmium (Cd) accumulation in wheat grains occurs via three key physiological processes: root uptake, root-to-shoot translocation and/or shoot Cd distribution. Wheat ZIP transporters are hypothesized to involved in these pathways, their functional roles remain poorly characterized. Here, we identified and functionally characterized TpZIP3-2A from dwarf Polish wheat (DPW,Triticum polonicumL., AABB), which mediates Cd, Zn, Fe and Co transport. Expression pattern and subcellular localization analysis revealed that TpZIP3-2Aencoding a plasma membrane protein, was mainly expressed in roots, flag leaves, peleas, lemmas and grains of DPW, which was growth stage-dependent. Its transcript in roots was up-regulated by Zn or Fe deficiency and Co or Cd supplementation. Expression of TpZIP3-2A in yeast increased the sensitivities and concentrations of Cd (by 104.84 %), Zn (by 36.12 %) and Co (by 81.87 %). The TpZIP3-2A-overexpressing lines of Arabidopsisshowed sensitivity to Cd or Co stress and tolerance to Zn or Fe deficiency, and had higher root and shoot concentrations of Cd (61.17 % and 125.82 %), Co (27.65 % and 88.81 %), Zn (36.87 % and 70.04 %) and Fe (46.02 % in shoots), as well as root-to-shoot translocation factors (24.27 %–54.50 %). However, Tpzip3-2a (a mutation of  TpZIP3-2A lacking the first transmembrane domain) had no ability to transport Cd, Zn and Fe. The study provides new insights into the molecular mechanisms regulating Cd uptake and translocation in wheat and offers potential applications for breeding low-Cd accumulating wheat cultivars.