The TaWRKY22–TaCOPT3D Pathway Governs Cadmium Uptake in Wheat

Cadmium (Cd) is a toxic non–essential element to plants, and its accumulation in crops has significant adverse effects on human health. The cross–talk between copper (Cu) and Cd has been reported, but the molecular mechanisms remain unknown. Here, the function of wheat Cu transporter 3D (TaCOPT3D) in Cd tolerance was investigated. The TaCOPT3D transcripts significantly accumulated in wheat roots under Cd exposure. To test whether TaCOPT3D was involved in response to Cd stress, overexpressing lines with altered expression of TaCOPT3D transporters were compared to wild–type (WT) plants. The results showed that, under 20 μM Cd treatment, TaCOPT3D–overexpression lines exhibited more biomass and lower Cd accumulation in roots, shoots, and grains compared to WT plants. In addition, the TaCOPT3D–overexpression lines demonstrated less reactive oxygen species (ROS) and a greater amount of active antioxidant enzymes under Cd conditions than WT plants. Moreover, TaCOPT3D–overexpression lines highly reduced Cd accumulation under exposure to 20 μM Cu. The regulation pathway of TaCOPT3D in response to Cd stress was investigated, and transcription factor (TF) TaWRKY22, which targeted the TaCOPT3D promoter, was identified. Therefore, TaCOPT3D can serve as a candidate gene for decreasing Cd accumulation in wheat through genetic engineering.