BjZIP1, a plasma membrane-localized transporter, mediates cadmium and zinc uptake in Brassica juncea

BjZIP1 is a plasma membrane-localized protein. Overexpression of BjZIP1 in yeast, Arabidopsis thaliana, and Brassica juncea hairy roots confirmed its role in promoting Cd/Zn uptake. Heavy metal contamination in agricultural soils significantly threatens global food security. While Brassica juncea is recognized as a promising hyperaccumulator for phytoremediation, the specific transporters mediating its metal uptake remain largely unexplored. Here, we identify BjZIP1, a plasma membrane-localized protein that functions as a transporter for cadmium (Cd) and zinc (Zn) uptake in B. juncea. Heterologous expression of BjZIP1 in Cd-sensitive yeast mutant (Δyap1) increased intracellular accumulation of Cd and Zn by 17.8% and 25.0%, respectively, and consequently enhanced metal sensitivity. In Arabidopsis thaliana, BjZIP1 overexpression lines accumulated 31.1-58.3% more Cd and 1.68-2.48-fold higher Zn in roots under metal stress, which was accompanied by a growth inhibition phenotype. Crucially, BjZIP1-overexpressing B. juncea hairy roots accumulated 1.05-1.30-fold more Cd and 1.42-1.92-fold more Zn, alongside a concomitant exacerbation of cellular damage under Cd exposure. Collectively, our results establish BjZIP1 as a plasma membrane transporter responsible for Cd and Zn uptake in B. juncea, thereby providing a promising molecular target for genetic enhancement of phytoremediation efficiency.