CRISPR/Cas9-mediated editing of ZmNRAMPL5 generates maize with reduced cadmium accumulation and uncompromised yield

Cadmium (Cd) in agricultural soils readily accumulates in crop grains and shoots, posing serious risks to food and feed safety, especially in maize ( Zea mays L.). Natural resistance-associated macrophage proteins (NRAMPs) constitute a key family of metal transporters; however, their role in Cd uptake in maize remains unclear. In this study, the maize gene ZmNRAMPL5 mediated Cd uptake when expressed in yeast. ZmNRAMPL5 knockout mutants, which exhibited no differences from wild type under normal conditions but showed reduced Cd accumulation, alleviated toxicity, increased tolerance under Cd stress. Pot experiments under simulated light and moderate Cd-contaminated soils further showed that knockout lines maintained silage biomass and exhibited over 60 % and 80 % increases in grain yield per ear compared with wild type, respectively. Moreover, Cd concentrations in stems, leaves, and grains of knockout lines were significantly reduced and remained well below China’s national safety thresholds. Thus, ZmNRAMPL5 might be used in developing Cd-tolerant, low-Cd maize germplasm for grain and feed production in Cd-contaminated farmlands.