Advances in the mechanisms and multi-omics approaches to nitrogen fertilizer regulation of cadmium uptake and translocation in crops

Soil cadmium (Cd) pollution poses a serious threat to agricultural product safety and human health. As an important agronomic practice in crop production, nitrogen fertilizer management not only sustains crop productivity but also plays a critical role in regulating Cd uptake and accumulation in crops. This review systematically summarizes the multilevel mechanisms underlying the effects of nitrogen fertilizer forms and application rates on Cd uptake and translocation in crops. These mechanisms involve changes in soil chemical properties, such as pH and cation exchange capacity; root physiological processes, including cell wall immobilization and subcellular compartmentalization; and the expression and functions of metal transporter gene families, including natural resistance-associated macrophage proteins (NRAMPs), heavy metal ATPases (HMAs), and zinc-regulated transporter/iron-regulated transporter-related proteins (ZIPs). Particular emphasis is placed on the application of multi-omics approaches, including transcriptomics, proteomics, and metabolomics, to elucidate the integrated regulatory network linking nitrogen signaling, gene expression, protein function, and metabolic responses. Furthermore, this review discusses how different nitrogen forms enhance crop tolerance to Cd stress by regulating key genes and promoting the biosynthesis of detoxification-related metabolites. Finally, we highlight the prospects of integrating multi-omics data with emerging biotechnologies to develop nitrogen management strategies that reduce Cd accumulation while maintaining crop yield, thereby providing a theoretical basis for safer crop production and food security.