Mutation of TaNRAMP5 impacts cadmium transport in wheat

Cadmium (Cd) pollution significantly impacts the normal growth, development, and food safety of wheat. Employing modern molecular biology techniques represents an effective strategy for cultivating low-Cd wheat. Natural resistance-associated macrophage protein 5 (NRAMP5) is a critical heavy metal transporter, however, its function in wheat, particularly in response to Cd stress, remains largely unexplored. Here, we employed the CRISPR/Cas9 gene-editing technology to generate TaNRAMP5 knockout lines (KO). Cd content in wheat was detected by inductively coupled plasma mass spectrometry (ICP-MS). And RNA sequencing was used to explore the key factors of Cd stress response in wheat. The results indicated that under Cd stress, the KO lines exhibited significantly reduced Cd accumulation in the roots compared to the wild type (WT) plants, while the shoots showed an opposite trend. Notably, the knockout of TaNRAMP5 resulted in a 33.46 % reduction in Cd concentration in the grains. Furthermore, the knockout of TaNRAMP5 led to a decrease in wheat grain yield; however, the application increased amounts of compound fertilizers can mitigate the yield loss associated with the TaNRAMP5 mutant. Additionally, transcriptome sequencing revealed significant differences in gene expression profiles between KO and WT plants under Cd stress, particularly in the root samples. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that the differently expressed genes (DEGs) induced by Cd stress were primarily involved in processes of "plant hormone signal transduction", "starch and sucrose metabolism", and "phenylpropanoid biosynthesis". Overall, our results suggested that the knockout of TaNRAMP5 can effectively reduce Cd accumulation in wheat. These findings may provide a potential genetic basis for the improving of wheat varieties to reduce Cd contamination in grains and ensure food safety.