Potassium alters cadmium accumulation and translocation by regulating root cell wall biosynthesis in Brassica napus

• K decreased Cd accumulation and translocation in Brassica napus . • K enhanced Cd chelation in RCW by promoting lignin and cellulose contents. • FTIR showed that K promoted the functional groups related to lignin and cellulose. • K promoted the gene expressions related to root cell wall biosynthesis. • K affected gene expressions responsible for Cd uptake and translocation. Large areas of soil in southern China are contaminated with cadmium (Cd) and deficient in potassium (K). The aim of this study was to investigate the biochemical and molecular mechanisms underlying the effect of K on Cd accumulation in Brassica napus ( B. napus ) under different K (0.3 and 6 mM) and Cd conditions (0 and 5 μM). High K application significantly decreased Cd concentrations in both shoots and roots by 67.06 % and 27.15 %, respectively, and reduced the Cd translocation factor from 0.074 to 0.034. More Cd was sequestered within the cell wall, resulting in a 60 % increase in root cell wall Cd concentration under high K levels. Transcriptome sequencing revealed that K induced the upregulation of genes responsible for cellulose and lignin biosynthesis, thereby enhancing their contents. Furthermore, K notably stimulated the expression of pectin methylesterase (PME) genes, which can increase Cd binding sites through the demethylation of pectin. In conclusion, our findings suggest that K application primarily reduces Cd accumulation by promoting its retention in the root cell wall.