Multilevel mechanisms of potassium-mediated cadmium detoxification in Brassica napus: Insights from physiological, biochemical, and transcriptomic analyses

. Mechanistically, this alleviation was linked to a fortified antioxidant defense system, evidenced by enhanced activities of catalase (CAT) and peroxidase (POD) by 54.2 % and 15.7 %, respectively. Transcriptomic analysis provided deeper insights, revealing that K-mediated tolerance involves enhanced Cd(II) sequestration. K supplementation significantly up-regulated genes encoding tonoplast-localized transporters (CAX and HMA) responsible for vacuolar Cd(II) import, while simultaneously down-regulating the vacuolar Cd(II) efflux gene NRAMP4. This was complemented by an increase in ion-bound pectin and cellulose in the cell wall, further restricting Cd(II) mobility. Furthermore, K appeared to modulate key signaling pathways, as the expression of PYL genes, encoding abscisic acid (ABA) receptors, was significantly induced. Collectively, our findings demonstrate that K alleviates Cd(II) toxicity in B. napus through a multi-pronged strategy encompassing the enhancement of antioxidant capacity and the promotion of Cd(II) sequestration in both vacuoles and cell walls, potentially regulated via an ABA-dependent pathway. This research provides a theoretical basis for optimizing K fertilization to improve phytoremediation efficiency in Cd-contaminated agricultural soils.