Physiological, transcriptomic, and metabolomic integrated analyses reveal key factors involved in manganese sulfate mitigating cadmium toxicity in wheat.

Manganese (Mn) has been reported to play a beneficial role in alleviating heavy metal toxicity in plants. However, the molecular mechanisms through which manganese sulfate (MnSO4) mitigates cadmium (Cd) toxicity in wheat remain poorly understood. Herein, we conducted a hydroponic experiment to explore the Cd and Mn accumulation, cell wall components, antioxidative system, transcriptomic and metabolomic responses of wheat seedlings after MnSO4 application under Cd stress. Results showed that MnSO4 application significantly decreased root and shoot Cd contents (69.98 % and 29.04 %) by increasing root and shoot Mn contents, fixing Cd in cell walls (22.57 %) and pectin (51.23 %), upregulating the expression of lignin and pectin synthesis-related genes, and increasing cell wall structure-related metabolites. Additionally, MnSO4 regulated the absorption and efflux of Cd in wheat roots by altering the expression of genes related to membrane transporters and vesicle formation, and increasing the contents of non-protein sulfhydryl and phytochelatins. Furthermore, MnSO4 alleviated Cd toxicity by regulating genes related to signal transduction and metabolites related to tricarboxylic acid, amino acid, and fatty acid synthesis. Overall, we demonstrated that MnSO4 alleviates Cd toxicity in wheat roots by regulating cell wall polysaccharides, membrane transporters, and antioxidative substances through signaling pathways at both transcriptional and metabolic levels. These findings enhanced our understanding of the molecular mechanism by which MnSO4 promotes Mn biofortification and mitigates Cd accumulation in wheat, providing a theoretical basis for the future application of functional fertilizers in Cd-contaminated wheat fields.