Multi-Omics-Identified StAPR3 Enhances Potato Cd Tolerance and Tuber Quality via Sulfur Metabolism and Glutathione Redox Homeostasis

Cadmium (Cd) in agricultural soils inhibits potato growth, disrupts tuber development, and causes Cd accumulation in edible tubers, thereby threatening food safety. Here, we determined the EC50 of Cd in potatoes, which induced oxidative stress and chloroplast damage. Transcriptomic and metabolomic coanalysis identified StAPR3, an APS reductase involved in sulfur metabolism, as a Cd-responsive candidate. Heterologous yeast expression and potato overexpression demonstrated that StAPR3 enhanced Cd tolerance. Under Cd treatment, StAPR3-overexpressing lines maintained superior growth, while wild-type plants showed an oxidative burst and photosynthetic dysfunction. Transgenic tubers exhibited increased yield, higher dry matter, starch, amino acids, and K, Ca, and Mg, lower reducing sugars, and reduced Cd accumulation. Enzymatic assays confirmed that StAPR3 catalyzes APS to AMP; LC-MS/MS showed elevated AMP, cysteine, and glutathione in transgenic lines. Thus, StAPR3 improves Cd tolerance, tuber yield, nutritional quality, and edible safety, offering a genetic target for breeding safe, high-quality potato cultivars on Cd-contaminated soils.