α ‐Ketoglutarate Mitigates Cadmium Accumulation and Enhances Cadmium Tolerance in Rice via Concentration‐Dependent Regulation of Antioxidant Defence and Root Radial Transport Restriction

ABSTRACT Rice is a major crop in China with a strong tendency to accumulate cadmium (Cd), posing serious risks to grain safety. α ‐Ketoglutarate (AKG), a key tricarboxylic acid cycle intermediate, has known roles in abiotic stress responses, but its effects on Cd tolerance and accumulation in rice remain unexplored. Exogenous AKG (50 μmol/L) was applied to investigate the mechanism regulating Cd tolerance and accumulation under both hydroponic and soil conditions. Under hydroponic experiments, exogenous AKG significantly reduced Cd translocation by 56.8%–63.9%, and decreased shoot Cd accumulation by 54.9%–60.6%. It alleviated photoinhibition and oxidative damage by enhancing photosynthesis and antioxidant activities while lowering H 2 O 2 and MDA. Mechanistically, multi‐omics analyses showed AKG confers Cd tolerance and Cd restriction concentration dependently. Under moderate Cd stress, AKG predominantly enhances the ascorbate–glutathione cycle and flavonoid biosynthesis for antioxidative defence, while upregulating OsHMA3 and reinforcing the endodermal barrier to restrict Cd transport. Under severe Cd stress, AKG shifts to activating melatonin biosynthesis and further suppressing transporters like OsIRT1 . Additionally, AKG reduced grain Cd by 40.7% and increased yield by 31.6% under soil conditions. These results demonstrated the effective role of AKG in integrated Cd mitigation and provide a novel strategy for safe rice production in Cd‐contaminated soils.