Endogenous Mechanisms of Selenium-Induced Antagonism against Cadmium Toxicity in Crops: Integration and Reconstruction of a Multilevel Defense Network

Selenium (Se) orchestrates a multilevel endogenous defense network in crops against cadmium (Cd) toxicity. This network operates from rhizosphere immobilization (e.g., Cd-Se complexes, microbiome interactions, iron plaque, and root exudates) and subcellular sequestration via transporter regulation (e.g., OsNramp5, OsHMA3) to antioxidant enhancement and selenoprotein activation. Critically, Se acts as a signaling initiator, engaging pathways (e.g., GATA3-COMT1-melatonin) to systemically reprogram stress responses. This review highlights that Se's antagonistic efficacy is form-, dose-, and genotype-dependent, providing a mechanistic basis for precision agronomic strategies. Future efforts must bridge laboratory findings to field applications by elucidating molecular switches and developing integrated predictive technologies.