Simultaneous inhibition of Cd and As absorption and transport in rice via coordinated cell wall sequestration, transporter regulation, and chelating ligand synthesis

Simultaneous inhibition of cadmium (Cd) and arsenic (As) absorption and transport in rice (Oryza sativa L.) remains a critical challenge for safeguarding food security. This study investigated the mitigating effects of dicarboxylicdimethylammonium chloride ([Glu][Cl]) on combined Cd and As stress in rice seedlings through hydroponic experiments and identified the underlying physiological and molecular mechanisms. Exogenous [Glu][Cl] application effectively and simultaneously reduced Cd and As accumulation in rice seedlings. At 1.5 mmol·L^-1 [Glu][Cl], Cd and As content in roots decreased by 46.0 %-47.3 % and 53.8 %-56.5 %, respectively, and in the shoots by 37.5 %-38.7 % and 39.5 %-42.8 %, respectively. [Glu][Cl] significantly increased the proportion of Cd and As in the rice cell wall. Additionally, [Glu][Cl] downregulated OsNramp5 expression and upregulated OsGLR3 expression, which is associated with the transmembrane transport of Cd. OsLsi1,2 expression was down-regulated, which mediate the entry of As into cells and xylem. Quantum chemical calculations indicated that Cd/As can be chelated by glutamate, Cysteine, glutathione, and other substances, whose synthesis was promoted by the addition of [Glu][Cl]. In conclusion, [Glu][Cl] inhibited Cd/As absorption and transport in rice by enhancing cell wall sequestration, regulating relevant gene expression, and promoting the synthesis of chelating ligands, which provides new strategies for safe rice production in heavy metal-contaminated environments.