Abstract: Cadmium (Cd) pollution severely threatens the safe production of rice, while silicon (Si) exhibits potential in mitigating Cd-induced toxicity. To elucidate the mechanism of Si-mediated alleviation of Cd toxicity, we analyzed the variations in Si and Cd contents in rice lines with differential Lsi1 expression levels (WT, Lsi1-OE, and Lsi1-RNAi) during the tillering and grain-filling stages. The results showed that Cd stress treatment significantly increased Cd accumulation in various rice organs at both growth stages, following the order: Lsi1-RNAi line > WT > Lsi1-OE line. Exogenous Si application significantly reduced Cd accumulation in rice at both stages, with the most pronounced decrease being observed in the Lsi1-OE line. During the grain-filling stage, Cd content in roots, stems, sheaths, and leaves decreased by 56.72%, 55.01%, 36.58%, and 29.70%, respectively. Cd stress inhibited Si accumulation across different rice lines, particularly in the Lsi1-RNAi line, where Si content in roots, stems, sheaths, and leaves decreased by 7.83%, 21.89%, 28.74% and 17.66%, respectively, at the tillering stage. In contrast, WT and Lsi1-OE lines showed relatively little reductions. Exogenous Si application significantly enhanced Si accumulation in roots, stems, sheaths, and leaves of Lsi1-OE plants at both growth stages. In contrast, there were no significant changes in Lsi1-RNAi plants under the same treatment, indicating their limited capacity for Si accumulation under Cd stress. Correlation analysis further confirmed the negative relationship between Cd and Si in rice. The combined approach of Lsi1 overexpression and Si application is an effective strategy for reducing Cd toxicity in rice.

Key words: rice (Oryza sativa), silicon, cadmium, growth stage