Synergistic effect of silicon and selenium on the alleviation of cadmium toxicity in rice plants

Highlights: • A strong synergistic effect of Si and Se on Cd toxicity alleviation was observed. • Si-Se interaction up-regulated OsNramp1 and OsMHA3, and down-regulated OsHMA2. • Si-Se interaction increased glutathione (GSH) and phytochelatin (PC) content. • Si-Se interaction made more Cd distributed in cell walls and organelles. • Si-Se interaction decreased Cd transport coefficient and accumulation in shoots. Silicon (Si) and selenium (Se), two beneficial elements that alleviate cadmium (Cd) toxicity, are important for agricultural production and human health. However, the effects and related mechanisms of Si-Se interaction on Cd toxicity alleviation are still poorly understood. Herein, a hydroponic experiment was employed to evaluate the effects of Si and Se alone and together, on the growth, Cd content, and biochemical parameters of Cd-treated rice plants. The results revealed that both Si and Se can effectively alleviate Cd toxicity, and a strong synergistic effect of Si and Se was observed. Simultaneous use of Si and Se significantly promoted rice plant growth, decreased malondialdehyde (MDA) content in both the roots and shoots, and reduced Cd translocation factor leading to a significant 73.2 % decrease in shoot Cd content. Additionally, Si-Se interaction increased glutathione (GSH) content, phytochelatin (PC) content and Cd distribution in root cell walls and organelles. Furthermore, the relative expression of OsHMA2 was down-regulated, while those of OsNramp1 and OsMHA3 were up-regulated. The above findings suggest that synergistic effect of Si and Se on Cd toxicity amelioration occurs mainly via regulating gene expression, sequestering Cd in the root cell walls and organelles, and reducing Cd transfer to the shoots.