Abstract: Arsenic (As) enters rice roots mainly through the silicon and phosphorus transport channels. Thus, the rational application of silicon and phosphate fertilizers could effectively regulate the uptake and transport of As in rice plants. The effects and molecular mechanism of silicon- or phosphorus-enriched rice seedlings on the As content in brown rice after transplanting to As-contaminated soil were studied. The results show that, in silicon- or phosphorus-enriched seedlings, the total accumulated amounts of silicon or phosphorus in the seedling were increased to 19.6 and 2.3 times that of the control, respectively, without affecting plant growth. Compared with conventionally raised seedlings, the contents of total As, As(Ⅲ), As(Ⅴ) and dimethylated As (DMA) in brown rice of silicon-enriched seedlings were decreased by 31.1%, 32.1%, 58.3%, and 33.5%, respectively. In phosphorus-enriched seedlings, no significant effect was observed on the total As content in brown rice, but the As(Ⅴ) content in brown rice was reduced by 59.2%. The silicon- or phosphorus-enriched seedlings could result in significant increase of the retention of As in the roots of rice plants, and the transfer coefficients between different parts of the rice plant were affected to different degrees. The relative expression levels of As transport-related genes in the roots of silicon- and phosphorus-enriched seedlings were examined. No significant effect was observed on the relative expression of OsLsi1 in silicon-enriched seedlings, but the relative expression level of OsLsi2 was decreased by 26%. The relative expression of OsABCC1 was up-regulated by 203% in silicon-enriched seedlings. The relative expression level of OsPT1 was not significantly affected by the raising of phosphorus-enriched seedlings, but the relative expression levels of OsPT4 and OsPT8 were decreased by 51% and 71%, respectively. The relative expression level of OsABCC1 was up-regulated by 22% in phosphorus-enriched seedlings. In conclusion, the raising of silicon- or phosphorus-enriched seedlings affects the uptake and transport of As in rice plants by regulating the expression of As-related transport genes in the roots, thereby reducing the As content in brown rice. The results provide an important reference for controlling the risk of As contamination in paddy fields.

Key words: seedling raising, silicon, phosphorus, transporter gene, arsenic species