Effects of silicon on the uptake and accumulation of arsenite and dimethylarsinic acid in rice (Oryza sativa L.).

Accumulation of arsenite [As(III)] and dimethylarsinic acid (DMA) in rice grainsposes a threat to human health. Although silicon (Si) has been reported to reduce As uptake, the mechanisms involved are not fully understood. In this study, we first confirmed that the concurrent addition of Si and As in solution decreased As accumulation in rice. Then, the effect of Si previously deposited in shoots by the pretreatment of rice seedlings with Si for one week was investigated by using lsi2 mutant and its wild type. The uptake of both As(III) and DMA decreased in rice subjected concurrently to Si and As (III)/DMA in solution, without effects on OsLsi1 and OsLsi2 expression. This concurrent treatment also decreased total As concentration in the root cell walls and xylem sap, which might have restrained apoplastic transport of As to shoots. Silicon previously deposited in the shoots decreased root-to-shoot As(III) translocation and down-regulated OsLsi1, OsLsi2 and OsNRAMP1, but did not affect As concentration in the roots, and had no effect on DMA uptake and accumulation in shoots and roots either. This study sheds light on the role of silicon in solution and rice shoots in As(Ⅲ) and DMA uptake and transport by rice.