Opaline silica bodies (phytoliths) are found in plants, particularly grasses, and primarily contribute to plant strength and protection. They form from silicic acid, which is transported from the soil to the leaves - a process that is still being researched. Key transmembrane proteins involved in this transport are Lsi1, Lsi2, Lsi3, and Lsi6, with Lsi1 being the most well understood. Our study focuses on determining the structures of Lsi2, Lsi3, and Lsi6 in rice, revealing an α-helix composition and heterogeneous silicon transport sites, with findings validated using AlphaFold2. Lsi1 and Lsi6 share highly comparable structures, while Lsi2 and Lsi3 also show significant structural similarities. Previous research has shown that in certain regions, the pore sizes of Lsi1 proteins are smaller than Si(OH)4, facilitating effective silicic acid transport through hydrogen bonding with amino acids. Molecular dynamics (MD) simulations over 200 ns demonstrate that this hydrogen bonding enhances the transport of Si(OH)4 during protein conformational changes. Using quantitative real-time PCR (qRT-PCR), the OsLsi3 gene was expressed most strongly in the root, in both wild and cultivated rice plants. Spectrophotometric analysis revealed significant variations in silicon content across different tissues, with the root displaying the highest intensity around ∼ 415 nm, indicating greater silicon concentration. Together, these structural, expression, and compositional analyses provide new insights into the organisation and potential functional roles of silicon transporters in rice. Our research paves the way for improving secure and sustainable rice yield through the precise manipulation of the selectivity of Lsi2, Lsi3, and Lsi6.
Sepay et al. (2026) studied this question.