Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume using an unknown biological factor. Using bioinformatics tools, we identified a previously uncharacterized protein in Sorghum bicolor, which we named Siliplant1 (Slp1). Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. We found Slp1 RNA in sorghum immature leaf and immature inflorescence. In leaves, transcription was highest just before the active silicification zone (ASZ). There, Slp1 was localized specifically to developing silica cells, packed inside vesicles and scattered throughout the cytoplasm or near the cell boundary. These vesicles fused with the membrane, releasing their content in the apoplastic space. A short peptide that is repeated five times in Slp1 precipitated silica in vitro at a biologically relevant silicic acid concentration. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell types. Our results show that Slp1 precipitates silica in sorghum silica cells.

中文翻译：

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Siliplant1 (Slp1) 蛋白在高粱二氧化硅细胞中沉淀二氧化硅。

硅以硅酸的形式被植物根部吸收。酸随着蒸腾流移动到枝条，并矿化为二氧化硅。在草中，称为二氧化硅细胞的叶表皮细胞使用未知的生物因子在其大部分体积中沉积二氧化硅。使用生物信息学工具，我们在双色高粱中鉴定了一种以前未表征的蛋白质，我们将其命名为 Siliplant1 (Slp1)。Slp1 是一种碱性蛋白质，具有七个富含脯氨酸、赖氨酸和谷氨酸的重复单元。我们找到了Slp1高粱未成熟叶和未成熟花序中的 RNA。在叶子中，就在活性硅化区 (ASZ) 之前转录最高。在那里，Slp1 专门定位于发育中的二氧化硅细胞，填充在囊泡内并分散在整个细胞质或细胞边界附近。这些囊泡与膜融合，在质外体空间释放它们的内容物。在 Slp1 中重复五次的短肽在生物相关的硅酸浓度下在体外沉淀二氧化硅。Slp1 在高粱中的瞬时过表达导致所有叶表皮细胞类型中的异位二氧化硅沉积。我们的结果表明 Slp1 在高粱二氧化硅细胞中沉淀二氧化硅。