A multi-step protocol to identify silicon- binding proteins

Silicon (Si) is an essential plant nutrient that strongly correlates with stress mitigation. While studies have shown changes in gene expression and enzymatic activity in response to silicon fertilization, few have examined the direct effect silicates and/or silicic acid has on plant proteins or metabolites. Here we report, for the first time, the development of an assay that identifies putative silicon-binding plant proteins. The method identified a Nicotiana tabacum thioredoxin h-type protein (NtTrxH1), that was expressed and shown to bind to the silica-gel matrix. Predictive modeling suggested that silicic acid, Si(OH)4, may interact near the cysteine residues present in the active site of NtTrxH1. However, mutations within the active site of this protein did not alter silica-binding. The use of this Si-binding assay could help identify other candidates important for silicon’s function at the cellular level within plants.