Effects of selenium on sulfate transporter genes in rice and the functional characterization of the OsSULTR1;1 gene in selenium homeostasis in arabidopsis

Sulfate transporters in rice are reported to be involved in abiotic and heavy metal stresses. However, the regulation of these transporters and their functional characterization in relation to selenate treatment remain elusive. The focus of this research was to analyze the expression profiles of rice sulfate transporters at vegetative and reproductive stages. The transporters exhibited diverse expression patterns in response to Se treatment and displayed tissue specificity, suggesting their varied functional roles. OsSULTR1;1 was selected as a candidate gene due to its expression under low sulfur (S) conditions (15 µM) and its high root tissue specificity, both of which were further enhanced by Se treatment. Subcellular localization revealed that the OsSULTR1;1 protein localizes to the plasma membrane, implicating its role in root uptake of Se. To further characterize this gene, it was genetically transformed into Arabidopsis thaliana. Overexpression (OX) of the gene in Arabidopsis resulted in enhanced growth, development, and uptake of mineral nutrients compared to wild-type (WT) plants, suggesting a role in efficient nutrient acquisition. OX plants subjected to time- and concentration-dependent Se treatment accumulated significant levels of Se in their tissues. Se was found to be toxic for both OX and WT plants at higher concentrations (10, 25, and 50 µM), suggesting its beneficial effects at low concentrations. The significantly enhanced Se levels in seed and shoot tissues of OX plants compared to WT plants indicate the functional role of OsSULTR1;1 in Se uptake from the rhizosphere. A rhizosphere acidification assay revealed that OX Arabidopsis plants exude more efficiently, causing a significant change in rhizosphere pH compared to WT plants. This suggests a secondary active transport mechanism. OX plants exhibited increased tolerance to abiotic stresses such as heat, cadmium, lead, and aluminum. Taken together, these findings suggest that OsSULTR1;1 is a potential candidate gene for Se accumulation for biofortification purposes. It may also play a role in plant tolerance to climate change and environmental stresses, potentially contributing to sustainable agricultural productivity under global warming conditions.