Influence of nitrate on uptake and translocation of organophosphate esters in wheat (Triticum aestivum L.)

Tris(2-chloroethyl) phosphate (TCEP) and tributyl phosphate (TnBP) are the typical organophosphate esters (OPEs), and detected in high concentrations and frequencies in environment. Nitrate, as an essential plant nutrient, can regulate the environmental behaviors and fates of pollutants within plants. However, the underlying mechanisms of mediation of nitrate on environmental behaviors of OPEs in plants remained unclear. This study integrated compound-specific stable isotope analysis, transcriptomics, and molecular docking simulations to systematically investigate the effects of nitrate on the uptake and translocation of TCEP and TnBP in wheat. Results showed that nitrate with low (LN, 40 mg/L NaNO 3 ) and high levels (HN, 100 mg/L NaNO 3 ) significantly inhibited the root uptake and translocation to shoots of TCEP and TnBP, with the higher inhibition effects for LN than HN. Compound-specific stable isotope analysis revealed that nitrate reduced TCEP uptake via aquaporins in wheat roots, specifically inhibiting the transmembrane transport of TCEP molecules with heavy carbon isotopes. Transcriptomic and molecular docking simulations consistently demonstrated that the nitrate-specific transporters of SLAH2 and NRT1 were involved in mediating the transmembrane transport of TCEP, and nitrate inhibited TCEP transport via the downregulation of gene expression of SLAH2 and NRT1 and competitive binding to active sites of these two transporters with TCEP. Overall, this study clarified that nitrate could effectively suppress the root uptake of TCEP and TnBP in wheat, providing a basis for developing application of nitrate to mitigate OPE contamination in crops.