Physiological and molecular modeling investigations of the relationship between sulfate and chromium VI uptake in Vicia faba L.

Abstract

According to previous studies, Cr(VI) uses membrane transporters of other molecules like the sulfate to penetrate into root cells. The objective of our work is to study the interaction between sulfate and Cr(VI). To visualize this interaction, we used three concentrations of S (10 mM (S10), 50 mM (S50) and 100 mM (S100)) added alone or in combination with 50 ppm Cr(VI). At the morpho-physiological scale the variation of aerial, leaf and root biomass, total chlorophyll content, H2O2 content, CAT and APX activity were determined. At the molecular level, we used molecular docking to study the interaction between Cr(VI)/SO42− and the sulfate transporter, we chose the Arabidopsis thaliana sulfate transporter (AtSULTR) as a module in our study. The findings of our work showed that Cr(VI) reduced the morpho-physiological parameters and induced the hyperproduction of H2O2 and consequently stimulated the antioxidant activities. The addition of MgSO4 significantly improved all the studied parameters, restored and neutralized the harmful effect of Cr (VI) on the faba bean plants while restoring the morpho-physiological parameters to normal levels. The molecular docking results show that the Cr2O72− structure is more compatible to binding towards the AtSULTR receptor than the SO42− structure and achieves the physiological mechanism with high selectivity. As a result, under increasing MgSO4 concentrations, Vicia faba L. can tolerate and contain chromium (Cr). All these results confirmed that there is a close relationship between the sulfate transporter and Cr(VI) uptake by plant, which explains the penetration of Cr(VI) into the cells despite the absence of specific chromium transporters.