Modulation and significance of nitrogen and sulfur metabolism in cadmium challenged plants

As a result of rapidly increasing anthropogenic activities, input of varied metal(loids) such as cadmium (Cd) to worldwide agricultural soils and its subsequent accumulation, and obvious toxicity in plants are increasing. The role of mineral nutrients in the mitigation of Cd-accrued consequences in plants has been credibly suggested. In isolated studies, two essential mineral nutrients such as nitrogen (N) and sulfur (S) have been reported to minimize Cd-impacts in plants, and improve overall plant growth, metabolism and productivity under Cd-exposure. However, the information on the significance of N and S metabolism, and also on cross-talks on the coordination therein in Cd-challenged plants is lacking. Given the highlighted lacunae, in the light of recent research outcomes, the present review attempts to: (a) overview Cd in soil, and its major toxicity and mitigation avenues in plants, (b) appraise Cd-mediated modulation of N and S metabolism, (c) summarize the role of exogenously-sourced N and S for the mitigation of Cd toxicity, (d) critically discuss the significance of coordination between N and S metabolism for Cd-impact-mitigation, and finally to (e) highlight the major aspects to explore in the current context. The literature appraised herein suggests that a fine coordination among major pathways of N and S assimilation can enhance defense metabolites and enzymes that in turn can strengthen overall defense system, and efficiently mitigate Cd-impacts in plants. However, efforts are required to get more insights into the mechanism(s) of (co)regulation of sulfate and nitrate assimilation at the molecular level. Additionally, molecular approaches should be narrowed to enhance the production of thiols, and their products in plants through manipulating major enzymes involved in sulfate and nitrate assimilation in plants under Cd-challenged environment.