Nitric oxide and hydrogen peroxide mediated regulation of chromium (VI) toxicity in wheat seedlings involves alterations in antioxidants and high affinity sulfate transporter.

ABSTRACT

Chromium contamination of the soil is a major scientific concern with reference to crop productivity and human health. In recent years, several approaches are being employed in managing metal toxicity in crop plants. Here, we have investigated about potential and probable crosstalk of nitric oxide (NO) and hydrogen peroxide (H2O2) in mitigating hexavalent chromium [Cr(VI)] toxicity in wheat seedlings. Cr(VI) toxicity reduced the fresh mass and overall growth due to accumulation of reactive oxygen species (ROS) and decreased efficiency of AsA-GSH cycle and downregulation of high affinity sulfate transporter. However, exogenous treatment of NO and H2O2 significantly alleviated Cr toxicity. Application of NO and ROS scavengers reversed stress mitigating effects of NO and H2O2, respectively suggesting that endogenous NO and H2O2 are necessary for rendering Cr toxicity tolerance. Furthermore, NO rescued negative effect of diphenylene iodonium (DPI, NADPH oxidase inhibitor) and H2O2 reversed the negative effect of c-PTIO suggesting that they exhibit independent signalling in mitigating Cr stress. Altogether, data indicated that NO and H2O2 rendered mitigation of Cr stress by up-regulating enzymes (activity and relative gene expression) and metabolites of AsA-GSH cycle, high affinity sulfate transporter (relative gene expression) and glutathione biosynthesis which collectively controlled occurrence of oxidative stress.