Nitric oxide mediated amelioration of arsenic toxicity which alters the alternative oxidase (Aox1) gene expression in Hordeum vulgare L.

• This study elucidates the alleviating role of nitric oxide against arsenic toxicity.
• Nitric oxide altered the arsenic induced genotoxicity and oxidative stress.
• Nitric oxide triggered up-regulation of enzymatic antioxidants which regulated the levels of ROS in Vicia faba seedlings and thus protected against As stress.

The role of nitric oxide (NO) as a key molecule in the signal transduction pathway of a biotic stress response has already been described. Recent studies indicate that it also participate in the signaling of abiotic stresses. In the present study, we showed the altered expression of stress responsive gene alternative oxidase (Aox1) in seedlings of barley (Hordeum vulgare L.) in response to arsenic toxicity. Arsenic toxicity decreased the germination percentage, biomass, chlorophyll and carotenoid content whereas, arsenic toxicity enhanced the MDA content and proline content in a dose dependent manner. Other enzyme activities like catalase and superoxide dismutase increased with the increase in concentrations but it fell down at higher concentration of arsenic. Pretreatment of nitric oxide results in the enhanced expression of alternative oxidase which showed the adaptation of alternative pathway during the arsenic stress and it also enhances the growth ability and adaptability towards the arsenic stress. The results support the conclusion that nitric oxide ameliorates the arsenic toxicity not only at the level of antioxidant defense but also by affecting other mechanism of detoxification.