Selenium alleviates arsenic induced stress by modulating growth, oxidative stress, antioxidant defense and thiol metabolism in rice seedlings.

ABSTRACT

This study aims to investigate the potentiality of selenium in modulating arsenic stress in rice seedlings. Arsenate accumulation along with its transformation to arsenite was enhanced in arsenate exposed seedlings. Arsenite induced oxidative stress and severely affected the growth of the seedlings. Arsenate exposure caused an elevation in ascorbate and glutathione levels along with the activities of their metabolizing enzymes viz., ascorbate peroxidase, glutathione reductase, glutathione-S-transferase, and glutathione peroxidase. Phytochelatins content was increased under arsenic stress to subdue the toxic effects in the test seedlings. Co-application of arsenate and selenate in rice seedlings manifested pronounced alteration of oxidative stress, antioxidant defense, and thiol metabolism as compared to arsenate treatment only. ANOVA analysis (Tukey's HSD test) demonstrated the relevance of using selenate along with arsenate to maintain the normal growth and development of rice seedlings. Thus, exogenous supplementation of selenium will be a beneficial approach to cultivate rice seedlings in arsenic polluted soil.

Arsenic toxicity in the environment is a global concern, causes chronic signs of poisoning to plants and humans, leads to ecological imbalance. Selenium is known for its antagonistic characteristics and has been found to be effective in combating the adversities of arsenic at low concentrations (5 µM). The present study was performed to explore the comparative responses of rice seedlings during the joint application of selenium and arsenic in terms of growth, generation of oxidative stress, antioxidant defense, and thiol metabolism. Although the molecular basis of arsenic­selenium interaction is widely known a small number of reports were listed about the physio-chemical role of selenium against arsenic stress. Thus, we investigated the influence of selenium to alleviate arsenic-induced toxic effects by modulating the activities of antioxidant enzymes and reducing the levels of oxidative stress markers. It has been noted that selenium regulates thiol metabolism which is known to play a key role in growth preservation by restriction of arsenic translocation. The outcome from the study would be useful in field trials for sustainable agriculture in arsenic-contaminated soil.