The current study investigated the putative role of salicylic acid (SA) in modulating Pb2+-induced DNA and oxidative damage in Allium cepa roots. Pb2+ exposure enhanced free radical generation and reduced DNA integrity and antioxidant machinery after 24 h; however, SA pre-treatment (for 24 h) ameliorated Pb2+ toxicity. Pb2+ exposure led to an increase in malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation and enhanced superoxide radical and hydroxyl radical levels. SA improved the efficiency of enzymatic antioxidants (ascorbate and guaiacol peroxidases [APX, GPX], superoxide dismutases [SOD], and catalases [CAT]) at 50-μM Pb2+ concentration. However, SA pre-treatment could not improve the efficiency of CAT and APX at 500 μM of Pb2+ treatment. Elevated levels of ascorbate and glutathione were observed in A. cepa roots pre-treated with SA and exposed to 50 μM Pb2+ treatment, except for oxidized glutathione. Nuclear membrane integrity test demonstrated the ameliorating effect of SA by reducing the number of dark blue-stained nuclei as compared to Pb2+ alone treatments. SA was successful in reducing DNA damage in cell exposed to higher concentration of Pb2+ (500 μM) as observed through comet assay. The study concludes that SA played a major role in enhancing defense mechanism and protecting against DNA damage by acclimatizing the plant to Pb2+-induced toxicity.
Keywords: DNA integrity; Free radicals; Metal toxicity; Nuclear integrity; Onion root tips; ROS metabolism.
© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.