Low-dose Priming of Gamma Radiation Enhanced Cadmium Tolerance in Chlamydomonas Reinhardtii by Modulating Physio-biochemical Pathways

Microalgae, the key components of aquatic environments, are executive natural biotic models for exploring genotoxic effect of heavy metals, irradiation and other external stimuli and the toxicant elimination. In the current scenario, removal of metal contaminants is a significant challenge. Recently, the effective removal of heavy metals from the aquatic environment using microalgae has gained immense intention. However, the concurrent toxicity has limited their use as bio-accumulants to reduce the concentration of heavy metals and promote heavy metal tolerance. Few studies opined that low dose priming with non-ionizing radiations, such as gamma radiation, increased heavy metal tolerance in plant as well as aquatic photosynthetic microalgae. In the present study, we have hypothesized the growth inhibitory physio-chemical properties by cadmium (Cd) in the green algae Chlamydomonas reinhardtii , and analysed the protective role of low-dose gamma radiations priming against Cd induced growth inhibition. In addition, we have specially emphasized on the mechanism of cell survival in the experimental species with effective notation to antioxidant defence system during Cd induced toxicity. Experimentally, we primed the Chlamydomonas reinhardtii with low-dose gamma radiation prior to Cd treatment. On the other hand, gamma-radiated and Cd-treated organisms were considered as positive controls. We calculated the rate of cell death, the deployment of antioxidant enzymes such as catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), glutathione reductase (GSR), and superoxide dismutase (SOD). Furthermore, the role of oxidative stress related genes was analysed computationally to delineate their involvement in cell death/survival, suggesting that the low-dose priming of gamma radiation enhances the Cd tolerance by alterating cell/death pathways and other biochemical responses.