Regulation of redox homeostasis in cadmium stressed rice field cyanobacteria by exogenous hydrogen peroxide and nitric oxide.

In the present study, defensive strategies of HO mediated NO signaling were analyzed in Cd stressed Nostoc muscorum and Anabaena sp. Exogenously supplied SNP (10 µM) and HO (1 µM) lessen the toxicity of Cd (6 µM) but without NO; HO was unable to release the stress from cyanobacterial cells potentially. The reduced contents of exopolysaccharide, protein content, endogenous NO and enzymatic antioxidants (SOD, POD, CAT, and GST) due to Cd toxicity, were found increased significantly after exogenous application of HO and SNP thereafter, cyanobacterial calls flourished much better after releasing toxic level of Cd. Moreover, increased level of ROS due to Cd stress also normalized under exogenous application of HO and SNP. However, chelation of NO hindered the signaling mechanism of HO that diminished its potential against Cd stress while signaling of NO has not been hindered by chelation of HO and NO potentially released the Cd stress from cyanobacterial cells. In conclusion, current findings demonstrated the synergistic signaling between HO and NO towards the improvement of cyanobacterial tolerance to Cd stress, thereby enhancing the growth and antioxidant defense system of test cyanobacteria that improved fertility and productivity of soil even under the situation of metal contamination.