Heterologous expression and characterization of novel manganese superoxide dismutase (Mn-SOD) - A potential biochemical marker for heat stress-tolerance in wheat (Triticum aestivum).

Heat stress causes oxidative bursts damaging the organelles and nascent proteins. Plants have inherited antioxidant defense system to neutralize the effect of reactive oxygen species. Superoxide dismutase provides first line of defense against the HS by regulating the accumulation of peroxide radicals inside the cells. Here, we report identification and cloning of putative manganese superoxide dismutase (Mn-SOD) gene of ~733 nt from wheat cv. HD2985 through de novo assembly. The gene was observed to localize on Chr 6D with a mitochondrial targeting peptide sequence and iron/manganese domain. We predicted 147 homologs of Mn-SOD in eukaryotes with diverse speciation nodes. A recombinant Mn-SOD protein of ~25.5 kDa was purified through heterologous expression system. Kinetics assay of recombinant protein showed optimum pH of 8.0, optimum temperature of 35 °C and K and V values of 1.51 μM and 9.45 U/mg proteins, respectively. Maximum expression and activity of Mn-SOD was observed in leaves from Raj3765, as compared to stem and spike during milky-ripe stage under differential HS. In gel activity assay showed the appearance of all the three isoforms of SOD in thermotolerant cv. under HS. Mn-SOD, being active at pivotal position, can be also used as potential biochemical marker in wheat breeding program.