Comparative Analyses of Superoxide Dismutase (SOD) Gene Family and Expression Profiling under Multiple Abiotic Stresses in Water Lilies

Plants in their natural habitat frequently face different biotic and abiotic stresses, which lead to the production of reactive oxygen species (ROS) that can damage cell membranes, cause peroxidation and deterioration of macromolecules, and ultimately result in cell death. Superoxide dismutase (SOD), a class of metalloenzymes, is primarily found in living organisms and serves as the principal line of defense against ROS. The SOD gene family has not yet been characterized in any species of water lily from the genus Nymphaea. The present study aims to conduct a genome-wide study to discover SOD genes in four representative water lily species. In our present comparative study, we discovered 43 SOD genes in the genomes of four water lily species. The phylogenetic investigation results revealed that SOD genes from water lily and closely related plant species formed two distinct groups, as determined by their binding domains with high bootstrap values. Enzymatic ion-binding classified the SOD gene family into three groups, FeSOD, Cu/ZnSOD, and MnSOD. The analysis of gene structure indicated that the SOD gene family exhibited a relatively conserved organization of exons and introns, as well as motif configuration. Moreover, we discovered that the promoters of water lily SODs contained five phytohormones, four stress-responsive elements, and numerous light-responsive cis-elements. The predicted 3D protein structures revealed water lily SODs form conserved protein dimer signatures that were comparable to each other. Finally, the RT-qPCR gene expression analysis of nine NcSOD genes revealed their responsiveness to heat, saline, cold, cadmium chloride, and copper sulphate stress. These findings establish a basis for further investigation into the role of the SOD gene family in Nymphaea colorata and offer potential avenues for genetic enhancement of water lily aquaculture.