Molecular characterization of superoxide dismutase (SOD) genes for optimizing nitrogen-use efficiency and enhancing crop resilience against drought stress in rice

Superoxide dismutase (SOD) proteins play a vital role as antioxidant enzymes, essential in mediating plant responses to drought and salinity stress. The SOD gene family has been identified across numerous plant species; however, updated genome assemblies can revise gene models and reveal overlooked members, creating a need to evaluate SOD repertoires in rice. The current study explored the whole rice genome having 11 OsSOD genes that were phylogenetically classified as, 3 FeSODs, 3 MnSODs, and 5 Cu/ZnSODs, distributed across eight of the twelve chromosomes. Among these, the same subgroup exhibits identical subcellular localization. The phylogenetic investigation was additionally validated through the analysis of sequence motifs, exon-intron structure, and three-dimensional protein structures. Each grouping displayed a similar gene and protein structure. Promoter analysis identified cis-regulatory elements associated with drought-responsive signaling, suggesting transcriptional regulation under water-deficit conditions. Furthermore, the RNA-seq data analysis demonstrated that higher OsSOD expression in roots than shoots tissues. This was further confirmed via qRT-PCR revealing that OsMn-SOD2, OsFe-SOD3, OsCu/Zn-SOD1, OsCu/Zn-SOD4, and OsCu/Zn-SOD5 had a higher expression in roots than shoot under drought and nitrogen (N) stresses. These patterns were further supported through antioxidant activity and secondary metabolites analysis. Collectively, our results provide a foundation for further understanding the involvement of OsSOD genes which may be associated with mitigating the N stress by potentially influencing N-related pathways involved in the nitrate uptake, assimilation, and N-partitioning within the rice plants. These OsSOD candidates provide targets for functional validation and for breeding/biotechnological improvement of drought resilience and nitrogen-use efficiency in rice.