Genome-Wide Identification of the Soybean OXS3 Gene Family and Functional Characterization of GmOXS3-1 in Regulating Alkaline Tolerance

The Oxidative Stress 3 (OXS3) gene family encodes plant-specific proteins that play crucial roles in abiotic stress tolerance and chromatin remodeling. However, genome-wide identification and characterization of the OXS3 gene family in soybean have not been systematically conducted. Here, we identified 19 GmOXS3 genes from the soybean genome. Phylogenetic analysis assigned these genes to three subfamilies (I–III). Members within the same subfamily exhibited conserved motif compositions. The promoter regions of GmOXS3 genes contained various cis-acting regulatory elements associated with stress and phytohormone responses. Analysis of transcriptome data revealed that GmOXS3 genes exhibited different expression patterns in various organs. RT-qPCR further confirmed their differential expression under salt and alkaline stresses, with the most pronounced up-regulation observed for GmOXS3-1 and GmOXS3-14 under alkaline stress. Among them, GmOXS3-1 was further characterized, and it negatively regulates alkaline tolerance in soybean hairy roots. These results provide a foundation for elucidating GmOXS3-1-mediated alkaline stress signaling and highlight its potential as a breeding target for improving alkaline tolerance.