Genome-Wide Analysis of the 12-Oxo-Phytodienoic Acid Reductase Gene Family in Peanut and Functional Characterization of AhOPR6 in Salt Stress

12-oxo-phytodienoic acid reductases (<i>OPR</i>s) have been substantiated as pivotal in plant growth and response to biotic and abiotic stresses. However, the functional characterization of <i>OPR</i> genes in the peanut genome remains limited. In this study, we identified a total of 20 <i>OPR</i> genes in a tetraploid cultivar and two diploid peanut species, categorizing them into two subfamilies, OPRI and OPRII. The gene structure and conserved protein motifs within each subfamily were elucidated. Additionally, our findings indicate an uneven chromosomal distribution of peanut <i>OPR</i> genes. Gene duplication events were identified as pivotal in the expansion of the <i>OPR</i> gene family. An analysis of cis-acting elements within <i>OPR</i> gene promoters revealed the presence of numerous phytohormone- and stress-related cis-elements. Furthermore, peanut <i>OPR</i> genes exhibited tissue-specific and stress-inducible expression patterns, underscoring their crucial role in peanut growth and stress response. Additionally, plants overexpressing <i>AhOPR6</i> exhibited significantly enhanced resistance to salt stress, and the <i>AhOPR6</i>-OE lines demonstrated a higher ability to scavenge reactive oxygen species (ROS). Collectively, these findings offer deeper insights into the roles of peanut <i>OPR</i> genes in stress responses, suggesting that <i>AhOPR6</i> could serve as a potential candidate gene for improving peanut salt tolerance through genetic transformation.