Genome-Wide Analysis of the POD Gene Family in <i>Avena sativa</i>: Insights into Lignin Biosynthesis and Responding to Powdery Mildew

The class III peroxidase (POD) gene family encodes redox enzymes involved in the catalytic processes of hydrogen peroxide, phenolic compounds, and reactive oxygen species. These enzymes play crucial roles in lignin biosynthesis and stress responses. To explore the functions of the oat (<i>Avena sativa</i>) <i>POD</i> (<i>AsPOD</i>) gene family in resistance to powdery mildew, we performed a genome-wide analysis and bioinformatics characterization. A total of 97 <i>AsPOD</i> genes were identified, unevenly distributed across 21 chromosomes. Structural predictions indicated that α-helices are the predominant structural components of AsPOD proteins, and phylogenetic analysis revealed six clades of AsPOD proteins, with high homology to POD proteins in the Poaceae family. Cis-regulatory element analysis revealed that three <i>AsPOD</i> genes are associated with hormone signaling, light response, and stress resistance. Analysis of duplication events in the oat <i>POD</i> gene family indicates that there are a total of 55 pairs of gene segment duplications among the 69 <i>AsPOD</i> genes. Expression profiling of powdery mildew-infected oat varieties showed significant up- or downregulation of several <i>AsPOD</i> genes (<i>AsPOD51</i>, AsPOD55, AsPOD63, AsPOD89), identifying them as key candidates for disease resistance studies. Furthermore, resistant oat varieties exhibited higher lignin content than susceptible ones. Correlation analysis indicated that <i>AsPOD51</i>, AsPOD55, AsPOD63, AsPOD88, and <i>AsPOD89</i> showed a stronger positive association with lignin content in resistant varieties. After inoculation with the powdery mildew pathogen, the H₂O₂ content rapidly increases, and POD activity first rises and then decreases. Those findings provide a foundation for further research into the role of <i>AsPOD</i> genes in oat disease resistance.