Abstract
Class III peroxidases are plant-specific enzymes that play indispensable roles in catalyzing oxidative-reductive reactions, which are integral to numerous biochemical processes in plants. In this study, we identified 69 members of the class III peroxidase (POD) gene family in the Populus simonii genome and classified them into four subfamilies based on phylogenetic analysis. Chromosomal localization revealed that these PsPOD genes are unevenly distributed across 19 chromosomes, with chromosomes 3 and 7 harboring the highest densities. Conserved domain and motif analyses demonstrated that all PsPOD proteins contain the characteristic peroxidase domain and share highly conserved motif structures. Cis-acting element analysis of promoter regions revealed the presence of numerous regulatory elements associated with light responsiveness, phytohormone signaling, stress responses, and plant growth and development. Transcriptome data showed that the expression of PsPOD genes varies significantly across different tissues and organs and under various stress conditions, suggesting their involvement in both developmental processes and abiotic stress responses. These findings were further validated by qRT-PCR analysis of selected PsPOD genes. Notably, PsPOD45, PsPOD69, PsPOD33, and PsPOD64 were identified as central hub genes in the protein-protein interaction network, making them promising candidates for further functional characterization. Overall, this study provides a comprehensive overview of the PsPOD gene family in P. simonii, laying a solid foundation for future functional studies and offering valuable insights for comparative research in other plant species.