Genome-wide analysis reveals tissue-specific responses of class III peroxidase genes to PEG-induced osmotic stress in Pennisetum glaucum

Class III peroxidases (PRXs) are plant-specific oxidoreductases involved in reactive oxygen species homeostasis and abiotic stress responses. Pennisetum glaucum is a drought-resilient food and forage crop, but its PRX gene family remains poorly characterized. Here, we identified 120 putative PgPRX family members through integrated bioinformatic analyses. These genes were unevenly distributed across seven chromosomes, and 54 encoded proteins (45%) were predicted to localize to chloroplasts. Phylogenetic and structural analyses classified the family into four subfamilies. Four tandem duplication clusters were identified, supporting a role for tandem duplication in PgPRX family expansion. Comparative synteny analysis detected 98 collinear gene pairs between P. glaucum and rice but only three between P. glaucum and Arabidopsis thaliana , indicating greater conservation among monocots. Promoter analysis revealed abundant cis-acting elements associated with phytohormone signaling and abiotic stress responses. Transcriptome analysis under 20% PEG-6000-induced osmotic stress revealed marked tissue- and time-specific expression patterns, with 108 PgPRX genes significantly differentially expressed in at least one comparison. RT-qPCR analysis of six selected genes further revealed distinct tissue- and time-dependent responses to PEG treatment, with PgPRX22 and PgPRX41 showing contrasting expression trends between leaves and roots and PgPRX74 exhibiting a marked tissue-dependent response. These findings provide a genomic and expression framework for the PgPRX family and prioritize candidate genes for further functional investigation of stress responses in P. glaucum.