Transcriptome Analysis of DAMP-Induced Root Growth Regulation and Defense in Foxtail Millet

Foxtail millet (<i>Setaria italica</i> L.), a representative C4 species, is recognized for its efficient nutrient utilization and robust abiotic stress responses. However, the molecular mechanisms mediating its tolerance to biotic stresses are poorly understood. In this study, we investigated the root transcriptomic response of foxtail millet to the damage-associated molecular pattern (DAMP), the plant elicitor peptide 1 (Pep1). Transcriptome analysis of Pep1-treated roots identified 401 differentially expressed genes (DEGs), comprising 144 up-regulated and 257 down-regulated genes. Gene Ontology (GO) enrichment analysis revealed a significant enrichment of 'peroxidase activity'. This finding was corroborated by DAB staining, which confirmed H₂O₂ accumulation, along with elevated malondialdehyde (MDA) levels, collectively indicating oxidative stress. Notably, Pep1 treatment also resulted in a marked up-regulation of the pathogenesis-related protein 1 (<i>PR1</i>) gene in leaves, suggesting the activation of systemic acquired resistance. Together, these results demonstrate that Pep1 triggers substantial transcriptional reprogramming in roots, induces oxidative stress, and activates systemic defense signaling in foxtail millet.