Evolutionary and Functional Insights into Rice Universal Stress Proteins in Response to Abiotic Stresses

Universal Stress Protein (USP) plays crucial roles in plant stress adaptation, yet their evolutionary dynamics, regulatory mechanisms, and functional diversification in rice (<i>Oryza sativa</i>) remain poorly understood. This study aimed to conduct a genome-wide identification and characterization of the <i>OsUSP</i> gene family to elucidate its role in abiotic stress responses using integrated bioinformatics approaches. Here, we identified 46 <i>OsUSP</i> genes that are unevenly distributed across 11 rice chromosomes and exhibit significant divergence in protein length, molecular weight, and subcellular localization. Phylogenetic analysis classified <i>OsUSPs</i> into three subfamilies, with conserved motif and domain architectures within groups but distinct structural variations across subfamilies. Evolutionary analysis revealed strong collinearity between rice and other monocots, which suggests functional conservation in grasses, whereas limited synteny with dicots indicates lineage-specific divergence. <i>Cis</i>-regulatory element analysis showed enrichment in ABA, MeJA, drought, and hypoxia response motifs, implicating <i>OsUSPs</i> in hormonal and stress signaling. Expression profiling indicated tissue-specific patterns, with subfamily III genes broadly expressed, while subfamily II members were anther-enriched. Stress response profiling revealed that 24 <i>OsUSPs</i> were significantly induced, while <i>LOC_Os02g54590</i> and <i>LOC_Os05g37970</i> emerged as particularly notable due to their broad-spectrum responsiveness, being upregulated under all tested stress conditions. Protein-protein interaction (PPI) analysis indicated that OsUSP proteins potentially interact with Leo1/TPR-domain proteins and are involved in stress response and phosphorylation signaling pathways. This study yields key insights into OsUSP-mediated stress adaptation in rice and pinpoints promising candidate genes to facilitate the breeding of climate-resilient rice.