Genome-Wide Identification, Characterization, and Expression Analysis under Abiotic Stresses of the UBP Gene Family in Rice (Oryza sativa L.)

The ubiquitin-specific protease (UBP) family represents a type of deubiquitinase (DUB) that plays a significant role in plant abiotic stress responses, growth, and development. Although UBP genes have been characterized in many species, a genome-wide systematic analysis and the potential functions under abiotic stresses have not yet been reported in rice (Oryza sativa L.). In this study, we identified 21 UBP gene family members in the genome of rice, all of which had UCH domains containing short but highly conserved Cys-box and His-box. The DUF4220 and DUF594 domains, which are found in monocotyledonous plants, were unique. Phylogenetic analysis suggested that OsUBP7 and OsUBP12 genes had the closest genetic relationships with AtUBP12 and AtUBP13, implying that OsUBP7 and OsUBP12 might have similar biological functions to AtUBP12 and AtUBP13. Synteny analysis revealed that OsUBP genes were expanded through segmental duplication under purifying selection. Meanwhile, they had closer evolutionary relationships with monocotyledonous plants. Additionally, all OsUBP genes had an ABRE cis-element, which was related to abscisic acid (ABA) stress hormone response. Protein interaction analysis suggested that OsUBP22 might modulate gene regulation through OsGCN5- and OsADA2-mediated chromatin modification, and OsUBP10 might regulate salt stress through modulating OsDNA2_4 stability. Specifically, the expression profiles and the transcriptional levels of 11 representative OsUBPs suggested the potential important functions of OsUBP9 and OsUBP17 under drought and cold stresses. Taken together, our study provided a systematic analysis of OsUBPs and preliminarily explored their potential roles under abiotic stresses. Our results lay a foundation for further research on the functions of the OsUBP gene family under abiotic stresses.