Identification and differential regulation of proteasome β family genes by viral infection and cytokines in grass carp (Ctenopharyngodon idella).

Proteasome β (PSMB) subunits are essential components of the proteasome complex and play important roles in antigen processing and immune regulation. In this study, we identified 14 Psmb genes in grass carp (Ctenopharyngodon idella), including seven constitutive Psmbs (Psmb1-7), three immunoproteasome genes (Psmb8-10), two thymoproteasome-related paralogs (Psmb11a and Psmb11b), and two telelost-specific members (Psmb12 and Psmb13). Comparative genomic analyses showed that grass carp Psmb genes are highly conserved in genomic organization, gene synteny, and predicted β-subunit-like protein structures, supporting the evolutionary conservation of the proteasome β-subunit family in fish. Phylogenetic and syntenic analyses further revealed lineage-specific expansion of immunoproteasome-related Psmb genes in teleost fish, with Psmb12 and Psmb13 likely derived from duplications of Psmb9 and Psmb10, respectively. Tissue expression analysis suggested functional divergence among duplicated Psmb members, as constitutive Psmbs were relatively enriched in the brain, whereas immunoproteasome-related and teleost-specific Psmbs were highly expressed in immune- and mucosa-associated tissues. Moreover, GCRV-I infection rapidly induced Psmb8-10 and Psmb11b expression in CIK cells. IFN-γ induced a broader set of Psmb genes than IFNa, whereas IL-10 selectively suppressed several Psmbs. Together, these findings highlight the evolutionary conservation, expansion, and immune-related diversification of the Psmb family in teleost fish.