Background: Blunt snout bream (Megalobrama amblycephala) is sensitive to hypoxia. A new blunt snout bream strain, “Pujiang No.2”, was developed to overcome this shortcoming. As a proteasome inhibitor, bortezomib (PS-341) has been shown to affect the adaptation of cells to a hypoxic environment. In the present study, bortezomib was used to explore the hypoxia adaptation mechanism of “Pujiang No.2”. We examined how acute hypoxia alone (hypoxia-treated, HN: 1.0 mg·L^− 1), and in combination with bortezomib (hypoxia-bortezomib-treated, HB: Use 1 mg bortezomib for 1 kg fish), impacted the hepatic ultrastructure and transcriptome expression compared to control fish (normoxia-treated, NN). Results: Hypoxia tolerance was significantly decreased in the bortezomib-treated group (LOE_crit, loss of equilibrium, 1.11 mg·L^− 1 and 1.32 mg·L^− 1) compared to the control group (LOE_crit, 0.73 mg·L^− 1 and 0.85 mg·L^− 1). The HB group had more severe liver injury than the HN group. Specifically, the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the HB group (52.16 U/gprot, 32 U/gprot) were significantly (p < 0.01) higher than those in the HN group (32.85 U/gprot, 21. 68 U/gprot). In addition, more severe liver damage such as vacuoles, nuclear atrophy, and nuclear lysis were observed in the HB group. RNA-seq was performed on livers from the HN, HB and NN groups. KEGG pathway analysis disclosed that many DEGs (differently expressed genes) were enriched in the HIF-1, FOXO, MAPK, PI3K-Akt and AMPK signaling pathway and their downstream. Conclusion: We explored the adaptation mechanism of “Pujiang No.2” to hypoxia stress by using bortezomib, and combined with transcriptome analysis, accurately captured the genes related to hypoxia tolerance advantage.

Grass carp hemorrhagic disease is caused by the grass carp reovirus (GCRV). The disease spreads rapidly and has a high fatality rate, which seriously affects grass carp culture. Moreover, the molecular mechanisms underlying grass carp hemorrhagic disease remain unclear. To decipher the effects of GCRV on grass carp tissues, resistant grass carp A (GA) and susceptible grass carp B (GB) were selected through GCRV treatment, and control grass carp C (GC) was also established. The gill, liver, and muscle tissues exhibited different onset symptoms under the influence of GCRV by histological observation. We selected muscle samples with significant differences in symptoms for Illumina RNA sequencing. Analyses using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes revealed 3512, 3074, and 1853 differentially expressed genes between "GC vs. GB," "GC vs. GA," and "GA vs. GB," respectively. Additionally, 40 differential immune-related genes and 28 differential interferon-stimulating genes (ISGs) related to the interferon (IFN) pathway were identified. The expression of immunogene-related genes of GB and GA, such as MDA5, IL-34, NF-KB, TRIM25, SOCS3, CEBPB, and BCL2, and genes associated with the JAK-STAT signaling pathway, such as IRF4, STAT1, STAT3, JAK 1, and JAK 2, was significantly upregulated. The IFN and JAK-STAT signaling pathways were closely related to anti-GCRV infection. The transcriptome data and predicted immune genes and ISGs in this study provide novel insights into the treatment of GCRV.