Nilonema gymnarchi (Nematoda: Philometridae) and trace metals in Gymnarchus niloticus of Epe lagoon in Lagos State, Nigeria

Comparative transcriptomics combined with physiological and functional analysis reveals the regulatory mechanism of rainbow trout (Oncorhynchus mykiss) under acute hypoxia stress

Hypoxia, largely triggered by global warming and water contamination, has become an environmental issue of great concern, posing a great threat to aquatic ecosystem. As one of the world's most economically important fish, rainbow trout (Oncorhynchus mykiss) is extremely intolerant of hypoxic environments, however, little is known about the roles of non-coding RNAs (ncRNAs) in the response of rainbow trout to hypoxia stress. Herein, effects of moderate (Tm12L) and severe hypoxia for 12 h (Ts12L) and 12 h reoxygenation on histology, biochemical parameters (antioxidant, metabolism and immunity) and transcriptome (lncRNA, miRNA and mRNA) in rainbow trout liver were investigated. We further validated the regulatory relationships between LOC110519952, novel-m0023-5p and glut1a via dual‑luciferase reporter, overexpression and silencing assays. Compared with Tm12L, the liver in Ts12L showed more severe oxidative damage. Anaerobic, lipid and protein metabolism was enhanced under hypoxia stress, especially in Ts12L. We also found that Tm12L could strengthen innate immune response, which was inhibited in Ts12L. Besides, several hypoxia-related genes (glut1a, vegfaa, hmox, epoa, foxo1a and igfbp1) and ceRNA networks were identified from 1824, 427 and 545 differentially expressed mRNAs, miRNAs and lncRNAs, including LOC118965299-novel-m0179-3p-epoa, LOC110519952-novel-m0023-5p-glut1a, MSTRG.7382.2-miR-184-y-hmox and LOC110520012-miR-206-y-vegfaa. Through in vitro and in vivo functional analysis, we demonstrated that glut1a is a target of novel-m0023-5p, and LOC110519952 can positively regulate glut1a by targeting novel-m0023-5p. Introduction of LOC110519952 could attenuate the promoting effects of novel-m0023-5p on rainbow trout liver cell viability and proliferation. This study highlights the differences in the regulatory mechanism of rainbow trout under different concentrations of hypoxia stress and provides valuable data for further research on the molecular mechanisms of fish adaptation to hypoxic environments.

Integrated analysis of immune parameters, miRNA-mRNA interaction, and immune genes expression in the liver of rainbow trout following infectious hematopoietic necrosis virus infection

Rainbow trout (Oncorhynchus mykiss) is an important economical cold-water fish worldwide. However, infection with infectious hematopoietic necrosis virus (IHNV) has severely restricted the development of aquaculture and caused huge economic losses. Currently, little is known about the immune defense mechanisms of rainbow trout against IHNV. In this study, we detected the changes of immune parameters over different post-infection periods (6-, 12-, 24-, 48-, 72-, 96-, 120-, and 144 hours post-infection (hpi)), mRNA and miRNA expression profiles under 48 hpi (T48L) compared to control (C48L), and key immune-related genes expression patterns in rainbow trout liver following IHNV challenge through biochemical methods, RNA-seq, and qRT-PCR, and the function of miR-330-y was verified by overexpression and silencing in vitro and in vivo. The results revealed that alkaline phosphatase (AKP), alanine aminotransferase (ALT), catalase (CAT), and total superoxide dismutase (T-SOD) activities, and lysozyme (LZM) content showed significant peaks at 48 hpi, whereas malondialdehyde (MDA) content and aspartate aminotransferase (AST) activity decreased continuously during infection, and acid phosphatase (ACP) activity varied slightly. From RNA-seq, a total of 6844 genes and 86 miRNAs were differentially expressed, and numerous immune-related differentially expressed genes (DEGs) involved in RIG-I-like receptor signaling pathway, Toll-like receptor signaling pathway, NOD-like receptor signaling pathway, cytokine-cytokine receptor interaction, and antigen processing and presentation were significantly upregulated in T48Lm group, including IFIH1, DHX58, MAVS, TRAF3, IRF3, IRF7, MX1, TLR3, TLR8, MYD88, NOD1, NOD2, IL-8, CXCR1, CD209, CD83, and TAP1. Integrated analysis identified seven miRNAs (miR-425-x, miR-185-x, miR-338-x, miR-330-y, miR-361-x, miR-505-y, and miR-191-x) that target at least three key immune-related DEGs. Expression analysis showed that IFIH1, DHX58, IRF3, IRF7, MX1, TLR3, TLR8, and MYD88 showed a marked increase after 24 hpi during infection. Further research confirmed TAP1 as one of the targets of miR-330-y, overexpression of miR-330-y with mimics or agomir significantly reduced the expression levels of TAP1, IRF3, and IFN, and the opposite effects were obtained by inhibitor. These results facilitate in-depth understanding of the immune mechanisms in rainbow trout against IHNV.