Identification and characterization of circular RNAs in the skin of rainbow trout (Oncorhynchus mykiss) infected with infectious hematopoietic necrosis virus.

Rainbow trout (Oncorhynchus mykiss) is an economically significant freshwater-farmed fish worldwide, and the frequent outbreaks of infectious hematopoietic necrosis (IHN) in recent years have gravely compromised the healthy growth of the rainbow trout aquaculture industry. Fish skin is an essential immune barrier against the invasion of external pathogens, but it is poorly known about the role of circRNAs in rainbow trout skin. Therefore, we examined the expression profiles of circRNAs in rainbow trout skin following IHNV infection using RNA-seq. A total of 6607 circRNAs were identified, of which 34 circRNAs were differentially expressed (DE) and these DE circRNA source genes were related to immune-related pathways such as Toll-like receptor signaling pathway, NOD-like receptor signaling pathway, Cytokine-cytokine receptor interaction, ubiquitin mediated proteolysis, and ferroptosis. We used qRT-PCR, Sanger sequencing, and subcellular localization to validate the chosen DE circRNAs, confirming their localization and expression patterns in rainbow trout skin. Further, 12 DE circRNAs were selected to construct the circRNA-miRNA-mRNA regulatory network, finding one miRNA could connect one or more circRNAs and mRNAs, and some miRNAs were reported to be associated with antiviral immunity. The functional prediction findings revealed that novel_circ_002779 and novel_circ_004118 may act as sponges for miR-205-z and miR-155-y to regulate the expression of target genes TLR8 and PIK3R1, respectively, and participated in the antiviral immune responses in rainbow trout. These results shed light on the immunological mechanism of circRNAs in rainbow trout skin and offer fundamental information for further research on the innate immune system and breeding rainbow trout resistant to disease.

Dietary supplementation of Chinese herbal medicines enhances the immune response and resistance of rainbow trout (Oncorhynchus mykiss) to infectious hematopoietic necrosis virus.

Rainbow trout is a widely farmed economical cold-water fish worldwide, but the prevalence of infectious hematopoietic necrosis virus (IHNV) presents a severe risk to the aquaculture industry, resulting in high mortality and huge economic losses. In this study, the impacts of different concentrations (0, 10, 20, and 30 g/kg) of Chinese herbal medicine mixture (CHMM) on the immune response and resistance of rainbow trout to IHNV infection were evaluated. The results show that CHMM noticeably increased (P < 0.05) T-SOD, CAT, AST, ALT, ACP, and AKP activities and decreased MDA content. NF-κB, TNF-α, IFN-ß, IL-1ß, JAK1, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while SOCS2 expression was downregulated (P < 0.05). Following infection with IHNV, feeding rainbow trout with varying amounts of CHMM resulted in noticeably increased (P < 0.05) T-SOD, ACP, and AKP activities and significantly decreased (P < 0.05) MDA content and AST and ALT activities. TNF-α, IFN-ß, IL-1ß, HSP70, and HSP90 expressions were significantly upregulated (P < 0.05) in all CHMMs, while the expressions of JAK1 and SOCS2 were downregulated. The expression level of the IHNV G protein gene at a dosage of 20 g/kg was notably lower than that of the other CHMM feeding groups. This study provides a solid scientific basis for promoting CHMM as an immunostimulant for boosting antiviral immunity in rainbow trout.

Integrative mRNA-miRNA interaction analysis associated with the immune response in the head kidney of rainbow trout (Oncorhynchus mykiss) after infectious hematopoietic necrosis virus infection.

Rainbow trout (Oncorhynchus mykiss) is an important cold-water fish widely cultivated in China. The frequent occurrence of viral diseases caused by infectious hematopoietic necrosis virus (IHNV) seriously restricted the healthy development of the rainbow trout farming industry. However, the immune defense mechanism induced by IHNV in rainbow trout has not been fully elucidated. In the present study, we detected mRNA and miRNA expression profiles in rainbow trout head kidney after IHNV infection using RNA-seq and identified key immune-related genes and miRNAs. The results showed that a total of 7486 genes and 277 miRNAs were differentially expressed, and numerous differentially expressed genes (DEGs) enriched in the immune-related pathways such as Toll-like receptor signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, cytokine-cytokine receptor interaction, and JAK-STAT signaling pathway were significantly up-regulated, including LGP2, MDA5, TRIM25, IRF3, IRF7, TLR3, TLR7, TLR8, MYD88, and IFN1. Integration analysis identified six miRNAs (miR-141-y, miR-200-y, miR-144-y, miR-2188-y, miR-725-y, and miR-203-y) that target at least six key immune-related genes (TRIM25, LGP2, TLR3, TLR7, IRF3, and IRF7). Further, we verified selected immune-related mRNAs and miRNAs through qRT-PCR and confirmed the reliability of the RNA-seq results. These findings improve our understanding of the immune mechanism of rainbow trout infected with IHNV and provide basic data for future breeding for disease resistance in rainbow trout.

Histological, Physiological and Transcriptomic Analysis Reveal the Acute Alkalinity Stress of the Gill and Hepatopancreas of Litopenaeus vannamei.

The pacific white shrimp (Litopenaeus vannamei) has gradually become a promising economic species in the development of saline-alkali water fishery. The study related to the stress reaction of pacific white shrimp under alkalinity stress is still limited, which is also a critical limiting factor for its saline-alkaline aquaculture. In this study, we aim to analyse the stress reaction of pacific white shrimp under acute alkalinity stress between control group (alkalinity:40 mg/L) and treatment group (alkalinity:350 mg/L) through histological observation, physiological determination and transcriptome. In the present study, during the process of acute alkalinity stress, the activities of Na+-K+-ATPase, carbonic anhydrase, sodium/hydrogen exchanger in gill related to homeostasis were significantly changed, the activities of superoxide dismutase and catalase related to antioxidant were decreased in both gill and hepatopancreas, and the activities of protease, lipase and amylase in hepatopancreas were decreased. At the same time, different degrees of histological damages were occured in the gill and hepatopancreas under acute alkalinity stress. There were 194 and 236 different expressed genes identified in gill and hepatopancreas respectively. Functional enrichment assessment indicated that the alkalinity stress-related genes in both gill and hepatopancreas were primarily involved in fatty acid metabolism, glycolysis/gluconeogenesis, glycerophospholipid metabolism. The results indicated that the functions of homeostasis regulation, antioxidation and digestion of pacific white shrimp were decreased under acute alkalinity stress, at the same time, the energy metabolism in gill and hepatopancreas were modified to cope with alkalinity stress. This work provides important clues for understanding the response mechanism of pacific white shrimp under acute alkalinity stress.