Analysis of lncRNA and mRNA expression profiles in peripheral blood leukocytes of the half-smooth tongue sole (Cynoglossus semilaevis) treated with chitosan oligosaccharide

SHP-1 negatively regulates LPS-induced M1 polarization, phagocytic activity, inflammation and oxidative stress in primary macrophages of Chinese tongue sole (Cynoglossussemilaevis)

Macrophages serve as the primary effector cells in antibacterial immunity in teleost, engaging in both innate and adaptive immune response. However, the specific role of SHP-1, a multi-functional protein tyrosine phosphatase, in teleost macrophages remains elusive. In this study, we first established a cellular immune model using lipopolysaccharide (LPS), a major pathogenic component of Gram-negative bacteria, and then we comprehensively elucidated the function of SHP-1 in primary macrophages derived from Chinese tongue sole. Our results demonstrated that overexpression of SHP-1 inhibited M1 polarization, phagocytosis, respiratory burst of primary macrophages, suppressing the generation of excessive reactive oxygen species (ROS), malondialdehyde (MDA), and proinflammatory cytokines (il-1β, il-6), but increasing the expression of superoxide dismutase (SOD) and anti-inflammatory cytokine (il-10). Whereas SHP-1 silencing (through siRNA or inhibitor) exerted completely opposite effects, further emphasizing its roles as a negative regulator. More in-depth, we revealed that SHP-1 suppressed the activation/transduction of the TLR5-MYD88-NFκB and JAK-STAT3 signal pathways, thereby mitigating the excessive immune reaction in macrophages of Chinese tongue sole. In summary, our findings systematically delineate the functions of SHP-1 and offer mechanistic insights into the management of oxidative stress/inflammation-related diseases, which will contribute to the sustainable development of aquaculture.

Interactions of interleukin 2 (IL-2) and IL-2 receptors mediate the activities of B lymphocytes in flounder (Paralichthys olivaceus)

Interleukin 2 (IL-2) is an immunoregulatory cytokine that plays significant role in the activation and proliferation of immune cells. In teleost, the functions of IL-2 signaling on the proliferation and differentiation of T lymphocytes were well documented. However, there is still unclear about the effects of IL-2 signaling on B cell immunity in fish. Hence, in this study, full-length transcriptome sequencing was performed to investigate the activation of IL-2 on flounder (Paralichthys olivaceus) lymphocytes in vitro, the effects of IL-2 on the immunity of B cells after its receptors (IL-2Rβ or IL-2Rγ) blocked were further investigated. The results shown that the differentially expressed genes in lymphocytes after IL-2 stimulation were annotated to the pathways related to the immune response of B cells. The percentages of mIgM⁺ B cells were increased, and the capacities of antibody secretion and phagocytosis of B cells were enhanced after IL-2 stimulation. However, the function of IL-2 on B lymphocytes immunity was significantly inhibited after IL-2 receptors were blocked, especially after IL-2Rβ was blocked. Collectively, we can conclude that IL-2 is able to promote the proliferation of B lymphocytes, antibody secretion, and enhance their phagocytosis in flounder, and these effects are mediated through IL-2/IL-2R signaling.

Long non‐coding RNA, a supreme post‐transcriptional immune regulator of bacterial or virus‐driven immune evolution in teleost

The global aquaculture boom, fuelled by a reduction in wild population and detection of novel viruses, has created a demanding market, hence, there is a pressing need to investigate the immune system of fish, further. As the most diverse community of vertebrates and a central contributor to the progressing global aquaculture market, teleost continues to draw vast scientific interest. Recent breakthroughs in multi‐omics technologies have provided a platform to understand the role of long non‐coding RNA (lncRNA) in the host immune system during infection. Emerging evidence shows that teleost lncRNA might have a regulatory role in immune responses, mostly through lncRNA–microRNA (miRNA) sponging. Teleost lncRNA shares a functionally active short sequence complement to target the miRNA which is conserved among the several fish species. Recent report suggests that rhabdovirus exploits a lncRNA in teleost and, to dodge the host immune mechanism and negatively regulate the immune system. This observation reveals the essentiality of lncRNA in pathogen‐driven immunity in teleost. Reports available on the function of teleost lncRNA are still in early stages and experimental verifications are a limiting factor. Unravelling the lncRNA‐mediated immune regulation in fishes could be used against the invading pathogens to strengthen the aquaculture production. This review elaborates on the experimentally identified and functionally characterized lncRNA and its regulatory role in the teleost immune response during infection and pathogen‐driven host immune evolution, which could eventually lead to achieving high standards in aquaculture productivity.

Divergent Carry-Over Effects of Hypoxia during the Early Development of Abalone

After being exposed to environmental stimuli during early developmental stages, some organisms may gain or weaken physiological regulating abilities, which would have long-lasting effects on their performance. Environmental hypoxia events can have significant effects on marine organisms, but for breeding programs and other practical applications, it is important to further explore the long-term physiological effects of early hypoxia exposure in economically significant species. In this study, the Pacific abalone Haliotis discus hannai was exposed to moderate hypoxia (∼4 mg/L) from zygote to trochophora, and the assessments of hypoxia tolerance were conducted on the grow-out stage. The results revealed that juvenile abalones exposed to hypoxia at the early development stages were more hypoxia-tolerant but with slower weight growth, a phenomenon called the trade-off between growth and survival. These phenotypic effects driven by the hypoxia exposure were explained by strong selection of genes involved in signal transduction, autophagy, apoptosis, and hormone regulation. Moreover, long non-coding RNA regulation plays an important role modulating carry-over effects by controlling DNA replication and repair, signal transduction, myocardial activity, and hormone regulation. This study revealed that the ability to create favorable phenotypic differentiation through genetic selection and/or epigenetic regulation is important for the survival and development of aquatic animals in the face of rapidly changing environmental conditions.

Identification and characterization of lncRNAs and the interaction of lncRNA-mRNA in Epinephelus coioides induced with Singapore grouper iridovirus infection

Singapore grouper iridovirus (SGIV) is a highly pathogenic double-stranded DNA virus, and the fatality rate of SGIV-infected grouper is more than 90%. Up to now, there is no effective methods to control the disease. Long non-coding RNAs (lncRNAs) might play an important role in individual growth and development, immune regulation and other life processes. In this study, lncRNAs were identified in Epinephelus coioides, an important economic aquaculture marine fish in China and Southeast Asia, and the regulatory relationships of lncRNAs and mRNA response to SGIV infection were analyzed. A total of 11,678 lncRNAs were identified and classified from the spleen and GS (grouper spleen) cells. 105 differentially expressed lncRNAs (DElncRNAs) were detected during SGIV infection. The lncRNAs and the regulated mRNAs were analyzed using co-expression network, lncRNA target gene annotation and GO enrichment. At 24 and 48 h after SGIV infection, 118 and 339 lncRNA-mRNA pairs in GS cells were detected, and 728 and 688 differentially expressed lncRNA-mRNA pairs in spleen were obtained, respectively. GO and KEGG were used to predict the DE lncRNAs' target genes, and deduce the DE lncRNAs-affected signaling pathways. In GS cells, lncRNAs might participate in cell part, binding and catalytic activity; and lncRNAs might be involved in immune system process and transcription factor activity in spleen. These data demonstrated that lncRNAs could regulate the expression of immune-related genes response to viral infection, and providing a new insight into understanding the complexity of immune regulatory networks mediated by lncRNAs during viral infection in teleost fish.

Full-length transcriptome and analysis of bmp-related genes in Platypharodon extremus

Platypharodon extremus is an endemic species on the Qinghai–Tibet Plateau. As a secondary protected species in China, the basic genomic information of this species has not yet been reported. Here, through third-generation sequencing, the full-length transcriptome of P. extremus was obtained. We identified 323,290 CCS sequences, and a total of 50,083 unigenes were extracted after correction with second-generation sequencing data and the removal of redundant reads. A total of 50,067 transcripts were annotated with the various databases. Based on the sequence information, three members in the bone morphogenetic proteins (bmps) family and their receptors, were identified. We found that the special structures of these proteins (zinc-dependent metalloproteinase domain, CUB domains, EGF-like domains and TGF-β domain) are highly conserved in fish and that they are closely evolutionarily related to the bmps and bmp receptors of Cyprinidae fishes. This is the first study to sequence the full-length transcriptome of P. extremus, which will help us to further understand its biology.

The Emerging Role of Long Non-Coding RNAs in Development and Function of Gilthead Sea Bream (Sparus aurata) Fast Skeletal Muscle

Long non-coding RNAs (lncRNAs) are an emerging group of ncRNAs that can modulate gene expression at the transcriptional or translational levels. In the present work, previously published transcriptomic data were used to identify lncRNAs expressed in gilthead sea bream skeletal muscle, and their transcription levels were studied under different physiological conditions. Two hundred and ninety lncRNAs were identified and, based on transcriptomic differences between juveniles and adults, a total of seven lncRNAs showed potential to be important for muscle development. Our data suggest that the downregulation of most of the studied lncRNAs might be linked to increased myoblast proliferation, while their upregulation might be necessary for differentiation. However, with these data, as it is not possible to propose a formal mechanism to explain their effect, bioinformatic analysis suggests two possible mechanisms. First, the lncRNAs may act as sponges of myoblast proliferation inducers microRNAs (miRNAs) such as miR-206, miR-208, and miR-133 (binding energy MEF < -25.0 kcal). Secondly, lncRNA20194 had a strong predicted interaction towards the myod1 mRNA (ndG = -0.17) that, based on the positive correlation between the two genes, might promote its function. Our study represents the first characterization of lncRNAs in gilthead sea bream fast skeletal muscle and provides evidence regarding their involvement in muscle development.