Study on the osmotic response and function of myo-inositol oxygenase in euryhaline fish nile tilapia (Oreochromis niloticus).

To understand the role of myo-inositol oxygenase (miox) in the osmotic regulation of Nile tilapia, its expression was analyzed in various tissues. The results showed that the expression of miox gene was highest in the kidney, followed by the liver, and was significantly upregulated in the kidney and liver under 1 h hyperosmotic stress. The relative luminescence efficiency of the miox gene transcription starting site (-4,617 to +312 bp) under hyperosmotic stress was measured. Two fragments (-1,640/-1,619 and -620/-599) could induce the luminescence activity. Moreover, the -1,640/-1,619 and -620/-599 responded to hyperosmotic stress and high-glucose stimulation by base mutation, suggesting that osmotic and carbohydrate response elements may exist in this region. Finally, the salinity tolerance of Nile tilapia was significantly reduced after the knocking down of miox gene. The accumulation of myo-inositol was affected, and the expression of enzymes in glucose metabolism was significantly reduced after the miox gene was knocked down. Furthermore, hyperosmotic stress can cause oxidative stress, and MIOX may help maintain the cell redox balance under hyperosmotic stress. In summary, MIOX is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting myo-inositol accumulation, glucose metabolism, and antioxidant performance.NEW & NOTEWORTHY Myo-inositol oxygenase (MIOX) is the rate-limiting enzyme that catalyzes the first step of MI metabolism and determines MI content in aquatic animals. To understand the role of miox in the osmotic regulation of Nile tilapia, we analyzed its expression in different tissues and its function under hyperosmotic stress. This study showed that miox is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting myo-inositol accumulation, glucose metabolism, and antioxidant performance.

Aggregation-Induced Emission Photosensitizer Boosting Algal Growth and Lipid Accumulation.

Mass production of microalgae is a research focus owing to their promising aspects for sustainable food, biofunctional compounds, nutraceuticals, and biofuel feedstock. This study uses a novel approach to enhance microalgae-derived biomass and metabolites by using an aggregation-induced emission (AIE) photosensitizer (PS), CN-TPAQ-PF6 ([C32H23N4]+). The unique AIE features of CN-TPAQ-PF6 facilitate nano-aggregation in aquatic media for an effective light spectral shift for photosynthetic augmentation in a green microalga, Chlamydomonas reinhardtii. The high reactive oxygen species (ROS) production capacity and redox-based cellular modulations reveal its potential to upsurge algal growth and lipid biosynthesis and fabricate fatty acid profiles in the metabolic pathways. Algal cells are labeled with other AIE-based nanoprobes, which are suitable as an in vivo visualization toolkit with superior fluorescence. Furthermore, cytotoxicity analysis of CN-TPAQ-PF6 on the HaCat cell line confirms that this AIE PS is biocompatible without adverse impact on living cells. The results demonstrate the property of AIE PS for the first time in enhancing algal growth and lipid accumulation simultaneously.

The interaction between lipid and vitamin D3 impacts lipid metabolism and innate immunity in Chinese mitten crabs Eriocheir sinensis.

As a fat-soluble vitamin, vitamin D3 relies on fat to perform its biological function, affecting lipid metabolism and innate immunity. This study used different percentages of lipid and vitamin D3 diets to evaluate the synergistic effects on the growth, lipid metabolism and immunity of juvenile Eriocheir sinensis (5.83 ± 0.01 g) for 56 days, including low lipid (LL, 1.5%) and normal lipid (NL, 7.5%) and three levels of vitamin D3: low (LVD, 0 IU/kg), medium (MVD, 9000 IU/kg) and high (HVD, 27,000, IU/kg). The synergistic effect of lipid and vitamin D3 was not significant on growth but significant on ash content, total protein, hepatopancreas lipid content, hemolymph 1α,25-hydroxy vitamin D3 [1α,25(OH)2D3] content, hepatopancreas lipolysis and synthesis genes. Crabs fed normal lipid (7.5%) and medium vitamin D3 (9000 IU/kg) had the highest hepatopancreas index, hemolymph 1α,25(OH)2D3 content, antibacterial ability, immune-related genes and hepatopancreatic lipid synthesis genes expression, but down-regulated the lipolysis genes expression. In contrast, crabs fed diets with low lipid percentage (1.5%) had low growth performance, hemolymph 1α,25(OH)2D3, mRNA levels of lipid synthesis genes, antibacterial ability and immune-related gene expression. At the 1.5% lipid level, excessive or insufficient vitamin D3 supplementation led to the obstruction of ash and protein deposition, reduced growth and molting, aggravated the reduction in antioxidant capacity, hindered antimicrobial peptide gene expression and reduced innate immunity, and resulted in abnormal lipid accumulation and the risk of oxidative stress. This study suggests that diets' lipid and vitamin D3 percentage can enhance antioxidant capacity, lipid metabolism and innate immunity in E. sinensis. A low lipid diet can cause growth retardation, reduce antioxidant capacity and innate immunity, and enhance lipid metabolism disorder.

Growth and Hepatopancreas Health of Juvenile Chinese Mitten Crab (Eriocheir sinensis) Fed Different Levels of Black Soldier Fly (Hermetia illucens) Larvae Meal for Fish Meal Replacement.

A 56-day feeding trial assessed the effects of black soldier fly larvae meal (BSFLM) on the growth performance and hepatopancreas health of juvenile Eriocheir sinensis. Six isoproteic and isolipidic diets with 0% (FM), 10% (BSFLM10), 20% (BSFLM20), 30% (BSFLM30), 40% (BSFLM40), or 50% (BSFLM50) replacement of fish meal by BSFLM were formulated. Compared to FM, replacing 10%-40% of fish meal with BSFLM did not significantly affect the weight gain rate (WGR) or specific growth rate (SGR), while BSFLM50 significantly decreased the WGR and SGR. Crabs fed BSFLM50 had significantly lower T-AOC activity than those fed other diets, and crabs fed BSFLM30, BSFLM40, or BSFLM50 had significantly lower activities of antioxidant enzymes (SOD and GSH-Px) in the hepatopancreas than those fed FM or BSFLM10. Compared to FM, BSFLM10, BSFLM20, and BSFLM30 did not affect the relative expression of genes related to the nonspecific immunity, while BSFLM40 and BSFLM50 upregulated the relative expression of these genes. Furthermore, histological analysis showed that the hepatopancreas was deformed in the BSFLM50 group, with widened lumens and loss of basal membrane integrity. In summary, BSFLM replacing 50% of fish meal reduced growth and structural damage to the hepatopancreas. An immune response was activated when the replacement level was over 30%. Therefore, the replacement level of dietary fish meal by BSFLM is recommended to be not more than 30% of the juvenile E. sinensis feed.

Changes in transcriptome regulations of a marine rotifer Brachionus plicatilis under methylmercury stress.

Mercury (Hg), a heavy metal pollutant worldwide, can be transformed into methylmercury (MeHg) by various aquatic microorganisms in water, thus accumulating along the aquatic food chain and posing a particular challenge to human health. Zooplankton plays a crucial role in aquatic ecosystems and serves as a major component of the food chain. To evaluate the effects of MeHg on the rotifer Brachionus plicatilis and reveal the underlying mechanism of these effects, we exposed B. plicatilis to MeHg by either direct immersion or by feeding with MeHg-poisoned Chlorella pyrenoidesa, respectively, and conducted a transcriptomic analysis. The results showed that B. plicatilis directly exposed to MeHg by immersion showed significant enrichment of the glutathione metabolism pathway for detoxification of MeHg. In addition, the exposure to MeHg by feeding induced a significant enrichment of lysosome and notch signaling pathways of rotifers, supporting the hypothesis that MeHg can induce autophagy dysfunction in cells and disturb the nervous system of rotifers. In two different routes of MeHg exposure, the pathway of cytochrome P450 in rotifers showed significant enrichment for resisting MeHg toxicity. Our results suggest further studies on the potential mechanism and biological responses of MeHg toxicity in other links of the aquatic food chain.

Quantitative proteomic and metabolomic profiling reveals different osmoregulation mechanisms of tilapia cells coping with different hyperosmotic stress.

This study aimed to investigate the different regulatory mechanisms of euryhaline fish under regular hyperosmotic and extreme hyperosmotic stress. The OmB (Oreochromis mossambicus brain) cells were exposed to three treatments: control, regular hyperosmotic stress and extreme hyperosmotic stress. After 12 h exposure, proteomics, metabolomics analyses and integrative analyses were explored. Both kinds of stress lead to lowering cell growth and morphology changes, while under regular hyperosmotic stress, the up-regulated processes related with compatible organic osmolytes synthesis are crucial strategy for the euryhaline fish cell line to survive; On the other hand, under extreme hyperosmotic stress, the processes related with cell apoptosis and cell cycle arrest are dominant. Furthermore, down-regulated pyrimidine metabolism and several ribosomal proteins partially participated in the lowered cell metabolism and increased cell death under both kinds of hyperosmotic stress. The PI3K-Akt and p53 signaling pathways were involved in the stagnant stage of cell cycles and induction of cell apoptosis under both kinds of hyperosmotic stress. However, HIF-1, FoxO, JAK-STAT and Hippo signaling pathways mainly contribute to disrupting the cell cycle, metabolism and induction of cell apoptosis under extreme hyperosmotic stress. SIGNIFICANCE: In the past, the research on fish osmoregulation mainly focused on the transcription factors and ion transporters of osmoregulation, the processes between osmotic sensing and signal transduction, and the associations between signaling pathways and regulation processes have been poorly understood. Investigating fish cell osmoregulation and potential signal transduction pathways is necessary. With the advancements in omics research, it is now feasible to investigate the relationship between environmental stress and molecular responses. In this study, we aimed to explore the signaling pathways and substance metabolism mode during hyper-osmoregulation in OmB cell line, to reveal the key factors that are critical to cell osmoregulation.

Identification of B-cell epitope on the N protein of type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) using monoclonal antibody and construction of epitope-mutated virus.

The escalating epidemic of PRRSV-1 in China has prompted widespread concern regarding the evolution of strains, disparities in pathogenicity to herds, and immunological detection of emerging strains. The nucleocapsid (N) protein, as a highly conserved protein with immunogenic properties in PRRSV, is a subject of intensive study. In this research, the recombinant His-N protein was expressed based on the N gene of PRRSV-1 using a prokaryotic expression system and then administered to BALB/c mice. A cell fusion protocol was implemented between SP2/0 cells and splenocytes, resulting in the successful screening of a monoclonal antibody against the N protein, designated as mAb 2D7, by indirect ELISA. Western Blot analysis and Indirect Immunofluorescence Assay (IFA) confirmed that mAb 2D7 positively responded to PRRSV-1. By constructing and expressing a series of truncated His-fused N proteins, a B-cell epitope of N protein, 59-AAEDDIR-65, was identified. A sequence alignment of two genotypes of PRRSV revealed that this epitope is relatively conserved in PRRSV, yet more so in genotype 1. Cross-reactivity analysis by Western blot analysis demonstrated that the B-cell epitope containing D62Y mutation could not be recognized by mAb 2D7. The inability of mAb 2D7 to recognize the epitope carrying the D62Y mutation was further determined using an infectious clone of PRRSV. This research may shed light on the biological significance of the N protein of PRRSV, paving the way for the advancement of immunological detection and development of future recombinant marker vaccine.