Bei Wang

Trachinotus ovatus (golden pompano) represents one of the dominant high-value mariculture fish species farmed across coastal regions of China. In intensive farming modes, intestinal damage and immune suppression are frequent issues in golden pompano; the widespread application of antibiotics in disease control has also triggered increasing worries about ecological risks and aquatic product safety. Host-origin probiotics have been widely recognized as a green and safe strategy to mitigate health risks and promote growth in farmed fish. Nevertheless, the regulatory roles and mechanisms of autochthonous E. faecalis strains on the intestinal health of golden pompano are still poorly understood. In this study, a 42-day feeding trial was conducted using golden pompano reared in a large-capacity floating net-cage system. The experimental fish were fed diets supplemented with different concentrations of E. faecalis SZ07 (1 × 10⁵ to 1 × 10⁹ CFU/g feed). Dietary supplementation with SZ07 at suitable doses (1 × 10⁷ to 1 × 10⁸ CFU/g feed) notably improved intestinal tissue structure, elevated the activities of digestive, antioxidant, and immune enzymes, and modulated the mRNA levels of key immune genes in the spleen. Analysis of the gut microbiota revealed that dietary E. faecalis SZ07 reshaped the intestinal microbial community, with an increased abundance of beneficial taxa and a decreased proportion of opportunistic pathogens. Taken together, our results indicate that autochthonous E. faecalis SZ07 acts as an effective probiotic to enhance intestinal health and immune function of golden pompano and offers technical support for the healthy development of its aquaculture industry.

Non-specific cytotoxic cells (NCCs) are critical first-line defenses against bacterial pathogens in teleosts, yet the molecular mechanisms governing their activity remain poorly understood. This study characterized LOC109197777, a novel long non-coding RNA (lncRNA) from Nile tilapia (Oreochromis niloticus), as a positive regulator of NCC-mediated immunity against Streptococcus agalactiae. Bioinformatic and experimental analyses confirmed its non-coding potential and predominant cytoplasmic localization. In vitro, overexpression of LOC109197777 in tilapia head kidney cells upregulated NCC activation receptors while downregulating effector molecules and pro-inflammatory cytokines, indicating a "primed but restrained" activation state; conversely, siRNA-mediated knockdown reduced NCC cytotoxicity. In vivo, intraperitoneal delivery of LOC109197777 significantly enhanced survival following S. agalactiae challenge and reduced bacterial burdens in the head kidney and spleen. Furthermore, tissue-specific expression profiling revealed that LOC109197777 orchestrates spatially distinct regulatory programs: rapid activation in the head kidney, sustained responses in the spleen, early responses in the liver, and prolonged mucosal immunity in the intestine. Notably, the lncRNA differentially regulated perforin-1 and granzyme B in a tissue and time-dependent manner, balancing effective pathogen clearance with immune homeostasis. These findings establish LOC109197777 as the first characterized lncRNA regulator of NCC activity in teleosts, operating through a tissue-specific, temporally coordinated mechanism. This study provides a novel molecular target for genetic enhancement of disease resistance in tilapia aquaculture and offers a theoretical foundation for developing lncRNA-based immunomodulatory strategies.

The molecular coordination between the central nervous system and peripheral organs is fundamental to euryhalinity. This study elucidates the distinct adaptive strategies of the brain and gills in the four-finger threadfin (Eleutheronema tetradactylum), an aquaculture species of growing importance, during long-term (30-day) acclimation to low salinity (5 versus 25 control). A profound dichotomy in tissue-specific plasticity was uncovered: while the brain maintained remarkable transcriptional stability with only 10 differentially expressed genes (DEGs), the gills underwent extensive remodeling with 702 DEGs. Gill DEGs were functionally enriched in ion transport and metabolic remodeling, highlighted by the significant upregulation of the Na⁺-Cl⁻ cotransporter (slc12a10) and the prolactin receptor (prlr), coupled with a profound downregulation (log₂FC = −5.97) of aquaporin-1 (aqp1). This indicates a concerted strategy to enhance ion uptake while minimizing water permeability. In contrast, the brain’s subtle response was dominated by the upregulation of key neuroendocrine hormones, including growth hormone (gh), prolactin (prl), and pro-opiomelanocortin (pomc). This suggests a top-down regulatory cascade. Integrative pathway analysis identified the PI3K-Akt and JAK-STAT signaling pathways as the primary conduits linking central hormonal signals to peripheral physiological adjustments. These results demonstrate that the euryhalinity of E. tetradactylum is achieved through a highly efficient strategy: a transcriptionally stable brain provides precise endocrine commands that orchestrate robust peripheral remodeling in the gills. This study deciphers the molecular basis of the brain–gill axis in osmoregulation and provides a rich repository of candidate genes for the genetic improvement of low salinity tolerance in aquaculture.

Thioredoxin (TRX) is an important redox-related protein, which plays a key role in maintaining redox balance in cells. However, the role of TRX in ammonia exposure of Oreochromis niloticus is still unknown. In this study, we successfully cloned the TRX gene (OnTRX) of O. niloticus and performed systematic bioinformatics analysis. The results of multi-sequence alignment and phylogenetic tree analysis showed that OnTRX is highly conserved in vertebrates, but exhibits low sequence similarity with TRX homologs from arthropods (crustaceans). The tissue distribution of OnTRX and its transcriptional response to ammonia challenge were determined by qRT-PCR, and we further investigated the relationship between OnTRX and the response of the Nile tilapia epithelial cell line (TSE-04) to NH₄Cl treatment. The results showed that OnTRX exhibited tissue-specific expression, with a relatively high expression level in gill tissue. Ammonia exposure could significantly induce the expression of OnTRX in the gill, head kidney, intestine, skin, liver, and spleen of tilapia. In TSE-04 cells, OnTRX overexpression was associated with reduced NH₄Cl-induced morphological damage, a lower proportion of apoptotic cells, and altered transcript levels of several stress-related genes. Collectively, these findings indicate that OnTRX is likely involved in the regulatory response of Nile tilapia to ammonia-induced stress, while the underlying molecular mechanisms thereof remain to be further elucidated.

This study aimed to elucidate the key characteristics of the humoral immune response and the tissue distribution of specific antibody-secreting cells (ASCs) in Nile tilapia (Oreochromis niloticus). A specific immune model was established by immunizing fish with human IgG. Lymphocytes were isolated from the head kidney, spleen, and peripheral blood and subjected to antigen stimulation in vitro. The MTT assay, reflecting cell metabolic activity and viability, identified the optimal culture conditions as a cell concentration of 2.5 × 10⁶ cells/mL, an antigen concentration of 2 μg/mL, and a culture duration of 72 h. Under these conditions, peripheral blood lymphocytes exhibited the most increase in metabolic activity, followed by head kidney lymphocytes, while splenic lymphocytes showed no significant response. Subsequent dynamic monitoring of antibody-secreting cells (ASCs) using ELISPOT revealed that, in the absence of antigen stimulation, ASC numbers from all three tissues declined over time. Notably, head kidney ASCs retained approximately 50% of their initial number by day 5, whereas ASCs in peripheral blood and spleen decayed to barely detectable or completely undetectable levels, respectively. These findings suggest that the head kidney may serve as a primary site for ASC persistence during the effector phase, potentially contributing to sustained humoral immunity. Although antigen stimulation did not induce significant ASC expansion, it significantly slowed their decay rate (p < 0.05), indicating an antigen-dependent maintenance role. ELISA detection of antibody levels in the culture supernatants showed a consistent trend with the ELISPOT results, further confirming the sustained functional support of antigen for ASCs. Additionally, LPS stimulation experiments demonstrated that all three tissues contained plasmablasts activatable by non-specific stimuli, with peripheral blood showing the highest proliferation fold (4–6 times). In conclusion, this study provides insights into the tissue-specific distribution, in vitro persistence, and antigen-dependent maintenance of ASCs in Nile tilapia, providing insights into the cellular basis that may contribute to humoral immune memory and laying a theoretical foundation for the rational design and application of tilapia vaccines.

Aquaculture is the fastest‐growing food‐producing sector globally, yet intensive farming in China has led to severe ecological degradation of coastal marine pastures, including habitat loss, disease outbreaks, and dysbiosis of cultured species. Probiotics (beneficial live microorganisms) and prebiotics (non‐digestible substrates that promote beneficial microbiota) offer eco‐friendly alternatives to antibiotics and chemicals, aligning with China’s “Blue Granary” and marine ecological restoration initiatives. Recent advances demonstrate that multi‐strain probiotics (including Lactobacillus , Bacillus , and marine‐derived Vibrio spp.) and prebiotics (including mannan oligosaccharides, fructooligosaccharides, and seaweed‐derived polysaccharides) significantly enhance growth performance, immune responses, and disease resistance in key Chinese aquaculture species such as sea cucumber ( Apostichopus japonicus ), shrimp ( Litopenaeus vannamei ), and large yellow croaker ( Larimichthys crocea ). These biotics modulate gut and water microbiota, improve nutrient utilization, suppress pathogenic Vibrio populations, and mitigate environmental stress. In marine ranching and pasture restoration projects, probiotic‐prebiotic synbiotics have accelerated the recovery of degraded seaweed beds and benthic communities while reducing harmful algal blooms (HABs) and organic sediment loads. This review synthesizes evidence from Chinese and international studies (2018–2025) and highlights successful field‐scale applications in Bohai Bay, the Yellow Sea, and the South China Sea restoration zones. Integrating probiotics and prebiotics into feed and water management supports antibiotic‐free aquaculture, enhances carbon sequestration in marine pastures, and advances China’s goals of ecological civilization and sustainable blue economy.

Hemolysin co-regulated protein 2 (Hcp2) is a core component of the type VI secretion system 2 in Vibrio alginolyticus, a widespread marine pathogen that infects humans and aquaculture species. Deletion of hcp2 (Δhcp2) significantly attenuated virulence in zebrafish larvae, showing reduced abdominal edema and impaired toll-like receptor (tlr)2 and tlr4-mediated innate immune activation compared with the wildtype strain. Enzyme-linked immunosorbent assay and cell lysis assays revealed that the Δhcp2 strain exhibited decreased levels of lipopolysaccharide (LPS) and peptidoglycan (PGN), along with increased cell permeability and abnormal cell wall structures observed by transmission electron microscopy. Proteomic and transcriptional analyses further demonstrated that expression of the Sec system components SecB, SecD, and SecF was markedly reduced in the Δhcp2 strain and positively regulated by hcp2. Bioinformatic prediction combined with protein–DNA docking analysis suggested that the transcription of secB, secD, and secF was co-regulated by the cAMP and cAMP Receptor Protein (cAMP–CRP) complex and RNA polymerase sigma D factor (RpoD), although rpoD expression itself remained unaffected. Together with previous evidence that Hcp2 positively regulates cAMP–CRP, these findings suggested that Hcp2 modulated LPS and PGN translocation, probably through the cAMP–CRP pathway, thereby maintaining cell wall integrity and virulence in V.alginolyticus.