Preliminary analysis of pathways and their implications during salinity stress in abalone.

Transcriptome sequencing has offered immense opportunities to study non-model organisms. Abalone is an important marine mollusk that encounters harsh environmental conditions in its natural habitat and under aquaculture conditions; hence, research that increases molecular information to understand abalone physiology and stress response is noteworthy. Accordingly, the study used transcriptome sequencing of the gill tissues of abalone exposed to low salinity stress. The aim is to explore some enriched pathways during salinity stress and the crosstalk and functions of the genes involved in the candidate biological processes for future further analysis of their expression patterns. The data suggest that abalone genes such as YAP/TAZ, Myc, Nkd, and Axin (involved in the Hippo signaling pathway) and PI3K/Akt, SHC, and RTK (involved in the Ras signaling pathways) might mediate growth and development. Thus, deregulation of the Hippo and Ras pathways by salinity stress could be a possible mechanism by which unfavorable salinities influence growth in abalone. Furthermore, PEPCK, GYS, and PLC genes (mediating the Glucagon signaling pathway) might be necessary for glucose homeostasis, reproduction, and abalone meat sensory qualities; hence, a need to investigate how they might be influenced by environmental stress. Genes such as MYD88, IRAK1/4, JNK, AP-1, and TRAF6 (mediating the MAPK signaling pathway) could be useful in understanding abalone's innate immune response to environmental stresses. Finally, the aminoacyl-tRNA biosynthesis pathway hints at the mechanism by which new raw materials for protein biosynthesis are mobilized for physiological processes and how abalone might respond to this process during salinity stress. Low salinity clearly regulated genes in these pathways in a time-dependent manner, as hinted by the heat maps. In the future, qRT-PCR verification and in-depth study of the various genes and proteins discussed would provide enormous molecular information resources for the abalone biology.

Effects of autochthonous strains mixture on gut microbiota and metabolic profile in cobia (Rachycentron canadum).

The fish immune system is a topic or subject that offers a unique understanding of defensive system evolution in vertebrate heredity. While gut microbiota plays several roles in fish: well-being, promoting health and growth, resistance to bacterial invasion, regulation of energy absorption, and lipid metabolism. However, studies on fish gut microbiota face practical challenges due to the large number of fish varieties, fluctuating environmental conditions, and differences in feeding habits. This study was carried out to evaluate the impacts of supplemented three autochthonous strains, Bacillus sp. RCS1, Pantoea agglomerans RCS2, and Bacillus cereus RCS3 mixture diet on cobia fish (Rachycentron canadum). Also, chromatography, mass spectrometry and high throughput sequencing were combined to explore composition and metabolite profile of gut microbiota in juvenile cobia fed with supplemented diet. In the trial group, juvenile cobia received diets supplemented with 1 × 1012 CFU mL-1 autochthonous strains for ten weeks and a control diet without supplementation. Juvenile cobia receiving diets supplementation exhibited significantly improved growth than those without additives (control). Haematological indices, such as red blood cells, white blood cells, corpuscular haemoglobin concentration, mean corpuscular volume, haemoglobin, and mean corpuscular haemoglobin, were higher in the supplemented group. Similarly, digestive enzymes (trypsin, lipase, amylase, pepsin and cellulose, activities) activities were higher in supplemented diet with an indigenous isolates mixture. Serum biochemical parameters albumin, globulin, and total protein were significantly higher, while triglyceride, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and cholesterol showed no significant difference. On the other hand, glucose was significantly (P < 0.05) higher in the group without supplementation. On gene expression in the midgut, Immunoglobulin, Colony-stimulating factor receptor 1, major histocompatibility complex 1 were up-regulated by native isolates while T cell receptor beta, and Major histocompatibility complex 2 showed no significant difference. Gut bacterial composition was altered in fish receiving supplemented diet with autochthonous strains. Metabolomics also revealed that some metabolic pathways were considerably enriched in fish fed with supplemented diet; pathway analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed that differentially expressed metabolites were involved in galactose metabolism, tryptophan metabolism, carbohydrate digestion and absorption, purine metabolism, and ABC transporters. Functional analysis of bacterial community showed that differences in enriched metabolic pathways generally comprised carbohydrate and its metabolites, nucleotide and its metabolites, amino acid and its metabolites, heterocyclic compounds, and tryptamines, cholines, pigments. The current investigation results showed that autochthonous strains mixture has significantly enhanced the growth, survival, and innate and adaptive immunities of juvenile cobia.

Dietary soybean antigen impairs growth and health through stress-induced non-specific immune responses in Pacific white shrimp, Litopenaeus vannamei.

In order to compare the effect of substituting fish meal with fermented soybean meal and soybean meal, and confirmed whether the benefit from the two feed materials was related to the content of inclusive soybean antigen protein, two experiments were designed. In experiment 1, one of the two practical diets contained 24.9% soybean meal (SBM), the other one containing 8% fermented soybean meal and 16.95% soybean meal (FSBM); in experiment 2, two semi-purified diets were included with high antigen protein (SPD1) and low antigen protein (SPD2) approximately equal to SBM and FSBM group respectively in experiment 1. Diets were fed to Litopenaeus vannamei (initial weight: 7.48 ±â€¯0.24 g) for 60 days. The results showed that in experiment 1, growth performance was not significantly different between two groups, the enzyme activity (AKP, AST, ALT, SOD and LZM) and mRNA expression levels of TLR, LZM, IMD and HSP70 were significantly higher in the SBM group; In experiment 2, weight gain and specific growth rate were significantly higher in the SPD2 group, while higher activities of AKP, ALT and LZM, lower expression levels of TLRmRNA, LZMmRNA and IMDmRNA and higher expression level of HSP70mRNA were found in SPD1 group. These results implied SBM was more likely to induce stress reaction in shrimp than FSBM, which were closely related to the antigen protein in SBM.

Suppression of miR-26a attenuates physiological disturbances arising from exposure of Nile tilapia (Oreochromis niloticus) to ammonia.

MicroRNAs may affect stress responses because they act as rapid responders at the post-translation level. In this study, we found that miR-26a is abundantly expressed in the brain and gill tissues of tilapia. Expression of miR-26a in the brain decreased significantly with increasing ammonia concentrations using stem-loop qPCR. To analyze the function of miRNA in vivo, miR-26a was stably knocked down with an antagomir in tilapia. Following ammonia challenge, miR-26a antagomir treatment significantly suppressed blood ammonia/[Cl-]/[K+] concentration and the reactive oxygen species production, while it markedly enhanced glutamine accumulation and antioxidant enzyme activity in the brain of tilapia, indicating that miR-26a may be involved in the remission of physiological disturbances resulting from ammonia stress. We strongly conclude that there is a direct link between miR-26a and the responses to ammonia in tilapia. Furthermore, bioinformatics analysis and luciferase assays demonstrated that miR-26a regulates HSP70 (heat shock protein 70) and GS (glutamine synthetase) expression by targeting their 3'-UTR and that the suppression of miR-26a could increase the intracellular level of HSP70 and GS in vivo.