Molecular identification and functional analysis of MyD88 in giant freshwater prawn (Macrobrachium rosenbergii) and expression changes in response to bacterial challenge

Identification of toll-like receptor family and the immune function of new Sptlr-6 gene of Scylla paramamosain

As a crucial member of pattern-recognition receptors (PRRs), the Tolls/Toll-like receptors (TLRs) gene family has been proven to be involved in innate immunity in crustaceans. In this study, nine members of TLR gene family were identified from the mud crab (Scylla paramamosain) transcriptome, and the structure and phylogeny of different SpTLRs were analyzed. It was found that different SpTLRs possessed three conserved structures in the TIR domain. Meanwhile, the expression patterns of different Sptlr genes in examined tissues detected by qRT-PCR had wide differences. Compared with other Sptlr genes, Sptlr-6 gene was significantly highly expressed in the hepatopancreas and less expressed in other tissues. Therefore, the function of Sptlr-6 was further investigated. The expression of the Sptlr-6 gene was up-regulated by Poly I: C, PGN stimulation and Vibrio parahaemolyticus infection. In addition, the silencing of Sptlr-6 in hepatopancreas mediated by RNAi technology resulted in the significant decrease of several conserved genes involved in innate immunity in mud crab after V. parahaemolyticus infection, including relish, myd88, dorsal, anti-lipopolysaccharide factor (ALF), anti-lipopolysaccharide factor 2 (ALF-2) and glycine-rich antimicrobial peptide (glyamp). This study provided new knowledge for the role of the Sptlr-6 gene in defense against V. parahaemolyticus infection in S. paramamosain.

Bacillus-supplemented diet improves growth performance in Jeju native pigs by modulating myogenesis and adipogenesis

Probiotics are used in pigs as nutritional supplements to improve health and induce the development of muscle and adipose tissue for enhancing growth performance and harvesting quality meat. In this study, we investigated the effects of Bacillus-based probiotic supplementation on the physiological and biochemical changes in Jeju native pigs (JNPs), including growth performance, backfat layers, blood parameters, serum IgG levels, myogenic and adipogenic markers, and expression of inflammatory markers. Average daily gain and feed efficiency were higher in the Bacillus diet group than in the basal diet group, while backfat thickness was lower in the Bacillus diet group than in the basal diet group. Blood biochemical parameters and hematological profiles were not altered significantly by Bacillus-based probiotic supplementation. Serum IgG concentration increased in the Bacillus diet group compared to the basal diet group. The Bacillus diet group showed increased adipogenic and myogenic markers expression in the longissimus dorsi muscle and adipose tissues. Overall, the data suggest that the Bacillus-based probiotics-supplemented diet regulates myogenesis and adipogenesis in JNPs and improves growth performance. We postulate that this may be due to the changes in the gut microbiota of pigs due to probiotic supplementation.

Transcriptomic profiling and characterization of microRNAs in Macrobrachium rosenbergii potentially involved in immune response to Enterobacter cloacae infection

Enterobacter cloacae is a member of the Enterobacter family, which could prevent Macrobrachium rosenbergii from growing and cause mass mortality. However, no research has focused on microRNA immunity in M. rosenbergii infected with E. cloacae. To clarify the immune response mechanisms, transcriptomic analysis was performed on the miRNAs of M. rosenbergii infected with E. cloacae YZ3 strain. Following quality screening, 10,616,712 clean reads were obtained from the control group and 12,726,421 from the infected group. Among 899 known miRNAs, 446 differentially expressed miRNAs (DEMs) were identified. Meanwhile, 59 novel miRNAs were predicted, along with 39 DEMs. Target genes of DEMs have been predicted in order to gain a deeper understanding of the immune-related functions. GO and KEGG pathway analysis revealed the biological functions and signaling pathways of target genes. The results indicated that E. cloacae significantly affected the NOD-like receptor, RIG-I-like receptor and Toll-like receptor pathways. Ten DEMs were randomly selected, and their expression level was verified by Quantitative Real-time PCR technology. Overall, this study highlights the influential role of miRNAs in the innate immune system of M. rosenbergii, which has important implications for developing new strategies to prevent and treat related diseases in the future.

A novel tumor necrosis factor receptor-associated factor 6 (TRAF6) gene from Macrobrachiumrosenbergii involved in antibacterial defense against Aeromonas hydrophila

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is an adapter protein that triggers downstream cascades mediated by both TNFR and the interleukin-1 receptor/Toll-like receptor (IL-1R/TLR) superfamily. TRAF6 is involved in various biological processes, including innate and adaptive immunity. In the present study, a homolog of TRAF6 from Macrobrachium rosenbergii (MrTRAF6) was identified and characterized. The full-length cDNA of MrTRAF6 consisted of 2,114 nucleotides with an open reading frame (ORF) of 1,695 nucleotides encoding a 564-amino acid protein that contained a conserved TRAF family motif including two RING-type zinc fingers and a C-terminal meprin and TRAF homology (MATH) domain. The putative amino sequence of MrTRAF6 shared 45.5-97.3% identity with TRAF6s from other crustacean species with the highest identity to Macrobrachium nipponense TRAF6. Phylogenetic analysis revealed that MrTRAF6 was closely related to TRAF6 of invertebrates and clustered with crustaceans. According to gene expression analysis, the MrTRAF6 transcript demonstrated broad expression in all tissues tested, with the highest expression level in gill and the lowest in muscle tissues. Upon immune challenge with Aeromonas hydrophila, significant upregulation of MrTRAF6 expression was found in the gill, hepatopancreas, hemocyte, and muscle. Furthermore, an RNA interference assay showed that silencing MrTRAF6 by dsRNA could reduce the expression of mannose-binding lectin (MBL) and crustin, but no significant change was detected in anti-lipopolysaccharide factor 5 (ALF5) levels. In addition, the cumulative mortality rate of MrTRAF6-silenced M. rosenbergii was significantly increased after A. hydrophila infection. These findings indicated that MrTRAF6 is involved in antibacterial activity and plays a critical role in the innate immune response of M. rosenbergii.

Dietary Astragalus polysaccharides improve the growth and innate immune response of giant freshwater prawn Macrobrachium rosenbergii: Insights from the brain-gut axis

Supplementation with Astragalus polysaccharides (APS) has beneficial effects on aquatic animals. Herein, we aimed to investigate the effects of different doses of APS on the growth, innate immune response, and brain-gut axis of Macrobrachium rosenbergii. The molecular weight and the monosaccharide composition of APS were analyzed. APS were added at concentration of 0 (control), 0.05, 0.10, 0.15, and 0.20 % in practical diets. Growth performance increased significantly under 0.05 to 0.20 % APS, with enhanced lipase and protease activities in intestinal tissues. Prawns receiving APS supplementation had significantly lower amounts of pathogenic intestinal bacteria (Vibrio and Aeromonas) and a markedly different microbial community structure compared with those of the control group. The fecal short chain fatty acid (SCFA) and neurotransmitters γ-aminobutyric acid contents increased in the brains of prawns receiving APS, which was potentially associated with increased Lactobacillus and Bacillus levels. Prawns receiving APS supplementation displayed a significantly enhanced immune function (such as total hemocyte count, total protein concentration, phenoloxidase activity, serum agglutination titer, and lysozyme activity) and improved disease resistance to Vibrio anguillarum compared those in the control group. Thus, dietary APS positively affected the gut-brain axis by altering the microbiota composition, increasing the fecal SCFA content, and enhancing prawn immunity.

Effects of Copper Exposure on Oxidative Stress, Apoptosis, Endoplasmic Reticulum Stress, Autophagy and Immune Response in Different Tissues of Chinese Mitten Crab (Eriocheir sinensis)

High concentrations of copper (Cu²⁺) pose a great threat to aquatic animals. However, the mechanisms underlying the response of crustaceans to Cu²⁺ exposure have not been well studied. Therefore, we investigated the alterations of physiological and molecular parameters in Chinese mitten crab (Eriocheir sinensis) after Cu²⁺ exposure. The crabs were exposed to 0 (control), 0.04, 0.18, and 0.70 mg/L of Cu²⁺ for 5 days, and the hemolymph, hepatopancreas, gills, and muscle were sampled. The results showed that Cu²⁺ exposure decreased the antioxidative capacity and promoted lipid peroxidation in different tissues. Apoptosis was induced by Cu²⁺ exposure, and this activation was associated with the mitochondrial and ERK pathways in the hepatopancreas. ER stress-related genes were upregulated in the hepatopancreas but downregulated in the gills at higher doses of Cu²⁺. Autophagy was considerably influenced by Cu²⁺ exposure, as evidenced by the upregulation of autophagy-related genes in the hepatopancreas and gills. Cu²⁺ exposure also caused an immune response in different tissues, especially the hepatopancreas, where the TLR2-MyD88-NF-κB pathway was initiated to mediate the inflammatory response. Overall, our results suggest that Cu²⁺ exposure induces oxidative stress, ER stress, apoptosis, autophagy, and immune response in E. sinensis, and the toxicity may be implicated following the activation of the ERK, AMPK, and TLR2-MyD88-NF-κB pathways.