Comparative analysis of quantitative phosphoproteomics between two tilapias (Oreochromis niloticus and Oreochromis aureus) under low-temperature stress.

As an important farmed fish, tilapia has poor tolerance to low-temperatures. At the same time, different tilapia strains have apparent differences in low-temperature tolerance. In this study, using the iTRAQ method, the phosphorylated proteomics of two tilapia strains (Oreochromis niloticus and Oreochromis aureus) with different tolerances to low-temperature stress were quantitatively and comparatively analyzed, to clarify the physiological mechanism of tilapia's response to low-temperature stress. Through the GO and IPR analyses of differentially phosphorylated proteins, a number of similarities in physiological activities and regulatory effects were found between the two tilapias in response to low-temperature stress. Many differentially phosphorylated proteins are mainly involved in lipid metabolism, cell proliferation and apoptosis. However, the difference in endurance of low temperature of these two tilapias might be related to the differences in categories, expression and modification level of genetic products which were involved in the aforementioned physiological processes. And meanwhile, the enrichment results of KEGG showed the changes of multiple immune-related and growth-related phosphorylated proteins in the cytokine-cytokine receptor interaction pathway in O. aureus are more prominent. Furthermore, the significantly enriched pathway of carbohydrate digestion and absorption in O. niloticus may indicate that low-temperature stress exerts a more severe impact on energy metabolism. The relative results would help elucidating the molecular mechanism by which tilapia responds to low-temperature stress, and developing culture of tilapia species.

Differentially Expressed miRNAs and mRNAs in Regenerated Scales of Rainbow Trout (Oncorhynchus mykiss) under Salinity Acclimation.

In order to explore the potential effects of salinity acclimation on bone metabolism of rainbow trout (Oncorhynchus mykiss), transcriptional information of regenerated scales under salinity acclimation (sea water, SW) was compared to those of fish under fresh water (FW) environments. According to the high-throughput sequencing results, a total of 2620 significantly differentially expressed genes (DEGs) were identified in the data of SW vs. FW. Compared with the FW group, six significantly downregulated and 44 significantly upregulated miRNAs were identified in the SW scales (p < 0.05). Furthermore, a total of 994 significantly differentially expressed target genes (DETGs) were identified from the 50 significantly differentially expressed miRNAs (DE miRNAs). Gene ontology analysis of the aforementioned DETGs was similar to the results of the differentially expressed genes (DEGs) obtained from mRNA-seq data, these genes were mainly related to ion metabolism. KEGG enrichment analysis of the DEGs and DETGs suggested that many significantly enriched pathways were related to the energy metabolism pathway.

Effects of Dietary Protein Level on the Gut Microbiome and Nutrient Metabolism in Tilapia (Oreochromis niloticus).

Dietary protein is one of the most important nutritional factors in aquaculture. The aim of this study was to examine the effects of dietary protein levels on the gut microbiome and the liver and serum levels of metabolites in tilapia. Tilapia were fed a diet with a low (20%), moderate (30%), or high (40%) content of crude protein, and the homeostasis of the gut microbiome and metabolic profile of the liver and serum were analyzed. The results showed no significant differences in the diversity and richness of the gut microbiome among the groups; however, there were differences in the microbial composition of the gut. The metabolome analysis of liver samples revealed a difference in the glucose level among the groups, with the highest glucose level in fish fed a high protein diet. In addition, there were significant differences in the levels of tyrosine, guanosine, and inosine among the metabolome analysis of serum samples of these groups. In summary, diets with different protein levels could affect the composition of gut microbiota and the dynamic balance of microbial communities. Dietary protein content can also affect glycolysis and amino acid metabolism in tilapia.

Comparative analysis of growth performance and liver transcriptome response of juvenile Ancherythroculter nigrocauda fed diets with different protein levels.

This study aimed at investigating the effects of dietary protein levels on the growth and liver transcriptome in juvenile Ancherythroculter nigrocauda. Six semi-purified diets were formulated containing 25 (control), 30, 35, 40, 45, and 50% protein. Each diet was fed to three groups of 35 fish (mean initial weight: 5.86 ±â€¯0.10 g) for 56 days. The rate of weight gain and specific growth rate increased with dietary protein levels from 25% to 40%, but remained unchanged when fed with 45 or 50% dietary protein. The feed conversion ratio was significantly influenced by the dietary protein levels, being the lowest in fish fed 40% protein. Illumina RNA-seq analysis was performed to investigate liver gene expression changes under different dietary protein treatments. A total of 367.78 million clean reads were obtained from the six libraries. Compared with 25% protein treatment library, there were 734, 1946, 1755, 2726, and 1523 upregulated genes, and 407, 1882, 1865, 2216 and 1624 downregulated genes in the 30, 35, 40, 45, and 50% protein treatment libraries, respectively. Trend analysis of these differentially expressed genes (DEGs) identified six statistically significant trends. A series of DEGs that related to protein metabolism, growth and development, lipid metabolism and immune and stress response were identified. Moreover, gene ontology enrichment analysis of the DEGs demonstrated that cellular process, single-organism process, metabolic process and biological regulation were the most highly overrepresented biological processes. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that protein processing in endoplasmic reticulum, PPAR signaling pathway, complement and coagulation cascades, and cytochrome P450 (CYP450s) were significantly enriched in the dietary protein treatment groups. Furthermore, qPCR results showed excellent agreement on those of RNA-seq for both up- and down-regulated genes (including fasn, accα, SCD, CPT-I, igf1, ST, AST, trdmt1, hsp70, cyp450, MHC-II, C4, tgfß, ube4b, apoE and abcb7). Thus, our results provide the baseline information for the feed formulation and nutritional research for A. nigrocauda.

Effects of dietary manipulation on compensatory growth of juvenile genetically improved farmed tilapia (Oreochromis niloticus).

A 40-day feeding trial was conducted to investigate whether feeding a low-protein diet (25%) once daily for either 10 (L10H30) or 20 (L20H20) days then re-feeding a high-protein diet (35%) thrice daily elicit compensatory growth (CG) in genetically improved farmed tilapia (GIFT), Oreochromis niloticus (11.02 ± 0.05 g). Fish on the control treatment were fed 35% protein diet over 40 days (H40). Fish were stocked into nine 100-L tanks (30 fish per tank) with 3 replicate tanks for each group. Growth performance, feed utilization, proximate composition of body compartment, serum biochemical parameters, and hepatopancreatic histology and expressions of some genes related to inflammatory cytokine were evaluated every 10 days. Growth of L10H30 fish were similar to the control, whereas the weight of L20H20 fish were lower (P < 0.05) at day 20, but this significant difference disappeared at the end of the experiment. During 20-30 days, specific growth rate and feed intake were significantly higher (P < 0.05) and feed efficiency was lower (P < 0.05) in L20H20 fish than those in H40 fish. Dietary manipulations did not affect (P > 0.05) viscerosomatic and hepatosomatic indices, condition factors, serum biochemical parameters, and hepatopancreatic histology. Significant differences (P < 0.05) in proximate composition were observed only in viscera and muscle between L20H20 fish and H40 fish at day 20. The mRNA expressions of heat shock protein 70 kDa, tumor necrosis factor-α and interleukin (IL)-1ß were higher (P < 0.05) in L10H30 and L20H20 fish at day 10, while IL-1ß mRNA expression was lower (P < 0.05) in L20H20 fish at day 30 than those in H40 fish. Our results indicated that L20H20 fish elicited a complete CG and induced reversible physiological variations in juvenile GIFT.

Dietary phosphatidylcholine impacts on growth performance and lipid metabolism in adult Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia Oreochromis niloticus.

This study aimed to determine the effects of supplementing the diet of adult Nile tilapia Oreochromis niloticus with phosphatidylcholine (PC) on growth performance, body composition, fatty acid composition and gene expression. Genetically Improved Farmed Tilapia fish with an initial body weight of 83·1 (sd 2·9) g were divided into six groups. Each group was hand-fed a semi-purified diet containing 1·7 (control diet), 4·0, 6·5, 11·5, 21·3 or 41·0 g PC/kg diet for 68 d. Supplemental PC improved the feed efficiency rate, which was highest in the 11·5 g PC/kg diet. Weight gain and specific growth rate were unaffected. Dietary PC increased PC content in the liver and decreased crude fat content in the liver, viscera and body. SFA and MUFA increased and PUFA decreased in muscle with increasing dietary PC. Cytoplasmic phospholipase A 2 and secreted phospholipase A 2 mRNA expression were up-regulated in the brain and heart in PC-supplemented fish. PC reduced fatty acid synthase mRNA expression in the liver and visceral tissue but increased expression in muscle. Hormone-sensitive lipase and lipoprotein lipase expression increased in the liver with increasing dietary PC. Growth hormone mRNA expression was reduced in the brain and insulin-like growth factor-1 mRNA expression in liver reduced with PC above 6·5 g/kg. Our results demonstrate that dietary supplementation with PC improves feed efficiency and reduces liver fat in adult Nile tilapia, without increasing weight gain, representing a novel dietary approach to reduce feed requirements and improve the health of Nile tilapia.

Growth arrest specific gene 2 in tilapia (Oreochromis niloticus): molecular characterization and functional analysis under low-temperature stress.

BACKGROUND: Growth arrest specific 2 (gas2) gene is a component of the microfilament system that plays a major role in the cell cycle, regulation of microfilaments, and cell morphology during apoptotic processes. However, little information is available on fish gas2. In this study, the tilapia (Oreochromis niloticus) gas2 gene was cloned and characterized for the first time. RESULTS: The open reading frame was 1020 bp, encoding 340 amino acids; the 5'-untranslated region (UTR) was 140 bp and the 3'-UTR was 70 bp, with a poly (A) tail. The highest promoter activity occurred in the regulatory region (-3000 to -2400 bp). The Gas2-GFP fusion protein was distributed within the cytoplasm. Quantitative reverse transcription-polymerase chain reaction and western blot analyses revealed that gas2 gene expression levels in the liver, muscle, and brain were clearly affected by low temperature stress. The results of gas2 RNAi showed decreased expression of the gas2 and P53 genes. CONCLUSION: These results suggest that the tilapia gas2 gene may be involved in low temperature stress-induced apoptosis.

Molecular cloning and gene/protein expression of FAT/CD36 from grass carp (Ctenopharyngodon idella) and the regulation of its expression by dietary energy.

Fatty acid translocase/cluster of differentiation 36 (FAT/CD36) functions as a membrane long-chain fatty acid transporter in various tissues in land animals. Not much is known about the CD36 molecule in teleost fish. Therefore, we studied CD36 in grass carp (Ctenopharyngodon idella, ciCD36). The full-length complementary DNA sequence of ciCD36 was 1976 bp, with an ORF of 468 amino acids, which had high sequence similarity to the CD36 of common carp. The messenger RNA (mRNA) expression of ciCD36 was high in the intestine, heart, liver, visceral tissue, and brain, but absent in the kidney. The protein expression of ciCD36 was high in the brain, intestine, liver, heart, muscle, eye, visceral tissue, gonad, and gill, but not in the kidney. Four groups of grass carp (16 tanks) were fed three times daily to satiation with 17.2 kJ gross energy/g diet (control, CON), 19.4 kJ gross energy/g diet (more energy supplied by proteins, HP), 19.9 kJ gross energy/g diet (more energy supplied by fat, HF), and 19.1 kJ gross energy/g diet (more energy supplied by carbohydrate, HC) for 11 weeks, respectively. At the end of the feeding experiment, the fish were fasted for 48 h, and the brain, heart, intestine, and liver were sampled and designated as the 0-h samples. The fish were then fed a single meal of the above four diets, and these tissues were collected at 8- and 24-h intervals after refeeding to analyze ciCD36 mRNA and protein expression levels. The results showed that at the transcriptional and translational levels, ciCD36 expression was significantly affected by refeeding time and the different diets (P < 0.05), and the regulation of its transcription in different tissues varied. At the translational level, the protein expression levels decreased in the CON and HC groups, and increased in the HP and HF groups after refeeding. The results indicated that ciCD36 has a modulatory role in the adaptation to dietary high energy in grass carp. Translational regulation might be responsible for the observed variations in ciCD36 expression.

Identification of a C-type lectin from tilapia (Oreochromis niloticus) and its functional characterization under low-temperature stress.

C-type lectin, which plays an important role in fish innate immunity, was cloned from tilapia and its functional characterization under low-temperature stress is reported. Its ORF is 453 bp, encoding 150 amino acids, and has a 5'UTR of 83 bp, a 3'UTR of 559 bp, and a poly (A) tail. The tilapia C-type lectin genomic DNA was acquired with a length of 5714 bp, containing six exons and five introns. Its promoter sequence was cloned and has a length of 2251 bp. The highest promoter activity occurs in the regulatory region (-900 bp to -450 bp). A hemagglutination assay of recombinant tilapia C-type lectin protein showed positive hemagglutination of rabbit and tilapia erythrocytes. RT-qPCR and western blot assays showed that its expression in the liver, spleen, and intestine were clearly affected by low-temperature stress. Thus, tilapia C-type lectin appear to be affected by abiotic stress, as well as by biological stress.

The complete mitochondrial genome sequence of Hemibagrus sp. (Siluriformes: Bagridae), molecular data for species identification.

In this study, we determined and described the complete mitogenome sequence of Hemibagrus sp. for the first time, which is 16,513 bp in length, and contains 37 genes, including 13 protein-coding genes, 2 rRNAs, 22 tRNAs, 1 origin of replication on the light-strand (OL) and a putative control region. The overall base composition was 31.1% A, 26.9% T, 26.9% C, 15.1% G, with a slight AT bias (58.0%). All protein-coding genes shared the start codon ATG, except for COI, which began with GTG. The tRNA-Ser(UGC) couldn't be folded into the typical cloverleaf secondary structure because its dihydrouridine arm is replaced by a simple loop. These results are expected to provide useful molecular data for species identification and further phylogenetic studies of Bagridae and Siluriformes.

Analysis of differential gene expression under low-temperature stress in Nile tilapia (Oreochromis niloticus) using digital gene expression.

Tilapia (Oreochromis niloticus) do not survive well at low temperatures. Therefore, improvement of the low-temperature resistance has become an important issue for aquaculture development of tilapia. The objective of this study was to construct a digital gene expression tag profile to identify genes potentially related to low temperature in tilapia. In this study, tilapia was treated at 30°C to lethal temperature 10°C in decrement of 1°CD(-1). Digital gene expression analysis was performed using the Illumina technique to investigate differentially expressed genes in tilapia cultured at different temperatures (30°C, 26°C, 20°C, 16°C, and 10°C). A total of 206,861, 188,082, 185,827, 188,067, and 214,171 distinct tags were obtained by sequencing these five libraries, respectively. Compared with the 30°C library, there were 304, 407, 709, and 772 upregulated genes and 342, 793, 771, and 1466 downregulated genes in 26°C, 20°C, 16°C, and 10°C libraries, respectively. Trend analysis of these differentially expressed genes identified six statistically significant trends. Functional annotation analysis of the differentially expressed genes identified various functions associated with the response to low-temperature stress. When tilapia are subjected to low-temperature stress, expression changes were observed in genes associated with nucleic acid synthesis and metabolism, amino acid metabolism and protein synthesis, lipid and carbohydrate content and types, material transport, apoptosis, and immunity. The differentially expressed genes obtained in this study may provide useful insights to help further understand the effects of low temperature on tilapia.

Dietary lipid levels impact lipoprotein lipase, hormone-sensitive lipase, and fatty acid synthetase gene expression in three tissues of adult GIFT strain of Nile tilapia, Oreochromis niloticus.

The objective of this study was to assess the effects of dietary lipids on growth performance, body composition, serum parameters, and expression of genes involved in lipid metabolism in adult genetically improved farmed tilapia (GIFT strain) of Nile tilapia, Oreochromis niloticus. We randomly assigned adult male Nile tilapia (average initial body weight = 220.00 ± 9.54 g) into six groups consisting of four replicates (20 fish per replicate). Fish in each group were hand-fed a semi-purified diets containing different lipid levels [3.3 (the control group), 28.4, 51.4, 75.4, 101.9, and 124.1 g kg(-1)] for 8 weeks. The results indicated that there was no obvious effect in feeding rate among all groups (P > 0.05). The highest weight gain, specific growth rate, and protein efficiency ratio in 75.4 g kg(-1) diet group were increased by 23.31, 16.17, and 22.02 % than that of fish in the control group (P < 0.05). Protein retention ratio was highest in 51.4 g kg(-1) diet group. The results revealed that the optimum dietary lipid level for maximum growth performance is 76.6-87.9 g kg(-1). Increasing dietary lipid levels contributed to increased tissue and whole body lipid levels. Saturated and monounsaturated fatty acids (MUFAs) decreased, and polyunsaturated fatty acids increased with increasing dietary lipid levels. With the exception of MUFAs, the fatty acid profiles of liver and muscle were similar. Dietary lipid levels were negatively correlated with low-density lipoprotein- cholesterol content and positively with triacylglycerol and glucose contents. In the lipid-fed groups, there was a significant down-regulation of fatty acid synthase (FAS) mRNA in liver, muscle, and visceral adipose tissues. There was a rapid up-regulation of lipoprotein lipase (LPL) mRNA in muscle and liver with increasing dietary lipid levels. In visceral adipose tissue, LPL mRNA was significantly down-regulated in the lipid-fed groups. Dietary lipids increased hormone-sensitive lipase (HSL) mRNA expression levels in the three tissues. These results strongly suggested that moderate dietary lipid levels were beneficial for adult tilapia growth performance and feed efficiency. However, excessive dietary lipid levels contributed to lipid deposition. Additionally, excessive dietary lipids may induce a competition between lipolysis and lipogenesis. FAS did not have tissue-specific regulation; however, the regulation of dietary lipids on LPL expression is tissue specific. FAS was a negative feedback regulator on fat deposition, and HSL was an indicator of fat content in tilapia.

The complete mitochondrial genome of Spinibarbus sinensis (Bleeker).

The mitogenome of Spinibarbus sinensis was 16,591 bp long containing two rRNA, 22 tRNA, 13 protein-coding genes and one D-loop region. Eight tRNA genes and one protein-coding gene were encoded on light strand, the others on heavy strand. The base composition and gene arrangement of S. sinensis mitogenome was identical to typical vertebrate.

Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle.

Genetic sex determination by W and Z chromosomes has developed independently in different groups of organisms. To better understand the evolution of sex chromosomes and the plasticity of sex-determination mechanisms, we sequenced the whole genomes of a male (ZZ) and a female (ZW) half-smooth tongue sole (Cynoglossus semilaevis). In addition to insights into adaptation to a benthic lifestyle, we find that the sex chromosomes of these fish are derived from the same ancestral vertebrate protochromosome as the avian W and Z chromosomes. Notably, the same gene on the Z chromosome, dmrt1, which is the male-determining gene in birds, showed convergent evolution of features that are compatible with a similar function in tongue sole. Comparison of the relatively young tongue sole sex chromosomes with those of mammals and birds identified events that occurred during the early phase of sex-chromosome evolution. Pertinent to the current debate about heterogametic sex-chromosome decay, we find that massive gene loss occurred in the wake of sex-chromosome 'birth'.

Molecular cloning and multifunctional characterization of GRIM-19 (gene associated with retinoid-interferon-induced mortality 19) homologue from turbot (Scophthalmus maximus).

GRIM-19 (gene associated with retinoid-interferon-induced mortality 19), a novel cell death regulatory gene, plays important roles in cell apoptosis, embryogenesis, mitochondrial respiratory chain and immune response. To date, little information is known about fish GRIM-19 characteristics except orange-spotted grouper (Epinephelus coioides). Here a new GRIM-19 gene is identified and characterized from turbot (Scophthalmus maximus), an economic marine fish in China and Europe. Briefly, turbot GRIM-19 is a 595-bp gene encoding a 144 amino acids protein, which shares the closest relationship with Atlantic halibut (Hippoglossus hippoglossus). The expression of turbot grim-19 in liver, spleen and kidney is up-regulated by the infection of Vibrio anguillarum and LCDV (lymphocystis disease virus). Subsequently, a recombinant protein of turbot GRIM-19 is acquired and the anti-bacterial function is proved by liquid culture inhibition experiment. The subcellular location indicates that turbot GRIM-19 is co-localized with STAT3 in the cytoplasm, which is mainly determined by GRIM-19 41-84 amino acids and STAT3 1-321 amino acids. Finally, the involvements of turbot GRIM-19 in cell apoptosis and NF-κB pathway are investigated. All these data help to understand GRIM-19 function in fish, as well as provide the application possibility of GRIM-19 in fish disease resistance breeding.

The complete mitochondrial genome of Aspiorhynchus laticeps and its phylogenetic analysis.

The complete nucleotide sequence of the mitochondrial genome (mitogenome) of Aspiorhynchus laticeps was determined. The length of the complete mitochondrial DNA sequence of A. laticeps is 16,591 bp, which consists of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a non-coding region 'D-loop'. Except for the D-loop, another non-coding region named replication origin of L-strand (OL) region was also found. According to the phylogenetic analysis, A. laticeps has a closer relationship with Schizothorax.

Molecular cloning, subcelluar location and expression profile of signal transducer and activator of transcription 2 (STAT2) from turbot, Scophthalmus maximus.

Signal transducer and activator of transcription 2 (STAT2) is an important molecule involved in the type I interferon signalling pathway. To date, little STAT2 homologue is available in fish except Atlantic salmon and goldfish. In this paper, STAT2 was firstly cloned and characterized from turbot, a marine flatfish with high economic value. Briefly, turbot STAT2 cDNA is 3206 bp in length encoding a predicted protein of 793 amino acids. The phylogenetic tree shows that turbot STAT2 protein shared the closest relationship with Atlantic salmon. Analysis of subcellular distribution indicates that STAT2 is mainly present in the cytoplasm of TK cells. Stat2 mRNA is constitutively expressed in widespread tissues and induced by several folds in turbot tissues and TK cells after stimulation with Vibrio anguillarum and lymphocystis disease virus (LCDV). Unlike the higher vertebrate STAT2, turbot STAT2 nuclear export signal (NES) exists not in the C-terminal 79 amino acids but in N-terminal 137-312 amino acids (STAT_alpha domain). The nuclear translocation of turbot STAT2 after Poly(I:C) treatment proved its transcription activity in TK cells. All these results suggested that STAT2 may be involved in the immune response in turbot as a transcription factor.

Screening and analysis of PoAkirin1 and two related genes in response to immunological stimulants in the Japanese flounder (Paralichthys olivaceus).

A member of the NF-κB signaling pathway, PoAkirin1, was cloned from a full-length cDNA library of Japanese flounder (Paralichthys olivaceus). The full-length cDNA comprises a 5'UTR of 202 bp, an open reading frame of 564 bp encoding a 187-amino-acid polypeptide and a 521-bp 3'UTR with a poly (A) tail. The putative protein has a predicted molecular mass of 21 kDa and an isoelectric point (pI) of 9.22. Amino acid sequence alignments showed that PoAkirin1 was 99% identical to the Scophthalmus maximus Akirin protein (ADK27484). Yeast two-hybrid assays identified two proteins that interact with PoAkirin1: PoHEPN and PoC1q. The cDNA sequences of PoHEPN and PoC1q are 672 bp and 528 bp, respectively. Real-time quantitative reverse-transcriptase polymerase chain reaction analysis showed that bacteria could induce the expressions of PoAkirin1, PoHEPN and PoC1q. However, the responses of PoHEPN and PoC1q to the bacterial challenge were slower than that of PoAkirin1. To further study the function of PoAkirin1, recombinant PoAkirin1 and PoHEPN were expressed in Escherichia coli and would be used to verify the PoAkirin1-PoHEPN binding activity. These results identified two proteins that potentially interact with PoAkirin1 and that bacteria could induce their expression.

Iron-metabolic function and potential antibacterial role of Hepcidin and its correlated genes (Ferroportin 1 and Transferrin Receptor) in turbot (Scophthalmus maximus).

Antimicrobial peptide plays an important role in fish immunity. The small molecular antimicrobial peptide Hepcidin in turbot was studied and reported in this paper. The Ferroportin 1 (FPN1) and Transferrin Receptor (TFR) genes, which are related to Hepcidin, were cloned in turbot. The characteristics of Hepcidin and its related genes were studied, including an analysis of the expression patterns and cloning of the Hepcidin promoter, the relationship between Hepcidin and NF-κB and the regulation of iron-metabolism. The results showed that the promoter of SmHepcidin contains the binding sites of NF-κB, and NF-κB may directly or indirectly receive feedback signals from SmHepcidin. In the liver, spleen and kidney, in which there was an increased SmHepcidin expression level, SmFPN1 dramatically decreased and SmTFR was also either decreased or exhibited no obvious change after bacterial/viral infection and an injection of exogenous Hepcidin protein. RNAi experiments in turbot kidney cells confirmed the expression changes of these gene patterns. Furthermore, the administration of exogenous Hepcidin protein, which regulates the level of chelatable iron in cells, further confirmed the function of Hepcidin in iron metabolism. It is speculated that the rapidly increased expression of SmHepcidin may induce changes in the expression of related genes, and that the in vivo chelatable iron concentration which participates in the antibacterial process was also changed when exogenous pathogens are present in turbot. It is suggested that SmHepcidin plays a defensive role against pathogenic infection.

Cloning, characterization and expression analysis of a cold shock domain family member YB-1 in turbot Scophthalmus maximus.

The Y-box proteins are a family of highly conserved nucleic acid binding proteins. In this report we have identified a new member, YB-1 from turbot (Scophthalmus maximus) spleen cDNA library. The full-length cDNA sequence of turbot YB-1 was obtained and then the expression at transcriptional level was researched by qRT-PCR. In normal organs, the expression of YB-1 was higher in liver, brain, gill and heart, respectively. YB-1 had the highest expression level at gastrula stage during the early stages of embryo development. In the liver, kidney and spleen, the turbot YB-1 expression level was the highest at 72 h after challenge with lymphocystis disease virus (LCDV) and the highest at 12 h after challenge with Vibrio anguillarum (V. anguillarum). Furthermore, the expression of turbot YB-1 also distinctly increased in turbot kidney cells (TK) at 24 h after challenge with V. anguillarum and LCDV. These results indicated that the turbot YB-1 protein may play a significant role in the immune response of turbot.