Identification and expression analysis of irak1 gene in common carp Cyprinus carpio L.: indications for a role of antibacterial and antiviral immunity

A review of soluble factors and receptors involved in fish skin immunity: The tip of the iceberg

The immune system of fish possesses soluble factors, receptors, pathways and cells very similar to those of the other vertebrates' immune system. Throughout evolutionary history, the exocrine secretions of organisms have accumulated a large reservoir of soluble factors that serve to protect organisms from microbial pathogens that could disrupt mucosal barrier homeostasis. In parallel, a diverse set of recognition molecules have been discovered that alert the organism to the presence of pathogens. The known functions of both the soluble factors and receptors mentioned above encompass critical aspects of host defense, such as pathogen binding and neutralization, opsonization, or modulation of inflammation if present. The molecules and receptors cooperate and are able to initiate the most appropriate immune response in an attempt to eliminate pathogens before host infection can begin. Furthermore, these recognition molecules, working in coordination with soluble defence factors, collaboratively erect a robust and perfectly coordinated defence system with complementary specificity, activity and tissue distribution. This intricate network constitutes an immensely effective defence mechanism for fish. In this context, the present review focuses on some of the main soluble factors and recognition molecules studied in the last decade in the skin mucosa of teleost fish. However, knowledge of these molecules is still very limited in all teleosts. Therefore, further studies are suggested throughout the review that would help to better understand the functions in which the proteins studied are involved.

Molecular characterization and expression analyses of five genes involved in the MyD88-dependent pathway of yellow catfish (Pelteobagrus fulvidraco) responding to challenge of Aeromonas hydrophila

MyD88-dependent pathway mediated by Toll-like receptor is one of the vital ways activating immune responses. In order to identify the role of MyD88-dependent signaling pathway in yellow catfish, the Pf_MyD88, Pf_IRAK4, Pf_IRAK1, Pf_TRAF6 and Pf_NFκB1 (p105) (Pf: abbreviation of Pelteobagrus fulvidraco) were cloned and characterized respectively. The Pf_MyD88, Pf_IRAK4, Pf_IRAK1 and Pf_TRAF6 were all highly conserved among species and showed the highest homology to that of Pangasianodon hypophthalmus. Pf_NFκB1 showed the highest homology to that of Ictalurus punetaus. All of the five genes showed similar expression patterns in various tissues, with the highest expression level in the liver. These genes also showed similar expression levels in different embryonic development stages, except Pf_IRAK4. The higher expression level was detected from fertilized eggs to 1 day post hatching (dph), lower expression from 3 dph to 30 dph. After stimulation of inactivated Aeromonas hydrophila, the mRNA expressions of Pf_MyD88, Pf_IRAK4, Pf_IRAK1, Pf_TRAF6 and Pf_NFκB1 were significantly increased at 24 h in the liver, spleen, head kidney and trunk kidney, suggesting that all the five genes were involved in the innate immune response of yellow catfish. These results showed that MyD88-dependent signaling pathway plays important roles for disease defensing in the innate immune response. Meanwhile, inactivated A. hydrophila can cause strong innate immune response, which provides theoretical bases for the application of inactivated vaccines in defense against bacterial diseases of teleost.

Negative regulation of interferon regulatory factor 6 (IRF6) in interferon and NF-κB signalling pathways of common carp (Cyprinus carpio L.)

BACKGROUND

Interferon (IFN) regulatory factors (IRFs) is a kind of transcription factors, which play an important role in regulating the expression of type I IFN and related genes. In mammals, IRF6 is not relevant with IFN expression, while zebrafish IRF6 was reported to be a positive regulator of IFN expression and could be phosphorylated by both MyD88 and TBK1. However, the role of IRF6 in the immune response and IFN transcription of common carp is unknown.

RESULTS

In the present study, the cDNA of IRF6 gene (CcIRF6) was cloned from common carp using RACE technique, with a total length of 1905 bp, encoding 471 amino acid residues, which possesses two functional domains of DBD and IAD. Similarity analysis showed that CcIRF6 had more than 50% similarity with IRFs of other vertebrates, and had the highest similarity with grass carp and zebrafish, among which the DBD domain was much more conserved. The phylogenetic analysis showed that CcIRF6 is in the branch of Osteichthyes and has the closest relationship with grass carp. In healthy common carp, the CcIRF6 was expressed in all the examined tissues, with the highest level in the oral epithelium, and the lowest level in the head kidney. After intraperitoneal injection of poly(I:C) or Aeromonas hydrophila, the expression of CcIRF6 increased in spleen, head kidney, foregut and hindgut of common carp. Moreover, poly(I:C), LPS, PGN and flagellin induced the expression of CcIRF6 in peripheral leukocytes and head kidney leukocytes of common carp in vitro. In EPC cells, CcIRF6 inhibited the expression of some IFN-related genes and pro-inflammatory cytokines, and dual luciferase reporter assay showed that CcIRF6 reduced the activity of IFN and NF-κB reporter genes.

CONCLUSIONS

The present study suggests that CcIRF6 is involved in the antiviral and antibacterial immune response of common carp, and negatively regulate the expression of IFN and NF-κB signalling pathways, which provides a theoretical basis for the study and prevention of fish disease pathogenesis.

Activation of the NLRP1 inflammasome and its ligand recognition in the antibacterial immune response of common carp (Cyprinus carpio)

NLRP1 (NLR family pyrin domain containing 1) is the first member of NOD-like receptors (NLRs) which can form inflammasome and play critical roles in innate immunity and pathogenesis of various diseases. To date, many NLRs and inflammasome-related genes have been identified in teleost, however, the activation of NLRP1 inflammasome is only found in zebrafish, and the activator of fish NLRP1 is unclear. In the present study, the activation of CcNLRP1 inflammasome and its function in innate immune defence of common carp was investigated. The expression of CcNLRP1 was induced in immune-related tissues of common carp upon challenge with Edwardsiella tarda and Aeromonas hydrophila. The colocalization of CcNLRP1 and CcASC, ASC oligomerization, and interaction between CcNLRP1^CARD and CcASC was observed in 293T, Hela and EPC cells, suggesting that the CcNLRP1 inflammasome was activated in common carp. Furthermore, we found that MDP may be the specific ligand of CcNLRP1, which can activate the CcNLRP1 inflammasome. Taken together, the present study identifies a new inflammasome in common carp, and is beneficial to the control of infectious diseases in carp farming.

Commensal and Opportunistic Bacteria Present in the Microbiota in Atlantic Cod (Gadus morhua) Larvae Differentially Alter the Hosts' Innate Immune Responses

The roles of host-associated bacteria have gained attention lately, and we now recognise that the microbiota is essential in processes such as digestion, development of the immune system and gut function. In this study, Atlantic cod larvae were reared under germ-free, gnotobiotic and conventional conditions. Water and fish microbiota were characterised by 16S rRNA gene analyses. The cod larvae’s transcriptional responses to the different microbial conditions were analysed by a custom Agilent 44 k oligo microarray. Gut development was assessed by transmission electron microscopy (TEM). Water and fish microbiota differed significantly in the conventional treatment and were dominated by different fast-growing bacteria. Our study indicates that components of the innate immune system of cod larvae are downregulated by the presence of non-pathogenic bacteria, and thus may be turned on by default in the early larval stages. We see indications of decreased nutrient uptake in the absence of bacteria. The bacteria also influence the gut morphology, reflected in shorter microvilli with higher density in the conventional larvae than in the germ-free larvae. The fact that the microbiota alters innate immune responses and gut morphology demonstrates its important role in marine larval development.

Molecular characterization and immune functional analysis of IRF2 in common carp (Cyprinus carpio L.): different regulatory role in the IFN and NF-κB signalling pathway

BACKGROUND

Interferon regulatory factor 2 (IRF2) is an important transcription factor, which can regulate the IFN response and plays a role in antiviral innate immunity in teleost.

RESULTS

In the present study, the full-length cDNA sequence of IRF2 (CcIRF2) was characterized in common carp (Cyprinus carpio L.), which encoded a protein containing a conserved DNA-binding domain (DBD) and an IRF-associated domain (IAD). Phylogenetic analysis showed that CcIRF2 was most closely related with IRF2 of Ctenopharyngodon idella. CcIRF2 transcripts were detectable in all examined tissues, with higher expression in the gills, spleen and brain. CcIRF2 expression was upregulated in immune-related tissues of common carp upon polyinosinic:polycytidylic acid (poly (I:C)) and Aeromonas hydrophila stimulation and induced by poly (I:C), lipopolysaccharide (LPS), peptidoglycan (PGN) and flagellin in the peripheral blood leucocytes (PBLs) and head kidney leukocytes (HKLs). In addition, overexpression of CcIRF2 decreased the expression of IFN and IFN-stimulated genes (ISGs), and a dual-luciferase reporter assay revealed that CcIRF2 could increase the activation of NF-κB.

CONCLUSIONS

These results indicate that CcIRF2 participates in antiviral and antibacterial immune response and negatively regulates the IFN response, which provide a new insight into the regulation of IFN system in common carp, and are helpful for the prevention and control of infectious diseases in carp farming.

Identification and functional characterization of a fish-specific tlr19 in common carp (Cyprinus carpio L.) that recruits TRIF as an adaptor and induces ifn expression during the immune response

Toll-like receptor 19 (Tlr19) is a fish-specific TLR that plays a critical role in innate immunity. In the present study, we aimed to identify tlr19 from common carp (Cyprinus carpio L.) and explored its expression profile, localization, adaptor, and signaling pathways. A novel tlr19 cDNA sequence (Cctlr19) was identified in common carp. Phylogenetic analysis revealed that CcTlr19 was most closely related to Danio rerio Tlr19. Subcellular localization analysis indicates that CcTlr19 was synthesized in the free ribosome and then transported to early endosomes. Cctlr19 was constitutively expressed in all the examined tissues, with the highest expression in the brain. After poly(I:C) and Aeromonas hydrophila injection, the expression of Cctlr19 was significantly upregulated in immune-related organs. In addition, the expression of Cctlr19 was upregulated in head kidney leukocytes (HKL) upon stimulation with different ligands. Immunofluorescence and luciferase analyses indicate that CcTlr19 recruited TRIF as an adaptor. Furthermore, CcTlr19 can activate the expression of ifn-1 and viperin. Taken together, these findings lay the foundation for future research to investigate the mechanisms underlying fish tlr19.

Cloning and functional characterization of IRAK1 from rainbow trout (Oncorhynchus mykiss)

As a key molecule in innate immune signalling pathway, interleukin (IL)-1 receptor-associated kinase 1 (IRAK1) mediates downstream signalling cascades in immune response. In the present study, an IRAK1 orthologue was characterized from rainbow trout (Oncorhynchus mykiss), with a 2115 bp open reading frame (ORF), encoding a protein of 704 amino acids (aa). Multiple alignments showed that IRAK1 contains highly conserved features among different species, with a conservative N-terminal death domain (DD) and a C-terminal conserved serine/threonine protein kinase (STKc) domain. Expression analysis indicated that IRAK1 was widely expressed in examined organs/tissues, with the highest level observed in muscle and lowest in stomach. In RTG-2 cell line, the induced expression of IRAK1 was observed following the stimulation by the fish bacterial pathogen Flavobacterium columnare. Luciferase activity assays revealed that IRAK1 induced significantly the activity of NF-κB in Human embryonic kidney 293T (HEK293T) cell line; but after co-transfected with rainbow trout IL-1 receptor-associated kinase 4 (IRAK4), the induction was significantly down-regulated when compared with the expression of IRAK1 alone. Co-immunoprecipitation (Co-IP) assays indicated that IRAK1 was associated with rainbow trout myeloid differentiation factor 88 (MyD88), IRAK4 and TNF receptor associated factor 6 (TRAF6) in transfected HEK293T cells, and may form a complex with MyD88, IRAK4 and TRAF6 during the signalling pathway.

Mini review: immunologic functions of dual oxidases in mucosal systems of vertebrates

Abstract Mucosal epithelial cells act as the first immunologic barrier of organisms, and contact directly with pathogens. Therefore, hosts must have differential strategies to combat pathogens efficiently. Reactive oxygen species (ROS), as a kind of oxidizing agents, participates in the early stage of killing pathogens quickly. Recent reports have revealed that dual oxidase (DUOX) plays a key role in mucosal immunity. And the DUOX is a transmembrane protein which produces ROS as their primary enzymatic products. This process is an important pattern for eliminating pathogens. In this review, we highlight the DUOX immunologic functions in the respiratory and digestive tract of vertebrates.

Identification of an IRF10 gene in common carp (Cyprinus carpio L.) and analysis of its function in the antiviral and antibacterial immune response

Background

Interferon (IFN) regulatory factors (IRFs), as transcriptional regulatory factors, play important roles in regulating the expression of type I IFN and IFN- stimulated genes (ISGs) in innate immune responses. In addition, they participate in cell growth and development and regulate oncogenesis.

Results

In the present study, the cDNA sequence of IRF10 in common carp (Cyprinus carpio L.) was characterized (abbreviation, CcIRF10). The predicted protein sequence of CcIRF10 shared 52.7–89.2% identity with other teleost IRF10s and contained a DNA-binding domain (DBD), a nuclear localization signal (NLS) and an IRF-associated domain (IAD). Phylogenetic analysis showed that CcIRF10 had the closest relationship with IRF10 of Ctenopharyngodon idella. CcIRF10 transcripts were detectable in all examined tissues, with the highest expression in the gonad and the lowest expression in the head kidney. CcIRF10 expression was upregulated in the spleen, head kidney, foregut and hindgut upon polyinosinic:polycytidylic acid (poly I:C) and Aeromonas hydrophila stimulation and induced by poly I:C, lipopolysaccharide (LPS) and peptidoglycan (PGN) in peripheral blood leucocytes (PBLs) and head kidney leukocytes (HKLs) of C. carpio. In addition, overexpression of CcIRF10 was able to decrease the expression of the IFN and IFN-stimulated genes PKR and ISG15.

Conclusions

These results indicate that CcIRF10 participates in antiviral and antibacterial immunity and negatively regulates the IFN response, which provides new insights into the IFN system of C. carpio.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02674-z.

Grass carp (Ctenopharyngodon idella) IRAK1 and STAT3 up-regulate synergistically the transcription of IL-10

In vertebrates, IL-10 is an anti-inflammatory factor that serves as a key inhibitory role in a wide range of immune responses. IRAK1 (IL-1 receptor-associated kinase 1), a key molecule in the inflammatory signal of IL-1R/TLR, plays an important pivotal role in regulating the autoimmunity of body. STAT3 (Signal transducer and activator of transcription 3) activated by IRAK1 participates in inflammation, tumorigenesis, metabolic disorders and immune response. Under the stimulation of LPS, IRAK1 enters the nucleus to form a dimer with STAT3 and regulates the expression of IL-10. However, the relationship between fish IRAK1 and STAT3 has not been reported. To explain the anti-inflammation in fish, we amplified and identified the complete open reading frame of grass carp IRAK1 (CiIRAK1) and STAT3 (CiSTAT3) based on the existing sequences. The expression of CiIRAK1 and CiSTAT3 were up-regulated significantly under the stimulation of LPS. This result suggests that both CiIRAK1 and CiSTAT3 may be involved in LPS-induced TLR4 pathway. The subcellular localization experiment revealed that CiIRAK1 is distributed in cytoplasm and enters nucleus after LPS stimulation. CiSTAT3 is distributed in both cytoplasm and nucleus with or without LPS stimulation. Immunoprecipitation assay revealed that CiIRAK1 interacted with CiSTAT3 under LPS stimulation. However in absence of LPS stimulation, CiIRAK1 and CiSTAT3 cannot interact with each other. Subsequently, immunofluorescence colocalization experiment further proved the interaction of CiIRAK1 and CiSTAT3 in nucleus under LPS stimulation. The dual luciferase reporter assays indicated that the binding of CiIRAK1 and CiSTAT3 synergistically enhanced the activity of CiIL-10 promoter.

Transcriptome Profiling of Pacu (Piaractus mesopotamicus) Challenged With Pathogenic Aeromonas hydrophila: Inference on Immune Gene Response

Pacu (Piaractus mesopotamicus) is a Neotropical fish of major importance for South American aquaculture. Septicemia caused by Aeromonas hydrophila bacteria is currently considered a substantial threat for pacu aquaculture that have provoked infectious disease outbreaks with high economic losses. The understanding of molecular aspects on progress of A. hydrophila infection and pacu immune response is scarce, which have limited the development of genomic selection for resistance to this infection. The present study aimed to generate information on transcriptome of pacu in face of A. hydrophila infection, and compare the transcriptomic responses between two groups of time-series belonging to a disease resistance challenge, peak mortality (HM) and mortality plateau (PM) groups of individuals. Nine RNA sequencing (RNA-Seq) libraries were prepared from liver tissue of challenged individuals, generating ∼160 million 150 bp pair-end reads. After quality trimming/cleanup, these reads were assembled de novo generating 211,259 contigs. When the expression of genes from individuals of HM group were compared to individuals from control group, a total of 4,413 differentially expressed transcripts were found (2,000 upregulated and 2,413 downregulated candidate genes). Additionally, 433 transcripts were differentially expressed when individuals from MP group were compared with those in the control group (155 upregulated and 278 downregulated candidate genes). The resulting differentially expressed transcripts were clustered into the following functional categories: cytokines and signaling, epithelial protection, antigen processing and presentation, apoptosis, phagocytosis, complement system cascades and pattern recognition receptors. The proposed results revealing relevant differential gene expression on HM and PM groups which will contribute to a better understanding of the molecular defense mechanisms during A. hydrophila infection.

Novel module and hub genes of distinctive breast cancer associated fibroblasts identified by weighted gene co-expression network analysis

BACKGROUND

As abundant and heterogeneous stromal cells in tumor microenvironment, carcinoma-associated fibroblasts (CAFs) are critically involved in cancer progression.

METHODS

To identify co-expression module and hub genes of distinctive breast CAFs, weighted gene co-expression network analysis (WGCNA) was conducted based on the expression array results of CAFs from seven chemo-sensitive breast cancer (BC) patients and seven chemo-resistant ones before neo-adjuvant chemotherapy.

RESULTS

A total of 4916 genes were included in WGCNA, and 12 modules were determined. Module-trait assay showed that the blue module (cor = 0.97, P < 0.001) was associated with CAF-related chemo-resistance, which was enriched mainly as "inflammatory response", "interferon-gamma-mediated signaling" and "NIK/NF-kappaB signaling" pathways. Moreover, CXCL8, CXCL10, CXCL11, PLSCR1, RIPK2 and USP18 were found to be potentially associated with chemo-resistance related to CAFs and prognosis of BC.

CONCLUSIONS

Our current data offered valuable insights into the molecular mechanisms of distinctive breast CAFs, which was beneficial for revealing how chemo-resistance of BC was initiated.

Alteration of cell junctions during viral infection

Cell junctions serve as a protective barrier for cells and provide an important channel for information transmission between cells and the surrounding environment. Viruses are parasites that invade and commandeer components of host cells in order to survive and replicate, and they have evolved various mechanisms to alter cell junctions to facilitate viral infection. In this review, we examined the current state of knowledge on the action of viruses on host cell junctions. The existing evidence suggests that targeting the molecules involved in the virus-cell junction interaction can prevent the spread of viral diseases.

Molecular characterization and expressional modulation of IRAK1 as downstream signaling adaptor molecule of TLR-signaling pathways in Labeo rohita following PAMPs stimulation and bacterial infections

Interleukin-1 receptor associated kinase (IRAK1) is one of the crucial signal transduction mediators in TLR/IL-1R signaling pathways in host immune system. To investigate about it in rohu (Labeo rohita), one of the economically important freshwater fish species in the Indian subcontinent, we cloned, characterized and analyzed its expression following bacterial infection and pathogens associated molecular patterns (PAMPs) stimulation. The full-length cDNA of rohu IRAK1 (LrIRAK1) consisted of 2765 nucleotide (nt) having an ORF of 2115 nt encoding a polypeptide of 704 amino acids (aa) with a molecular mass of 70.4 kDa. Structurally, LrIRAK1 consisted of twenty-nine helix, twelve strands and forty one coils making one N-terminal death domain (19-94 aa) and a central serine threonine kinase catalytic domain (or kinase domain) (188-489aa). In addition to these two prominent domains, LrIRAK1 also contained highly conserved amino acids viz., lysine ²¹⁵ and aspartic acid ³¹⁴ and threonine ^{185, 361} which were reported to be important for kinase and phosphorylation activity respectively in other animals. Similar to higher vertebrates, LrIRAK1 also consisted of CDK1 (cyclin-dependent kinase1) at 338-352 aa; NEK2 (NIMA-related kinase 2) at 47-61 aa; NEK6 (NIMA-related kinase 6) at 581-595 aa and AMPK (AMP- activated protein kinase) motif at 518-538 aa. Phylogenetically, LrIRAK1 is closely related to cave fish, common carp exhibiting high similarity (~95%) and identity (~90%). In the uninfected fish, the LrIRAK1 expression was highest in liver (~11.5 fold) and lowest in blood. In response to Aeromonas hydrophila, Edwardsiella tarda and Bacillus subtilis infection and various TLR and NLR-ligands stimulation, the expression of LrIRAK1 was markedly enhanced at various time points in almost all the tested tissues. These results together suggest the key role of LrIRAK1 in pattern recognition receptors (PRRs)-mediated host defense against pathogenic insults.

Identification and functional characterization of the transcription factor NF-κB subunit p65 in common carp (Cyprinus carpio L.)

p65 is an important subunit of the transcription factor NF-κB in the regulation of immune response. In the present study, the p65 cDNA was identified from common carp (Cyprinus carpio L.) (named Ccp65). Phylogenetic analysis revealed that Ccp65 located in the same clade as piscine p65 and exhibited closest relationship to that of Ctenopharyngodon idella. Ccp65 was constitutively expressed in all the examined tissues. Aeromonas hydrophila and poly(I:C) can induce the expression of Ccp65 in the designated tissues and the Ccp65 expression was up-regulated in HKLs following LPS and poly(I:C) stimulation. In addition, the nuclear localization signal (NLS) and C-terminal domain are the important elements of Ccp65. Immunofluorescence assay revealed that the nuclear localization signal deletion mutation of Ccp65 (Ccp65ΔNLS) failed to translocate to the nucleus even though stimulation with poly(I:C) or LPS, and the C-terminal domain deletion mutation of Ccp65 (Ccp65ΔC) did not up-regulate the luciferase activity. Furthermore, Ccp65 can induce the expression of il-1β and tnf-α. And LPS and poly(I:C) inducing the expression of il-1β and tnf-α, is dependent on the Ccp65. Taken altogether, these findings lay the foundations for future research to investigate the mechanisms underlying fish p65.

Identification of modules and hub genes associated with platinum-based chemotherapy resistance and treatment response in ovarian cancer by weighted gene co-expression network analysis

High-grade serous ovarian carcinoma (HGSOC) is the most prevalent and malignant ovarian tumor.To identify co-expression modules and hub genes correlated with platinum-based chemotherapy resistant and sensitive HGSOC, we performed weighted gene co-expression network analysis (WGCNA) on microarray data of HGSOC with 12 resistant samples and 16 sensitive samples of GSE51373 dataset.A total of 5122 genes were included in WGCNA, and 16 modules were identified. Module-trait analysis identified that the module salmon (cor = 0.50), magenta (cor = 0.49), and black (cor = 0.45) were discovered associated with chemotherapy resistant, and the significance for these platinum-resistant modules were validated in the GSE63885 dataset. Given that the black module was validated to be the most related one, hub genes of this module, alcohol dehydrogenase 1B, cadherin 11, and vestigial like family member 3were revealed to be expressional related with platinum resistance, and could serve as prognostic markers for ovarian cancer.Our analysis might provide insight for molecular mechanisms of platinum-based chemotherapy resistance and treatment response in ovarian cancer.

Common Carp mef2 Genes: Evolution and Expression

The MEF2 (myocyte enhancer factor 2) family belongs to the MADS-box superfamily of eukaryotic transcription factors. The vertebrate genes compose four distinct subfamilies designated MEF2A, -B, -C, and -D. There are multiple mef2 genes in the common carp (Cyprinus carpio). So far, the embryonic expression patterns of these genes and the evolution of fish mef2 genes have been barely investigated. In this study, we completed the coding information of C. carpio mef2ca2 and mef2d1 genes via gene cloning and presented two mosaic mef2 sequences as evidence for recombination. We also analyzed the phylogenetic relationship and conserved synteny of mef2 genes and proposed a new evolutionary scenario. In our version, MEF2B and the other three vertebrate subfamilies were generated in parallel from the single last ancestor via two rounds of whole genome duplication events that occurred at the dawn of vertebrates. Moreover, we examined the expression patterns of C. carpio mef2 genes during embryogenesis, by using whole-mount in situ hybridization, and found the notochord to be a new expression site for these genes except for mef2ca1&2. Our results thus provide new insights into the evolution and expression of mef2 genes.

Molecular characterization and functional analysis of interferon regulatory factor 9 (irf9) in common carp Cyprinus carpio: a pivotal molecule in the Ifn response against pathogens

In the present study, interferon (IFN) regulatory factor (IRF) 9 gene (irf9) was identified and characterized in common carp Cyprinus carpio. The predicted protein sequence of Irf9 contains a DNA binding domain (DBD) that possess five tryptophans, an IRF association domain (IAD) and two nuclear localisation signals (NLS). Alignment of Irf9 of C. carpio with the corresponding Irf9 proteins of other species showed that the DBD is more highly conserved than the IAD. The putative Irf9 protein sequence of C. carpio shares higher identities with teleosts (53.8-82.3%) and lower identities with mammals (30.2-31.0%). Phylogenetic studies of the putative amino-acid sequence of IRF9 based on the neighbour-joining method showed that Irf9 of C. carpio has the closest relationship with the grass carp Ctenopharyngodon idella. Tissue distribution analysis showed that irf9 transcripts were detectable in all examined tissues with the highest expression in the skin and the lowest expression in the head kidney. Poly I:C and Aeromonas hydrophila stimulation up-regulated irf9 expression in the spleen, head kidney, foregut and hindgut at different time intervals. In addition, irf9 was induced by Poly I:C and lipopolysaccharides (LPS) in vitro. These results indicate that Irf9 participates in antiviral and antibacterial immunity. Transfection of irf9 up-regulated the expression of cytokines, including type I IFN, protein kinase R (PKR), interferon-stimulated gene (ISG)15 and tumour necrosis factor (TNF)α in epithelioma papulosum cyprini cells (EPC) upon poly I:C and LPS stimulation. A dual-luciferase reporter assay revealed that Irf9 has no effect on NF-κB activation. The present study on Irf9 provides new insights into the IFN system of C. carpio and a valuable experimental platform for future studies on the immune system of fish.

Proteomics of the mediodorsal thalamic nucleus of rats with stress-induced gastric ulcer

BACKGROUND

Stress-induced gastric ulcer (SGU) is one of the most common visceral complications after trauma. Restraint water-immersion stress (RWIS) can cause serious gastrointestinal dysfunction and has been widely used to study the pathogenesis of SGU to identify medications that can cure the disease. The mediodorsal thalamic nucleus (MD) is the centre integrating visceral and physical activity and contributes to SGU induced by RWIS. Hence, the role of the MD during RWIS needs to be studied.

AIM

To screen for differentially expressed proteins in the MD of the RWIS rats to further elucidate molecular mechanisms of SGU.

METHODS

Male Wistar rats were selected randomly and divided into two groups, namely, a control group and an RWIS group. Gastric mucosal lesions of the sacrificed rats were measured using the erosion index and the proteomic profiles of the MD were generated through isobaric tags for relative and absolute quantitation (iTRAQ) coupled with two-dimensional liquid chromatography and tandem mass spectrometry. Additionally, iTRAQ results were verified by Western blot analysis.

RESULTS

A total of 2853 proteins were identified, and these included 65 dysregulated (31 upregulated and 34 downregulated) proteins (fold change ratio ≥ 1.2). Gene Ontology (GO) analysis showed that most of the upregulated proteins are primarily related to cell division, whereas most of the downregulated proteins are related to neuron morphogenesis and neurotransmitter regulation. Ingenuity Pathway Analysis revealed that the dysregulated proteins are mainly involved in the neurological disease signalling pathways. Furthermore, our results indicated that glycogen synthase kinase-3 beta might be related to the central mechanism through which RWIS gives rise to SGU.

CONCLUSION

Quantitative proteomic analysis elucidated the molecular targets associated with the production of SGU and provides insights into the role of the MD. The underlying molecular mechanisms need to be further dissected.

Detection of Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium based on cell elongation induced by beta-lactam antibiotics

Pathogenic bacteria such as Shiga toxigenic Escherichia coli and Salmonella can cause severe food-borne diseases. Rapid and sensitive detection of these foodborne pathogens is essential to ensure food safety. In this study, a novel method based on cell elongation induced by beta-lactam antibiotics for direct microscopic counting of Gram-negative bacteria was established. Combined with the sample preparation steps of membrane filtration and magnetic separation, the detection of E. coli O157:H7 and Salmonella enterica serotype Typhimurium was achieved by direct optical microscopic counting of the number of elongated bacteria. The limit of detection of E. coli O157:H7 and S. typhimurium could reach 20 CFU mL^-1. The recovery tests for E. coli O157:H7 and S. typhimurium in water and milk samples showed acceptable recovery values between 93.6% and 106.2%. This method is sensitive, cost effective, and rapid (<2 h) and shows great potential for the detection of Gram-negative pathogens in various environmental and food samples.

An immunofiltration strip method based on the photothermal effect of gold nanoparticles for the detection of Escherichia coli O157:H7

An immunofiltration strip is a promising rapid and powerful tool for the routine monitoring of foodborne pathogenic bacteria. However, the strip assay is generally less sensitive than other immunological techniques. A novel immunofiltration strip method based on the photothermal effect of gold nanoparticles (GNPs) was developed for the sensitive, rapid, simple handheld and low-cost detection of Escherichia coli O157:H7. The photothermal effect of GNPs was used to achieve the amplification of signals to improve the sensitivity of the strip method. The thermal contrasts caused by the photothermal effect were proportional to the bacteria concentrations and yield an almost logarithmic relation. Under optimal conditions, the detection limit was 1.95 × 104 CFU mL-1, and the sensitivity was improved about ten times compared to that of the conventional visual strip method. In brief, the photothermal based immunofiltration strip could be used for the rapid and sensitive detection of other pathogens as a great potential food quality control technique.

Thymosin participates in antimicrobial immunity in zebrafish

Thymosin hormones, which were shown to be involved in immune system development and differentiation in previous studies, have antimicrobial functions in different animals. Zebrafish are a useful model for immunology research. Although thymosin has been reported to be involved in the embryonic development of zebrafish, it is necessary to uncover the antimicrobial function of thymosin in zebrafish. In this study, we expressed thymosin β (Tβ) in zebrafish in vitro and studied its antimicrobial function. The Tβ protein consists of 45 amino acids and is conserved among its family members, especially the actin-binding motif (LKKTET). Tβ was expressed in all tested tissues and was highly expressed in the brain, liver and hindgut. After Aeromonas hydrophila challenge, the Tβ transcript level increased in the skin, liver, kidney, spleen, thymus, foregut, gills and midgut. Purified recombinant thymosin β (rTβ) protein was used to study the antimicrobial mechanism. rTβ could inhibit the growth of Staphylococcus aureus, Aeromonas hydrophila, Vibrio anguillarum, Pseudomonas aeruginosa and Klebsiella pneumoniae. rTβ also binds to and agglutinates certain bacteria. Further study showed that rTβ could combine with the polysaccharides from gram-negative and gram-positive bacterial walls. All results suggested that the Tβ of zebrafish plays a significant role in innate antibacterial immune responses.

Interleukin-1 Receptor Associated Kinase 1 Mediates the Maintenance of Neuropathic Pain after Chronic Constriction Injury in Rats

Neuropathic pain (NP) has complicated pathogenesis as it mainly involves a lesion or dysfunction of the somatosensory nervous system and its clinical treatment remains challenging. Chronic constriction injury (CCI) model is a widely used neuropathic pain model and involved in mechanisms including both nerve inflammatory and injury. Cytokines and their receptors play essential roles in the occurrence and persistence of neuropathic pain, but the underlying mechanisms have not well been understood. Therefore, Interleukin-1 receptor-associated kinase 1 (IRAK1) is chosen to explore the possible mechanisms of NP. In the present study, IRAK1 was found to persistently increase in the dorsal root ganglion (DRG) and spinal cord (SC) during CCI detected by western blot. The staining further confirmed that IRAK1 was mainly co-located in the DRG astrocytes or SC neurons, but less in the DRG microglia or SC astrocytes. Moreover, the region of increased IRAK1 expression was observed in superficial laminae of the spinal dorsal horn, which was the nociceptive neuronal expression domain, suggesting that IRAK1 may mediated CCI-induced pain by nociceptive primary afferent. In addition, intrathecal injection of Toll-like receptor 4 (TLR4) inhibitor or IRAK1 siRNA decreased the expression of IRAK1 accompanied with the alleviation of CCI-induced neuropathic pain. The upregulation of p-NF-κB expression was reversed by IRAK1 siRNA in SC, and intrathecal injection of p-NF-κB inhibitor relieved neuropathic pain. Taking together, targeting IRAK1 may be a potential treatment for chronic neuropathic pain.

Phylostratigraphic analysis of gene co-expression network reveals the evolution of functional modules for ovarian cancer

Ovarian cancer (OV) is an extremely lethal disease. However, the evolutionary machineries of OV are still largely unknown. Here, we used a method that combines phylostratigraphy information with gene co-expression networks to extensively study the evolutionary compositions of OV. The present co-expression network construction yielded 18,549 nodes and 114,985 edges based on 307 OV expression samples obtained from the Genome Data Analysis Centers database. A total of 20 modules were identified as OV related clusters. The human genome sequences were divided into 19 phylostrata (PS), the majority (67.45%) of OV genes was already present in the eukaryotic ancestor. There were two strong peaks of the emergence of OV genes screened by hypergeometric test: the evolution of the multicellular metazoan organisms (PS5 and PS6, P value = 0.002) and the emergence of bony fish (PS11 and PS12, P value = 0.009). Hence, the origin of OV is far earlier than its emergence. The integrated analysis of the topology of OV modules and the phylogenetic data revealed an evolutionary pattern of OV in human, namely, OV modules have arisen step by step during the evolution of the respective lineages. New genes have evolved and become locked into a pathway, where more and more biological pathways are fixed into OV modules by recruiting new genes during human evolution.

Targeted inhibition of histone deacetylase 6 in inflammatory diseases

Targeting epigenetic modification of gene expression represents a promising new approach under investigation for the treatment of inflammatory diseases. Accumulating evidence suggests that epigenetic mechanisms, such as histone modification, play a crucial role in a number of inflammatory diseases, including rheumatoid arthritis, asthma, and contact hypersensitivity. Consistent with this role, histone deacetylase (HDAC) inhibitors have shown efficacy in the treatment of inflammatory diseases. In particular, selective inhibitors of HDAC6, a cytoplasmic member of the HDAC family that contains two deacetylase domains, are under investigation as a potential treatment strategy for inflammatory diseases due to their ability to regulate inflammatory cells and cytokines. Here, we review recent findings highlighting the critical roles of HDAC6 in a variety of inflammatory diseases, and discuss the therapeutic potential of HDAC6 inhibitors in these settings.

Molecular characterization and expression analysis of two peptidoglycan recognition proteins (CcPGRP5, CcPGRP6) in larvae ontogeny of common carp Cyprinus carpio L. and upon immune stimulation by bacteria

Background

Although teleost fish developed acquired immunity firstly in evolution, innate immunity is still very important for them. Innate immunity depends on pattern recognition receptors (PRRs) to distinguish “self” and “non-self”, Peptidoglycan (PGN) recognition protein (PGRP) is one of the receptors and it can bind to multiple components of bacterial envelope.

Results

We report the cloning and expression analysis of two PGRPs (Ccpgrp5 and Ccpgrp6) from common carp (Cyprinus carpio L). The Ccpgrp5 gene encodes a protein of 199 amino acid (aa) with PGRP domain, Ami_2 domain and four Zn²⁺ binding sites required for amidase activity, but without signal peptide and transmembrane domain. The Ccpgrp6 gene encodes a protein of 446 aa with PGRP domain, Ami_2 domain, signal peptide, five Zn²⁺ binding sites required for amidase activity and two sites for N-glycosylation. The phylogenetic analysis revealed that the CcPGRP5 and CcPGRP6 are closely related to Ctenopharyngodon idella and Danio rerio. Ccpgrp5 and Ccpgrp6 were expressed in all tissues examined including liver, spleen, muscle, oral epithelium, head kidney, gill, skin, gonad, brain, foregut and hindgut and showed different distribution characteristics. During the embryonic and early larval developmental stages of common carp, Ccpgrp6 was detected to be highly expressed at 10 days post fertilization(dpf) and 36 dpf, while Ccpgrp5 were hardly detected using Real-time quantitative PCR. After being challenged with Aeromonas hydrophila, Ccpgrp5 in adult common carp was induced and up-regulated in all the tissues, especially in gill and spleen, but not in head kidney, while Ccpgrp6 was up-regulated in all the tissues, especially in liver, head kidney and gill. The varied expression profiling of Ccpgrp5 and Ccpgrp6 indicated they had different roles in the host immune response.

Conclusions

These results indicated the two PGRPs, especially Ccpgrp6, played an important role in the immune defense of common carp during larva development and against Aeromonas hydrophila, providing insight to further exploration of protecting fish against bacteria infectious disease.

Identification and functional characterization of amphioxus Miple, ancestral type of vertebrate midkine/pleiotrophin homologues

Midkine (MK) and pleiotrophin (PTN) are the only two members of heparin-binding growth factor family. MK/PTN homologues found from Drosophila to humans are shown to have antibacterial activities and their antibacterial domains are conserved during evolution. However, little is known about MK/PTN homologue in the basal chordate amphioxus, and overall, information regarding MK/PTN homologues is rather limited in invertebrates. In this study, we identified a single MK/PTN homologue in Branchiostoma japonicum, termed BjMiple, which has a novel domain structure of PTN-PTNr1-PTNr2, and represents the ancestral form of vertebrate MK/PTN family proteins. BjMiple was expressed mainly in the ovary in a tissue-dependent fashion, and its expression was remarkably up-regulated following challenge with bacteria or their signature molecules LPS and LTA, suggesting its involvement in antibacterial responses. Functional assays revealed that BjMiple had strong antimicrobial activity, capable of killing a panel of Gram-negative and Gram-positive bacteria via a membranolytic mechanism, including interaction with bacterial membrane via LPS and LTA, membrane depolarization and high intracellular levels of ROS. Importantly, strong antibacterial activity was localized in PTN_42-61 and PTNr1_42-66. Additionally, BjMiple and its derived peptides PTN_42-61 and PTNr1_42-66 were not cytotoxic to human RBCs and mammalian cells. Taken together, our study suggests that amphioxus Miple is the ancestral type of vertebrate MK/PTN family homologues, and can play important roles as innate peptide antibiotics, which renders it a promising template for the design of novel peptide antibiotics against multi-drug resistant bacteria.

Therapeutic targeting of cellular stress responses in cancer

Similar to bacteria, yeast, and other organisms that have evolved pathways to respond to environmental stresses, cancer cells develop mechanisms that increase genetic diversity to facilitate adaptation to a variety of stressful conditions, including hypoxia, nutrient deprivation, exposure to DNA-damaging agents, and immune responses. To survive, cancer cells trigger mechanisms that drive genomic instability and mutation, alter gene expression programs, and reprogram the metabolic pathways to evade growth inhibition signaling and immune surveillance. A deeper understanding of the molecular mechanisms that underlie the pathways used by cancer cells to overcome stresses will allow us to develop more efficacious strategies for cancer therapy. Herein, we overview several key stresses imposed on cancer cells, including oxidative, metabolic, mechanical, and genotoxic, and discuss the mechanisms that drive cancer cell responses. The therapeutic implications of these responses are also considered, as these factors pave the way for the targeting of stress adaption pathways in order to slow cancer progression and block resistance to therapy.

Identification of a fish-specific NOD-like receptor subfamily C (NLRC) gene from common carp (Cyprinus carpio L.): Characterization, ontogeny and expression analysis in response to immune stimulation

Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are a large group of cytoplasmic pattern recognition receptors (PRRs), which play an important role in pathogen recognition and regulation of innate immune response. In fish, NLRs are divided into three distinct subfamilies: NLR-A resembling mammalian NODs, NLR-B resembling mammalian NALPs and fish-specific NLR-C. Presently, no data is available about the common carp NLR gene, and meanwhile the studies concerning fish NLR-C subfamily genes are relatively poor. In the present study, we cloned and characterized a novel NLRC gene (CcNLRC) from common carp. The full-length cDNA of CcNLRC was 3642 bp, with an ORF of 3078 bp encoding 1025 amino acids. CcNLRC appears to be unique to fish, consisting of a fish-specific NACHT associated (FISNA) domain, a NACHT domain, three LRR motifs and an extra B30.2 domain at C-terminus. Expression analysis revealed that CcNLRC was constitutively expressed in various healthy tissues, and during early developmental stages CcNLRC had two expression peaks (1 dpf and 24 dpf). In vivo stimulation with polyI:C and V. anguillarum showed significant up-regulation of CcNLRC expression in some immune-related tissues including liver, spleen, foregut, hindgut and skin. Additionally, in vitro study in common carp PBLs and HKLs stimulated with different ligands such as polyI:C, flagellin and PGN showed enhanced gene expression of CcNLRC. These results suggested that CcNLRC might play an important role in the innate immune defense of common carp against pathogen invasion.

Carp Toll-like receptor 8 (Tlr8): An intracellular Tlr that recruits TIRAP as adaptor and activates AP-1 pathway in immune response

Toll-like receptor 8 (Tlr8) is a member of intracellular TLRs family and play a critical role in the innate immunity. In the present study, we aimed to identify tlr8 from common carp (Cyprinus carpio L.), and explored its expression profile, localization, adaptor, and signaling pathways. A novel tlr8 cDNA sequence (Cctlr8) was identified from the carp, containing a signal peptide, a LRR-N-terminal (LRR-NT), 14 leucine-rich repeats, a LRR-C-terminal (LRR-CT), a transmembrane region and a TIR domain. Phylogenetic analysis revealed that CcTlr8 exhibited closest relationship to that of Ctenopharyngodon idella and Danio. rerio. Subcellular localization analysis indicated that CcTlr8 was localized to the endoplasmic reticulum in both HeLa cells and EPC cells. Quantitative Real-Time PCR analysis demonstrated that Cctlr8 was constitutively expressed in all the examined tissues, with the highest expression observed in the spleen. After poly (I:C) injection, the expression of Cctlr8 was significantly up-regulated in all the tested tissues. In addition, the expression of Cctlr8 was up-regulated in both PBLs and HKLs following poly (I:C) stimulation. The results of immuofluorescence and coimmunoprecipitation analysis indicated that CcTlr8 might recruit TIRAP as the adaptor. Furthermore, Luciferase reporter assays revealed that CcTlr8 could activate AP-1 in 293 T cells. Taken altogether, these findings lay the foundations for future research to investigate the mechanisms underlying fish tlr8.

Molecular characterization of three novel perforins in common carp (Cyprinus carpio L.) and their expression patterns during larvae ontogeny and in response to immune challenges

Background

In the host immune system, perforin is a cytotoxic effector molecule that eliminate virus-infected and malignant cells. Moreover, some recent studies also imply the involvement of perforin in antibacterial immunity. Common carp (Cyprinus carpio L.), one of the most economically important fish species in China, has a high susceptibility to viruses and bacteria. Thus far, in common carp, no data are available regarding the identification and immunologic function of the perforin.

Results

In the present study, the cDNA and genomic DNA sequences of three perforin isoform genes were cloned and characterized in common carp, named CcPRF1, CcPRF2 and CcPRF3. Amino acid sequences of the three CcPRFs were quite different, with identities ranged from 37.3 to 39.5%. Phylogenetic analysis showed that three CcPRFs, each in a separate sub-branch, possessed closer evolutionary relationship with other teleost perforins, especially with cyprinid fishes, than higher vertebrates. Expression analysis revealed that each CcPRF gene was differentially expressed in all of the nine tested tissues. During larvae ontogeny, each CcPRF displayed a distinct expression pattern, while with a common expression peak at 22 days post hatching (dph). Moreover, in vivo or in vitro, after stimulation with polyI:C, LPS and Aeromonas hydrophila, each CcPRF was induced significantly, with differential expression dynamics.

Conclusions

Our findings suggest that perforin might play significant roles in larval immune system and in the immune defense of common carp against viral and bacterial pathogens. Meantime, the differential expression dynamics seem to imply possible different cellular locations or functional differences across various CcPRF isoforms.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1613-y) contains supplementary material, which is available to authorized users.

Applications of SERS in the Detection of Stress-Related Substances

A wide variety of biotic and abiotic stresses continually attack plants and animals, which adversely affect their growth, development, reproduction, and yield realization. To survive under stress conditions, highly sophisticated and efficient tolerance mechanisms have been evolved to adapt to stresses, which consist of the variation of effector molecules playing vital roles in physiological regulation. The development of a sensitive, facile, and rapid analytical methods for stress factors and effector molecules detection is significant for gaining deeper insight into the tolerance mechanisms. As a nondestructive analysis technique, surface-enhanced Raman spectroscopy (SERS) has unique advantages regarding its biosensing applications. It not only provides specific fingerprint spectra of the target molecules, conformation, and structure, but also has universal capacity for simultaneous detection and imaging of targets owing to the narrow width of the Raman vibrational bands. Herein, recent progress on biotic and abiotic stresses, tolerance mechanisms and effector molecules is summarized. Moreover, the development and promising future trends of SERS detection for stress-related substances combined with nanomaterials as substrates and SERS tags are discussed. This comprehensive and critical review might shed light on a new perspective for SERS applications.

Analysis of Biomolecules Based on the Surface Enhanced Raman Spectroscopy

Analyzing biomolecules is essential for disease diagnostics, food safety inspection, environmental monitoring and pharmaceutical development. Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for detecting biomolecules due to its high sensitivity, rapidness and specificity in identifying molecular structures. This review focuses on the SERS analysis of biomolecules originated from humans, animals, plants and microorganisms, combined with nanomaterials as SERS substrates and nanotags. Recent advances in SERS detection of target molecules were summarized with different detection strategies including label-free and label-mediated types. This comprehensive and critical summary of SERS analysis of biomolecules might help researchers from different scientific backgrounds spark new ideas and proposals.

Molecular characterization and expression patterns of a non-mammalian toll-like receptor gene (TLR21) in larvae ontogeny of common carp (Cyprinus carpio L.) and upon immune stimulation

Background

In the host innate immune system, various pattern recognition receptors (PRRs) recognize conserved pathogen-associated molecular patterns (PAMPs) and represent an efficient first line of defense against invading pathogens. Toll-like receptors (TLRs) are a major class of PRRs, which are able to recognize a wide range of PAMPs and play a central role in initiating innate immune responses. TLR21 is one of the non-mammalian TLRs identified in some bird and fish species.

Results

In the present study, we reported the cloning and identification of a TLR21 cDNA from the head kidney of common carp (Cyprinus carpio L.), named CcTLR21. The full-length CcTLR21 cDNA was 3557 bp long, including an open reading frame (ORF) of 2895 bp, which encoded a putative protein of 964 amino acids. The putative CcTLR21 protein was found to comprise a signal peptide, 14 LRR domains in the extracellular region and a TIR domain in the cytoplasmic region, which fits with the characteristic TLR domain architecture. The phylogenetic analysis showed that CcTLR21 possessed high amino acid identities with the TLR21s in other freshwater teleosts. A Real-time PCR assay showed that CcTLR21 mRNA was expressed in almost all tissues examined in healthy common carp, while the levels obviously varied among different tissues. During the embryonic and early larval developmental stages of common carp, the CcTLR21 showed two peaks of expression, with the first at 1 dpf and the second at 10 dpf. When challenged with poly(I:C) (a viral model) or Aeromonas hydrophila, the expression level of CcTLR21 was up-regulated in a variety of common carp tissues.

Conclusions

Our findings indicate that CcTLR21 plays a significant role in innate immune defense during larvae ontogeny and in responses to viral or bacterial pathogens.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1474-4) contains supplementary material, which is available to authorized users.

Molecular mechanisms underlying stress response and adaptation

Environmental stresses are ubiquitous and unavoidable to all living things. Organisms respond and adapt to stresses through defined regulatory mechanisms that drive changes in gene expression, organismal morphology, or physiology. Immune responses illustrate adaptation to bacterial and viral biotic stresses in animals. Dysregulation of the genotoxic stress response system is frequently associated with various types of human cancer. With respect to plants, especially halophytes, complicated systems have been developed to allow for plant growth in high salt environments. In addition, drought, waterlogging, and low temperatures represent other common plant stresses. In this review, we summarize representative examples of organismal response and adaptation to various stresses. We also discuss the molecular mechanisms underlying the above phenomena with a focus on the improvement of organismal tolerance to unfavorable environments.

Non-mammalian Toll-like receptor 18 (Tlr18) recognizes bacterial pathogens in common carp (Cyprinus carpio L.): Indications for a role of participation in the NF-κB signaling pathway

Toll-like receptors are important pattern recognition receptors that can recognize pathogen-associated molecular patterns (PAMPs) and play a critical role in innate immunity. In the present study, tlr18 was identified from common carp (Cyprinus carpio L.) (named Cctlr18). The deduced amino acid sequence contained only a signal peptide, eight LRR (leucine-rich repeat) motifs, a transmembrane region and a TIR (Toll/IL-1 receptor) domain. Phylogenetic analysis showed that CcTlr18 was most closely related to Ctenopharyngodon idella Tlr18. Quantitative real-time PCR analysis showed that Cctlr18 was constitutively expressed in all investigated tissues with the highest expression level in the skin and lowest expression in the gonad. After injection with inactivated Aeromonas hydrophila, Cctlr18 expression was significantly up-regulated in the head kidney, foregut, hindgut and skin. Moreover, significant up-regulation of Cctlr8 was observed in the spleen, head kidney, hindgut and skin after immersion with live A. hydrophila. In addition, the expression of Cctlr18 was up-regulated in PGN or flagellin-stimulated HKLs. Luciferase reporter assays showed that Cctlr18 activated NF-κB in 293 T cells and that NF-κB activity was enhanced in Cctlr18 and Ccmyd88 co-transfected cells. Furthermore, Cctlr18 could induce the expression of cytokines genes, including ifn, il-1β and il-10, in EPC cells. The results suggested that Cctlr18 plays an important role in the immune response and provides basic information for investigating the mechanisms of fish tlr18.

Molecular characterization and expression pattern of X box-binding protein-1 (XBP1) in common carp (Cyprinus carpio L.): Indications for a role of XBP1 in antibacterial and antiviral immunity

X box-binding protein-1 (XBP1) is a transcription factor that is essential for the unfolded protein response (UPR) and the differentiation of plasma cells, and some findings have also uncovered its function in innate immunity. XBP1 typically has two different transcripts, un-spliced (XBP1u) and spliced forms (XBP1s), but XBP1s is an active transcription factor in the regulation of target genes. To date, there is no evidence about the identification and function of XBP1 in common carp. Moreover, no data are currently available regarding the role of fish XBP1 in innate immunity. Thus, to determine whether XBP1 is involved in innate immune response in common carp, we cloned CcXBP1s and examined the expression of XBP1s and a XBP1s stimulated gene (IL-6) after Aeromonas hydrophila (A. hydrophila) and polyinosinic-polycytidylic acid (polyI:C) challenges. The results imply that CcXBP1s, as an active transcription factor, might play regulation roles in the antibacterial and antiviral innate immune responses of common carp. This allows us to gain new insights into the immunological function of XBP1 in fish innate immunity and the evolution of this important class of genes across vertebrates.

The complete mitochondrial genome of the parasitic sheep ked Melophagus ovinus (Diptera: Hippoboscidae)

The complete mitochondrial genome (15,573 bp) of an understudied sheep parasite Melophagus ovinus was sequenced and characterized. Its organization and characteristics, including the size, structure, gene order, start/stop codon usage and gene overlaps, are largely typical for Diptera. It exhibits very high A + T bias (81%). Posterior probability values in the inferred phylogenetic dendrogram were very high, but Oestroidea and Muscoidea superfamilies were both paraphyletic. The sequence was nested within the Oestridae clade, thus also rendering the family paraphyletic. A larger number of Hippoboscoidea mitogenomes will have to be available to achieve a better phylogenetic resolution.

Characterization, expression, and functional study of IRAK-1 from grouper, Epinephelus coioides

As crucial components of the toll-like receptor (TLR) and interleukin-1 (IL-1) receptor (IL-1R) signaling pathways, interleukin-1 receptor associated kinase (IRAK) family members play essential roles in an animal's immune response. In this study, an IRAK family member, designated EcIRAK-1, was identified in the orange-spotted grouper Epinephelus coioides, and its role in signal transduction investigated. The full-length EcIRAK-1 gene is 2822 bp, encoding a 760-amino-acid protein that has the typical characteristics of mammalian IRAK-1, including an N-terminal death domain, a ProST domain, a central kinase domain, and C-terminal C1 and C2 domains. EcIRAK-1 shares 42%-79% sequence identity with other fish IRAK-1 proteins, and the death and kinase domains are more conserved than the other domains. Several important amino acids and motifs of mammalian IRAK-1 are also conserved in the grouper and other piscine IRAK-1s. In healthy grouper, EcIRAK-1 was broadly expressed in all the tissues tested, with the highest expression in the gill and skin. After infection with Cryptocaryon irritans, EcIRAK-1 expression increased in the gill and spleen. After its exogenous expression in HEK293T cells, EcIRAK-1 significantly activated nuclear factor kappaB (NF-κB). The death domain, ProST domain, and some conserved amino acids, such as T58, T207, K237, and T387, in EcIRAK-1 are required for its signaling function. These data demonstrate that piscine IRAK-1 has the same structural characteristics as its mammalian counterpart and that its function is conserved among vertebrates.

Molecular and functional characterization of Toll-like receptor (Tlr)1 and Tlr2 in common carp (Cyprinus carpio)

Toll-like receptors (TLRs) are fundamental components of innate immunity that play significant roles in the defence against pathogen invasion. In this study, we present the molecular characterization of the full-length coding sequence of tlr1, tlr2a and tlr2b from common carp (Cyprinus carpio). Each is encoded within a single exon and contains a conserved number of leucine-rich repeats, a transmembrane region and an intracellular TIR domain for signalling. Indeed, sequence, phylogenetic and synteny analysis of carp tlr1, tlr2a and tlr2b support that these genes are orthologues of mammalian TLR1 and TLR2. The tlr genes are expressed in various immune organs and cell types. Furthermore, the carp sequences exhibited a good three-dimensional fit with the heterodimer structure of human TLR1-TLR2, including the potential to bind to the ligand Pam3CSK4. This supports the possible formation of carp Tlr1-Tlr2 heterodimers. However, we were unable to demonstrate Tlr1/Tlr2-mediated ligand binding in transfected cell lines through NF-κB activation, despite showing the expression and co-localization of Tlr1 and Tlr2. We discuss possible limitations when studying ligand-specific activation of NF-κB after expression of Tlr1 and/or Tlr2 in human but also fish cell lines and we propose alternative future strategies for studying ligand-binding properties of fish Tlrs.