Differential profiles of gene expression in grouper Epinephelus coioides, infected with Singapore grouper iridovirus, revealed by suppression subtractive hybridization and DNA microarray

Grouper cGAS is a negative regulator of STING-mediated interferon response

Cyclic GMP-AMP synthase (cGAS) is one of the classical pattern recognition receptors that recognizes mainly intracytoplasmic DNA. cGAS induces type I IFN responses to the cGAS-STING signaling pathway. To investigate the roles of cGAS-STING signaling pathway in grouper, a cGAS homolog (named EccGAS) was cloned and identified from orange-spotted grouper (Epinephelus coioides). The open reading frame (ORF) of EccGAS is 1695 bp, encodes 575 amino acids, and contains a Mab-21 typical structural domain. EccGAS is homologous to Sebastes umbrosus and humans at 71.8% and 41.49%, respectively. EccGAS mRNA is abundant in the blood, skin, and gills. It is uniformly distributed in the cytoplasm and colocalized in the endoplasmic reticulum and mitochondria. Silencing of EccGAS inhibited the replication of Singapore grouper iridovirus (SGIV) in grouper spleen (GS) cells and enhanced the expression of interferon-related factors. Furthermore, EccGAS inhibited EcSTING-mediated interferon response and interacted with EcSTING, EcTAK1, EcTBK1, and EcIRF3. These results suggest that EccGAS may be a negative regulator of the cGAS-STING signaling pathway of fish.

Epinecidin-1, a highly potent marine antimicrobial peptide with anticancer and immunomodulatory activities

BACKGROUND

Antibiotic-resistant pathogens are an emerging threat in this century. Epinecidin-1 is a multi-functional Antimicrobial Peptide (AMP) produced by Orange-spotted grouper (Epinephelus coioides) has been shown to have extensive potentials as an alternative for current antibiotics. Due to the huge costs for the study and the production of a new drug, if an antimicrobial peptide has other beneficial functions in addition to antimicrobial activities, it would be preferred.

METHODS

In this study, properties and applications of Epinecidin-1 were investigated and addressed comprehensively. To achieve this, the Google Scholar search engine and three databases of PubMed, Scopus, and Web of Science were used.

RESULTS

Epinecidin-1 is a cationic AMP with an alpha-helical structure. Seven functional usages of this peptide have been reported in the literature including antibacterial, antifungal, antiviral, antiprotozoal, anticancer, immunomodulatory, and wound healing properties. Moreover, this peptide has high potential to be used as an active ingredient in cleaning solutions as well as application in vaccine production.

CONCLUSION

Due to significant antimicrobial activities tested on bacteria such as Staphylococcus aureus and Helicobacter pylori and also wound healing properties, Epi-1 has high potential to be considered as an important candidate for the production of new drugs and treatment of various infections including diabetic foot ulcer and peptic ulcer. Moreover, adjuvant-like properties of Epi-1 make it a suitable candidate for the studies related to an adjuvant. Other attractive properties such as anticancer effects have also been reported for this peptide which encourages further studies on this peptide.

TRAF6 is a critical factor in fish immune response to virus infection

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is one of the key adaptor molecule in Toll-like receptor signal transduction that triggers downstream cascades involved in innate immunity. In our previous study, the molecular characteristics of EtTRAF6 (TRAF6 from Epinephelus tauvina), the tissue distributions, expression patterns after challenging with bacterial and viral pathogens were investigated. Here we identified EtTRAF6 as an important regulator of virus-triggered signaling pathway. Overexpression of EtTRAF6-ORF and truncated forms of EtTRAF6, including EtTRAF6-C (delete the MATH domain), EtTRAF6-N (delete the RING domain) and EtTRAF6-MATH, inhibited IFN-β activity strongly in grouper spleen (GS) cells. Overexpression of EtTRAF6 repressed virus-induced production of type I IFNs. When EtTRAF6 cotransfected with EcIRF3 or EcIRF7, EtTRAF6 inhibited IRF-induced activation of IFN-β. Over-expressed EtTRAF6 inhibited the transcription of SGIV genes significantly in GS cells. Although TRAF6 has a role in apoptosis regulation, it is not known if EtTRAF6 has any role in apoptosis regulation. Strikingly, when over-expressed in fathead minnow (FHM) cells, EtTRAF6 protected them from cell death induced by SGIV. Therefore, these results suggest that TRAF6 may play a critical role in their response to SGIV infection, through regulation of a cell death pathway that is common to fish and humans.

Hypoxic stress -responsive genes in air breathing catfish, Clarias magur (Hamilton 1822) and their possible physiological adaptive function

The Indian catfish, Clarias magur (previous name C. batrachus) is an air breathing fish, inhabitant of aquatic bodies characterized by low dissolved oxygen levels. It is exposed to hypoxic conditions in its natural habitat. Thus, it can be useful model to study the mechanism of hypoxia stress tolerance. In C. magur, molecular processes facilitating its adaptation to hypoxia stress remain largely unexplored, in part due to unavailability of genomic resources. The suppression subtractive hybridization technique (SSH) was employed to compare the differential expression of transcripts under experimental hypoxic conditions, to that of normoxic conditions. Twelve subtracted cDNA libraries (six each forward and reverse) were constructed from brain, heart, liver, muscle, spleen and head kidney tissues. A total of 2020 clones were screened and sequenced, resulting into 1805 high quality expressed sequence tags (ESTs). Annotation of these differentially expressed ESTs resulted into the identification of genes involved in vast majority of pathways/processes affecting metabolism, cellular processes, signal transduction and/or immune functions. Additionally, 18 potential novel genes expressed in hypoxia stress exposed fish were also identified. The study had catalogued the differentially expressed genes from hypoxia stress induced C. magur, where most of them are reported for the first time in a hypoxia-tolerant fish species. The results not only provided insights for the hypoxia stress altered cellular functions in C. magur, but also generated a valuable functional genomics resource to assist targeted studies on functional genomics and future genome projects.

Function analysis of fish Tollip gene in response to virus infection

Toll-interacting protein (Tollip) is one of the important regulatory proteins of Toll-like receptor (TLR) signaling pathways. In previous studies, a Tollip sequence of grouper (Epinephelus coioides) was identified and the signal transduction functions of Tollip were studied. However, the response of Tollip to virus infection has not been characterized from grouper. In the present paper, the Tollip homolog (EtTollip) from grouper (Epinephelus tauvina) was cloned and its immune response to Singapore grouper iridovirus (SGIV) was investigated. EtTollip shares significant similarities to other mammalian Tollips, which contain a centrally localized protein kinase C conserved region 2 (C2) domain and a C-terminal CUE domain. After challenging with SGIV, the expression levels of EtTollip were altered in the spleen and head kidney of grouper. EtTollip mainly aggregated in the cytoplasm in a condensed state and was also distributed on the membranes of GS cells. EtTollip significantly inhibited the activities of NF-κB and IFN-β luciferase reporter when transfected into grouper spleen (GS) cells. SGIV can increase the activities of NF-κB and IFN-β luciferase reporter, especially to IFN-β. When transfected EtTollip with EcMyd88, the activity of NF-κB was increased, while transfected EtTollip with EcIRF3, the activity of IFN-β was significantly increased. Over-expressed EtTollip inhibited the transcription of SGIV genes significantly in GS cells, and silencing of EtTollip with siRNA led to increase of SGIV genes loads. Taken together, the results provide new insights in to the importance of Tollip as evolutionarily conserved molecule for grouper innate immunity against virus infection.

Comprehensive identification and profiling of host miRNAs in response to Singapore grouper iridovirus (SGIV) infection in grouper (Epinephelus coioides)

microRNAs (miRNAs) are an evolutionarily conserved class of non-coding RNA molecules that participate in various biological processes. Employment of high-throughput screening strategies greatly prompts the investigation and profiling of miRNAs in diverse species. In recent years, grouper (Epinephelus spp.) aquaculture was severely affected by iridoviral diseases. However, knowledge regarding the host immune responses to viral infection, especially the miRNA-mediated immune regulatory roles, is rather limited. In this study, by employing Solexa deep sequencing approach, we identified 116 grouper miRNAs from grouper spleen-derived cells (GS). As expected, these miRNAs shared high sequence similarity with miRNAs identified in zebrafish (Danio rerio), pufferfish (Fugu rubripes), and other higher vertebrates. In the process of Singapore grouper iridovirus (SGIV) infection, 45 and 43 miRNAs with altered expression (>1.5-fold) were identified by miRNA microarray assays in grouper spleen tissues and GS cells, respectively. Furthermore, target prediction revealed 189 putative targets of these grouper miRNAs.

Isolation and function analysis of apolipoprotein A-I gene response to virus infection in grouper

Apolipoproteins, synthesized mainly in liver and intestine and bounded to lipids, play important roles in lipid transport and uptake through the circulation system. In this study, an apolipoprotein A-I gene homologue was cloned from orange-spotted grouper Epinephelus coioides (designed as Ec-ApoA-I) by rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA of Ec-ApoA-I was comprised of 1278 bp with a 792 bp open reading frame (ORF) that encodes a putative protein of 264 amino acids. Quantitative real-time PCR (qPCR) analysis revealed that Ec-ApoA-I was abundant in liver and intestine, and the expression in liver was significantly (P < 0.01) up-regulated after the stimulation of LPS, Poly(I:C), Vibrio alginolyticus, and Singapore grouper iridovirus (SGIV). Recombinant Ec-ApoA-I (rEc-ApoA-I) was produced in Escherichia coli BL21 (DE3) expression system exhibited bacteriolyticactivity against Microcococcus lysodeikticus and Aeromonas hydrophila. Intracellular localization revealed that Ec-ApoA-I distributed in both cytoplasm and nucleus, and predominantly in the cytoplasm. Overexpression of Ec-ApoA-I in grouper Brain (GB) cells could inhibit the replication of SGIV. These results together indicated that Ec-ApoA-I perhaps is involved in the responses to bacterial and viral challenge.

Probiotic Bacillus pumilus SE5 shapes the intestinal microbiota and mucosal immunity in grouper Epinephelus coioides

The health benefits of probiotics are thought to occur, at least in part, through an improved intestinal microbial balance in fish, although the molecular mechanisms whereby probiotics modulate the intestinal microbiota by means of activation of mucosal immunity are rarely explored. In this study, the effects of viable and heat-inactivated probiotic Bacillus pumilus SE5 on the intestinal dominant microbial community and mucosal immune gene expression were evaluated. The fish were fed for 60 d with 3 different diets: control (without probiotic), and diets T1 and T2 supplemented with 1.0 × 10⁸ cells g⁻¹ viable and heat-inactivated B. pumilus SE5, respectively. Upregulated expression of TLR1, TLR2 and IL-8, but not MyD88 was observed in fish fed the viable probiotic, while elevated expression of TLR2, IL-8 and TGF-β1, but not MyD88 was observed in fish fed the heat-inactivated B. pumilus SE5. The induced activation of intestinal mucosal immunity, especially the enhanced expression of antibacterial epinecidin-1, was consistent with the microbial data showing that several potentially pathogenic bacterial species such as Psychroserpens burtonensis and Pantoea agglomerans were suppressed by both the viable and heat-inactivated probiotic B. pumilus SE5. These results lay the foundation for future studies on the molecular interactions between probiotics, intestinal microbiota and mucosal immunity in fish.

Isolation and characterization of tumor necrosis factor receptor-associated factor 6 (TRAF6) from grouper, Epinephelus tauvina

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is one of the key adapter molecules in Toll-like receptor signal transduction that triggers downstream cascades involved in innate immunity. In the present study, a TRAF6 (named as Et-TRAF6) was identified from the marine fish grouper, Epinephelus tauvina by RACE PCR. The full-length cDNA of Et-TRAF6 comprised 1949 bp with a 1713 bp open reading frame (ORF) that encodes a putative protein of 570 amino acids. Similar to most TRAF6s, Et-TRAF6 includes one N-terminal RING domain (78aa-116aa), two zinc fingers of TRAF-type (159aa-210aa and 212aa-269aa), one coiled-coil region (370aa-394aa), and one conserved C-terminal meprin and TRAF homology (MATH) domain (401aa-526aa). Quantitative real-time PCR analysis revealed that Et-TRAF6 mRNA is expressed in all tested tissues, with the predominant expression in the stomach and intestine. The expression of Et-TRAF6 was up-regulated in the liver after challenge with Lipoteichoic acid (LTA), Peptidoglycan (PGN), Zymosan, polyinosine-polycytidylic acid [Poly(I:C)] and Polydeoxyadenylic acid · Polythymidylic acid sodium salt [Poly(dA:dT)]. The expression of Et-TRAF6 was also up-regulated in the liver after infection with Vibrio alginolyticus, Singapore grouper iridovirus (SGIV) and grouper nervous necrosis virus (GNNV). Recombinant Et-TRAF6 (rEt-TRAF6) was expressed in Escherichia BL21 (DE3) and purified for mouse anti-Et-TRAF6 serum preparation. Intracellular localization revealed that Et-TRAF6 is distributed in both cytoplasm and nucleus, and predominantly in the cytoplasm. These results together indicated that Et-TRAF6 might be involved in immune responses toward bacterial and virus challenges.

Differential transcription of fathead minnow immune-related genes following infection with frog virus 3, an emerging pathogen of ectothermic vertebrates

Frog virus 3 (FV3) and other ranaviruses are responsible for die-offs involving wild, farmed, and captive amphibians, fish, and reptiles. To ascertain which elements of the immune system respond to infection, we explored transcriptional responses following infection of fathead minnow cells with either wild type (wt) FV3 or a knock out (KO) mutant targeting the 18 kDa immediate early gene (18K). At 8h post infection we observed marked upregulation of multiple transcripts encoding proteins affecting innate and acquired immunity. Sequences expressed 4-fold or higher in wt-infected cells included transcripts encoding interferon (IFN), IFN regulatory factors (IRFs), IFN stimulated genes (ISGs) such as Mx and MHC class I, and interleukins IL-1β, IL-8, IL-17C and IL-12. Cells infected with the 18K KO mutant (∆18K) showed qualitative differences and lower levels of induction. Collectively, these results indicate that ranavirus infection induced expression of multiple cellular genes affecting both innate and acquired immunity.

Singapore grouper iridovirus-encoded semaphorin homologue (SGIV-sema) contributes to viral replication, cytoskeleton reorganization and inhibition of cellular immune responses

Semaphorins are a large, phylogenetically conserved family of proteins that are involved in a wide range of biological processes including axonal steering, organogenesis, neoplastic transformation, as well as immune responses. In this study, a novel semaphorin homologue gene belonging to the Singapore grouper iridovirus (SGIV), ORF155R (termed SGIV-sema), was cloned and characterized. The coding region of SGIV-sema is 1728 bp in length, encoding a predicted protein with 575 aa. SGIV-sema contains a ~370 aa N-terminal Sema domain, a conserved plexin-semaphorin-integrin (PSI) domain, and an immunoglobulin (Ig)-like domain near the C terminus. SGIV-sema is an early gene product during viral infection and predominantly distributed in the cytoplasm with a speckled and clubbed pattern of appearance. Functionally, SGIV-sema could promote viral replication during SGIV infection in vitro, with no effect on the proliferation of host cells. Intriguingly, ectopically expressed SGIV-sema could alter the cytoskeletal structure of fish cells, characterized by a circumferential ring of microtubules near the nucleus and a disrupted microfilament organization. Furthermore, SGIV-sema was able to attenuate the cellular immune response, as demonstrated by decreased expression of inflammation/immune-related genes such as IL-8, IL-15, TNF-α and mediator of IRF3 activation (MITA), in SGIV-sema-expressing cells before and after SGIV infection. Ultimately, our study identified a novel, functional SGIV gene that could regulate cytoskeletal structure, immune responses and facilitate viral replication.

Mining antimicrobial peptides from small open reading frames in Ciona intestinalis

Though being able to encode various kinds of bioactive peptides, small open reading frames (sORFs) are poorly annotated in many genomic data. The present study was conducted to evaluate the potential of sORFs in encoding antimicrobial peptides (AMPs) in the basal chordate model Ciona intestinalis. About 4.8 m genomic sequence was first retrieved for sORFs mining by the program sORF finder, then the sORFs were translated into amino acid sequences for AMP prediction via CAMP server, and thereafter, ten putative AMPs were selected for expression and antimicrobial activity validation. In total, over 180 peptides deduced from the sORFs were predicted to be AMPs. Among the ten tested peptides, six were found to have significant expressed sequence tag matches, providing strong evidence for gene expression; five were proved to be active against the bacterial strains. These results indicate that many sORFs in C. intestinalis genome contain AMP information. This work can serve as an important initial step to investigate the role of sORFs in the innate defense of C. intestinalis.

Orange-spotted grouper (Epinephelus coioides) toll-like receptor 22: molecular characterization, expression pattern and pertinent signaling pathways

The toll-like receptors (TLRs) are an important gene family in host innate immunologic surveillance. The TLR22 gene is an essential member of the TLRs that is only found in aquatic animals and has been detected in some bony fish. Here, a TLR22 homolog, EcTLR22, was characterized in the orange-spotted grouper (Epinephelus coioides) via homology cloning. The 3321 bp full-length cDNA sequence of EcTLR22 was obtained, which included an open reading frame of 2880 bp encoding a putative peptide of 960 amino acids containing three highly typical domains with the characteristics of TLR family members. The deduced amino acid sequence of EcTLR22 showed a relatively high similarity to flounder TLR22. Phylogenetic analysis showed that the orange-spotted grouper TLR22 sequence was clustered with those of Perciforme, such as flounder and croaker. Real-time quantitative PCR analysis revealed broad expression of EcTLR22, with relatively high expression detected in the head kidney, trunk kidney, spleen, peripheral blood leukocytes (PBLs) and heart of orange-spotted grouper. After injection with Vibrio alginolyticus, there was significant up-regulation of the expression of EcTLR22 in the spleen. In evaluating unstimulated/stimulated head kidney leukocytes and spleen leukocytes, a significant increase in EcTLR22 mRNA expression was detected, which implied a sensitive immune response. Furthermore, four important molecules for signal transduction, MyD88, TRIF, TNF-α and IRF3, were chosen to analyze the role of the EcTLR22 signaling pathway in anti-pathogen responses. Upon LPS or Poly I:C challenge, expression of the four genes was induced, with an increasing tendency detected in head kidney leukocytes, suggesting that the four genes might work with EcTLR22 in host defense against pathogenic microbes.

Subtractive libraries for prospecting differentially expressed genes in the soybean under water deficit

Soybean has a wide range of applications in the industry and, due to its crop potential, its improvement is widely desirable. During drought conditions, soybean crops suffer significant losses in productivity. Therefore, understanding the responses of the soybean under this stress is an effective way of targeting crop improvement techniques. In this study, we employed the Suppressive Subtractive Hybridization (SSH) technique to investigate differentially expressed genes under water deficit conditions. Embrapa 48 and BR 16 soybean lines, known as drought-tolerant and -sensitive, respectively, were grown hydroponically and subjected to different short-term periods of stress by withholding the nutrient solution. Using this approach, we have identified genes expressed during the early response to water deficit in roots and leaves. These genes were compared among the lines to assess probable differences in the plant transcriptomes. In general, similar biochemical processes were predominant in both cultivars; however, there were more considerable differences between roots and leaves of Embrapa 48. Moreover, we present here a fast, clean and straightforward method to obtain drought-stressed root tissues and a large enriched collection of transcripts expressed by soybean plants under water deficit that can be useful for further studies towards the understanding of plant responses to stress.

Transcriptional analysis of orange-spotted grouper reacting to experimental grouper iridovirus infection

Disease caused by grouper iridovirus (GIV) has resulted in economic losses due to high mortality in grouper culture. Thirty-eight up- and 48 down-regulated known entities have been identified using a GIV-infected grouper kidney cDNA microarray chip. Further quantitative validation was executed in the head-kidney and spleen for 24 candidate genes and 7 immune factors following GIV inoculation. Significant induction with various patterns could be seen in 30 tested genes in the spleen. However, only 23 genes had induction in the head-kidney and meanwhile 5 genes showed reduction. Transcriptional expression profiles of selected genes in response to lipopolysaccharide (LPS) or polyinosinic:polycytidylic acid (PIC) were also established to compare with the GIV-stimulated expression. The results indicated that the responses of most genes facing GIV invasion have more similarities to PIC treatment than LPS. Seven genes are thought to be interferon-related factors: RNA helicase DHX58, ISG15, viperin, HECT E3 ligase (HECT), CD9, urokinase plasminogen activator surface receptor (PLAUR) and Mx-1. Following immunization with inactivated GIV, significant induction could be seen in DHX58, viperin, IL-1β, IL-8, COX-2, HECT, PLAUR, IgM, Mx-1, very large inducible GTPase-1 (VLIG1) and TNF-α in the head-kidney or spleen, and the latter 6 genes also had a gradual increasing pattern by a boosting immunization. These factors might play important roles in adaptive antiviral protection. Thus, we have characterized the temporal response patterns of virus responsive genes and have also identified several potential immune markers to further investigate host antiviral defense mechanisms.

Transcriptome analysis of orange-spotted grouper (Epinephelus coioides) spleen in response to Singapore grouper iridovirus

Background

Orange-spotted grouper (Epinephelus coioides) is an economically important marine fish cultured in China and Southeast Asian countries. The emergence of infectious viral diseases, including iridovirus and betanodavirus, have severely affected food products based on this species, causing heavy economic losses. Limited available information on the genomics of E. coioides has hampered the understanding of the molecular mechanisms that underlie host-virus interactions. In this study, we used a 454 pyrosequencing method to investigate differentially-expressed genes in the spleen of the E. coioides infected with Singapore grouper iridovirus (SGIV).

Results

Using 454 pyrosequencing, we obtained abundant high-quality ESTs from two spleen-complementary DNA libraries which were constructed from SGIV-infected (V) and PBS-injected fish (used as a control: C). A total of 407,027 and 421,141 ESTs were produced in control and SGIV infected libraries, respectively. Among the assembled ESTs, 9,616 (C) and 10,426 (V) ESTs were successfully matched against known genes in the NCBI non-redundant (nr) database with a cut-off E-value above 10^-5. Gene ontology (GO) analysis indicated that "cell part", "cellular process" and "binding" represented the largest category. Among the 25 clusters of orthologous group (COG) categories, the cluster for "translation, ribosomal structure and biogenesis" represented the largest group in the control (185 ESTs) and infected (172 ESTs) libraries. Further KEGG analysis revealed that pathways, including cellular metabolism and intracellular immune signaling, existed in the control and infected libraries. Comparative expression analysis indicated that certain genes associated with mitogen-activated protein kinase (MAPK), chemokine, toll-like receptor and RIG-I signaling pathway were alternated in response to SGIV infection. Moreover, changes in the pattern of gene expression were validated by qRT-PCR, including cytokines, cytokine receptors, and transcription factors, apoptosis-associated genes, and interferon related genes.

Conclusion

This study provided abundant ESTs that could contribute greatly to disclosing novel genes in marine fish. Furthermore, the alterations of predicted gene expression patterns reflected possible responses of these fish to the virus infection. Taken together, our data not only provided new information for identification of novel genes from marine vertebrates, but also shed new light on the understanding of defense mechanisms of marine fish to viral pathogens.

A new leukocyte cell-derived chemotaxin-2 from marine fish grouper, Epinephelus coioides: molecular cloning and expression analysis

Leukocyte cell-derived chemotaxin-2 (LECT2) is a multifunctional protein involved in cell growth, differentiation and autoimmunity. In this study, a new leukocyte cell-derived chemotaxin-2 (EcLECT2) gene was cloned from grouper, Epinephelus coioides, by rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA sequence of EcLECT2 was 595 bp in size, containing a 5'-untranslated region (UTR) of 44 bp and a 3'-UTR of 83 bp. The deduced protein sequence of the open reading frame (465 bp) showed highest similarity (81%) to the LECT2 of the fresh-water fish Larimichthys crocea. An abundant transcription of the determined EcLECT2 mRNA has been detected in liver and skin of grouper, E. coioides. Furthermore, the expression of EcLECT2 was differentially up-regulated in liver after infection with Staphyloccocus aureus, Vibrio vulnificus, Vibrio parahaemolyticus, Saccharomyces cerevisiae and Singapore grouper iridovirus (SGIV), while the expression was down-regulated after stimulation with Concanavalin A (Con A). Recombinant mature EcLECT2 (rEcLECT2) was successfully expressed in Escherichia coli BL21 (DE3), and the antiserum against EcLECT2 was obtained for further investigations. EcLECT2 may be an important molecule in the innate immunity of grouper.

Molecular cloning and characterization of two novel hepcidins from orange-spotted grouper, Epinephelus coioides

Orange-spotted grouper, Epinephelus coioides is one of the most important economic species of marine-cultured fish in China and Southeast Asia countries. However, very little information of the innate immune mechanisms against microbial pathogens is available in grouper, Epinephelus sp. Hepcidin, as an antimicrobial peptide (AMP), is a very important component in the innate immune system and widespread in fish. In this study, two novel types of hepcidin gene (designated EC-hepcidin1 and EC-hepcidin2) were cloned from E. coioides. They consist of open reading frames (ORFs) of 267 bp and 263 bp encoding the putative peptides of 88 and 87 amino acids, respectively. The homologous identity of deduced amino acid sequences between EC-hepcidin1 and EC-hepcidin2 is up to 79%, and predicted mature regions of both them have four cysteines residues. Genomic DNAs of both EC-hepcidin1 and EC-hepcidin2 consist of three exons and two introns. RT-PCR results showed that EC-hepcidin1 transcript was most abundant in liver and less in stomach. However, the transcript of EC-hepcidin2 was only detected in liver. The expressions of both EC-hepcidins were up-regulated by microbial and viral challenges, and iron overload, respectively, and EC-hepcidin1 was more responsive. The growth of Gram-negative bacterium of Vibrio vulnificus and Gram-positive bacterium of Staphylococcus aureus was inhibited by synthetic EC-hepcidins, and EC-hepcidin1 displayed stronger antimicrobial activity. The replication of Singapore grouper iridovirus (SGIV) was inhibited in the EC-hepcidin1 and EC-hepcidin2 over-expressed stable transfected fish cell lines (GS/pcDNA-Hep1, GS/pcDNA-Hep2) indicative of the antiviral activity of EC-hepcidins. These data should offer important information on the antimicrobial and antiviral roles of EC-hepcidins, and will be help to the better understanding of molecular mechanisms of grouper innate immunity.