Gene expression in haemocytes of kuruma prawn, Penaeus japonicus, in response to infection with WSSV by EST approach

Experimental Infection Models and Their Usefulness for White Spot Syndrome Virus (WSSV) Research in Shrimp

White spot syndrome virus (WSSV) is marked as one of the most economically devastating pathogens in shrimp aquaculture worldwide. Infection of cultured shrimp can lead to mass mortality (up to 100%). Although progress has been made, our understanding of WSSV's infection process and the virus-host-environment interaction is far from complete. This in turn hinders the development of effective mitigation strategies against WSSV. Infection models occupy a crucial first step in the research flow that tries to elucidate the infectious disease process to develop new antiviral treatments. Moreover, since the establishment of continuous shrimp cell lines is a work in progress, the development and use of standardized in vivo infection models that reflect the host-pathogen interaction in shrimp is a necessity. This review critically examines key aspects of in vivo WSSV infection model development that are often overlooked, such as standardization, (post)larval quality, inoculum type and choice of inoculation procedure, housing conditions, and shrimp welfare considerations. Furthermore, the usefulness of experimental infection models for different lines of WSSV research will be discussed with the aim to aid researchers when choosing a suitable model for their research needs.

Comprehensive Transcriptomic and Metabolomic Analysis of the Litopenaeus vannamei Hepatopancreas After WSSV Challenge

Litopenaeus vannamei is the major farmed shrimp species worldwide. White spot disease due to white spot syndrome virus (WSSV) is severely affecting shrimp worldwide, causing extensive economic losses in L. vannamei culture. This is the first study that applied combined transcriptomic and metabolomic analysis to study the effects on the L. vannamei hepatopancreas after WSSV challenge. Our transcriptomic data revealed differentially expressed genes (DEGs) associated with immunity, apoptosis, the cytoskeleton and the antioxidant system in the hepatopancreas of L. vannamei. Metabolomic results showed that WSSV disrupts metabolic processes including amino acid metabolism, lipid metabolism and nucleotide metabolism. After challenged by WSSV, immune-related DEGs and differential metabolites (DMs) were detected in the hepatopancreas of L. vannamei, indicating that WSSV may damage the immune system and cause metabolic disorder in the shrimp. In summary, these results provide new insights into the molecular mechanisms underlying L. vannamei's response to WSSV.

iTRAQ-Based Quantitative Proteomics Analysis Reveals the Invasion Mechanism of Spiroplasma eriocheiris in 3T6 Cells

Background:

Spiroplasma eriocheiris is a novel pathogen of freshwater crustaceans and is closely related to S. mirum. They have no cell wall and a helical morphology. They have the ability to infect mammals with an unclear mechanism.

Objective:

In this study, our aim was to investigate the profile of protein expression in 3T6 cells infected with S. eriocheiris.

Methods:

The proteome of 3T6 cells infected by S. eriocheiris was systematically investigated by iTRAQ.

Results:

We identified and quantified 4915 proteins, 67 differentially proteins were found, including 30 up-regulated proteins and 37 down-regulated proteins. GO term analysis shows that dysregulation of adhesion protein , interferon and cytoskeletal regulation are associated with apoptosis. Adhesion protein Vcam1 and Interferon-induced protein GBP2, Ifit1, TAPBP, CD63 ,Arhgef2 were up-regulated. A key cytoskeletal regulatory protein, ARHGEF17 was down-regulated. KEGG pathway analysis showed the NF-kappa B signaling pathway, the MAPK signaling pathway , the Jak-STAT signaling pathway and NOD-like receptor signaling are closely related to apoptosis in vivo.

Conclusion:

Analysis of the signaling pathways involved in invasion may provide new insights for understanding the infection mechanisms of S. eriocheiris.

The potential of antimicrobial peptides isolated from freshwater crayfish species in new drug development: A review

The much-publicised increased resistance of pathogenic bacteria to conventional antibiotics has focused research effort on the characterization of new antimicrobial drugs. In this context, antimicrobial peptides (AMPs) extracted from animals are considered a promising alternative to conventional antibiotics. In recent years, freshwater crayfish species have emerged as an important source of bioactive compounds. In fact, these invertebrates rely on an innate immune system based on cellular responses and on the production of important effectors in the haemolymph, such as AMPs, which are produced and stored in granules in haemocytes and released after stimulation. These effectors are active against both Gram-positive and Gram-negative bacteria. In this review, we summarise the recent progress on AMPs isolated from the several species of freshwater crayfish and their prospects for future pharmaceutical applications to combat infectious agents.

Characteristics of Two Crustins from Alvinocaris longirostris in Hydrothermal Vents

Crustins are widely distributed among different crustacean groups. They are characterized by a whey acidic protein (WAP) domain, and most examined Crustins show activity against Gram-positive bacteria. This study reports two Crustins, Al-crus 3 and Al-crus 7, from hydrothermal vent shrimp, Alvinocaris longirostris. Al-crus 3 and Al-crus 7 belong to Crustin Type IIa, with a similarity of about 51% at amino acid level. Antibacterial assays showed that Al-crus 3 mainly displayed activity against Gram-positive bacteria with MIC₅₀ values of 10–25 μM. However, Al-crus 7 not only displayed activity against Gram-positive bacteria but also against Gram-negative bacteria Imipenem-resistant Acinetobacter baumannii, in a sensitive manner. Notably, in the effective antibacterial spectrum, Methicillin-sensitive Staphylococcus aureus, Escherichia coli (ESBLs) and Imipenem-resistant A. baumannii were drug-resistant pathogens. Narrowing down the sequence to the WAP domain, Al-crusWAP 3 and Al-crusWAP 7 demonstrated antibacterial activities but were weak. Additionally, the effects on bacteria did not significantly change after they were maintained at room temperature for 48 h. This indicated that Al-crus 3 and Al-crus 7 were relatively stable and convenient for transportation. Altogether, this study reported two new Crustins with specific characteristics. In particular, Al-crus 7 inhibited Gram-negative imipenem-resistant A. baumannii.

The sterol regulatory element binding protein homolog of Penaeus vannamei modulates fatty acid metabolism and immune response

The sterol regulatory element binding proteins (SREBPs) transcription factors family, which regulate the expression of genes involved in cellular lipid metabolism and homeostasis, have recently been implicated in various physiological and pathophysiological processes such as immune regulation and inflammation in vertebrates. Consistent with other invertebrates, we identified a single SREBP ortholog in Penaeus vannamei (designated PvSREBP) with transcripts ubiquitously expressed in tissues and induced by lipopolysaccharide (LPS), Vibrio parahaemolyticus and Streptococcus iniae. In vivo RNA interference (RNAi) of PvSREBP attenuated the expression of several fatty acid metabolism-related genes (i.e., cyclooxygenase (PvCOX), lipoxygenase (PvLOX), fatty acid binding protein (PvFABP) and fatty acid synthase (PvFASN)), which consequently decreased the levels of total polyunsaturated fatty acids (ΣPUFAs). In addition, PvSREBP silencing decreased transcript levels of several immune-related genes such as hemocyanin (PvHMC) and trypsin (PvTrypsin), as well as genes encoding for heat-shock proteins (i.e., PvHSP60, PvHSP70 and PvHSP90). Moreover, in silico analysis revealed the presence of SREBP binding motifs on the promoters of most of the dysregulated genes, while shrimp depleted of PvSREBP were more susceptible to V. parahaemolyticus infection. Collectively, we demonstrated the involvement of shrimp SREBP in fatty acids metabolism and immune response, and propose that PvSREBP and PvHMC modulate each other through a feedback mechanism to establish homeostasis. The current study is the first to show the dual role of SREBP in fatty acid metabolism and immune response in invertebrates and crustaceans.

Development and characterization of white spot disease linked microsatellite DNA markers in Penaeus monodon, and their application to determine the population diversity, cluster and structure

Pathogens that are introduced suddenly to natural populations can potentially cause quick changes to the genetics and diversity of the host. In the past three decades, white spot syndrome virus (WSSV) has caused damaging epizootics in Penaeus monodon populations. In this study, we developed WSSV resistance- or susceptibility-linked microsatellite DNA markers, and their effectiveness was validated experimentally. WSSV-resistant marker linked retroelements and genes that may have an important role in WSSV-resistance phenomena were partially identified. Allelic data of 1,694 samples from nine distinct geographic locations in India were revealed that populations from Digha and Kochi were highly dispersed, and also showed higher genetic diversity, higher population diversity, and lower prevalence of disease resistance. A very high level of gene flow was observed within all populations and a very high level of genetic variation was present within populations. Two genetically admixture population clusters were estimated in nature. WSSV-resistance has a significant link with genetic diversity, population cluster and population diversity. Microsatellite marker analysis characterized genetic divergence, diversity and structure among wild populations.

Effects of short-term fasting on the resistance of Nile tilapia (Oreochromis niloticus) to Streptococcus agalactiae infection

Short-term feed deprivation or fasting is commonly experienced by aquaculture fish species and may be caused by seasonal variations, production strategies, or diseases. To assess the effects of fasting on the resistance of Nile tilapia to Streptococcus agalactiae infection, vaccinated and unvaccinated fish were fasted for zero, one, three, and seven days prior to infection. The cortisol levels of both vaccinated and unvaccinated fish first decreased and then increased significantly as fasting time increased. Liver glycogen, triglycerides, and total cholesterol decreased significantly after seven days of fasting, but glucose content did not vary significantly between fish fasted for three and seven days. Hexokinase (HK) and pyruvate kinase (PK) activity levels were lowest after seven days of fasting, while phosphoenolpyruvate carboxykinase (PEPCK) activity levels varied in opposition to those of HK and PK. Serum superoxide dismutase (SOD) and catalase (CAT) activity levels first increased and then decreased as fasting time increased; SOD activity was highest after three days of fasting. Interleukin-1beta (IL-1β) and IL-6 mRNA expression levels first increased and then decreased significantly, peaking after three days of fasting. However, suppressor of cytokine signaling-1 (SOCS-1) mRNA expression levels were in opposition to those of IL-1β and IL-6. Specific antibody levels did not vary significantly among unvaccinated fish fasted for different periods. Although specific antibody level first increased and then decreased in the vaccinated fish as fasting duration increased, there were no significant differences in the survival rates of fasted vaccinated fish after challenge with S. agalactiae. The final survival rates of vaccinated fish fasted for zero, one, three, and seven days were 86.67 ± 5.44%, 80.00 ± 3.14%, 88.89 ± 6.28%, and 84.44 ± 8.32%, respectively. Among the unvaccinated fish, the survival rate was highest (35.56 ± 3.14%) in the fish fasted for three days and lowest (6.67 ± 3.14%) in the fish fasted for seven days. Therefore, our results indicated that short-term fasting (three days) prior to an infection might increase the resistance of unvaccinated Nile tilapia to S. agalactiae.

A new crustin is involved in the innate immune response of shrimp Litopenaeus vannamei

Crustin is an antimicrobial peptide (AMP) that plays a key role in the innate immunity of crustaceans. This study cloned a new crustin from Pacific white shrimp Litopenaeus vannamei, which we designated as LvCrustinB, using rapid amplification of cDNA ends (RACE). The full-length cDNA of LvCrustinB is 751 bp with an open reading frame (ORF) of 591 bp encoding a peptide of 196 amino acids that includes a putative signal sequence. LvCrustinB is a type II crustin that has a glycine-rich region and a single whey acidic protein domain (WAP) domain. The mRNA transcript of LvCrustinB was detected in all examined tissues and was found to be most abundantly expressed in the epithelium and muscle. The expression of LvCrustinB in hemocytes was significantly upregulated after L. vannamei was challenged with LPS, Vibrio parahaemolyticus, and white spot syndrome virus (WSSV). When LvCrustinB was knocked down with RNAi, the mortality rate of L. vannamei significantly increased after V. parahaemolyticus or WSSV infection. Recombinant LvCrustinB was produced using Pichia pastoris GS115 and was shown to bind to 2 g-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and 2 g-negative bacteria (Escherichia coli and V. parahaemolyticus) via polysaccharides, which included PGN, LTA, and LPS. In vivo, the recombinant LvCrustinB remarkably protected L. vannamei from V. parahaemolyticus infection. These results suggest that LvCrustinB plays an important role in innate immunity and may be potentially utilized as antibacterial agents in shrimp.

A Kunitz proteinase inhibitor (HcKuPI) participated in antimicrobial process during pearl sac formation and induced the overgrowth of calcium carbonate in Hyriopsis cumingii

Proteinase inhibitors with the ability to inhibit specific proteinases are usually closely connected with the immune system. Interestingly, proteinase inhibitors are also a common ingredient in the organic matrix of mollusk shells. However, the molecular mechanism that underlies the role of proteinase inhibitors in immune system and shell mineralization is poorly known. In this study, a Kunitz serine proteinase inhibitor (HcKuPI) was isolated from the mussel Hyriopsis cumingii. HcKuPI was specifically expressed in dorsal epithelial cells of the mantle pallium and HcKuPI dsRNA injection caused an irregular surface and disordered deposition on the aragonite tablets of the nacreous layer. These results indicated that HcKuPI plays a vital role in shell nacreous layer biomineralization. Moreover, the expression pattern of HcKuPI during LPS challenge and pearl formation indicated its involvement in the antimicrobial process during pearl sac formation and nacre tablets accumulation during pearl formation. In the in vitro calcium carbonate crystallization assay, the addition of GST-HcKuPI increased the precipitation rate of calcium carbonate and induced the crystal overgrowth of calcium carbonate. Taken together, these results indicate that HcKuPI is involved in antimicrobial process during pearl formation, and participates in calcium carbonate deposition acceleration and morphological regulation of the crystals during nacreous layer formation. These findings extend our knowledge of the role of proteinase inhibitors in immune system and shell biomineralization.

Effectiveness of traditional Chinese herbal medicine, San-Huang-San, in combination with enrofloxacin to treat AHPND-causing strain of Vibrio parahaemolyticus infection in Litopenaeus vannamei

The effects of oral administration of enrofloxacin (ENR) and San-Huang-San (SHS), singly or in combination, on the survival performance, disease resistance, and immunity of Litopenaeus vannamei were investigated. After challenge with an AHPND-causing strain of Vibrio parahaemolyticus (VP_AHPND), shrimp were immediately fed a drug-free diet, diets containing only ENR (20 mg·kg^-1) or SHS (500 mg·kg^-1) or diets containing low-dose (10 mg·kg^-1 ENR + 250 mg ·kg^-1 SHS), medium-dose (20 mg·kg^-1 ENR + 500 mg ·kg^-1 SHS), and high-dose (40 mg·kg^-1 ENR + 1000 mg ·kg^-1 SHS) drug combinations for 5 days. The cumulative shrimp mortality over 5 days after injection of VP_AHPND in the ENR + SHS combination groups was significantly lower than that in the ENR or SHS alone groups (p < 0.05). Immune parameters, including the vibrio density, total hemocyte counts (THCs), hemocyanin (HEM) concentration, antibacterial activity, activity levels of lysozyme (LZM), acid phosphatase (ACP), alkaline phosphatase (AKP), and phenoloxidase (PO) in cell-free hemolymph, and the expression levels of the immune-related genes anti-lipopolysaccharide factor (ALF), cathepsin B (catB), crustin, lectin (Lec), lysozyme (LZM), and Toll-like receptor (TLR) in hemocytes were determined in the shrimp. The results showed that the shrimp in drug combination groups cleared more VP_AHPND than that in the ENR or SHS group in the same time. The values for other immune parameters in the drug combination groups were higher than those in the ENR or SHS group (p < 0.05). Finally, in the histological examinations, the histological structural alignment and integrity of the hepatopancreatic tubules in the drug combination groups were better than that in the ENR and SHS groups. Under the experimental conditions, compared with ENR or SHS used alone, the combination use of ENR and SHS could improve immunity and disease resistance in shrimp after VP_AHPND infection, and could reduce the use of ENR when the better therapeutic effect was achieved.

RNase1 alleviates the Aeromonas hydrophila-induced oxidative stress in blunt snout bream

RNase1 is an enzyme important in host defense in vertebrates where it degrades the RNA of bacteria and viruses. We evaluated the effect of RNase1 on the resistance to Aeromonas hydrophila infection in Megalobrama amblycephala. The fish were randomly divided into four groups: a blank group (none-treated M. amblycephala), a control group (injected PBS), a challenge group (A. hydrophila-injected) and a treatment group (pre-treated with RNase1 24 h before the A. hydrophila injection), and we collected five tissues of each group. Then we recorded changes in the levels of glutathione (GSH), oxidized glutathione (GSSG), hepatic catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and lysozyme; and the relative mRNA expression of catalase (CAT), selenium-dependent glutathione peroxidase (GPx), Cu/Superoxide dismutase (Cu/Zn-SOD), glutamate-cysteine ligase (GCLC), glutathione reductase (GR) and nuclear factor erythroid 2-related factor 2 (Nrf2) for four groups. The expression of six genes was highest in liver and blood of the blank group. It was significantly higher in the gut of the treatment group (compared to control and challenge groups) 12 h after the infection. The treatment group exhibited a significant increase in GSH, SOD and CAT activity, and a decrease in GSSG, MDA and lysozyme content (compared to the control and challenge groups) 6 and 12 h after infection. These results suggest that supplementation with RNase1 protein can enhance resistance against A. hydrophila infections in M. amblycephala.

The State of "Omics" Research for Farmed Penaeids: Advances in Research and Impediments to Industry Utilization

Elucidating the underlying genetic drivers of production traits in agricultural and aquaculture species is critical to efforts to maximize farming efficiency. "Omics" based methods (i.e., transcriptomics, genomics, proteomics, and metabolomics) are increasingly being applied to gain unprecedented insight into the biology of many aquaculture species. While the culture of penaeid shrimp has increased markedly, the industry continues to be impeded in many regards by disease, reproductive dysfunction, and a poor understanding of production traits. Extensive effort has been, and continues to be, applied to develop critical genomic resources for many commercially important penaeids. However, the industry application of these genomic resources, and the translation of the knowledge derived from "omics" studies has not yet been completely realized. Integration between the multiple "omics" resources now available (i.e., genome assemblies, transcriptomes, linkage maps, optical maps, and proteomes) will prove critical to unlocking the full utility of these otherwise independently developed and isolated resources. Furthermore, emerging "omics" based techniques are now available to address longstanding issues with completing keystone genome assemblies (e.g., through long-read sequencing), and can provide cost-effective industrial scale genotyping tools (e.g., through low density SNP chips and genotype-by-sequencing) to undertake advanced selective breeding programs (i.e., genomic selection) and powerful genome-wide association studies. In particular, this review highlights the status, utility and suggested path forward for continued development, and improved use of "omics" resources in penaeid aquaculture.

White spot syndrome virus (WSSV) suppresses penaeidin expression in Marsupenaeus japonicus hemocytes

Penaeidins are a unique family of antimicrobial peptides specific to penaeid shrimp and have been reported mainly function as anti-bacterial and anti-fungal. In order to investigate whether penaeidins could also respond to virus or not, we examined the effect of WSSV on MjPen-II (penaeidin in kuruma shrimp, Marsupenaeus japonicus) expression. In the control group, MjPen-II transcript level can be detected in almost all test tissues but was expressed most strongly in hemocytes. After WSSV infection, MjPen-II transcript level was significantly downregulated in hemocytes. Moreover, the proportion of MjPen-II+ hemocytes was not significantly different between non-infected and WSSV-infected shrimp, but the number of MjPen-II+ highly expressing hemocytes decreased after infection. In addition, MjPen-II was observed in the cytoplasm of granule-containing hemocytes. These results suggest that WSSV suppresses MjPen-II expression in hemocytes.

iTRAQ-based quantitative proteomic analysis of Procambarus clakii hemocytes during Spiroplasma eriocheiris infection

As a new-found aquaculture pathogen, Spiroplasma eriocheiris, has resulted in inconceivable economic losses in aquaculture. In the infection of S. eriocheiris, the Procambarus clakii hemocytes have indicated to be major target cells. What was designed to examine in our study is the hemocytes' immune response at the protein levels. Before the pathogen was injected and after 192 h of post-injection, the differential proteomes of the crayfish hemocytes were analyzed immediately by isobaric tags for relative and absolute quantization (iTRAQ) labeling, followed by liquid chromatogramphytandem mass spectrometry (LC-MS/MS). This research had identified a total of 285 differentially expressed proteins. Eighty-three and 202 proteins were up-regulated and down-regulated, respectively, caused by the S. eriocheiris infection. Up-regulated proteins included alpha-2-macroglobulin (α2M), vitellogenin, ferritin, etc. Down-regulated proteins, involved with serine protease, peroxiredoxin 6, 14-3-3-like protein, C-type lectin, cdc42 homolog precursor, etc. The prophenoloxidase-activating system, antimicrobial action involved in the immune responses of P. clarkii is considered to be damaged due to S. eriocheiris infection. The present work could lay the foundation for future research on the proteins related to the susceptibility/resistance of P. clarkii to S. eriocheiris. In addition, it is helpful for our understanding molecular mechanism of disease processes in crayfishes.

Involvement of a newly identified atypical type II crustin (SpCrus5) in the antibacterial immunity of mud crab Scylla paramamosain

Crustins, the main AMP family in Crustacea, are generated as isoforms in many species and implicated in innate immune responses, but their detailed molecular mechanisms on susceptible bacteria remain largely unclear. Type II and type I crustins are distinguished by glycine-rich region (GRR), which is a major marker motif, and some type II crustins exhibit stronger antibacterial activities than their GRR deletion mutants. In the present study, a novel crustin, namely, SpCrus5, was functionally characterized from a commercially valuable crab Scylla paramamosain. SpCrus5 contained a typical cysteine-rich domain at the N-terminus, a conserved WAP domain in the center, and a special GRR at the C-terminus, which is located in a site that differs from that of GRRs in typical type II crustins found between signal peptides and cysteine-rich domains. SpCrus5 shared high similarities with most type II crustins, and it was more closely related to type II crustins than to other retrieved crustins. SpCrus5 was predominantly expressed in gills and remarkably upregulated after the crabs were challenged with Vibrio parahemolyticus or Staphylococcus aureus, suggesting that SpCrus5 might participate in antibacterial immune responses. To further elucidate how this C-terminal GRR affects the function of SpCrus5, we harvested a GRR deletion mutant (SpCrus5-ΔGRR) by deleting the GRR. Liquid growth inhibition assays demonstrated that the antimicrobial activity of SpCrus5 was stronger than that of SpCrus5-ΔGRR, and the antibacterial spectrum of the former toward Gram-negative bacteria was broader than that of the latter. Binding assays revealed that the microorganism-binding ability and polysaccharide-binding activity of SpCrus5 were stronger than those of SpCrus5-ΔGRR. SpCrus5 or SpCrus5-ΔGRR agglutinated all tested Gram-positive bacteria. Therefore, the antibacterial activities of SpCrus5 were stronger and broader than those of SpCrus5-ΔGRR, and the binding ability and agglutination activity might contribute to the antimicrobial activity of SpCrus5. These results revealed that the C-terminal GRR was necessary to produce an efficient antibacterial activity of SpCrus5. SpCrus5 was highly identical with most type II crustins and it functioned as many type II crustins did, indicating that SpCrus5 was more likely an atypical type II crustin than a type I crustin. This study revealed that SpCrus5 participated as an essential antimicrobial effector in immune responses and provided new insights into the underlying mechanisms of the sequence and function diversity of crustins.

Molecular Characterization of Viral Responsive Protein 15 and Its Possible Role in Nuclear Export of Virus in Black Tiger Shrimp Penaeus monodon

A viral responsive protein 15 from Penaeus monodon (PmVRP15) has been reported to be important for white spot syndrome virus (WSSV) infection in vivo. This work aims to characterize PmVRP15 and investigate its possible role in nuclear import/export of the virus. Circular dichroism spectra showed that PmVRP15 contains high helical contents (82%). Analytical ultracentrifugation suggested that PmVRP15 could possibly form oligomers in solution. A subcellular fractionation study showed that PmVRP15 was found in heavy and light membrane fractions, indicating that PmVRP15 may be associated with endoplasmic reticulum. Double-stranded RNAi-mediated knockdown of PmVRP15 gene expression in vitro showed no effect on WSSV copy number in whole hemocyte cells. However, PmVRP15 silencing resulted in an accumulation of WSSV DNA in the nucleus of PmVRP15-silenced hemocytes. Immunofluorescence confocal microscopy showed that PmVRP15 knockdown hemocytes had a much lower level of VP28 (WSSV envelope protein), in comparison to that in the control. It is likely that PmVRP15 may play a role in viral nuclear egress.

Characterization of molecular properties and regulatory pathways of CrustinPm1 and CrustinPm7 from the black tiger shrimp Penaeus monodon

CrustinPm1 and crustinPm7 are the two most abundant isoforms of crustins identified from the hemocytes of the black tiger shrimp, Penaeus monodon. CrustinPm1 inhibits only Gram-positive bacteria, while crustinPm7 acts against both Gram-positive and Gram-negative bacteria. This work aims to characterize the molecular properties of recombinant crustinPm1 and crustinPm7, and the regulatory pathways of these two crustins. Circular dichroism spectroscopy revealed that crustinPm1 contained 40.81% alpha-helix and 22.34% beta-sheet, whereas crustinPm7 is made up of 32.86% alpha-helix and 27.53% beta-sheet. CrustinPm1 and crustinPm7 bound to phosphatidic acid (PA) with positive cooperativity of Hill slope (H) > 2, indicating that at least two molecules of crustins bind with one PA molecule. It is worth noting that both crustins bound to PA with significantly higher affinity than to lipoteichoic acid (LTA) and lipopolysaccharide (LPS). We speculate that crustin might also achieve antimicrobial activity by targeting PA, a signaling lipid. Regulatory pathways of crustinPm1 and crustinPm7 were investigated by knockdown of PmRelish and PmMyD88. This study demonstrated that crustinPm1 is mediated through the Toll signaling pathway, while crustinPm7 is regulated via both Toll and Imd pathways.

Molecular Characterization of a Newly Identified Subfamily Member of Penaeidin from two Penaeid Shrimps, Fenneropenaeus indicus and Metapenaeus monoceros

Penaeidins are a major group of antimicrobial peptides found in penaeid shrimps. This study reports a new isoform of penaeidin from the hemocytes of Indian white shrimp, Fenneropenaeus indicus (Fi-PEN, JX657680), and the pink shrimp, Metapenaeus monoceros (Mm-PEN, KF275674). Mm-PEN is also the first antimicrobial peptide to be identified from M. monoceros. The complete coding sequences of the newly identified Fi-PEN and Mm-PEN consisted of an ORF of 338 bp encoding 71 amino acids with a predicted molecular weight of 5.66 kDa and a pI of 9.38. The penaeidins had its characteristic signal peptide region (19 amino acids), which was followed by a mature peptide with a proline-rich domain (24 amino acids) at the N-terminal region and a cysteine-rich domain (28 amino acids) at the C-terminal region, designating it to penaeidin-3 subgroup. Structural analysis revealed an alpha-helix in its secondary structure and an extended structure at the proline-rich domain. The newly identified penaeidin isoform showed maximum similarity of 63 % to a penaeidin-3 isoform of P. monodon, which further proves it to be a new isoform. Phylogenetic analysis showed that it possessed similar evolutionary status like other penaeidins, which has subsequently diverged at different phases of evolution. The wide distribution of penaeidins in penaeid shrimps indicates the importance of these AMPs in the innate immunity.

Evidence of Antibacterial Activities in Peptide Fractions Originating from Snow Crab (Chionoecetes opilio) By-Products

Antibacterial peptide fractions generated via proteolytic processing of snow crab by-products exhibited activity against Gram-negative and Gram-positive bacteria. Among the bacterial strains tested, peptide fractions demonstrated inhibitory activity against the Gram-negative bacteria such as Aeromonas caviae, Aeromonas hydrophila, Campylobacter jejuni, Listonella anguillarum, Morganella morganii, Shewanella putrefasciens, Vibrio parahaemolyticus and Vibrio vulnificus and against a few Gram-positive bacteria such as Listeria monocytogenes, Staphylococcus epidermidis and Streptococcus agalactiae. The principal bioactive peptide fraction was comprised mainly of proteins and minerals (74.3 and 15.5%, respectively). Lipids were not detected. The amino acid content revealed that arginine (4.6%), glutamic acid (5.3%) and tyrosine (4.8%) residues were represented in the highest composition in the antibacterial peptide fraction. The optimal inhibitory activity was observed at alkaline pH. The V. vulnificus strain, most sensitive to the peptide fraction, was used to develop purification methods. The most promising chromatography resins selected for purification, in order to isolate peptides of interest and to carry out their detailed biochemical characterization, were the SP-Sepharose™ Fast Flow cation exchanger and the Phenyl Sepharose™ High Performance hydrophobic interaction media. The partially purified antibacterial peptide fraction was analyzed for minimum inhibitory concentration (MIC) determination, and the value obtained was 25 μg ml(-1). Following mass spectrometry analysis, the active peptide fraction seems to be a complex of molecules comprised of several amino acids and other organic compounds. In addition, copper was the main metal found in the active peptide fraction. Results indicate the production of antibacterial molecules from crustacean by-products that support further applications for high-value bioproducts in several areas such as food and health.

iTRAQ-based quantitative proteomic analysis of Macrobrachium rosenbergii hemocytes during Spiroplasma eriocheiris infection

Spiroplasma eriocheiris, as a novel aquaculture pathogen, has led into catastrophic economic losses in aquaculture. The Macrobrachium rosenbergii hemocytes were major target cells in S. eriocheiris infection. Our study was designed to examine the hemocytes' immune response at the protein levels. The differential proteomes of the prawn hemocytes were analyzed immediately prior to injection with the pathogen, and at 192h post-injection by isobaric tags for relative and absolute quantization (iTRAQ) labeling, followed by liquid chromatogramphytandem mass spectrometry (LC-MS/MS). A total of 69 differentially expressed proteins were identified. Forty-nine proteins were up-regulated and 20 proteins were down-regulated resulting from a S. eriocheiris infection. Up-regulated proteins included vertebrate gliacolin-like protein, vitellogenin, Gram-negative binding protein 1, alpha2 macroglobulin isoform 2 (a2M), etc. Down-regulated proteins, involved with beta-1,3-glucan-binding protein (BGBP), immunoglobulin like, Rab7, lipopolysaccharide and β-1,3-glucan (LGBP), actin-related protein, etc. Selected bioactive factors (tachylectin, α2M and vitellogenin, BGBP, C-type lectin, LGBP and Rab7) were verified by their immune roles in the S. eriocheiris infection using real-time PCR. The present work could serve as a basis for future studies on the proteins implicated in the susceptibility/resistance of M. rosenbergii to S. eriocheiris, as well as contribute to our understanding of disease processes in prawns.

BIOLOGICAL SIGNIFICANCE

This is the first time using an iTRAQ approach to analyze proteomes of M. rosenbergii mobilized against S. eriocheiris infection and substantiated the hemocytes' proteomic changes in M. rosenbergii using an infection model. The results reported here can provide a significant step forward toward a more complete elucidation of the immune relationship between M. rosenbergii and the pathogen S. eriocheiris.

Elevated water temperature increases the levels of reo-like virus and selected innate immunity genes in hemocytes and hepatopancreas of adult female blue crab, Callinectes sapidus

Seasonal changes in water temperature directly affect the aquatic ecosystem. The blue crab, Callinectes sapidus, inhabiting the Chesapeake Bay has been adapted to seasonal changes of the environmental conditions. In this, the animals halt their physiological process of the growth and reproduction during colder months while they resume these processes as water temperatures increase. We aimed to understand the effect of the elevated temperatures on a disease progression of reo-like virus (CsRLV) and innate immunity of adult female C. sapidus. Following a rise in water temperature from 10 to 23 °C, CsRLV levels in infected crabs rose significantly in hemocytes and multiple organs. However, in hemocytes, the elevated temperature had no effect on the levels of three innate immune genes: Cas-ecCuZnSOD-2, CasPPO and CasLpR three carbohydrate metabolic genes: CasTPS, CasGlyP; and CasTreh and the total hemocyte counts (THC). Interestingly, the hemocytes of CsRLV infected animals exposed to 23 °C for 10 days had significantly elevated levels of Cas-ecCuZnSOD-2 and CasTPS, compared to those of the uninfected ones also exposed to the same condition and compared to hatchery-raised females kept at 23 °C. Despite the lack of changes in THC, the types of hemocytes from the animals with high CsRLV levels differed from those of uninfected ones and from hatchery animals kept at 23 °C: CsRLV-infected crabs had hemocytes of smaller size with less cytosolic complexity than uninfected crabs. It therefore appears that the change in temperature influences rapid replication of CsRLV in all internal tissues examined. This implies that CsRLV may have broad tissue tropism. Interestingly, the digestive tract (mid- and hindgut) contains significantly higher levels of CsRLV than hemocytes while hepatopancreas and ovary have lower levels than hemocytes. Innate immune responses differ by tissue: midgut and hepatopancreas with upregulated Cas-ecCuZnSOD-2 similar to that found in hemocytes. By contrast, hepatopancreas showed a down-regulated CasTPS, suggesting carbohydrate stress during infection.

Recent insights into host-pathogen interaction in white spot syndrome virus infected penaeid shrimp

Viral disease outbreaks are a major concern impeding the development of the shrimp aquaculture industry. The viral disease due to white spot syndrome virus (WSSV) observed in early 1990s still continues unabated affecting the shrimp farms and cause huge economic loss to the shrimp aquaculture industry. In the absence of effective therapeutics to control WSSV, it is important to understand viral pathogenesis and shrimp response to WSSV at the molecular level. Identification and molecular characterization of WSSV proteins and receptors may facilitate in designing and development of novel therapeutics and antiviral drugs that may inhibit viral replication. Investigations into host-pathogen interactions might give new insights to viral infectivity, tissue tropism and defence mechanism elicited in response to WSSV infection. However, due to the limited information on WSSV gene function and host immune response, the signalling pathways which are associated in shrimp pathogen interaction have also not been elucidated completely. In the present review, the focus is on those shrimp proteins and receptors that are potentially involved in virus infection or in the defence mechanism against WSSV. In addition, the major signalling pathways involved in the innate immune response and the role of apoptosis in host-pathogen interaction is discussed.

iTRAQ-based proteomic study of the effects of Spiroplasma eriocheiris on Chinese mitten crab Eriocheir sinensis hemocytes

Spiroplasma eriocheiris is as a novel pathogen of Chinese mitten crab Eriocheir sinensis tremor disease. The hemocytes have been shown to be major target cells in S. eriocheiris infection. The aim of this study was to examine the hemocytes' immune response at the protein levels. The differential proteomes of the crab hemocytes were analyzed immediately prior to injection with the pathogen, and at 10 d post-injection by isobaric tags for relative and absolute quantization (iTRAQ) labeling, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 1075 proteins were identified by LC-MS/MS and de novo sequencing data. Using a 1.2-fold change in expression as a physiologically significant benchmark, 76 differentially expressed proteins (7.07%) were reliably quantified by iTRAQ analysis. Thirty-five (3.26%) proteins were up-regulated and 41 (3.81%) proteins were down-regulated resulting from a S. eriocheiris infection. Approximately 20 differential proteins in hemocytes were involved in the stress and immune responses. Up-regulated proteins included alpha-2-macroglobulin (α2M), prostaglandin D synthase (GST), ferritin, and heat shock protein 60. Down-regulated proteins included two lectins (mannose-binding protein and hemocytin), three kinds of serine proteinase inhibitors (two serpins and pacifastin), three different kinds of serine proteases, mitogen-activated protein kinase kinase (MAPKK), and two thioredoxins (Trx), crustin, etc. Selected bioactive factors (α2M, GST, ferritin, tubulin, crustin, thioredoxin, clip domain serine protease and serpin) are verified by their immune roles in the S. eriocheiris infection using Real-time PCR. The variation trend of immune gene's mRNA expression is similar with the result of iTRAQ, except the tubulin. The prophenoloxidase-activating system, antimicrobial action and antioxidant system involved in the immune responses of E. sinensis is believed to be a resistance to S. eriocheiris infection. This is the first report of the proteome response of crab hemocytes against S. eriocheiris infection. These findings contribute to our understanding of tremor disease processes in crabs, and provide the first evidence to promote a search for potential biomarkers of the disease.

RNA-seq as a powerful tool for penaeid shrimp genetic progress

The sequences of all different RNA transcripts present in a cell or tissue that are related to the gene expression and its functional control represent what it is called a transcriptome. The transcripts vary between cells, tissues, ontogenetic and environmental conditions, and the knowledge that can be gained through them is of a solid relevance for genetic applications in aquaculture. Some of the techniques used in transcriptome studies, such as microarrays, are being replaced for next-generation sequencing approaches. RNA-seq emerges as a new possibility for the transcriptome complexity analysis as well as for the candidate genes and polymorphisms identification of penaeid species. Thus, it may also help to understand the determination of complex traits mechanisms and genetic improvement of stocks. In this review, it is first introduced an overview of transcriptome analysis by RNA-seq, followed by a discussion of how this approach may be applied in genetic progress within penaeid stocks.

Anti-stress properties and two HSP70s mRNA expressions of blunt snout bream (Megalobrama amblycephala) fed with all-plant-based diet

The influence of all-plant-based diet on fingerling blunt snout breams (Megalobrama amblycephala) was tested by examining growth performance, anti-stress properties and related gene expression. Healthy fish were randomly divided into triplicate groups per dietary treatment and fed with different formulated diets. The results showed that both weight gain, specific growth rate and protein efficiency ratio of all-plant-based diet group were significant higher than those of the control (p < 0.05). In contrast, FCR of all-plant-based diet group was significantly lower than that of the control (p < 0.05). Therefore, all-plant-based diets could not affect the growth performance of blunt snout breams. Compared to the control group, the lysozyme levels in serum and mucus, and glutamic-oxaloacetic transaminase activities in serum and liver decreased significantly (p < 0.05). In contrast, the glutamic-pyruvic transaminase activities in serum and liver increased significantly (p < 0.05). For blunt snout breams fed with all-plant-based diets, the superoxide dismutase activities in mucus, serum and liver as well as catalase activity in serum and liver were decreased significantly (p < 0.05) comparing with that of the control group. But malondialdehyde contents were higher (p < 0.05) in serum and liver than that of control group. The expression of HSC70 mRNA increased significantly (p < 0.05) in blunt snout breams fed with all-plant-based diet, whereas the HSP70 mRNA expression decreased significantly (p < 0.05) when compared with control group. In conclusion, all these results indicated that the application of all-plant-based diet could decrease the anti-stress properties (non-specific immunity, stress resistance and antioxidant ability) and HSP70 mRNA expression in blunt snout breams fingerling. Although all-plant-based diets could not affect the growth performance of blunt snout breams, the application of all-plant-based diet should be discreet in the production practice.

Sequencing and de novo analysis of the hemocytes transcriptome in Litopenaeus vannamei response to white spot syndrome virus infection

Background

White spot syndrome virus (WSSV) is a causative pathogen found in most shrimp farming areas of the world and causes large economic losses to the shrimp aquaculture. The mechanism underlying the molecular pathogenesis of the highly virulent WSSV remains unknown. To better understand the virus-host interactions at the molecular level, the transcriptome profiles in hemocytes of unchallenged and WSSV-challenged shrimp (Litopenaeus vannamei) were compared using a short-read deep sequencing method (Illumina).

Results

RNA-seq analysis generated more than 25.81 million clean pair end (PE) reads, which were assembled into 52,073 unigenes (mean size = 520 bp). Based on sequence similarity searches, 23,568 (45.3%) genes were identified, among which 6,562 and 7,822 unigenes were assigned to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. Searches in the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) mapped 14,941 (63.4%) unigenes to 240 KEGG pathways. Among all the annotated unigenes, 1,179 were associated with immune-related genes. Digital gene expression (DGE) analysis revealed that the host transcriptome profile was slightly changed in the early infection (5 hours post injection) of the virus, while large transcriptional differences were identified in the late infection (48 hpi) of WSSV. The differentially expressed genes mainly involved in pattern recognition genes and some immune response factors. The results indicated that antiviral immune mechanisms were probably involved in the recognition of pathogen-associated molecular patterns.

Conclusions

This study provided a global survey of host gene activities against virus infection in a non-model organism, pacific white shrimp. Results can contribute to the in-depth study of candidate genes in white shrimp, and help to improve the current understanding of host-pathogen interactions.

The role of CcTpt1 in scale and early embryo development in common carp (Cyprinus carpio, Cyprinidae)

The full length cDNA sequence of the Tpt1/TCTP (Tumor protein, Translationally-controlled1) gene was identified from Common Carp (Cyprinus carpio, Cyprinidae), and was designated as CcTpt1 gene. The CDS is 510 bp and encodes a 170-amino acid peptide with a typical Tpt1 signature 2 domain, and is a typical Tpt1 protein. The deduced amino acid sequence of Tpt1 shared significant identity with the Tpt1 from other animals. A phylogenetic tree analysis revealed that the Common Carp Tpt1 protein has the closest genetic relationship and evolutional distance with Tpt1 from Medaka (Oryzias Latipes). Analysis by RT-PCR showed that the Tpt1 mRNA was detected in heart, liver, gill, kidney, muscle and skin. In embryogenesis, the Tpt1 mRNA was expressed gradually stronger from two-cell stage until prim-5 stage by whole-mount in situ. In larval stage, the Tpt1 was specifically expressed at eyes and brain, later at the ear stone, intestines, gills and internal organs. In addition, the Tpt1 was also found to be expressed in skin matrix being developed into scales and gradually disappeared when the scales were fully formed. These data suggested that the CcTpt1 may play important roles in early embryogenesis and scale initiation in fish.

Differences in gene organization between type I and type II crustins in the morotoge shrimp, Pandalopsis japonica

Crustins are cysteine-rich cationic antimicrobial peptides (AMPs) found in decapod crustaceans. Six novel crustin genes (Paj-CrusIc, Id, Ie, If, IIb and IIc) were identified in the morotoge shrimp, Pandalopsis japonica. Deduced amino acid sequences of isolated Paj-Crus genes ranged from 99 to 178 amino acid residues (10.6-17.8 kDa). Sequence analysis of nine isolated Paj-Crus genes and 100 different crustins from various decapod crustaceans revealed that a splice site and KXXXCP motif within the WAP domain may be the main criteria for classifying type I and II crustins, suggesting that the two types of crustin genes may have been generated by different processes. We also identified three intron-less crustin I genes (Paj-Crus Id, Ie and If) for the first time, which may have been generated by gene duplication. The tissue distribution profiles showed that Paj-CrusI genes were expressed predominantly in the gill and epidermis, whereas Paj-CrusII genes were expressed ubiquitously, suggesting that the two types of crustins may play different roles in various tissues or under different physiological conditions. Differing from previous results, hemocyte-specific crustin was not isolated from Pandalopsis japonica. This study showed that both types of crustin genes (types I and II) exist in decapod crustaceans and their primary structure and expression profiles differ from each other, suggesting that they may play different biological roles. This will help to extend our knowledge of the crustacean innate immune response, which will provide important basic information of shrimp immunity against various pathogens.

Transcriptome analysis of Pacific white shrimp (Litopenaeus vannamei) hepatopancreas in response to Taura syndrome Virus (TSV) experimental infection

Background

The Pacific white shrimp, Litopenaeus vannamei, is a worldwide cultured crustacean species with important commercial value. Over the last two decades, Taura syndrome virus (TSV) has seriously threatened the shrimp aquaculture industry in the Western Hemisphere. To better understand the interaction between shrimp immune and TSV, we performed a transcriptome analysis in the hepatopancreas of L. vannamei challenged with TSV, using the 454 pyrosequencing (Roche) technology.

Methodology/Principal Findings

We obtained 126919 and 102181 high-quality reads from TSV-infected and non-infected (control) L. vannamei cDNA libraries, respectively. The overall de novo assembly of cDNA sequence data generated 15004 unigenes, with an average length of 507 bp. Based on BLASTX search (E-value <10−5) against NR, Swissprot, GO, COG and KEGG databases, 10425 unigenes (69.50% of all unigenes) were annotated with gene descriptions, gene ontology terms, or metabolic pathways. In addition, we identified 770 microsatellites and designed 497 sets of primers. Comparative genomic analysis revealed that 1311 genes differentially expressed in the infected shrimp compared to the controls, including 559 up- and 752 down- regulated genes. Among the differentially expressed genes, several are involved in various animal immune functions, such as antiviral, antimicrobial, proteases, protease inhibitors, signal transduction, transcriptional control, cell death and cell adhesion.

Conclusions/Significance

This study provides valuable information on shrimp gene activities against TSV infection. Results can contribute to the in-depth study of candidate genes in shrimp immunity, and improves our current understanding of this host-virus interaction. In addition, the large amount of transcripts reported in this study provide a rich source for identification of novel genes in shrimp.

Crustin, a WAP domain containing antimicrobial peptide from freshwater prawn Macrobrachium rosenbergii: immune characterization

Crustin (MrCrs) was sequenced from a freshwater prawn Macrobrachium rosenbergii. The MrCrs protein contains a signal peptide region at N-terminus between 1 and 22 and a long whey acidic protein domain (WAP domain) at C-terminus between 57 and 110 along with a WAP-type 'four-disulfide core' motif. Phylogenetic results show that MrCrs is clustered together with other crustacean crustin groups. MrCrs showed high sequence similarity (77%) with crustin from Pacific white shrimp Litopenaeus vannamei and Japanese spiny lobster Panulirus japonicas. I-TASSER uses the best structure templates to predict the possible structures of MrCrs along with PDB IDs such as 2RELA and 1FLEI. The gene expressions of MrCrs in both healthy M. rosenbergii and those infected with virus including infectious hypodermal and hematopoietic necrosis virus (IHHNV) and white spot syndrome virus (WSSV) and bacteria Aeromonas hydrophila (Gram-negative) and Enterococcus faecium (Gram-positive) were examined using quantitative real time PCR. To understand its biological activity, the recombinant MrCrs gene was constructed and expressed in Escherichia coli BL21 (DE3). The recombinant MrCrs protein agglutinated with the bacteria considered for analysis at a concentration of 25 μg/ml, except Lactococcus lactis. The bactericidal results showed that the recombinant MrCrs protein destroyed all the bacteria after incubation, even less than 6 h. These results suggest that MrCrs is a potential antimicrobial peptide, which is involved in the defense system of M. rosenbergii against viral and bacterial infections.

Immune gene discovery by expressed sequence tag (EST) analysis of hemocytes in the ridgetail white prawn Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda is one of the most important commercial species in eastern China. However, little information of immune genes in E. carinicauda has been reported. To identify distinctive genes associated with immunity, an expressed sequence tag (EST) library was constructed from hemocytes of E. carinicauda. A total of 3411 clones were sequenced, yielding 2853 ESTs and the average sequence length is 436 bp. The cluster and assembly analysis yielded 1053 unique sequences including 329 contigs and 724 singletons. Blast analysis identified 593 (56.3%) of the unique sequences as orthologs of genes from other organisms (E-value < 1e-5). Based on the COG and Gene Ontology (GO), 593 unique sequences were classified. Through comparison with previous studies, 153 genes assembled from 367 ESTs have been identified as possibly involved in defense or immune functions. These genes are categorized into seven categories according to their putative functions in shrimp immune system: antimicrobial peptides, prophenoloxidase activating system, antioxidant defense systems, chaperone proteins, clottable proteins, pattern recognition receptors and other immune-related genes. According to EST abundance, the major immune-related genes were thioredoxin (141, 4.94% of all ESTs) and calmodulin (14, 0.49% of all ESTs). The EST sequences of E. carinicauda hemocytes provide important information of the immune system and lay the groundwork for development of molecular markers related to disease resistance in prawn species.

Shrimp alpha-2-macroglobulin prevents the bacterial escape by inhibiting fibrinolysis of blood clots

Proteomic analysis of the hemocytic proteins of Penaeus monodon (Pm) has previously shown that alpha-2-macroglobulin (A2M) was among the proteins that showed substantially altered expression levels upon Vibrio harveyi infection. Therefore, in this study its potentially important role in the response of shrimp to bacterial infection was further characterized. The yeast two-hybrid system revealed that the receptor binding domain of PmA2M interacted with the carboxyl-terminus of one or both of the transglutaminase type II isoforms, which are key enzymes involved in the shrimp clotting system. In accord with this, PmA2M was found to be localized on the extracellular blood clots and to colocalize with clottable proteins. RNA interference (RNAi)-mediated knockdown of A2M transcript levels reduced the PmA2M transcript levels (∼94%) and significantly reduced the bacterial seizing ability of the clotting system, resulting in an up to 3.3-fold higher number of V. harveyi that systemically disseminated into the circulatory system at 5 min post-infection before subsequent clearance by the immune system. Furthermore, an appearance of PmA2M depleted clots in the presence of V. harveyi strikingly demonstrated fibrinolysis zones surrounding the bacteria. This study provides the first evidence of the vital role of PmA2M in enhancing bacterial sequestration by protecting blood clots against fibrinolysis.

Molecular characterization of three crustin genes in the morotoge shrimp, Pandalopsis japonica

Crustins are among the most important antimicrobial peptides (AMPs) found in decapod crustaceans. They are small cationic AMPs (5-7 kDa) characterized by a proline-rich amino-terminal domain and a cysteine-rich carboxyl-terminal domain. Here, the first 3 crustin-like cDNAs (Pj-crus Ia, Ib, and II) were identified from the morotoge shrimp, Pandalopsis japonica. The full-length cDNAs of Pj-crus Ia, Ib, and II consisted of 1135, 580, and 700 nucleotides and encoded putative proteins containing 109, 119, and 186 amino acids residues, respectively. All 3 identified Pj-crus sequences exhibited the conserved domain organization for crustins, including a signal sequence, a cysteine-containing region, a glycine-rich region, and a whey-acidic protein (WAP) domain. Amino acid sequence comparisons and phylogenetic analysis revealed that the Pj-crus Ia and Ib belong to type I crustins (e.g., carcinin), which have been mostly identified from Brachyura and Astacidea, whereas Pj-crus II was classified as belonging to the type II crustins, which are mainly found in Dendrobranchiata. An analysis of the organization of these 3 Pj-crus genes revealed that the splicing site within the WAP domain may be an important key for classifying types I and II crustin family members. The tissue distribution profile results showed that the Pj-crus I genes were expressed in a tissue-specific manner but that the Pj-crus II gene was expressed ubiquitously, suggesting that these crustins may play different roles in various tissues or under different physiological conditions. The bacterial challenge results suggested that the Pj-crus genes may be transcriptionally influenced by different bacterial types. This comparative study of various crustin family members will help extend the knowledge on the crustacean innate immune response, which will provide important basic information for controlling shrimp immunity against various pathogens.

Transglutaminase regulates immune-related genes in shrimp

Transglutaminase (TGase) is known to be involved in blood coagulation, a conserved defence mechanism among invertebrates. Gene silencing of TGase was previously shown to render shrimp susceptible to both bacterial and viral infections suggesting that TGase is an essential component of the shrimp immune system. Here, we examine the effects of the absence of TGase on the transcriptomic profile of kuruma shrimp by microarray analysis, focussing on genes that are involved in shrimp immunity. Total RNAs from shrimp haemocytes injected with dsRNA specific for TGase and control samples were isolated at 3 and 7 days p.i. and analyzed by microarray. Results revealed that TGase silencing affects the expression of genes in shrimp and caused significant down-regulation of the expressions of crustin and lysozyme. Furthermore, TGase-depleted samples were found to have lower haemocyte counts and higher total bacterial counts in their haemolymph. These results suggest that TGase is an important component of the shrimp immune response and is involved in the regulation of some immune-related genes particularly antimicrobial peptides.

Molecular cloning, sequence analysis and expression of Fein-Penaeidin from the haemocytes of Indian white shrimp Fenneropenaeus indicus

Penaeidins are members of a special family of antimicrobial peptide existing in penaeid shrimp and play an important role in the immunological defense of shrimp. Here, we report a penaeidin sequence cloned from the Indian white shrimp Fenneropenaus indicus (Fein-Penaeidin). The Fein-Penaeidin open reading frame encodes a 77 amino acid peptide including a 19 amino acid signal peptide. The deduced amino acid sequences of Fein-Penaeidin include a proline rich N-terminal domain and a carboxyl-domain that contains six cysteine residues. Structural analysis revealed an alpha-helix in its secondary structure and the predicted 3D structure indicated two-disulphide bridges in the alpha-helix. Phylogenetic analysis and sequence comparison with other known peaneidin suggest the gene shows high similarity to that of penaeidin from Peneaus monodon (95%), F. indicus (80%) and Fenneropenaeus chinensis (74%). Fein-Penaeidin was examined in normal and microbial challenged shrimp and was found to be constitutively expressed in haemocytes, Heart, gills, muscles, intestine, hepatopancreas and eyestalk. Bacterial challenge resulted in mRNA up-regulation, inducing expression at 6 h post injection indicating the penaeidin involved in the innate immunity.

Effects of anthraquinone extract from Rheum officinale Bail on the physiological responses and HSP70 gene expression of Megalobrama amblycephala under Aeromonas hydrophila infection

We evaluated the effect of dietary supplementation with anthraquinone extract (from Rheum officinale Bail) on the resistance to Aeromonas hydrophila infection in Megalobrama amblycephala. The fish were randomly divided into two groups: a control group (fed a standard diet) and a treatment group (standard diet supplemented with 0.1% anthraquinone extract) and fed for 10 weeks. We then challenged the fish with A. hydrophila and recorded mortality and changes in serum cortisol, lysozyme, alkaline phosphatase (ALP), total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and hepatic catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA) and the relative expression of heat shock protein 70 (HSP70) mRNA for a period of 5 d. Supplementation with 0.1% anthraquinone extract significantly increased serum lysozyme activity before infection, serum ALP activity at 24 h after infection, serum total protein concentration 12 h after infection, hepatic CAT activity 12 h after infection, hepatic SOD activity before infection, and the relative expression of hepatic HSP70 mRNA both before infection and 6 h after infection. In addition, the supplemented group had decreased levels of serum cortisol 6 h after infection, serum AST and ALT activities 12 h after infection, and hepatic MDA content 12 h after infection. Mortality was significantly lower in the treatment group (86.67%) than the control (100%). Our results suggest that ingestion of a basal diet supplemented with 0.1% anthraquinone extract from R. officinale Bail can enhance resistance against pathogenic infections in M. amblycephala.

A comparative study of antimicrobial properties of crustinPm1 and crustinPm7 from the black tiger shrimp Penaeus monodon

Several isoforms of crustin have been identified in the black tiger shrimp Penaeus monodon. These cationic cysteine-rich antimicrobial peptides contain a single whey acidic protein (WAP) domain at the C-terminus and exhibit antimicrobial activity against both Gram-positive and Gram-negative bacteria. In this paper, we investigate the binding properties and antimicrobial actions of crustinPm1 and crustinPm7, the two most abundant crustin isoforms found in the haemocyte of P. monodon. Previously, crustinPm1 showed strong inhibition against Gram-positive bacteria, whilst crustinPm7 acted against both Gram-positive and Gram-negative bacteria. A binding study showed that both crustins can bind to Gram-positive and Gram-negative bacterial cells. Enzyme-linked immunosorbent (ELISA) assay suggested that crustins bind to the cell wall components, lipoteichoic acid (LTA) and lipopolysaccharide (LPS) with positive cooperativity of Hill slope (H)>2. This indicates that at least two molecules of crustins interact with one LTA or LPS molecule. In addition, both crustins can induce bacterial agglutination and cause inner membrane permeabilization in Escherichia coli. Scanning Electron Microscopy (SEM) revealed the remarkable change on the cell surface of Staphylococcus aureus, Vibrio harveyi and E. coli after the bacteria were treated with the recombinant crustinPm7. Meanwhile, crustinPm1 can cause a visible change on the cell surface of S. aureus and E. coli only. This is in agreement with the fact that crustinPm1 has shown no antimicrobial activity against V. harveyi. It is likely that the antimicrobial activity of crustins mainly relies on their ability to agglutinate bacterial cells and to disrupt the physiochemical properties of bacterial surface.

Microarray analyses of shrimp immune responses

Shrimp aquaculture is one of the major foodproducing industries in the world. However, it is being impacted by several problems including diseases, antibiotic use, and environmental factors. The extent of the effects of these problems in the immune system of the shrimp at the molecular level is just beginning to be understood. Here, we review the gene expression profile of shrimp in response to some of these problems using the high-throughput microarray analysis, including white spot syndrome virus, yellow head virus, Vibrio spp., peptidoglycan, oxytetracycline, oxolinic acid, salinity, and temperature.

A review of the major penaeid shrimp EST studies and the construction of a shrimp transcriptome database based on the ESTs from four penaeid shrimp

By economic value, shrimp is currently the most important seafood commodity worldwide, and these animals are often the subject of scientific research in shrimp farming countries. High throughput methods, such as expressed sequence tags (ESTs), were originally developed to study human genomics, but they are now available for studying other important organisms, including shrimp. ESTs are short sequences generated by sequencing randomly selected cDNA clones from a cDNA library. This is currently the most efficient and powerful method for providing transcriptomic data for organisms with an uncharacterized genome. This review will summarize the sixteen major shrimp EST studies that have been conducted to date. In addition, we analyzed the EST data downloaded from NCBI dbEST for the four major penaeid shrimp species and constructed a database to host all of these EST data as well as our own analysis results. This database provides the shrimp aquaculture research community with an outline of the shrimp transcriptome as well as a tool for shrimp gene identification.

Shrimp molecular responses to viral pathogens

From almost negligible amounts in 1970, the quantity of cultivated shrimp (~3 million metric tons in 2007) has risen to approach that of the capture fishery and it constitutes a vital source of export income for many countries. Despite this success, viral diseases along the way have caused billions of dollars of losses for shrimp farmers. Desire to reduce the losses to white spot syndrome virus in particular, has stimulated much research since 2000 on the shrimp response to viral pathogens at the molecular level. The objective of the work is to develop novel, practical methods for improved disease control. This review covers the background and limitations of the current work, baseline studies and studies on humoral responses, on binding between shrimp and viral structural proteins and on intracellular responses. It also includes discussion of several important phenomena (i.e., the quasi immune response, viral co-infections, viral sequences in the shrimp genome and persistent viral infections) for which little or no molecular information is currently available, but is much needed.

Cationic antimicrobial peptides in penaeid shrimp

Penaeid shrimp aquaculture has been consistently affected worldwide by devastating diseases that cause a severe loss in production. To fight a variety of harmful microbes in the surrounding environment, particularly at high densities (of which intensive farming represents an extreme example), shrimps have evolved and use a diverse array of antimicrobial peptides (AMPs) as part of an important first-line response of the host defense system. Cationic AMPs in penaeid shrimps composed of penaeidins, crustins, and anti-lipopolysaccharide factors are comprised of multiple classes or isoforms and possess antibacterial and antifungal activities against different strains of bacteria and fungi. Shrimp AMPs are primarily expressed in circulating hemocytes, which is the main site of the immune response, and hemocytes expressing AMPs probably migrate to infection sites to fight against pathogen invasion. Indeed, most AMPs are produced as early as the nauplii developmental stage to protect shrimp larvae from infections. In this review, we discuss the sequence diversity, expression, gene structure, and antimicrobial activities of cationic AMPs in penaeid shrimps. The information available on antimicrobial activities indicates that these shrimp AMPs have potential therapeutic applications in the control of disease problems in aquaculture.

Differential gene expression profile from haematopoietic tissue stem cells of red claw crayfish, Cherax quadricarinatus, in response to WSSV infection

White spot syndrome virus (WSSV) is one of the most important viral pathogens in crustaceans. During WSSV infection, multiple cell signaling cascades are activated, leading to the generation of antiviral molecules and initiation of programmed cell death of the virus infected cells. To gain novel insight into cell signaling mechanisms employed in WSSV infection, we have used suppression subtractive hybridization (SSH) to elucidate the cellular response to WSSV challenge at the gene level in red claw crayfish haematopoietic tissue (Hpt) stem cell cultures. Red claw crayfish Hpt cells were infected with WSSV for 1h (L1 library) and 12h (L12 library), respectively, after which the cell RNA was prepared for SSH using uninfected cells as drivers. By screening the L1 and L12 forward libraries, we have isolated the differentially expressed genes of crayfish Hpt cells upon WSSV infection. Among these genes, the level of many key molecules showed clearly up-regulated expression, including the genes involved in immune responses, cytoskeletal system, signal transduction molecules, stress, metabolism and homestasis related genes, and unknown genes in both L1 and L12 libraries. Importantly, of the 2123 clones screened, 176 novel genes were found the first time to be up-regulated in WSSV infection in crustaceans. To further confirm the up-regulation of differentially expressed genes, the semi-quantitative RT-PCR were performed to test twenty randomly selected genes, in which eight of the selected genes exhibited clear up-regulation upon WSSV infection in red claw crayfish Hpt cells, including DNA helicase B-like, multiprotein bridging factor 1, apoptosis-linked gene 2 and an unknown gene-L1635 from L1 library; coatomer gamma subunit, gabarap protein gene, tripartite motif-containing 32 and an unknown gene-L12-254 from L2 library, respectively. Taken together, as well as in immune and stress responses are regulated during WSSV infection of crayfish Hpt cells, our results also light the significance of cytoskeletal system, signal transduction and other unknown genes in the regulation of antiviral signals during WSSV infection.

The possible role of penaeidin5 from the black tiger shrimp, Penaeus monodon, in protection against viral infection

Penaeidin class 5 (PEN5) has so far only been reported in the Chinese shrimp, Fenneropenaeus chinensis, and the black tiger shrimp, Penaeus monodon. The PEN5 homolog from F. chinensis (FenchiPEN5) exhibits antimicrobial activities against both Gram-positive and Gram-negative bacteria as well as fungi. Here, we characterized the PEN5 gene from P. monodon (PenmonPEN5) and evaluated its potential involvement in antiviral immunity. The deduced open reading frame of PenmonPEN5 encodes for a predicted 79 amino acid peptide including a 19 amino acid signal peptide. The gene structure of PenmonPEN5 contains two exons interrupted by one intron, whilst the 5' upstream sequence contains a putative TATA box and several GATA, GATA-3, AP-1 and dorsal transcription factor binding sites. PenmonPEN5 mRNA levels in P. monodon shrimps following a systemic infection with white spot syndrome virus (WSSV) were significantly induced at 24 h post infection, but was strongly down-regulated at 48 h post injection, compared to those of the uninfected control shrimps. The suppression of PenmonPEN5 transcript levels by RNA interference mediated gene silencing led to an increased susceptibility of shrimps to WSSV infection, suggesting a possible role of PenmonPEN5 in the shrimp's antiviral immunity.

Cationic antimicrobial peptides in penaeid shrimp

Penaeid shrimp aquaculture has been consistently affected worldwide by devastating diseases that cause a severe loss in production. To fight a variety of harmful microbes in the surrounding environment, particularly at high densities (of which intensive farming represents an extreme example), shrimps have evolved and use a diverse array of antimicrobial peptides (AMPs) as part of an important first-line response of the host defense system. Cationic AMPs in penaeid shrimps composed of penaeidins, crustins, and anti-lipopolysaccharide factors are comprised of multiple classes or isoforms and possess antibacterial and antifungal activities against different strains of bacteria and fungi. Shrimp AMPs are primarily expressed in circulating hemocytes, which is the main site of the immune response, and hemocytes expressing AMPs probably migrate to infection sites to fight against pathogen invasion. Indeed, most AMPs are produced as early as the nauplii developmental stage to protect shrimp larvae from infections. In this review, we discuss the sequence diversity, expression, gene structure, and antimicrobial activities of cationic AMPs in penaeid shrimps. The information available on antimicrobial activities indicates that these shrimp AMPs have potential therapeutic applications in the control of disease problems in aquaculture.

Involvement of WSSV-shrimp homologs in WSSV infectivity in kuruma shrimp: Marsupenaeus japonicus

White spot syndrome virus (WSSV) is pathogenic and specific to shrimp, and is capable of producing a persistent infection in the host. Moreover, shrimp are capable of persistently carrying a single or multiple viruses, allowing them to survive for long periods with latent infections. In order to identify genes that are specially involved in the intricate WSSV-shrimp association, we focused on homologs between the WSSV and shrimp genomes. We here investigated whether homologous WssvORFs (WssvORF285, WssvORF332) and their homologs in the kuruma shrimp genome (MjORF16, MjORF18) are important for WSSV infectivity by utilizing dsRNA-mediated RNA interference, and further proposed potential roles of homologous WssvORFs associated with the persistent viral infection stage. Homologous MjORFs were found to be highly up-regulated in several tested tissues upon WSSV infection. Injection of dsRNAs specific to homologous MjORFs, followed by WSSV challenge, led to reduced and delayed shrimp mortality when compared to that of shrimp without dsRNA injection. Silencing of homologous WssvORFs by specific dsRNAs sharply increased shrimp survival. WssvORF332 may function as a latency gene especially associated with the persistent WSSV infection stage while WssvORF285 may be classified into the same group as WssvVP28 and may play a role in virus penetration during the infection. Our results suggest that WSSV-shrimp homologs are involved in WSSV infectivity and support the hypothesis that homologous WssvORFs are related to WSSV latency and pathogenesis.