Gene expression and protein levels of thioredoxin in the gills from the whiteleg shrimp (Litopenaeus vannamei) infected with two different viruses: the WSSV or IHHNV

iTRAQ-based proteomic analysis of the hepatopancreas from Litopenaeus vannamei after trans-vp28 gene Synechocystis sp. PCC6803 immunization

Litopenaeus vannamei (Pacific white shrimp) is one of the most commercially important varieties of shrimp cultivated in the world. Shrimp farming is a high-risk, capital-intensive industry that is susceptible to periodic outbreaks of diseases caused by viral and bacterial pathogens. Thus, there is a need to develop economically viable methods of disease control. The hepatopancreas of crustaceans are known to have an important role in their innate immune response. In this study, we have explored the immune response of the hepatopancreas from L. vannamei fed with trans-vp28 gene Synechocystis sp. PCC6803 using iTRAQ-based proteomics. A total of 214 differentially expressed proteins (DEPs) were identified, of which 143 were up-regulated and 71 were down-regulated. These proteins have diverse roles in the cell cytoskeleton and cell phagocytosis, antioxidant defense process and the response of immune related proteins. Among these proteins, the immunity associated with the functional annotation of L. vannamei was further analysed. In addition, 4 DEPs (act1, N/A, H and C7M84_013542) were analysed using parallel reaction monitoring (PRM). This is the first report of proteomics in the hepatopancreas of L. vannamei immunized with trans-vp28 gene Synechocystis sp. PCC6803.

Air Exposure Affects Physiological Responses, Innate Immunity, Apoptosis and DNA Methylation of Kuruma Shrimp, Marsupenaeus japonicus

Air exposure stress is a common phenomenon for commercial crustacean species in aquaculture and during waterless transportation. However, the antioxidant responses to air exposure discussed in previous studies may be insufficient to present the complexities involved in this process. The comprehensive immune responses, especially considering the immune genes, cell apoptosis, and epigenetic changes, are still unknown. Accordingly, we investigated the multifaceted responses of Marsupenaeus japonicus to air exposure. The results showed that the expression profiles of the apoptosis genes (e.g., IAP, TXNIP, caspase, and caspase-3) and the hypoxia-related genes (e.g., hsp70, hif-1α, and HcY) were all dramatically induced in the hepatopancreas and gills of M. japonicus. Heart rates, T-AOC (total antioxidant capacity) and lactate contents showed time-dependent changes upon air exposure. Air exposure significantly induced apoptosis in hepatopancreas and gills. Compared with the control group, the apoptosis index (AI) of the 12.5 h experimental group increased significantly (p < 0.05) in the hepatopancreas and gills. Most individuals in the experimental group (EG, 12.5 h) had lower methylation ratios than the control group (CG). Air exposure markedly reduced the full-methylation and total-methylation ratios (31.39% for the CG and 26.46% for the EG). This study provided a comprehensive understanding of the antioxidant responses of M. japonicus considering its physiology, innate immunity, apoptosis, and DNA methylation levels, and provided theoretical guidance for waterless transportation.

Comprehensive expression analysis of the beta integrin from Penaeus monodon indicating its participation in innate immunity and ammonia nitrogen stress response

The aim of the present study was to investigate the function of the beta integrin (PmItgb) in Penaeus monodon. The 3011 bp cDNA sequence of PmItgb was cloned from P. monodon using rapid amplification of cDNA ends (RACE) PCR. Phylogenetic tree analyses indicated that the amino acid sequence of PmItgb should be merged into Fenneropenaeus chinensis (93%). Quantitative real-time PCR (q RT-PCR) revealed that PmItgb mRNA was highly expressed in the hemocytes. In addition, with regard to developmental stages, PmItgb showed significantly higher expression in oosperm, nauplius IV, zoea I and III, and post larval stages than that in other development stages. PmItgb expression in the shrimp epidermis was higher in the postmolt (B) stage, and lower in other molting stages. We also found that Vibrio harveyi and V. anguillarum challenge enhanced PmItgb expression in the hepatopancreas and gills. When PmItgb was inhibited, innate immunity-related genes such as ALF, crustin 1, crustin 7, penaeidin 3, and penaeidin 5 were significantly down-regulated. Furthermore, we demonstrated that PmItgb knock-down by specific dsRNA reduced bacterial clearance. In high ammonia nitrogen concentrations, PmItgb was significantly up-regulated in the hepatopancreas and gills. After PmItgb was silenced, the rate of mortality owing to high ammonia nitrogen concentrations decreased; the expression of related anti-apoptotic genes was up-regulated, and that of the apoptotic genes was slightly down-regulated. These results suggested that PmItgb may be involved in shrimp innate immunity and mediate apoptosis of hepatopancreatic cells induced by high ammonia nitrogen environments.

Roles of Carotenoids in Invertebrate Immunology

Carotenoids are biologically active pigments that are well-known to enhance the defense and immunity of the vertebrate system. However, in invertebrates, the role of carotenoids in immunity is not clear. Therefore, this study aims to review the scientific evidence for the role of carotenoids in invertebrate immunization. From the analysis of published literatures and recent studies from our laboratory, it is obvious that carotenoids are involved in invertebrate immunity in two ways. On the one hand, carotenoids can act as antioxidant enzymes to remove singlet oxygen, superoxide anion radicals, and hydroxyl radicals, thereby reducing SOD activity and reducing the cost of immunity. In some organisms, carotenoids have been shown to promote SOD activity by up-regulating the expression of the ZnCuSOD gene. Carotenoids, on the other hand, play a role in the expression and regulation of many genes involved in invertebrate immunity, including thioredoxins (TRX), peptidoglycan recognition receptor proteins (PGRPs), ferritins, prophenoloxidase (ProPO), vitellogenin (Vg), toll-like receptor (TLRs), heat shock proteins (HSPs), and CuZnSOD gene. The information in this review is very useful for updating our understanding of the progress of carotenoid research in invertebrate immunology and to help identify topics for future topics.

Selective cytotoxic effect of Plantago lanceolata L. against breast cancer cells

BACKGROUND

Plantago lanceolata L. is used in Iraqi folklore medicine to treat injuries, and its extract is prescribed by some herbalists for cancer patients. This research aimed to evaluate the effect of P. lanceolata leaf extract on breast cancer cell lines in vitro and to identify its active compounds. Crystal violet viability assay was used to determine the cytotoxicity of methanolic P. lanceolata leaf extract against various breast cancer cell lines. MCF7, AMJ13, MDAMB, and CAL51 human breast cancer cells were treated with different concentrations of the extract for 72 h. The morphology of the treated cells was examined under a phase-contrast inverted microscope. The clonogenic ability was assessed through a clonogenic assay. High-performance liquid chromatography (HPLC) analysis was performed to measure the concentrations of phenols and flavonoids in the extract.

RESULTS

The methanolic P. lanceolata leaf extract significantly inhibited the proliferation of triple-negative CAL51 cells but showed minor effect on the other breast cancer cells. In addition, at high doses, it induced cytopathic morphological changes. The clonogenic assay showed low colony formation in the exposed cells, especially CAL51 cells. Furthermore, HPLC study revealed that the methanolic extract contained important flavonoid glycosides, especially rutin, myricetin quercetin, and kaempferol.

CONCLUSIONS

P. lanceolata leaf extract selectively inhibited the proliferation of CAL51 triple-negative breast cancer cells and showed minor effect on the other breast cancer cells types studied. Thus, this study showed P. lanceolata as a possible natural source of selective anti-triple-negative breast cancer drugs.

White spot syndrome virus down-regulates expression of histones H2A and H4 of Penaeus vannamei to promote viral replication

The white spot syndrome virus (WSSV) is a highly lethal and contagious pathogen to most cultivated shrimp species. The WSSV genome contains the ICP11 gene and its encoded protein acts as a multifunctinal DNA mimic protein that disrupts the nucleosome assembly by binding to the histone proteins H2A and H3. In addition, WSSV provokes severe nuclear hypertrophy and DNA damage. However, little is known about the influence of WSSV on the expression of the host's genes encoding for histones. Therefore, we investigated the effect of WSSV infection on the expression of the genes encoding histones in shrimp Penaeus vannamei. An RT-qPCR assay was performed to evaluate the temporal expression of H2A and H4 transcripts in the shrimp. Significant changes were observed in the expression of these genes, which coincided with the dynamics of replication of the virus. H2A reached its maximum expression levels at 12 hpi. Thus, it may be suggested that this is a viral strategy to evade the host's immune response in order to promote viral replication.

Characterization and immune function of the thioredoxin-interacting protein (TXNIP) from Litopenaeus vannamei

The thioredoxin (Trx) system plays essential roles in maintenance and regulation of the redox state of cysteine residues in cellular proteins. The Trx-interacting protein (TXNIP) is a TRX inhibitory protein that works as a negative regulator in the TRX system. The function of TXNIP in invertebrates, in particular in immunity, remains unclear to date. In the current study, a novel TXNIP from Pacific white shrimp Litopenaeus vannamei was identified and characterized and its roles in immune responses was investigated. TXNIP could interact with Trx and inhibit its redox regulatory activity, suggesting that TXNIP was involved in regulation of the cellular redox state in shrimp. The expression of TXNIP was high in the stomach, gill, scape, eyestalk, epithelium, pyloric and muscle and low in the hepatopancreas, intestine, nerve, hemocytes and heart. Stimulations with pathogens white spot syndrome virus (WSSV) and Vibrio parahaemolyticus and immune stimulants poly (I:C) and LPS could significantly increase the expression of TXNIP in vivo. Silencing of TXNIP using RNAi strategy significantly facilitated the infection of V. parahaemolyticus but inhibited the infection of WSSV in shrimp. These indicated that TXNIP could be positively involved in antibacterial responses but negatively involved in antiviral responses in shrimp. Moreover, knockdown of TXNIP in vivo exerted opposite effects on expression of antimicrobial peptides anti-lipopolysaccharide factors and penaeidins and enhanced the phagocytic activity of hemocytes against bacteria. These suggested that TXNIP could play a complex role in regulation of humoral and cellular immune responses in shrimp.

Isolation and characterization of a Raf gene from Chinese shrimp Fenneropenaeus chinensis in response to white spot syndrome virus infection

Raf is a member in the Ras/Raf/MAPKK/MAPK signaling transduction pathway. To obtain a better understanding of Raf in the interaction between the Chinese shrimp Fenneropenaeus chinensis and white spot syndrome virus (WSSV), the sequence of cDNA of Raf from F. chinensis (FcRaf) was obtained. The FcRaf gene contained a 2421 bp open reading frame (ORF). The FcRaf shared most characteristic of Raf protein, such as the Raf-like Ras-binding domain (RBD), phorbol esters/diacylglycerol binding domain (C1 domain), and catalytic domain of the serine/threonine kinases, Raf (STKc_Raf). The sequence of functional domains of Raf protein was relatively conserved. The FcRaf mRNA was detected in the tissues of gill, muscle, and hepatopancreas from normal F. chinensis. The mRNA abundance level of FcRaf in the gill was the highest, which was 2.7-fold the level in the hepatopancreas. The expression level of FcRaf was significantly (P < 0.05) up-regulated in the tissues of gill, muscle, and hepatopancreas post WSSV-infection, which suggested that FcRaf might be involved in the interaction between F. chinensis and WSSV. Two SNP loci were identified in the ORF, one of which was a C-T mis-sense mutation, where an Ala was replaced by a Val, and induced the predicted protein secondary structure change. Considering the relatively low MAF (0.07), whether this mis-sense mutation was a detrimental mutation needs further investigation.

Identification of the thioredoxin-related protein of 14 kDa (TRP14) from Litopenaeus vannamei and its role in immunity

The thioredoxin system plays essential roles in maintenance and regulation of the redox state of cysteine residues in cellular proteins. The thioredoxin-related protein of 14 kDa (TRP14) is an important member of the TRX superfamily which acts on various substrate proteins, some of which are not overlapped with those of thioredoxin. The knowledge on the function of TRP14 in invertebrates is limited to date. In this study, a TRP14 gene was identified from Pacific white shrimp Litopenaeus vannamei (LvTRP14) and its role in immune responses was investigated. We demonstrated that the expression level of LvTRP14 was high in hepatopancreas and intestine, low in eyestalk, and medium in other tissues of healthy shrimp. The transcription of LvTRP14 in vivo was significantly down-regulated in Relish-silencing shrimp but up-regulated in STAT-silencing shrimp, indicating a complex regulation of LvTRP14 expression. Although the LvTRP14 expression showed little change after immune stimulation with different type of pathogens, knockdown of LvTRP14 expression using RNAi strategy could significantly facilitate the infection of white spot syndrome virus (WSSV) and Vibrio parahaemolyticus in shrimp. Dual luciferase reporter assays demonstrated that LvTRP14 enhanced the transcription factor activity of Relish but attenuated that of Dorsal. Furthermore, silencing of LvTRP14 in vivo had opposite effects on expression of different type of antimicrobial peptides. These suggested that LvTRP14 could play a complex role in shrimp immunity.

iTRAQ-based comparative proteome analysis for molecular mechanism of defense against acute ammonia toxicity in Pacific White shrimp Litopenaeus vannamei

In the practical farming of Litopenaeus vannamei, the intensive culture system and environmental pollution usually results in a high concentration of ammonia, which brings large detrimental effects to shrimp, such as increasing the susceptibility to pathogens and even causing high mortality. We have revealed that the survival time under acute ammonia stress varied substantially among different families and obtained ammonia-tolerant (LV_T) and ammonia-sensitive (LV_S) families. In order to understand the molecular mechanism of defense against ammonia toxicity in shrimp, we performed iTRAQ LC-MS/MS proteomic analysis between LV_T and LV_S groups of L. vannamei under acute ammonia stress to identify the key proteins and pathways that play an effective role for against ammonia toxicity. By comparative proteome analysis, 202 significantly differentially proteins (DEPs) were identified in LV_T compared to LV_S, and most of the DEPs (60%) were up-regulated. Excepting for the proteins without function reporting, the meaningful finding is that 77.8% of the DEPs have been reported mainly involving in immune defense and stress tolerant in crustacean species, such as hemocyanin, Rab7, Rab GTPase, Rac1, alpha 2 macroglobulin, Bip, peroxiredoxin, Cu/Zn SOD, glutathione peroxidase, thioredoxin, calreticulin, and Elongation Factor 1-alpha, etc. These DEPs might potentially play important role in against ammonia toxicity, and it also reflected a relation between ammonia tolerance and pathogen resistance. In addition, a total of 10 significantly changed KEGG pathways were detected, and the network diagram of these KEGG pathways showed that more critical nodes were up-regulated, which involved in protein synthesis and transport, and against stress stimuli. This study provided important information for understanding the molecular mechanism of defense against ammonia toxicity in shrimp at whole protein level.

WSSV-responsive gene expression under the influence of PmVRP15 suppression

The viral responsive protein 15 from black tiger shrimp Penaeus monodon (PmVRP15), is highly up-regulated and produced in the hemocytes of shrimp with white spot syndrome virus (WSSV) infection. To investigate the differential expression of genes from P. monodon hemocytes that are involved in WSSV infection under the influence of PmVRP15 expression, suppression subtractive hybridization (SSH) of PmVRP15-silenced shrimp infected with WSSV was performed. The 189 cDNA clones of the forward library were generated by subtracting the cDNAs from WSSV-infected and PmVRP15 knockdown shrimp with cDNAs from WSSV-infected and GFP knockdown shrimp. For the opposite subtraction, the 176 cDNA clones in the reverse library was an alternative set of genes in WSSV-infected shrimp hemocytes in the presence of PmVRP15 expression. The abundant genes in forward SSH library had a defense/homeostasis of 26%, energy/metabolism of 23% and in the reverse SSH library a hypothetical protein with unknown function was found (30%). The differential expressed immune-related genes from each library were selected for expression analysis using qRT-PCR. All selected genes from the forward library showed high up-regulation in the WSSV-challenged PmVRP15 knockdown group as expected. Interestingly, PmHHAP, a hemocyte homeostasis associated protein, and granulin-like protein, a conserved growth factor, are extremely up-regulated in the absence of PmVRP15 expression in WSSV-infected shrimp. Only transcript level of transglutaminase II, that functions in regulating hematopoietic tissue differentiation and inhibits mature hemocyte production in shrimp, was obviously down-regulated as observed from SSH results. Taken together, our results suggest that PmVRP15 might have a function relevant to hemocyte homeostasis during WSSV infection.

Characterization and expression analysis of a chitinase gene (PmChi-5) from black tiger shrimp (Penaeus monodon) under pathogens infection and ambient ammonia-N stress

Chitinases are crucial enzymes for crustaceans. Previous researches had already revealed that chitinases play important roles in digestion, molting and defense against viruses. In the present study, a chitinase cDNA was identified from black tiger shrimp (Penaeus monodon) and designated as PmChi-5. The full-length PmChi-5 cDNA was 2860 bp in size, containing an open reading frame (ORF) of 1731 bp that encoded a protein of 576 amino acids with a deduced molecular weight of 64.8 kDa. Expression of the PmChi-5 mRNA was ubiquitously detected in all selected tissues, with the highest level in the gill and hepatopancreas. PmChi-5 was expressed throughout the whole larvae stages, and the highest level at Mysis3 stage, which indicated that PmChi-5 may be involved in larval metamorphosis. After challenged with Streptococcus agalactiae and Vibrio harveyi, the transcripts of PmChi-5 were found to be up-regulated significantly both in hepatopancreas and gill. Besides, the ammonia nitrogen stress treatment was also carried out, PmChi-5 transcripts were significantly changed in hepatopancreas and gill. The results showed that PmChi-5 may be involved in molting, larval metamorphosis, the immune defenses to pathogens infection and ammonia-N stress.

Differential responses of a thioredoxin-like protein gene to Vibrio parahaemolyticus challenge in the noble scallop Chlamys nobilis with different total carotenoids content

Being lack of specific immune system, both enzymes and non-enzymatic antioxidants play crucial roles in immune of invertebrates. In the present study, in order to investigate immune roles of enzyme (thioredoxin, TRX) and antioxidants (carotenoids), Golden scallops with golden shell and golden muscle rich in carotenoids content and Brown scallops with brown shell and white muscle less carotenoids content of the noble scallop Chlamys nobilis were challenged by Vibrio parahaemolyticus for 48 h. Firstly, a cDNA of TRX protein gene from the scallop (named as CnTRX) was cloned and characterized. The cDNA contains 1280 bp, consisting of a 5' -UTR of 99 bp, a long 3' -UTR of 860 bp and a 321 bp open reading frame (ORF) encoding 106 amino acids. Phylogenetic analysis showed that CnTRX had a closer evolution relationship with TRX from Chlamys farreri. CnTRX was ubiquitously expressed in all examined tissues including intestine, adductor, mantle, gonad, gill, kidney, hepatopancreas and hemolymph, and the highest expression level was detected in the hemolymph. Next, CnTRX transcripts were significantly up-regulated in V. parahaemolyticus group in comparison with PBS control group. Moreover, CnTRX transcripts were significantly higher in Golden scallops than that of Brown ones at 6 h, 12 h and 24 h with bacteria challenge (P < 0.05). The present result indicates that both CnTRX and carotenoids are important factors involved in the immune defense against bacteria challenge in the noble scallop.

The identification of microRNAs involved in the response of Chinese shrimp Fenneropenaeus chinensis to white spot syndrome virus infection

MicroRNA (miRNA) is a class of small noncoding RNA, which is involved in the post-transcriptional regulation in all metazoan eukaryotes. MiRNAs might play an important role in the host response to virus infection. However, miRNAs in the aquatic crustacean species were not extensively investigated. To obtain a better understanding of the response of Chinese shrimp Fenneropenaeus chinensis to white spot syndrome virus (WSSV) infection, the sequence and expression profile of miRNAs in the hepatopancreas of WSSV-infected F. chinensis were obtained by the high-throughput Illumina HiSeq 2500 deep sequencing technique. A total number of 129 known miRNAs and 44 putative novel miRNAs were identified from the deep sequencing data. The peak size of miRNAs was 22 nt (37.0%). 25 miRNAs were significantly (P < 0.05) differentially expressed post WSSV infection. Six of the differentially expressed miRNAs were randomly selected for further verification by the real-time RT-PCR technique. The results showed that there was a consistency between the deep sequencing and real-time RT-PCR assay. The target genes of differentially expressed miRNAs were predicted. Each miRNA had 4 target genes on average. The results suggested that some specific miRNAs might be involved in the response of F. chinensis to WSSV infection, and further provided basic information for the investigation of specific miRNAs in F. chinensis.

Is dimerization a common feature in thioredoxins? The case of thioredoxin from Litopenaeus vannamei

The quaternary structure of the redox protein thioredoxin (Trx) has been debated. For bacterial Trx, there is no question regarding its monomeric state. In humans and other eukaryotes, the presence of a cysteine residue at the crystallographic symmetry axis points to the relevance of dimer formation in solution and in vivo. Crystallographic data for shrimp thioredoxin (LvTrx) obtained under different redox conditions reveal a dimeric arrangement mediated by a disulfide bond through residue Cys73 and other hydrophobic interactions located in the crystallographic interface, as reported for human Trx. Through the analysis of five mutants located at the crystallographic interface, this study provides structural and biochemical evidence for the existence in solution of monomeric and dimeric populations of wild-type LvTrx and five mutants. Based on the results of biochemical assays, SAXS studies and the crystallographic structures of three of the studied mutants (Cys73Ser, Asp60Ser and Trp31Ala), it is clear that the Cys73 residue is essential for dimerization. However, its mutation to Ser produces an enzyme which has similar redox activity in vitro to the wild type. A putative regulatory function of dimerization is proposed based on structural analysis. Nonetheless, the biological role of LvTrx dimerization needs to be experimentally unveiled. Additionally, the findings of this work reopen the discussion regarding the existence of similar behaviour in human thioredoxin, which shares a Cys at position 73 with LvTrx, a structural feature that is also present in some Trxs from vertebrates and crustaceans.

Characterization and expression analysis of a thioredoxin-like protein gene in the sea cucumber Apostichopus japonicus

As the most important disulfide bond reducates of intracellular oxidordeuctase, thioredoxin (TRX) plays a crucial role in maintaining reducing state of intracellular proteins to normally perform their function. In this study, a cDNA of TRX-like protein gene from Apostichopus japonicus (denoted as AjTRX) was cloned and characterized. The full-length cDNA of AjTRXwas of 1870 bp, consisting of a 5'-UTR of 101 bp, a long 3'-UTR of 887 bp and a 882 bp open reading frame (ORF) encoding a 293 amino acids. The predicted molecular mass and the theoretical PI of the deduced amino acids of AjTRX were 32.3 kDa and 5.52, respectively. Phylogenetic trees showed that AjTRX had a closer evolution relationship with TRX from Strongylocentrotus purpuratus. AjTRX was found to be ubiquitously expressed in all examined tissues including longitudinal muscle, coelomocytes, tube feet, intestine, respiratory tree and body wall indicating a general role in physiological processes. Temporal expression pattern of AjTRX in coelomocytes showed that AjTRX reached two peak expression levels at 8 h and 48 h after Vibrio splendidus challenge with a 8.6 and 9.3-fold increase compared to their control groups, respectively. The recombinant AjTRX protein (rAjTRX) displayed obvious antioxidant activity in a dose-dependent manner, and the higher reducing activity was detected in 20 μM experimental group. All these results strongly suggested that AjTRX could play an important role as an antioxidant in a physiological context, and might be involved in the process of bacterial challenge.

Isolation and expression analysis of an MAPKK gene from Fenneropenaeus chinensis in response to white spot syndrome virus infection

Mitogen-activated kinase kinase (MAPKK) is an important gene involved in the host-virus interaction process. To obtain a better understanding of MAPKK in the interaction process between the Chinese shrimp Fenneropenaeus chinensis and white spot syndrome virus (WSSV), we cloned the sequence of an MAPKK cDNA from F. chinensis (FcMAPKK) and investigated the effect of FcMAPKK on WSSV infection. The results showed that the FcMAPKK gene contained a 1227 bp open reading frame (ORF), which encoded a highly conserved protein with a serine/threonine protein kinase catalytic (S_TKc) domain. The deduced amino acid sequence of FcMAPKK shared identities between 11.9 and 92.6% with MAPKKs from vertebrate, invertebrate, plant and fungus species. The FcMAPKK was expressed in all the examined tissues in the normal F. chinensis. FcMAPKK expression level was highest in the hepatopancreas where it was approximately 2.6-fold the expression level in the gill, and lowest in the muscle where it was approximately 0.3-fold the expression level in the hepatopancreas. The FcMAPKK expression levels in the muscle, gill, and hepatopancreas were all changed post WSSV challenge. The FcMAPKK expression was significantly (P < 0.01) up-regulated in the muscle of F. chinensis at 48 h post WSSV infection. The WSSV began to replicate quickly in the normal F. chinensis at 48 h post infection, while the WSSV replication in the U0126-treated F. chinensis could be significantly (P < 0.05) inhibited. The results suggested that FcMAPKK might be involved in the WSSV infection process, and hijacking of FcMAPKK might be required for WSSV replication in F. chinensis.

Crystallographic studies evidencing the high energy tolerance to disrupting the interface disulfide bond of thioredoxin 1 from white leg shrimp Litopenaeus vannamei

Thioredoxin (Trx) is a small 12-kDa redox protein that catalyzes the reduction of disulfide bonds in proteins from different biological systems. A recent study of the crystal structure of white leg shrimp thioredoxin 1 from Litopenaeus vannamei (LvTrx) revealed a dimeric form of the protein mediated by a covalent link through a disulfide bond between Cys73 from each monomer. In the present study, X-ray-induced damage in the catalytic and the interface disulfide bond of LvTrx was studied at atomic resolution at different transmission energies of 8% and 27%, 12.8 keV at 100 K in the beamline I-24 at Diamond Light Source. We found that at an absorbed dose of 32 MGy, the X-ray induces the cleavage of the disulfide bond of each catalytic site; however, the interface disulfide bond was cleaved at an X-ray adsorbed dose of 85 MGy; despite being the most solvent-exposed disulfide bond in LvTrx (~50 Å2). This result clearly established that the interface disulfide bond is very stable and, therefore, less susceptible to being reduced by X-rays. In fact, these studies open the possibility of the existence in solution of a dimeric LvTrx.

iTRAQ analysis of gill proteins from the zebrafish (Danio rerio) infected with Aeromonas hydrophila

The gills are large mucosal surfaces and very important portals for pathogen entry in fish. The aim of this study was to determine the gill immune response at the protein levels, the differential proteomes of the zebrafish gill response to Aeromonas hydrophila infection were identified with isobaric tags for relative and absolute quantitation (iTRAQ) labeling followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 1338 proteins were identified and classified into the categories primarily related to cellular process (15.36%), metabolic process (11.95%) and biological regulation (8.29%). Of these, 82 differentially expressed proteins were reliably quantified by iTRAQ analysis, 57 proteins were upregulated and 25 proteins were downregulated upon bacterial infection. Gene ontology (GO) enrichment analysis showed that approximately 33 (8.8%) of the differential proteins in gills were involved in the stress and immune responses. Several upregulated proteins were observed such as complement component 5, serpin peptidase inhibitor clade A member 7, annexin A3a, histone H4, glyceraldehyde 3-phosphate dehydrogenase, creatine kinase, and peroxiredoxin. These protein expression changes were further validated at the transcript level using microarray analysis. Moreover, complement and coagulation cascades, pathogenic Escherichia coli infection and phagosome were the significant pathways identified by KEGG enrichment analysis. This is first report on proteome of fish gills against A. hydrophila infection, which contribute to understanding the defense mechanisms of the gills in fish.

Identification, cloning and characterization of an extracellular signal-regulated kinase (ERK) from Chinese shrimp, Fenneropenaeus chinensis

Extracellular signal-regulated kinase (ERK) is a serine/threonine-specific protein kinase, which participates in signaling transduction pathways that control intracellular events, including resumption of meiosis, embryogenesis, cell differentiation, cell proliferation, cell death and response to radiation. Some virus species evolved the ability to hijack the host cell ERK signaling transduction pathway for viral replications and gene expressions. To obtain a better understanding of ERK, we cloned a cDNA encoding ERK from the muscle of Fenneropenaeus chinensis (FcERK). The FcERK contained a 1098 bp open reading frame (ORF) encoding a protein of 365 amino acid residues with a conserved phosphorylation motif TEY in the kinase activation loop. Pair-wise and multiple sequence alignment revealed that ERK is highly conserved across taxa. The FcERK gene expressions in the hepatopancreas and gill were noticeably higher than the expression observed in the muscle. A challenge test was performed to reveal the responses of FcERK in different tissues to white spot syndrome virus (WSSV) infection. Post WSSV challenge, the FcERK expression in the gill significantly increased during the early stage of the viral infection, the FcERK expression in the muscle increased later than that in the gill, and the FcERK expression in the hepatopancreas significantly decreased. The FcERK gene expression profile accorded with the results that the virus primarily infects tissues originating from the ectoderm, with less infection of the tissues originating from the mesoderm, and hardly any infection in the tissues originating from the entoderm. Two single nucleotide polymorphisms (SNPs) were identified in the FcERK gene, involving C/T transition. The SNP genotypes of two groups of shrimps, respectively comprising 96 WSSV-resistant shrimps and 96 WSSV-susceptible shrimps were obtained using a high-resolution melting (HRM) method. In the two groups, the MAFs of both sites were greater than 0.05, and no site departed significantly (P < 0.05) from HWE. The genotype distributions of both mutation sites between the two groups were not significantly different. These results lead to a better understanding of the molecular mechanisms of the host-virus interaction and provide useful information for disease control.

Analysis of gene expression in Homarus americanus larvae exposed to sublethal concentrations of endosulfan during metamorphosis

Agricultural pesticide runoff has been suspected as the cause of numerous fish kills in rivers throughout Prince Edward Island but the impact on the surrounding marine environment is unknown. Endosulfan, an organochlorine pesticide, is a potent neurotoxin and molt inhibitor used to combat the Colorado potato beetle however it has the potential to affect non-target organisms including the American lobster (Homarus americanus). Metamorphosis is a critical stage of development and the effects of contaminant exposure during this time are largely unknown in lobster. A 14day endosulfan exposure was performed to identify the effects on survival, development and gene expression in lobster larvae during metamorphosis; all of which were predicted to be negatively impacted. The higher endosulfan concentrations resulted in greater mortality and a significant increase in the number of days required to reach metamorphosis in surviving animals. A custom made H. americanus microarray was used for monitoring the changes in expression of 14,592 genes at the termination of the exposure. Genes with >1.5 fold change and identified as being significant at p<0.05 using one-way ANOVA were selected for further analysis. A total of 707 genes were identified as being significantly differentiated, however with only ~40% annotation of the array, the majority of these genes were unknown. Annotated genes of interest were involved in many processes: development, metabolism, immunity and oxidative stress response and gene regulation. Nine genes of interest (histone H1, farnesoic acid O-methyltransferase, cuticle protein, glutathione S-transferase, thioredoxin, NADH dehydrogenase, ecdysone nuclear receptor Fushi tarazu F1 (FTZ-F1), ferritin and ecdysone inducible protein E75 (EIP-E75)) were selected for RT-qPCR validation of the microarray results. The RT-qPCR method was more sensitive than the microarray yet detected similar expression patterns. The two highest endosulfan concentrations resulted in increased mortalities, developmental delays in reaching metamorphosis and significant changes in gene expression. This research provides a foundation for using microarray gene expression profiles as screening tools for exploring the impact of environmental contaminants on lobster.

Expression, purification, crystallization and X-ray crystallographic studies of different redox states of the active site of thioredoxin 1 from the whiteleg shrimp Litopenaeus vannamei

Thioredoxin (Trx) is a 12 kDa cellular redox protein that belongs to a family of small redox proteins which undergo reversible oxidation to produce a cystine disulfide bond through the transfer of reducing equivalents from the catalytic site cysteine residues (Cys32 and Cys35) to a disulfide substrate. In this study, crystals of thioredoxin 1 from the Pacific whiteleg shrimp Litopenaeus vannamei (LvTrx) were successfully obtained. One data set was collected from each of four crystals at 100 K and the three-dimensional structures of the catalytic cysteines in different redox states were determined: reduced and oxidized forms at 2.00 Å resolution using data collected at a synchrotron-radiation source and two partially reduced structures at 1.54 and 1.88 Å resolution using data collected using an in-house source. All of the crystals belonged to space group P3212, with unit-cell parameters a = 57.5 (4), b = 57.5 (4), c = 118.1 (8) Å. The asymmetric unit contains two subunits of LvTrx, with a Matthews coefficient (VM) of 2.31 Å(3) Da(-1) and a solvent content of 46%. Initial phases were determined by molecular replacement using the crystallographic model of Trx from Drosophila melanogaster as a template. In the present work, LvTrx was overexpressed in Escherichia coli, purified and crystallized. Structural analysis of the different redox states at the Trx active site highlights its reactivity and corroborates the existence of a dimer in the crystal. In the crystallographic structures the dimer is stabilized by several interactions, including a disulfide bridge between Cys73 of each LvTrx monomer, a hydrogen bond between the side chain of Asp60 of each monomer and several hydrophobic interactions, with a noncrystallographic twofold axis.