Two Rab GTPases, EsRab-1 and EsRab-3, involved in anti-bacterial response of Chinese mitten crab Eriocheir sinensis

Rab7 GTPase, a direct target of miR-131-3p, limits intracellular Spiroplasma eriocheiris infection by modulating phagocytosis

Spiroplasma eriocheiris is a kind of intracellular pathogen without cell wall and the causative agent of Chinese mitten crab Eriocheir sinensis "tremor disease", which causes significant economic losses in the crustacean aquaculture. However, little is known about the intracellular transport of this pathogen and host innate immune response to this pathogen. Rab GTPases are key regulators for endocytosis and intracellular pathogen trafficking. In this study, we showed that S. eriocheiris infection upregulated the transcription of Rab7 through the downregulation of miR-131-3p. Subsequently, both hemocytes transfected with miR-131-3p mimics and hemocytes derived from Rab7 knockdown crabs exhibited reduced phagocytic activities and increased susceptibility to S. eriocheiris infection. Additionally, Rab7 could interact with the cell shape-determining protein MreB3 of S. eriocheiris, and its overexpression promoted S. eriocheiris internalization and fusion with lysosomes, thereby limiting S. eriocheiris replication in Drosophila S2 cells. Overall, these results demonstrated that Rab7 facilitated host cell phagocytosis and interacted with MreB3 of S. eriocheiris to prevent S. eriocheiris infection. Moreover, miR-131-3p was identified as a negative regulator of this process through its targeting of Rab7. Therefore, targeting miR-131-3p might be an effective strategy for controlling S. eriocheiris in crab aquaculture.

The identification, evolutionary analysis, and immune roles of Rab family members in red swamp crayfish, Procambarus clarkii

The Rab GTPase constitutes the largest family of small GTPases that regulate intracellular trafficking. Different eukaryotes possess varying numbers of Rab paralogs. However, limited knowledge exists regarding the evolutionary pattern of Rab family in most major eukaryotic supergroups. This study cloned 24 Rab genes from transcriptome data of Procambarus clarkii haemocytes. The multiple sequence alignment and phylogenetic tree analysis revealed a relatively high degree of conservation for PcRab. Furthermore, PcRab exhibited similarities in motif composition with all members showing presence of G, PM, RabF, and RabSF motifs. The tertiary structure indicated that PcRab proteins mainly consisted of α-helices and β-strands, and most PcRab proteins shared similar tertiary structures, and it was indicated that they have similar protein characteristics. Protein-protein interaction prediction identified a total of 20 interacting proteins involved in vesicle trafficking, phagocytosis, and signal transduction with 193 interactions. Expression analysis showed wide expression patterns for PcRab in P. clarkii organs. Upon infection by white spot syndrome virus and Aeromonas veronii, significant induction was observed for PcRab gene expression levels, indicating their involvement in pathogen response mechanisms. The present study represents the pioneering effort in comprehensively identifying and cloning the Rab family genes in crustacean, followed by a systematic investigation into their evolutionary patterns and immune response upon pathogen infection. The results provided valuable insights for further investigation into the molecular mechanism underlying the response of P. clarkii to pathogen infection.

Proteomics of the haemolymph of the terrestrial crustacean Porcellio scaber reveals components of its innate immunity under baseline conditions

The terrestrial crustacean Porcellio scaber is an established test organism in environmental research. We analysed the haemolymph proteome of P. scaber using a classical proteomic approach based on one-dimensional gel electrophoresis and tandem mass spectrometry. Using a publicly available protein database and our P. scaber transcriptome data, we have identified 76 proteins involved in cytoskeleton formation, protein degradation, vesicular transport, genetic information processing, detoxification, carbohydrate and lipid metabolism reflecting haemocyte metabolic activity, active intracellular transport, and intercellular communication. Compared with the data reported for other crustaceans, 28 of these P. scaber proteins have been linked to its immunity, among them hemocyanin, α-2-macroglobulin, phenoloxidase 3, superoxide dismutase, glutathione S-transferase, haemolymph clottable protein, and histones H4 and H2B. Our results thus provide a firm base for studying the innate immune response of P. scaber at the level of the haemolymph proteome. This knowledge is of particular importance in ecotoxicity studies with various environmental stressors where understanding physiological changes is important to reveal possible modes of action.

Transcriptome analysis of IHHNV infection in Penaeus vannamei at different developmental stages

Infectious hypodermal and haematopoietic necrosis virus (IHHNV) is the smallest known virus in shrimp, which causes runt-deformity syndrome (RDS) and leads to huge economic loss every year in penaeid shrimp farming. Previous studies have shown that the juvenile Penaeus vannamei is more susceptible to IHHNV infection than the adults, but the mechanism is still unclear. In order to investigate the mechanism of pathogenic differences in IHHNV infection of P. vannamei at different developmental stages, the juvenile and adult P. vannamei were studied by transcriptome high-throughput sequencing to analyze their response to IHHNV infection. GO and KEGG enrichment were analyzed to search for differentially expressed genes (DEGs) related to immunity, growth and metabolism. The results showed that many immune-related genes of the juvenile and adult P. vannamei responded differently to IHHNV infection. For the adult P. vannamei, the expression of most immune-related genes was significantly up-regulated, which means that a cellular defense response was triggered after IHHNV infection. However, most immune-related genes in juvenile P. vannamei were inhibited, indicating that the immune system of juvenile the P. vannamei is imperfect and makes it to be more susceptible to IHHNV. Similarly, the growth-related genes of P. vannamei were changed during IHHNV infection. For the juvenile P. vannamei, the growth-related genes were significantly down-regulated, which resulted in a growth hormone disorder and prevented the juvenile P. vannamei from growth. In the adult P. vannamei, most molting-related genes were significantly up-regulated, indicating that IHHNV infection leads the adult P. vannamei to early molting to eliminate pathogen in the body. Metabolic process data showed that energy metabolism pathway was affected when P. vannamei infected with IHHNV. The adult P. vannamei infected with IHHNV can cause energetically costly and lead to the disturbance of the metabolism, activate complex immune systems to resist the invasion of pathogens. The results of this study clarified the response mechanism of P. vannamei at different developmental stages to IHHNV infection, which can provide new insights to IHHNV effective control and a reference for the study of sensitive period of different shrimp virus to host infection.

A proteomics investigation of 'immune priming' in Penaeus vannamei as shown by isobaric tags for relative and absolute quantification

Invertebrates are considered completely dependent on their innate immunity to defend themselves against pathogens as they lack an adaptive immunity. However, a growing body of evidence has indicated a specific acquired immunity called 'immune priming' may exist. The Pacific white shrimp, Penaeus vannamei is one of the most economically important shrimp species in the world. In the previous research, we investigated the hepatopancreas immune response of shrimp immunized with trans -vp28 gene Synechocystis sp. PCC6803 at the protein level. In this study, on the basis of the previous research, the shrimp were then challenged with WSSV, and hepatopancreas analyzed using isobaric tags for relative and absolute quantification (i TRAQ) labeling. In total, 308 differentially expressed proteins (DEPs) were identified including 84 upregulated and 224 downregulated. Upregulated proteins such as calmodulin B and calreticulin, and downregulated proteins such as calnexin, and signaling pathways like Ras, mTOR were differentially expressed in both studies. Data from this study are more significant than previous work and indicate increased sensitivity to WSSV after immunization with trans-vp28 gene Synechocystis sp. PCC6803. In addition, selected DEPs (upregulated: A0A3R7QHH6 and downregulated: A0A3R7PEF6, A0A3R7MGX8, A0A423TPJ4, and A0A3R7QCC2) were randomly analyzed using parallel reaction monitoring (PRM). These data preliminarily confirm immune priming in P. vannamei, and show that the initial stimulation with trans -vp28 gene Synechocystis sp. PCC6803 regulate P. vannamei immune responses and they provide shrimp with enhanced immune protection against secondary stimulation.

Effect of pathogenic bacteria on a novel C-type lectin, hemocyte and superoxide dismutase/ alkaline phosphatase activity in Onchidium reevesii

Bacterial infection in the marine environment is a serious problem to maintain the stability of marine ecosystems. Nevertheless, there is little report so far for the biological effects of pathogenic bacteria in coastal ecosystems. Hence, we investigated the responses of shell-less Onchidium reevesii to resist against pathogenic bacterial infection. Analysis of data here could be used as fundamental information for assessment of innate immune response of O. reevesii. The full-length OrCTL cDNA was cloned and consists of 1849 base pair (bp) encoding protein of 192 amino acids. Constructing multiple alignments suggested that OrCTL has conserved carbohydrate recognition domain (CRD) of CTLs, containing an EPS (Glu-Pro-Ser) motif that may imply the function of recognition of carbohydrates like others invertebrate. OrCTL mRNAs were mainly detected in ganglion and hepatopancreas, and expression was highly up-regulated from 2 h after Vibrio harveyi challenge, rapidly decreased at 4 h, and significantly increased at 12 h. In addition, after challenge with Vibrio parahaemolytics, OrCTL gene expression was slightly up-regulated from 2 h, peaked at 12 h. Enzyme activity (in the hepatopancreas) and cell immune (in the hemolymph) were investigated along with Superoxide dismutase (SOD) activity, alkaline phosphatase (ALP) activity and cell cycle. SOD activities were significantly higher after V. harveyi and V. parahaemolytics challenge than that in the control group, respectively. By contrast, ALP activities were significantly inhibited after challenged with bacteria than that in the control group, respectively. Enzyme activities in the hepatopancreas obviously fluctuated, and ALP activity was more sensitive to bacteria. Cell responses illustrated that there were a significant higher percentage of cells in the S and G2/M phase in hemolymph after challenged with bacteria. Our results suggested that the immune response of O. reevesii could be activated by pathogenic bacteria, and the data will provide referent for the disease prevention of systematic investigation in aquatic animal.

TMT-based quantitative proteomic analysis of Eriocheir sinensis hemocytes and thoracic ganglion during Spiroplasma eriocheiris infection

Spiroplasma eriocheiris, a novel pathogen of Chinese mitten crab Eriocheir sinensis tremor disease, has led into catastrophic economic losses in aquaculture. S. eriocheiris invaded the hemocytes in the early stage, then invaded nerve tissue and caused typically paroxysmal tremors of pereiopod in the late stage of infection. The purpose of this study was to detect the infection mechanism of hemocytes in the early stage and thoracic ganglion in the late stage of S. eriocheiris infection at the protein level. Hemocytes and thoracic ganglion were collected at 24 h and 10 d after injection (the crabs with typical paroxysmal tremors of the pereiopod), respectively. TMT was performed with isobaric markers, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). In hemocytes, 127 proteins were up-regulated and 85 proteins were down-regulated in 2747 quantified proteins. Many proteins and process including proPO system proteins, hemolymph coagulation system proteins and lectins were differently expressed in hemocytes and involved in the early immune process of E. sinensis against S. eriocheiris infection. Meanwhile, 545 significantly different expression proteins (292 down-regulated and 253 up-regulated protein including a number of immune-associated, nervous system development and signal transmission related proteins) were identified in thoracic ganglion in the late stage of S. eriocheiris infection. The qRT-PCR analysis results shown that the selected significantly changed proteins in hemocytes and thoracic ganglion were consistent with the TMT proteomics. This paper reported for the first time to study the responses of crab hemocyte and thoracic ganglion against the S. eriocheiris infection at different stages. These findings help us understand the infection mechanism of S. eriocheiris at different stage with the different tissue.

Rab7 controls innate immunity by regulating phagocytosis and antimicrobial peptide expression in Chinese mitten crab

The Rab family is the most significant subfamily of small GTP-binding proteins. These proteins have widespread intracellular localization and play an important role in many biological processes. Rab7 plays a crucial role in the innate immune system of crustaceans. In the present study, we cloned and characterized Rab7 from Chinese mitten crab (Eriocheir sinensis), designated EsRab7. The full-length of the EsRab7 cDNA sequence is 1,257 bp and contains a 618-bp open reading frame encoding a 205-amino acid polypeptide. Bioinformatics analysis showed that the Rab7 protein was highly conserved during evolution. Quantitative real-time PCR showed the highest tissue expression in muscle, followed by hepatopancreas. EsRab7 was significantly upregulated in hemocytes after stimulation by Gram-positive Staphylococcus aureus or Gram-negative Vibrio parahaemolyticus. Further studies showed that EsRab7 knockdown during bacterial stimulation resulted in decreased bacterial phagocytosis. In addition, EsRab7 regulated the expression of antimicrobial peptides via the Toll signaling pathway. Collectively, these results demonstrate that EsRab7 plays critical roles in antimicrobial function in the Chinese mitten crab.

Differential proteomic profiles and characterizations between hyalinocytes and granulocytes in ivory shell Babylonia areolata

The haemocytes of the ivory shell, Babylonia areolata are classified by morphologic observation into the following types: hyalinocytes (H) and granulocytes (G). Haemocytes comprise diverse cell types with morphological and functional heterogene and play indispensable roles in immunological homeostasis of invertebrates. In the present study, two types of haemocytes were morphologically identified and separated as H and G by Percoll density gradient centrifugation. The differentially expressed proteins were investigated between H and G using mass spectrometry. The results showed that total quantitative proteins between H and G samples were 1644, the number of up-regulated proteins in G was 215, and the number of down-regulated proteins in G was 378. Among them, cathepsin, p38 MAPK, toll-interacting protein-like and beta-adrenergic receptor kinase 2-like were up-regulated in G; alpha-2-macroglobulin-like protein, C-type lectin, galectin-2-1, galectin-3, β-1,3-glucan-binding protein, ferritin, mega-hemocyanin, mucin-17-like, mucin-5AC-like and catalytic subunit of protein kinase A were down-regulated in G. The results showed that the most significantly enriched KEGG pathways were the pathways related to ribosome, phagosome, endocytosis, carbon metabolism, protein processing in endoplasmic reticulum and oxidative phosphorylation. For phagosome and endocytosis pathway, the number of down-regulation proteins in G was more than that of up-regulation proteins. For lysosome pathway, the number of up-regulation proteins in G was more than that of down-regulation proteins. These results suggested that two sub-population haemocytes perform the different immune functions in B. areolata.

Rac1 GTPase is a critical factor in phagocytosis in the large yellow croaker Larimichthys crocea by interacting with tropomyosin

The Rho family GTPase Rac1 acts as a molecular switch for signal transduction to regulate various cellular functions. Here, a Rac1 homolog (LcRac1) was identified in large yellow croaker (Larimichthys crocea), one of the most economically important marine fishes. The LcRac1 protein was expressed in Escherichia coli and purified. Subsequently the specific antibody was raised using the purified fusion protein (GST-LcRac1). LcRac1 was ubiquitously expressed in all 12 tissues we examined, with the highest expression in heart and blood and the weakest expression in head-kidney and spleen. Moreover, time course analysis revealed that LcRac1 expression was obviously up-regulated in liver, spleen and head-kidney after immunization with Poly I:C, LPS and Vibrio parahemolyticus. On the other hand, on the basis of protein interaction, it was found that the LcRac1 interacted with Tropomyosin, a crucial protein in the process of phagocytosis. Furthermore, RNAi assays indicated that the phagocytic percentage and phagocytic index were significantly decreased when the LcRac1 gene was silenced by sequence-specific siRNA. Fluorescence microscopy assays revealed FITC-labeled V. parahemolyticus were remarkably decreased after LcRac1 was silenced by sequence-specific siRNA at 24 h. These findings implicate the vital role of LcRac1 in innate immunity in the large yellow croaker.

Proteomic and metabolomic responses in hepatopancreas of whiteleg shrimp Litopenaeus vannamei infected by microsporidian Enterocytozoon hepatopenaei

Enterocytozoon hepatopenaei (EHP) causes hepatopancreatic microsporidiosis (HPM) in shrimp. HPM is not normally associated with shrimp mortality, but is associated with significant growth retardation. In this study, the responses induced by EHP were investigated in hepatopancreas of shrimp Litopenaeus vannamei using proteomics and metabolomics. Among differential proteins identified, several (e.g., peritrophin-44-like protein, alpha2 macroglobulin isoform 2, prophenoloxidase-activating enzymes, ferritin, Rab11A and cathepsin C) were related to pathogen infection and host immunity. Other proteomic biomarkers (i.e., farnesoic acid o-methyltransferase, juvenile hormone esterase-like carboxylesterase 1 and ecdysteroid-regulated protein) resulted in a growth hormone disorder that prevented the shrimp from molting. Both proteomic KEGG pathway (e.g., "Glycolysis/gluconeogenesis" and "Glyoxylate and dicarboxylate metabolism") and metabolomic KEGG pathway (e.g., "Galactose metabolism" and "Biosynthesis of unsaturated fatty acids") data indicated that energy metabolism pathway was down-regulated in the hepatopancreas when infected by EHP. More importantly, the changes of hormone regulation and energy metabolism could provide much-needed insight into the underlying mechanisms of stunted growth in shrimp after EHP infection. Altogether, this study demonstrated that proteomics and metabolomics could provide an insightful view into the effects of microsporidial infection in the shrimp L. vannamei.

Hydroxymethylation of protein-encoding genes in the testes involved in precocious puberty of Eriocheir sinensis

To investigate the possible effects of epigenetic modification of testis protein-encoding genes on precocious puberty of Eriocheir sinensis, we used MeDIP-seq and hMeDIP-seq techniques to compare the methylation and hydroxymethylation of 263 E. sinensis protein-encoding genes known in the NCBI database in precocious testes with those in normally developing testes. The results showed that total methylation level of those genes was lower than their total hydroxymethylation level. Moreover, their total hydroxymethylation level in precocious testes was significantly lower than that in normal testes. In addition, no methylated genes had significant difference, but there were 37 different hydroxymethylated genes (DhMGs) in the precocious testes compared to the normal ones. Among the DhMGs, 21 were hypo-hydroxymethylated and 16 were hyper-hydroxymethylated. The hypo-hydroxymethylated DhMGs were associated with development, cell structural and cytoskeletal proteins, and response to stress. However, the hyper-hydroxymethylated DhMGs included immune-related genes, free radicals removement-related genes, protein folding-related genes, and so on. In addition, some DhMGs were hyper-hydroxymethylated while their homologous DhMGs were hypo-hydroxymethylated. The results of a qRT-PCR assay showed that the expression levels of 5 DhMGs randomly chosen presented a positive correlation with their hydroxymethylation levels. It can be seen that hydroxymethylation might regulate the expression of genes and be involved in precocious puberty to cause high mortality of crabs. Therefore, the hydroxymethylation level of DhMGs may be used as an evaluation index with economically meaningful growth and breeding traits.

JAK/STAT signalling regulates antimicrobial activities in Eriocheir sinensis

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signalling pathway plays a significant role in immune responses to pathogens. In invertebrates, three core components (Domeless, Hopscotch and STAT92E) of the JAK/STAT pathway were first identified in Drosophila melanogaster. In the present study, we report the cloning and characterisation of DOME, JAK and STAT from Eriocheir sinensis. EsDOME, EsJAK and EsSTAT are 1299, 1110 and 794 amino acid proteins encoded by 4200, 3333 and 2385 bp open reading frames, respectively. Bioinformatics analysis revealed that all three share specific domains with corresponding functions. Quantitative real-time PCR showed that all three components were highly expressed in various tissues including the gill, hepatopancreas and hemocytes. Moreover, EsDOME, EsJAK and EsSTAT were upregulated significantly in hemocytes after bacterial challenge. In addition, the JAK/STAT signalling pathway positively regulates antimicrobial peptide expression during the antibacterial immune response. Thus, the JAK/STAT pathway plays a critical role in bacterial immune responses in E. sinensis.

Transcriptomic analysis of immune-related genes in the lipopolysaccharide-stimulated hepatopancreas of the mudflat crab Helice tientsinensis

The mudflat crab Helice tientsinensis is one of the most economically important aquaculture species in China. Nevertheless, it is susceptible to various diseases caused by viruses, bacteria and rickettsia-like organisms. A better understanding of the immune system and genes related to the responses to bacterial and viral infection is required. Herein, the hepatopancreas transcriptome of H. tientsinensis was analyzed by comparing control and lipopolysaccharide (LPS)-stimulated RNA-Seq data, yielding 91,885,038 bp and 13.78 Gb of clean reads. Following assembly and annotation, 93,207 unigenes with an average length of 883 bp were identified, of which 31,674 and 13,700 were annotated in Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, respectively. Following LPS, 4845 differentially expressed genes (DEGs) were identified, of which 2491 and 2354 were up- and down-regulated, respectively. To further investigate immune-related DEGs, KEGG enrichment analysis identified immune response pathways, most notably the peroxisome and Toll-like receptor signaling pathways. Quantitative real time-PCR (qRT-PCR) confirmed the up-regulation of a random selection of DEGs. This systematic transcriptomic analysis of the innate immune pathway in H. tientsinensis expands our understanding of the immune system in crabs.

Immune function of a Rab-related protein by modulating the JAK-STAT signaling pathway in the silkworm, Bombyx mori

The Rab-family GTPases mainly regulate intracellular vesicle transport, and play important roles in the innate immune response in invertebrates. However, the function and signal transduction of Rab proteins in immune reactions remain unclear in silkworms. In this study, we analyzed a Rab-related protein of silkworm Bombyx mori (BmRABRP) by raising antibodies against its bacterially expressed recombinant form. Tissue distribution analysis showed that BmRABRP mRNA and protein were high expressed in the Malpighian tubule and fat body, respectively. However, among the different stages, only the fourth instar larvae and pupae showed significant BmRABRP levels. After challenge with four pathogenic microorganisms (Escherichia coli, BmNPV, Beauveria bassiana, Micrococcus luteus), the expression of BmRABRP mRNA in the fat body was significantly upregulated. In contrast, the BmRABRP protein was significantly upregulated after infection with BmNPV, while it was downregulated by E. coli, B. bassiana, and M. luteus. A specific dsRNA was used to explore the immune function and relationship between BmRABRP and the JAK-STAT signaling pathway. After BmRABRP gene interference, significant reduction in the number of nodules and increased mortality suggested that BmRABRP plays an important role in silkworm's response to bacterial challenge. In addition, four key genes (BmHOP, BmSTAT, BmSOCS2, and BmSOCS6) of the JAK-STAT signaling pathway showed significantly altered expressions after BmRABRP silencing. BmHOP and BmSOCS6 expressions were significantly decreased, while BmSTAT and BmSOCS2 were significantly upregulated. Our results suggested that BmRABRP is involved in the innate immune response against pathogenic microorganisms through the JAK-STAT signaling pathway in silkworm.

A novel C-type lectin is involved in the innate immunity of Macrobrachium nipponense

C-type lectins (CTLs) play important roles in invertebrate innate immunity by recognizing and eliminating pathogens. In the present study, a low-density lipoprotein receptor class A (LDLa) domain-containing CTL was identified from the oriental river prawn Macrobrachium nipponense, designated as MnCTLDcp1. The full-length cDNA of MnCTLDcp1 was composed of 1462 bp, with a 999-bp ORF encoding a 332-aa protein. An LDLa and a single C-type lectin-like domain (CTLD) were found. The mRNA transcripts of MnCTLDcp1 was expressed the highest in heart. After the prawns were challenged by Aeromonas hydrophila and Staphylococcus aureus, the expression level of MnCTLDcp1 in heart and hemocytes were all significantly up-regulated. Sugar binding assay revealed that the MnCTLDcp1 could bind to the glycoconjugates of bacteria surface, such as LPS, PGN and they can compete with bacterial as competitors. The recombinant MnCTLDcp1 agglutinates Gram-positive (S. aureus and Bacillus subtilis) and Gram-negative bacteria (A. hydrophila, Vibrio parahaemolyticus, Escherichia coli and Pseudomonas aeruginosa) in the presence of calcium and also could bind to these bacteria. These results clearly suggested that MnCTLDcp1 functions as a pattern-recognition receptor involved in the innate immunity of M. nipponense.

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.

A Rac1 GTPase is a critical factor in the immune response of shrimp (Litopenaeus vannamei) to Vibrio alginolyticus infection

The small GTPase Rac1 acts as a molecular switch for signal transduction that regulates various cellular functions. However, its functions in crustaceans remain unclear. In this study, a cDNA encoding a RAS GTPase (LvRac1) in the Pacific white shrimp (L. vannamei) was identified and characterized. A recombinant variant of this GTPase, rLvRac1, was expressed in the model organism P. pastoris and its expression was confirmed by mass spectrometry. Biochemical assays indicated that the recombinant protein retained GTPase activity and was expressed in all of the organism's tested tissues. Injection of the bacterium V. alginolyticus into L. vannamei induced hepatopancreatic upregulation of LvRac1 expression. Moreover, knocking down LvRac1 in vivo significantly reduced the expression of the L. vannamei p53 and Cu/Zn superoxide dismutase genes (Lvp53 and LvCu/Zn SOD, respectively) while increasing that of the galectin gene (Lvgal). Hemolymph samples from control and LvRac1-silenced L. vannamei individuals were analyzed by flow cytometry, revealing that the latter exhibited significantly reduced respiratory burst activity and total hemocyte counts. Cumulative mortality in shrimp lacking LvRac1 was significantly greater than in control groups following V. alginolyticus challenge. The silencing of LvRac1 by double-stranded RNA injection thus increased the V. alginolyticus challenge sensitivity of L. vannamei and weakened its bacterial clearance ability in vivo. Suppressing LvRac1 also promoted the upregulation of Lvp53, LvCu/ZnSOD, and Lvgal following V. alginolyticus injection. Taken together, these results suggest that LvRac1 is important in the innate immune response of shrimp to V. alginolyticus infection.

Diversification of the duplicated Rab1a genes in a hypoxia-tolerant fish, common carp (Cyprinus carpio)

Common carp is a widely cultivated fish with longer than 2,000 years domestication history, due to its strong environmental adaptabilities, especially hypoxia tolerance. The common carp genome has experienced a very recent whole genome duplication (WGD) event. Among a large number of highly similar duplicated genes, a pair of Ras-associated binding-GTPase 1a (Rab1a) genes were found fast diverging. Four analogous Rab1a genes were identified in the common carp genome. Comparisons of gene structures and sequences indicated Rab1a-1 and Rab1a-2 was a pair of fast diverging duplicates, while Rab1a-3 and Rab1a-4 was a pair of less diverged duplicates. All putative Rab1a proteins shared conserved GTPase domain, which enabled the proteins serve as molecular switches for vesicular trafficking. Rab1a-1 and Rab1a-2 proteins varied in their C-terminal sequences, which were generally considered to encode the membrane localization signals. Differential expression patterns were observed between Rab1a-1 and Rab1a-2 genes. In blood, muscle, spleen, and heart, the mRNA level of Rab1a-1 was higher than that of Rab1a-2. In liver and intestine, the mRNA level of Rab1a-2 was higher. Expression of Rab1a-1 and Rab1a-2 showed distinct hypoxia responses. Under severe hypoxia, Rab1a-1 expression was down-regulated in blood, while Rab1a-2 expression was up-regulated in liver. Compared with the less diverged Rab1a-3/4 gene pair, common carp Rab1a-1/2 gene pair exhibited strong characteristics of sub-functionalization, which might contribute to a sophisticated and efficient Ras-dependent regulating network for the hypoxia-tolerant fish.

Rab3 is involved in cellular immune responses of the cotton bollworm, Helicoverpa armigera

Rab3, a member of the Rab GTPase family, has been found to be involved in innate immunity. However, the precise function of this GTPase in innate immunity remains unknown. In this study, we identified a Rab3 gene (Ha-Rab3) from the cotton bollworm, Helicoverpa armigera and studied its roles in innate immune responses. Expression of Ha-Rab3 was upregulated in the hemocytes of H. armigera larvae after the injection of Escherichia coli or chromatography beads. The dsRNA-mediated knockdown of Ha-Rab3 gene in H. armigera larval hemocytes led to significant reduction in the phagocytosis and nodulation activities of hemocytes against E. coli, significant increase in the bacterial load in larval hemolymph, and significant reduction in the encapsulation activities of hemocytes toward invading chromatography beads. Furthermore, Ha-Rab3 knockdown significantly suppressed spreading of plasmatocytes. These results suggest that Ha-Rab3 plays important roles in H. armigera cellular immune responses, possibly by mediating spreading of hemocytes.

Identification and function of 11 Rab GTPases in giant freshwater prawn Macrobrachium rosenbergii

Rab GTPases, members of the Ras-like GTPase superfamily, are central elements in endocytic membrane trafficking. However, little is known of the Rab genes in the giant freshwater prawn Macrobrachium rosenbergii. In this study, 11 Rab genes were identified from M. rosenbergii. All MrRabs have a RAB domain. Phylogenetic analysis showed that these 11 MrRabs were divided into different groups. The MrRab genes were ubiquitously expressed in heart, hemocytes, hepatopancreas, gills, stomach, and intestines. Real-time polymerase chain reaction revealed that the MrRab genes were significantly upregulated by white spot syndrome virus (WSSV) in the prawns, indicating that MrRabs might play an important role in innate immune response against WSSV. Moreover, after challenge with Vibrio parahaemolyticus, the expression levels of all MrRabs in the hepatopancreas were also upregulated, which might indicated the involvement of MrRabs in prawns antibacterial immunity. In all, these preliminary results showed that MrRabs were involved in innate immunity of M. rosenbergii.