Molecular characteristics and immune function of ubiquitin C-terminal hydrolase-L3 in Macrobrachium nipponense.

Ubiquitin C-terminal hydrolase-L3 (UCHL3) is a deubiquitinating enzyme involved in the repair mechanism of homologous recombinations of DNA double strand breaks (DBS). However, the role of UCHL3 in crustacean immune regulation has not been studied. In this experiment, we cloned and analyzed the expression profile of the UCHL3 gene from Macrobrachium nipponense (MnUCHL3). The obtained full-length cDNA of the MnUCHL3 transcript was 1192 bp, and it had a 687 bp open reading frame encoding a 228 amino acid protein, and the structure of UCHL3 is highly similar to that of other invertebrates. Real-time PCR results indicated that MnUCHL3 was expressed in all detected tissues, with the highest expression levels in the hepatopancreas, and the expression of MnUCHL3 in the gill and hepatopancreas was downregulated to different degrees within 48 h after the infection of viruses and bacteria. Furthermore, knockdown of MnUCHL3 expression by double-stranded RNA (dsRNA) injection in Aeromonas hydrophila-infected prawns increased prawn mortality and bacterial growth. In addition, overexpression of MnUCHL3 in HEK293T cells in vitro suggested that MnUCHL3 could activate the NF-κB signal path and the expression levels of NF-κB signaling cascade members and AMPs, exhibiting remarkable downregulation in the MnUCHL3-silenced group. The above experimental conclusions revealed that UCHL3 gene might be involved in the innate immune response to bacterial infection by regulating the synthesis of a series of AMPs, and these results might provide new insights into UCHL3 in invertebrates.

N-acetyl-ß-d-glucosaminidase activity in Palaemon serratus - Methodological optimisation and intrinsic variability.

Chitinolytic enzymes fulfil a key role in the moulting process of crustaceans, in degrading the endocuticle during apolysis. Measuring the enzyme activity is an interesting manner to monitor the moult process at sub-individual level, complementary to the classical observation of the integument morphogenesis, ecdysis success, or moult cycle duration. The present study aimed to optimise the methodology of using N-acetyl-ß-D-glucosaminidase (NAGase) activity to monitor moulting in the marine prawn Palaemon serratus, and to compare NAGase activity levels along the moult cycle of both male and female specimens. First, to optimise protocols for five different organs, different reaction medium compositions were tested, considering the type buffer, concentration of the substrate, and the load in enzymatic extract. Second, levels of NAGase activity were closely monitored during eight moulting stages in male prawns. Variations in NAGase activity were observed during the moult cycle, with an increase in activity in the late premoult phase of approximately 2.4-fold the level of the intermoult phase. This response profile was observed for each tested organ. The levels of NAGase activity of male and female specimens were compared during three stages of the premoult phase. The patterns observed for both sexes were similar for all the tested organs.

Silencing of prophenoloxidase (proPO) gene in freshwater prawn, Macrobrachium rosenbergii, makes them susceptible to white spot syndrome virus (WSSV).

Prophenoloxidase (proPO) is very important to protect the invertebrates from microbial infections. Our previous studies revealed that proPO was up-regulated in WSSV-injected Macrobrachium rosenbergii and is responsible for protecting M. rosenbergii from WSSV. In order to prove this mechanism, an attempt was made in the present study to silence the proPO gene in freshwater prawn by injection of dsRNA-proPO followed by WSSV challenge. Two partial fragments of proPO with the size of 251 and 331 bp were used to synthesize dsRNA using LITMUS38i vector and E. coli. The bacterially synthesized dsRNA-proPO was used to silence proPO gene to determine its involvement in developing resistance in prawn against WSSV. In proPO gene-silenced prawn, 100% mortality was observed after WSSV challenge whereas no mortality was observed in prawn injected with WSSV alone. The WSSV infection in gene-silenced prawn was confirmed by PCR, and its propagation was quantified by ELISA and real-time PCR at different time intervals. Real-time PCR assay revealed a significant reduction in the expression of proPO gene in WSSV-challenged proPO-silenced prawn when compared to normal prawn. Level of proPO was reduced significantly in the haemolymph of proPO-silenced prawn when compared to prawn injected with PBS.

Antioxidative enzyme activities in the Rhodeinae sinensis Gunther and Macrobrachium nipponense and multi-endpoint assessment under tonalide exposure.

Tonalide or acetyl hexamethyl tetralin (AHTN) is used as a fragrance additive in various household products. Recently, AHTN has drawn attention owing to its negative health effects on aquatic organisms. Data on AHTN toxicity toward aquatic species are limited. Therefore, this study tested the oxidative stress induced by AHTN exposure on the Rhodeinae sinensis Gunther and Macrobrachium nipponense. In this study, malonaldehyde (MDA) content and the activities of acetyl cholinesterase (AchE), superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT) in R. sinensis Gunther were tested after 30 days of exposure to 30.093, 34.005, 38.426, 43.421, 49.067, 55.444, 62.652, 70.800, and 80.000 µg/L AHTN, respectively. The MDA, AchE, SOD, GST and CAT in M. nipponense were tested after 40 days of exposure to 60.000, 72.000, 86.400, 103.680, 124.416, 149.299, 179.159, 214.991, and 257.989 µg/L AHTN, respectively. In addition, an integrated biomarker response (IBR) index was utilised to evaluate the integrated toxic effects of AHTN on R. sinensis Gunther and M. nipponense. Finally, the predicted no-effect concentrations (PNECs) of AHTN, based on reproduction, biochemistry, survival, chronic toxicity, and acute toxicity endpoints were derived. The results indicated that low concentrations of AHTN can induce significant changes of oxidative stress biomarkers. The no observed effect concentrations (NOECs) of SOD, GST, AchE, CAT, and MDA were 103.680, 72.000, <60.000, 72.000, and <60.000 µg/L for R. sinensis Gunther and 38.426, 43.421, 30.093, 30.093, and 38.426 µg/L for M. nipponense, respectively. The IBR calculation results showed that 149.299 µg/L AHTN caused the highest toxic effect on R. sinensis Gunther after 30 days of exposure, whereas 70.797 µg/L AHTN caused the greatest damage to M. nipponense after 40 days of exposure. The PNECs of AHTN based on the non-traditional endpoints of biochemistry and reproduction were 0.00145 µg/L and 0.000395 µg/L, respectively, which were significantly lower than the PNEC of 2.636 µg/L for traditional endpoint survival. Therefore, the protection of aquatic organisms based on non-traditional toxicity endpoints should be considered in ecological risk assessment.

Molecular cloning, expression, and in situ hybridization analysis of MnGPx-3 and MnGPx-4 from oriental river prawn, Macrobrachium nipponense, in response to hypoxia and reoxygenation.

Glutathione peroxidase (GPx) has been the focus of increased research because of its important role as an antioxidant and in reactive oxygen species (ROS) induced damage repair. Studies on GPxs have relevance with Macrobrachium nipponense because it has poor tolerance to hypoxia in Macrobrachium nipponense. The two subunits named as MnGPx-3 and MnGPx-4 according to the glutathione peroxidase nomenclature system. Both full-length cDNAs were cloned from the hepatopancreas. In this study, we analyzed the expression of two GPxs in Macrobrachium nipponense in response to changes in environmental oxygen. Expression levels of MnGPx-3 and MnGPx-4 indicated that both have strong responses to hypoxia. In situ hybridization showed that MnGPx-3 and MnGPx-4 were located in secretory and storage cells in hepatopancreas. These results suggest that GPx gene is expressed and released by secretory cells and released response to hypoxia. In the gill tissue, however, GPxs are located in blood cells, suggesting that they perform different functions in different tissues or organs. The results of in situ hybridization were consistent with those of quantitative Real-time PCR. This study provides a basis for understanding the oxidative stress response in M. nipponense under hypoxia.

CRISPR/Cas9-mediated deletion of one carotenoid isomerooxygenase gene (EcNinaB-X1) from Exopalaemon carinicauda.

During the immune defense reaction of invertebrate, a plenty of reactive oxygen species (ROS) could be induced to product. Though ROS can kill foreign invaders, the accumulation of these reactive molecules in animals will cause serious cell damage. Carotenoids could function as scavengers of oxygen radicals. In this research, cDNA and genomic DNA of one carotenoid isomerooxygenase gene (named EcNinaB-X1) were cloned from Exopalaemon carinicauda. EcNinaB-X1 gene was composed of 12 exons and 11 introns. EcNinaB-X1 knock-out (KO) prawns were produced via CRISPR/Cas9 technology and the change of their phenotypes were analyzed. Of the 400 injected one-cell stage embryos with cas9 mRNA and one sgRNA targeting the first exon of EcNinaB-X1 gene, 26 EcNinaB-X1-KO prawns were generated and the mutant rate reached 6.5% after embryo injection. The EcNinaB-X1-KO prawns had significant lower mortality than those in wild-type group when the prawns were challenged with Vibrio parahaemolyticus or Aeromonas hydrophila. In conclusion, we first demonstrate the function of the carotenoid isomerooxygenase gene in immune defense of E. carinicauda by performing directed, heritable gene mutagenesis.

Effects of ammonia-N exposure on the growth, metabolizing enzymes, and metabolome of Macrobrachium rosenbergii.

Ammonia nitrogen elevated is one of the commonest problem in the aquatic system, which caused a great threat to the survival and growth of prawn. However, little is know about the ammonia metabolism and detoxification strategy of prawn. In this study, the effects of ammonia-N (0, 0.108, 0.216, 0.324, or 0.54 mg L-1) on growth and metabolizing enzymes in hepatopancreas of Macrobrachium rosenbergii, including glutamine synthetase (GS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and glutamate dehydrogenase (GDH), were investigated. The metabolome of its muscle was also analyzed after exposure to ammonia-N (0, 0.108, 0.324, or 0.54 mg L-1) for 20 days. The survival rate of M. rosenbergii decreased significantly after treatment with 0.54 mg L-1 ammonia-N compared with that in the other groups. However, ammonia-N had no significant effect on the growth of the river prawn after exposure for 20 days. GS activity increased significantly after exposure to 0.108 mg L-1 ammonia-N compared with the control and other ammonia-N-treated groups. Hepatopancreatic GDH activity was lower in the prawns treated with 0.216, 0.324, or 0.54 mg L-1 ammonia-N than in the control by 34.70%, 38.80%, or 41.94%, respectively. Ammonia-N had no significant effect on hepatopancreatic AST or ALT activity. Urea nitrogen was higher in the prawns treated with 0.216 mg L-1 ammonia-N than in the control or those treated with 0.54 mg L-1 ammonia-N. Ammonia-N had significant effects on the lipid, carbohydrate. and protein metabolism of M. rosenbergii, including purine metabolism, amino sugar and nucleotide sugar metabolism, α-linolenic acid metabolism, arginine and proline metabolism, glutathione metabolism, and phosphonate and phosphate metabolism, and on the terpenoid biosynthesis, lysine degradation, and lysine biosynthesis pathways. High concentrations of ammonia-N stress increased the content of glutamate and arginine, which may participate in the urea cycle, which synthesizes glutamine or urea to eliminate ammonia toxicity.

Screening for Dmrt genes from embryo to mature Macrobrachium rosenbergii prawns.

The doublesex and mab-3 related transcription factor (Dmrt) gene family is known to be related to the sexual regulators doublesex of arthropods and mab-3 of annelids and to hold highly conserved functions in sexual determination and differentiation across phyla. Here, we report a study of the Dmrt gene family in the freshwater prawn Macrobrachium rosenbergii, a crustacean whose sexual differentiation has been widely researched. A wide transcriptomic screen, from the embryo to the adult M. rosenbergii, identified five novel Dmrt genes (MroDmrts) and confirmed two known MroDmrts. The seven MroDmrts encode proteins of 275-855 amino acids; each protein contained at least one conserved DNA-binding DM domain, which is typical of Dmrt proteins, and five proteins contained 1-4 transactivation domains (TADs). Importantly, in the embryonic, larval and post-larval stages, MroDmrt genes exhibited time-dependent expression patterns rather than sex-specific expression. In-silico screening of the expression of the MroDmrt genes in adult males revealed the enrichment of MroiDmrt1b and MroiDmrt1c in the androgenic gland (AG) as compared to the eyestalks. In vivo silencing of the androgenic gland insulin-like (IAG) encoding gene significantly decreased the expression of the above two Dmrt genes, while not affecting the expression of control genes, thereby suggesting the possible role of these two genes in the IAG-switch and in sex-differentiation processes.

Characterization, functional analysis, and expression levels of three carbonic anhydrases in response to pH and saline-alkaline stresses in the ridgetail white prawn Exopalaemon carinicauda.

Carbonate alkalinity, salinity, and pH are three important stress factors for aquatic animals in saline-alkaline water. Carbonic anhydrases (CAs) catalyze the reversible reaction of CO2 reported to play an important role in the acid-base regulation in vertebrates. To explore the molecular mechanism of CAs efficacy in shrimp after their transfer into saline-alkaline water, the cDNAs of three CAs (EcCAc, EcCAg, and EcCAb) were cloned from Exopalaemon carinicauda. Sequence analysis showed that EcCAc and EcCAg both possessed a conserved α-CA domain and a proton acceptor site, and EcCAb contained a Pro-CA domain. Tissue expression analysis demonstrated that EcCAc and EcCAg were most abundantly in gills, and EcCAb was highly expressed in muscle. The cumulative mortalities remained below 25% under exposure to pH (pH 6 and pH 9), low salinity (5 ppt), or high carbonate alkalinity (5 and 10 mmol/L) after 72 h of exposure. However, mortalities increased up to 70% under extreme saline-alkaline stress (salinity 5 ppt, carbonate alkalinity 10 mmol/L, and pH 9) after 14 days of exposure. The EcCAc and EcCAg expressions in gills were significantly upregulated during the early period of pH and saline-alkaline stresses, while the EcCAb expressions showed no regular or large changes. The two-way ANOVA found significant interactions between salinity and carbonate alkalinity observed in EcCAc, EcCAg, and EcCAb expressions (p < 0.05). Furthermore, an RNA interference experiment resulted in increased mortality of EcCAc- and EcCAg-silenced prawns under saline-alkaline stress. EcCAc knockdown reduced expressions of Na+/H+ exchanger (EcNHE) and sodium bicarbonate cotransporter (EcNBC), and EcCAg knockdown reduced EcCAc, EcNHE, EcNBC, and V-type H+-ATPase (EcVTP) expressions. These results suggest EcCAc and EcCAg as important modulators in response to pH and saline-alkaline stresses in E. carinicauda.

Kinetic characterization of the gill (Na+, K+)-ATPase in a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).

We provide a kinetic characterization of (Na+, K+)-ATPase activity in a posterior gill microsomal fraction from a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum. Sucrose density gradient centrifugation reveals two distinct membrane fractions showing considerable (Na+, K+)ATP-ase activity, but also containing other microsomal ATPases. Only a single immune-reactive (Na+, K+)-ATPase with Mr of ≈110 kDa is present that hydrolyzes ATP with VM = 130.3 ±â€¯4.8 nmol Pi min-1 mg protein-1 and K0.5 = 0.065 ±â€¯0.00162 mmol L-1, exhibiting site-site interactions. Stimulation by Na+ (VM = 127.5 ±â€¯5.3 nmol Pi min-1 mg protein-1, K0.5 = 5.3 ±â€¯0.42 mmol L-1), Mg2+ (VM = 130.6 ±â€¯6.8 nmol Pi min-1 mg protein-1, K0.5 = 0.33 ±â€¯0.042 mmol L-1), K+ (VM = 126.7 ±â€¯7.7 nmol Pi min-1 mg protein-1, K0.5 = 0.65 ±â€¯0.0079 mmol L-1) and NH4+ (VM = 134.5 ±â€¯8.6 nmol Pi min-1 mg protein-1, K0.5 = 1.28 ±â€¯0.44 mmol L-1) also obeys cooperative kinetics. Ouabain (KI = 0.18 ±â€¯0.058 mmol L-1) inhibits total ATPase activity by ≈70%. This study reveals considerable differences in the kinetic characteristics of the gill (Na+, K+)-ATPase in a hololimnetic population that appear to result from the adaptation of diadromous Macrobrachium amazonicum populations to different limnic habitats.

Molecular Cloning and Expression Analysis of Lactate Dehydrogenase from the Oriental River Prawn Macrobrachium nipponense in Response to Hypoxia.

Metabolic adaption to hypoxic stress in crustaceans implies a shift from aerobic to anaerobic metabolism. Lactate dehydrogenase (LDH) is a key enzyme in glycolysis in prawns. However, very little is known about the role of LDH in hypoxia inducible factor (HIF) pathways of prawns. In this study, full-length cDNA of LDH (MnLDH) was obtained from the oriental river prawn Macrobrachium nipponense, and was characterized. The full-length cDNA is 2267-bp with an open reading frame of 999 bp coding for a protein of 333 amino acids with conserved domains important for function and regulation. Phylogenetic analysis showed that MnLDH is close to LDHs from other invertebrates. Quantitative real-time PCR revealed that MnLDH is expressed in various tissues with the highest expression level in muscle. MnLDH mRNA transcript and protein abundance in muscle, but not in hepatopancreas, were induced by hypoxia. Silencing of hypoxia-inducible factor 1 (HIF-1) α or HIF-1ß subunits blocked the hypoxia-dependent increase of LDH expression and enzyme activity in muscle. A series of MnLDH promoter sequences, especially the full-length promoter, generated an increase in luciferase expression relative to promoterless vector; furthermore, the expression of luciferase was induced by hypoxia. These results demonstrate that MnLDH is probably involved a HIF-1-dependent pathway during hypoxia in the highly active metabolism of muscle.

Effects of Cu2+ on alkaline phosphatase from Macrobrachium rosenbergii.

To gain insight into the effect of Cu2+ on the activity and structure of alkaline phosphatase (ALP) from Macrobrachium rosenbergii, the enzyme was purified using ammonium sulfate fractionation, Sephacryl S-200, and DEAE anion exchange chromatography. We studied Cu2+-mediated inhibition and aggregation of ALP, and found that Cu2+ significantly inactivated ALP activity with an IC50 of 1.47 ±â€¯0.02 mM. We further revealed that Cu2+ reversibly inhibited ALP in a mixed-type manner with Ki = 0.41 ±â€¯0.02 mM. Time-interval kinetics showed that the inhibition followed first-order reaction kinetics. This process was associated with conformational changes and significant transient free-energy change. Spectrofluorometry results showed that Cu2+ induced ALP tertiary structural changes, including the exposure of hydrophobic surfaces that directly induced ALP aggregation. The results provide new information regarding ALP from M. rosenbergii.

Bioinformatics characterization of a cathepsin B transcript from the giant river prawn, Macrobrachium rosenbergii: Homology modeling and expression analysis after Aeromonas hydrophila infection.

Cathepsin B is a lysosomal proteolytic enzyme that has been suggested to play a role in pathological processes of immune system. In this study, the full-length cDNA sequence of cathepsin B transcript in the giant river prawn Macrobrachium rosenbergii (MrCTSB) was obtained from 454 pyrosequencing of cDNAs from hepatopancreas and muscle. It was 1158 bp in length, containing an open reading frame (ORF) of 987 bp corresponding to 328 amino acids. The predicted molecular mass and pI of MrCTSB protein was 36.04 kDa and 4.73. The major characteristics of MrCTSB protein consisted of a propeptide of C1 peptidase family at the N-terminus and a cysteine protease (Pept_C1) domain at the C-terminus. The 3-dimentional structure of MrCTSB was constructed by computer-assisted homology modeling. The folding of MrCTSB was highly conserved to human CTSB structure and the modeled MrCTSB displayed characteristics of cysteine proteinases superfamily. The docking study was performed to investigate binding interactions between known inhibitors against MrCTSB. Known inhibitors were oriented in the groove of catalytic site cleft. They bound to subsites from S2, S1, S1', and S2', respectively, with key residues in each subsite. Challenge of juvenile prawns with Aeromonas hydrophila revealed that the MrCTSB transcript in hepatopancreas significantly increased at 60-96 h post injection (hpi). This suggested that MrCTSB may play roles in innate immunity of M. rosenbergii. Our results provide useful information for a more comprehensive study in immune-related functions of MrCTSB.

Examining heat treatment for stabilization of the lipidome.

AIM: To confidently determine lipid-based biomarkers, it is important to minimize variation introduced during preanalytical steps. We evaluated reducing variation associated with lipid measurements in invertebrate sentinel species using a state-of-the-art heat treatment technique. MATERIALS AND METHODS: Earthworms (Eisenia fetida), house crickets (Acheta domestica) and ghost shrimp (Palaemonetes paludosus) were euthanized either by flash freezing or heat treatment. For both experiments, samples were either immediately extracted after removal from -80°C storage or incubated on ice for one hour prior to sample weighing and extraction. Lipidomics was performed on resulting extracts using liquid chromatography high resolution tandem mass spectrometry. LipidMatch and LipidSearch were used for lipid identification. RESULTS: Lipid enzymatic products (e.g., phosphatidylmethanols, diglycerides, lysoglycerophospholipids and ether-linked/oxidized lysoglycerophospholipids), were in higher concentrations in flash-frozen samples, when compared with heat-treated samples. Results suggest that heat treatment reduces phospholipase A and phospholipase D activity. CONCLUSION: Heat treatment reduced enzymatic products and increased precursors of these enzymatic products. We believe heat treatment warrants a closer interrogation for improving the robustness of lipid biomarker research, especially in tissue samples, where enzyme stabilizers are difficult to apply, and for use in field studies, where the stabilization of the collected sample is critical.

Acidic electrolysed water delays browning by destroying conformation of polyphenoloxidase.

BACKGROUND: Browning frequently occurs at fruits, vegetables and aquatic products during storage, and it drastically reduces the consumer's acceptability, with considerable financial loss. The objective of this paper was to investigate the effects of acidic electrolysed water (AEW) technology on polyphenoloxidase (PPO), which is an essential enzyme for browning. RESULTS: AEW ice exhibited a good ability in delaying browning in shrimp. Kinetic study revealed that AEW exhibited the mixed type inhibition of PPO with a Ki value of 1.96 mmol L-1 . Moreover, both the circular dichroism spectrum and Fourier transform infrared spectroscopy analyses revealed that the α-helix in PPO decreased whereas random coil increased which indicates that PPO conformation was destroyed. CONCLUSION: Thus, this paper may provide a deeper understanding of the application of AEW technology for preventing browning in the food industry. © 2017 Society of Chemical Industry.

Effect of Dietary Supplementation of Novel Probiotic Bacteria Bacillus vireti 01 on Antioxidant Defence System of Freshwater Prawn Challenged with Pseudomonas aeruginosa.

The aim of the present work was to isolate probiotic bacteria from the intestinal tract of healthy freshwater prawn Macrobrachium rosenbergii and to examine the effect of the isolated probiotic Bacillus vireti 01 in controlling Pseudomonas aeruginosa infection. This is probably the first report on the isolation of probiotic B. vireti 01 from the intestine of M. rosenbergii. The compounds present in B. vireti 01 were identified using GC-MS analysis. The effect of B. vireti 01-incorporated diet on survival and antioxidant enzymes was studied in M. rosenbergii for 2 weeks. Decreased mortality was observed in M. rosenbergii which were administered with the probiotic diet compared to control diet. The antioxidant defence enzymes activities such as SOD, catalase and GSH were analysed in various organs of M. rosenbergii probiotic-treated and control groups. Antioxidant enzyme activities were considerably lowered (p < 0.01) in the muscles, hepatopancreas and gills of prawns infected by P. aeruginosa when compared to that of prawns fed with the probiotic-supplemented diet. The histopathological results suggest that the hepatopancreas, gills and muscles infected with P. aeruginosa were altered structurally. The result of the present work demonstrates that the probiotic B. vireti 01 could be used as a substitute to antibiotics for treating P. aeruginosa infection in prawns.

Bactericidal and fungistatic activity of peptide derived from GH18 domain of prawn chitinase 3 and its immunological functions during biological stress.

Chitinases play a vital role during the pathogenic invasion and immunosuppression in various organisms including invertebrates and vertebrates. In this study, we have investigated the participation of MrChit-3 (Macrobrachium rosenbergii Chitinase-3) during host-pathogenic interaction in freshwater prawn, M. rosenbergii. Quantitative real-time PCR analysis showed that the expression of MrChit-3 was up-regulated during bacterial, viral and laminarin challenge. Moreover, to understand the antimicrobial role of the GH18 domain, a putative membrane-targeting antimicrobial peptide (MrVG) was identified from the GH18 domain region of the protein and it was chemically synthesized. Physico-chemical features of the GH18 derived antimicrobial peptide (AMP) was assessed by various in silico tools and the antimicrobial property of the peptide was confirmed from in vitro studies. The membrane targeting mechanism of the peptide was determined by flow cytometry (FACS) and scanning electron microscope (SEM) analysis. Interestingly, the peptide was able to inhibit the growth of a chitinolytic fungal pathogen, Aspergillus niger, which was isolated from the shells of M. rosenbergii. The toxicity studies such as hemolysis activity on human blood erythrocytes and cell viability assay with primary kidney cells, HEK293 of MrVG revealed that the peptide was not involved in inducing any toxicity.

Effect of stocking density on growth performance, digestive enzyme activities, and nonspecific immune parameters of Palaemonetes sinensis.

Palaemonetes sinensis is a new breed of shrimp with great potential for aquaculture, which has been confirmed in our previous production tests. However, there are limited reports about this species and its biological information is scarce. This study describes the effect of stocking density on the growth, digestive enzyme activities, and nonspecific immunity of P. sinensis with an initial average body weight was 0.25 ± 0.02 g. Groups of shrimps were reared at four different initial densities (2.5, 5, 10, and 20 individuals·L-1). After 30 days of culture, the results indicated that the final body weight, weight gain, and specific growth rate were higher in shrimps grown in groups of 10 individuals·L-1 than other groups, but the survival rates of these shrimp were significantly lower than those reared in group of 2.5 or 5 individuals·L-1. The trypsin, amylase, and lipase activities of shrimp significantly decreased with increase in stocking density. Nonspecific immune indicators decreased significantly with increase in density, but there were no significant differences between the 2.5 and 5 individuals·L-1 groups in terms of the total haemocyte count (THC), phenoloxidase activity (PO), lysozyme (LZM), catalase (CAT), and superoxide dismutase (SOD). These results suggest that increasing the stocking density from 2.5 to 5 individuals·L-1 did not affect any of the detected indicators of P. sinensis, but there are shelter in farming mode is better for culture of P. sinensis up to 10 individuals L-1.

Enzymatic characterization and functional analysis of EcChi3C from ridgetail white prawn Exopalaemon carinicauda.

Chitinase belongs to the glycosyl hydrolases family 18 and plays key role in the development and pathogen resistance of crustaceans. In this study, the enzymatic characterization of chitinase 3C (EcChi3C) of Exopalaemon carinicauda was analyzed. In addition, we analyzed the expression profiles of EcChi3C at different tissues and different molting stages. In the all tested tissues, it was predominantly expressed in hepatopancreas, and then stomach, but poor in other tissues. In all tested molting periods, it was mainly expressed in intermolt and molting stages, but poor in other stages. The results of molting, mortality and the uropod ultrastructure of prawns after being injected with EcChi3C dsRNA were in accordance with those of the control group. In addition, there is no difference for endopodite morphology between the survival and dead individuals in experimental group. After being challenged with bacteria, the expression of EcChi3C was up-regulated significantly at 12 h and followed with a comeback at 96 h. These results suggest that EcChi3C is an important immune related gene but not a necessary gene in the molting process of E. carinicauda.

Molecular Cloning and Functional Characterization of a Hexokinase from the Oriental River Prawn Macrobrachium nipponense in Response to Hypoxia.

Metabolic adjustment to hypoxia in Macrobrachium nipponense (oriental river prawn) implies a shift to anaerobic metabolism. Hexokinase (HK) is a key glycolytic enzyme in prawns. The involvement of HK in the hypoxia inducible factors (HIFs) pathway is unclear in prawns. In this study, the full-length cDNA for HK (MnHK) was obtained from M. nipponense, and its properties were characterized. The full-length cDNA (2385 bp) with an open reading frame of 1350 bp, encoded a 450-amino acid protein. MnHK contained highly conserved amino acids in the glucose, glucose-6-phosphate, ATP, and Mg+2 binding sites. Quantitative real-time reverse transcription PCR assays revealed the tissue-specific expression pattern of MnHK, with abundant expression in the muscle, and gills. Kinetic studies validated the hexokinase activity of recombinant HK. Silencing of HIF-1α or HIF-1ß subunit genes blocked the induction of HK and its enzyme activities during hypoxia in muscles. The results suggested that MnHK is a key factor that increases the anaerobic rate, and is probably involved in the HIF-1 pathway related to highly active metabolism during hypoxia.