Identification and cloning of a selenium-dependent glutathione peroxidase from tiger shrimp, Penaeus monodon, and its transcription following pathogen infection and related to the molt stages

Assessment of fish protein hydrolysate as a substitute for fish meal in white shrimp diets: Impact on growth, immune response, and resistance against Vibrio parahaemolyticus infection

This study investigated the effects of fish protein hydrolysate derived from barramundi on growth performance, muscle composition, immune response, disease resistance, histology and gene expression in white shrimp (Penaeus vannamei). In vitro studies demonstrated FPH enhanced mRNA expressions of key immune-related genes and stimulated reactive oxygen species (ROS) production and phagocytic activity in shrimp hemocytes. To evaluate the effects of substituting fish meal with FPH in vivo, four isoproteic (43 %), isolipidic (6 %), and isoenergetic diets (489 kcal/100 g) were formulated with fish meal substitution levels of 0 % (control), 30 % (FPH30), 65 % (FPH65), and 100 % (FPH100). After 8-week feeding, the growth performance of FPH65 and FPH100 were significantly lower than that of control and FPH30 (p < 0.05). Similarly, the midgut histological examination revealed the wall thickness and villi height of FPH100 were significantly lower than those of control (p < 0.05). The shrimps were received the challenge of AHPND + Vibrio parahaemolyticus at week 4 and 8. All FPH-fed groups significantly enhanced resistance against Vibrio parahaemolyticus at week 4 (p < 0.05). However, this protective effect diminished after long-period feeding. No significant difference of survival rate was observed among all groups at week 8 (p > 0.05). The expressions of immune-related genes were analyzed at week 4 before and after challenge. In control group, V. parahaemolyticus significantly elevated SOD in hepatopancreas and Muc 19, trypsin, Midline-fas, and GPx in foregut (p < 0.05). Moreover, hepatopancreatic SOD of FPH65 and FPH100 were significantly higher than that of control before challenge (p < 0.05). Immune parameters were measured at week 8. Compared with control, the phagocytic index of FPH 30 was significantly higher (p < 0.05). However, dietary FPH did not alter ROS production, phenoloxidase activity, phagocytic rate, and total hemocyte count (p > 0.05). These findings suggest that FPH30 holds promise as a feed without adverse impacts on growth performance while enhancing the immunological response of white shrimp.

Comparative Transcriptome Analysis of the Hepatopancreas from Macrobrachium rosenbergii Exposed to the Heavy Metal Copper

The contamination of aquatic ecosystems by the heavy metal copper (Cu) is an important environmental issue and poses significant risks to the physiological functions of aquatic organisms. Macrobrachium rosenbergii is one of the most important freshwater-cultured prawns in the world. The hepatopancreas of crustaceans is a key organ for immune defense, heavy metal accumulation, and detoxification, playing a pivotal role in toxicological research. However, research on the molecular response of the hepatopancreas in M. rosenbergii to Cu exposure is still lacking. In this study, the transcriptomic response in the hepatopancreas of M. rosenbergii was studied after Cu exposure for 3 and 48 h. Compared with the control group, 11,164 (7288 up-regulated and 3876 down-regulated genes) and 10,937 (6630 up-regulated and 4307 down-regulated genes) differentially expressed genes (DEGs) were identified after 3 and 48 h exposure, respectively. Most of these DEGs were up-regulated, implying that gene expressions were largely induced by Cu. Functional enrichment analysis of these DEGs revealed that immunity, copper homeostasis, detoxification, DNA damage repair, and apoptosis were differentially regulated by Cu. Seven genes involved in immunity, detoxification, and metabolism were selected for validation by qRT-PCR, and the results confirmed the reliability of RNA-Seq. All these findings suggest that M. rosenbergii attempts to resist the toxicity of Cu by up-regulating the expression of genes related to immunity, metabolism, and detoxification. However, with the excessive accumulation of reactive oxygen species (ROS), the antioxidant enzyme system was destroyed. As a result, DNA damage repair and the cellular stress response were inhibited, thereby exacerbating cell damage. In order to maintain the normal function of the hepatopancreas, M. rosenbergii removes damaged cells by activating the apoptosis mechanism. Our study not only facilitates an understanding of the molecular response mechanisms of M. rosenbergii underlying Cu toxicity effects but also helps us to identify potential biomarkers associated with the stress response in other crustaceans.

Immune regulation mediated by JAK/STAT signaling pathway in hemocytes of Pacific white shrimps, Litopenaeus vannamei stimulated by lipopolysaccharide

To understand the regulatory mechanism of Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT) signaling pathway on the immune system of the Pacific white shrimp, Litopenaeus vannamei, RNA interference technique was used to investigate the effects of JAK/STAT signaling pathway on the immune response of hemocyte in Litopenaeus vannamei stimulated by lipopolysaccharide (LPS). The results showed that 1) after 6 h of LPS stimulation, the expression levels of immune genes in hemocyte were significantly up-regulated (P < 0.05), the immune defense ability (hemocyte number, phagocytosis rate, hemagglutination activity, bacteriolytic activity, antibacterial activity, prophenoloxidase system activity) and the hemocyte antioxidant ability were significantly higher than the control group, especially at 12 h. 2) After 48 h of STAT gene interference, the expression levels of immune genes in hemocytes were significantly down-regulated, and the immune defense ability (hemocyte count, phagocytosis rate, plasma agglutination activity, lysozyme activity, antibacterial activity, proPO system activity) and the antioxidant ability were reduced and significantly lower than control. Concurrently, after LPS stimulation, the immune indexes were significantly up-regulated at 12 h to the maximum but was still lower the undisturbed LPS group. These results indicate that JAK/STAT signaling pathway is involved in the immune regulation mechanism of L. vannamei against LPS stimulation through positive regulation of cellular immune and humoral immune. These results provide a basis for further research on the role and status of JAK/STAT signaling pathway in the immune defense of crustaceans.

c-Jun N-terminal kinase (JNK) in Procambarus clarkii: Molecular characterization and involvement in oxidative stress-induced apoptosis during molting cycle

The present study was conducted to characterize the full-length cDNA of c-Jun N-terminal kinase (JNK) in Procambarus clarkii (Pcjnk) and evaluate its potential function under different molt cycle. The full-length cDNA of Pcjnk covered 2937 bp with an open reading frame of 1320 bp, encoding 439 amino acids. A typical conserved TPY motif (118Thr-Pro-120Tyr) was found in Pcjnk. Quantitative real-time PCR (qRT-PCR) analysis revealed a constitutive expression of Pcjnk in the tested tissue, with the highest expression occurring in the hepatopancreas. Additionally, the present study initially revealed that relative mRNA expression of Pcjnk and apoptosis level were significantly higher in the premolt stage (D1/D2 and D3/D4 stage) as compared to other molt stages. In contrast to the levels of superoxide dismutase (SOD) and malondialdehyde (MDA), catalase (CAT) and glutathione peroxidase (GPX) level decreased significantly from the intermolt stage (C stage) to the premolt stage (D1/D2 and D3/D4 stage), then increased from the premolt stage to the postmolt stage (A and B stage). The results obtained in the present study indicated that molt could cause apoptosis induced by oxidative stress through the activation of JNK in Procambarus clarkii.

Synergistic Effects of Dietary Selenomethionine and Vitamin C on the Immunity, Antioxidant Status, and Intestinal Microbiota in Sea Cucumber (Apostichopus japonicus)

A 30-day feeding trial was carried out to investigate the interactive effects of dietary selenium (selenomethionine) and vitamin C (Vc) in Apostichopus japonicus. Two selenium (0 and 5 mg/kg) and three vitamin C (0, 5000, and 10,000 mg/kg) combined groups of feed were formulated (Designated as LSeLVc, LSeMVc, LSeHVc, HSeLVc, HSeMVc and HSeHVc, respectively) and fed the sea cucumbers. Our results showed no significant effects on the growth-related parameters in sea cucumber (P > 0.05). Furthermore, the reciprocal action between Se and Vc had significant (P < 0.05) effects on Se accumulation in the respiratory tree and intestines. Also, the lysozyme, glutathione peroxidase activity, and the relative expression levels such as LZM, GPX, Hsp70, and Hsp90 in different tissues were significantly increased in the group of sea cucumber fed diet with 5 mg Se in combination with 5000 mg Vc compared with the control group (P < 0.05). However, MDA and H2O2 contents in the body wall were significantly reduced in the HSeHVc group (P < 0.05). In addition, analysis of intestinal flora revealed that Haloferula abundance was highest in the LSeMVc group than other treatment groups, and Vibrio abundance was decreased with combined Se and Vc supplement. Finally, the species diversity of the gut microbial community of sea cucumber in HSeMVc group was lower than those in other treatment groups. The results showed that the interaction of selenium and vitamin C had positive effects on improving the immune status, antioxidant capacity, and digestive ability of A. japonicus.

Acyclovir inhibits white spot syndrome virus replication in crayfish Procambarus clarkii

White spot syndrome virus (WSSV) is a fatal pathogen threatening global crustacean industry with no commercially available drugs to control WSSV. To address the urgent need for finding effective antiviral agents against WSSV, we examined the anti-WSSV activities of 11 common antiviral agents in crayfish Procambarus clarkia. The results showed that acyclovir displayed the highest inhibition on WSSV replication in vivo (92.59%, 50 mg/kg). Acyclovir repressed WSSV proliferation followed a dose-dependent fashion and pre- or post-treatment of acyclovir exerted strong inhibition on the viral loads. Further, we observed a markedly reduced expression levels of WSSV genes (immediate-early IE gene ie1, DNA polymerase gene DNApol and envelope protein gene Vp28) that are crucial in viral life cycle with the acyclovir treatment during the early infection. Meantime, we also found a significantly increased expressions of anti-oxidative as well as apoptosis related genes, suggesting that acyclovir could effectively suppress WSSV replication in vivo. Finally, acyclovir treatment could significantly improve the survival rate of WSSV-challenged crayfish by 56%. Taken together, acyclovir has the potential to be developed as a promising preventive or therapeutic agent against WSSV infection, and this finding may provide a reference for rapid discovery anti-WSSV agent in crustacean aquaculture.

Transcriptome analysis reveals the potential mechanism of dietary carotenoids improving antioxidative capability and immunity of juvenile Chinese mitten crabs Eriocheir sinensis

Carotenoids are known to be involved in the regulation of the antioxidative capability, immune response and stress resistance in crustacean species; however, very limited information is available on their underlying molecular mechanisms. This study performed transcriptome sequencing of hemolymph and hepatopancreas of juvenile Chinese mitten crabs (Eriocheir sinensis) that fed with three diets, i.e. diet A containing 90 mg kg^-1 dry weight of astaxanthin, diet B containing 200 mg kg^-1 dry weight of β-carotene and control diet without supplementation of dietary carotenoids. The results showed that there were 2955 and 497 differentially expressed genes (DEGs) in the hemolymph between the astaxanthin treatment and control groups, and between the β-carotene treatment and control groups, respectively. Moreover, compared with the control group, 833 and 1886 DEGs were obtained in the hepatopancreas of the astaxanthin treatment and the β-carotene treatment groups, respectively. The DEGs in the three groups were enriched in 255 specific KEGG metabolic pathways according to KEGG enrichment analysis. Through this study, a series of key genes involved in Nrf2 signalling, ROS production, intracellular antioxidant enzymes and chaperones were significantly affected by dietary carotenoids. Dietary carotenoids also significantly altered the expression levels of immune-related molecules associated with signal transduction, prophenoloxidase cascade, apoptosis, pattern recognition proteins/receptors and antimicrobial peptides. In conclusion, this transcriptomic study provides valuable information for understanding the molecular mechanism and potential pathway of dietary carotenoids improved the antioxidative capability and immunity of juvenile E. sinensis.

The feeding of dietary Codonopsis pilosula polysaccharide enhances the immune responses, the expression of immune-related genes and the growth performance of red swamp crayfish (Procambarus clarkii)

Polysaccharides have many functions in aquatic animals and are widely used as immunopotentiators. However, despite the emergence of serious diseases, few studies have explored the effects of Codonopsis pilosula polysaccharide (CPP) on crustaceans. We studied the effects of CPP on the growth performance, nonspecific immunity, antioxidant activity and disease resistance of red swamp crayfish (Procambarus clarkii). Healthy crayfish (5.80 ± 0.1 g) were fed diets supplemented with 0% (control), 0.05%, 0.1%, 0.15%, 0.20%, and 0.30% CPP for 8 weeks. At the end of the 8-week feeding trial, the optimal final body weight (FBW), weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR) were observed in the crayfish fed the diets with 0.15% and 0.20% CPP, followed by those fed the diet with 0.30% CPP and then those fed the diet with 0.10% CPP, whereas the values of these parameters were obtained with the control crayfish (P < 0.05). The crayfish fed the diets with 0.15% and 0.20% CPP exhibited a significantly higher total hemocyte count (THC) and significantly increased phenoloxidase (PO), lysozyme (LZM), hemocyte (Hc), acid phosphatase (ACP) and alkaline phosphatase (AKP) compared with those belonging to the other groups (P < 0.05). The crayfish fed the diets with 0.15% and 0.2% CPP exhibited significantly higher total superoxide dismutase (T-SOD) and glutathione peroxidase (GPx) activities, a significantly increased total antioxidant capacity (T-AOC) and a significantly lower malondialdehyde (MDA) content compared with the other groups (P < 0.05), which indicated that antioxidant capacity was significantly induced by the CPP-supplemented diets. Significantly upregulated expression of immune-related genes (anti-lipopolysaccharide factors (alf), peroxiredoxin (prx5), cathepsin B (ctsb), mitochondrial manganese superoxide dismutase (mtMnsod), cyclophilin A (cypa), glutathione peroxidase (gpx), Toll-like receptor 3 (tlr3), and heat shock protein 70 (hsp70)) was detected in the crayfish fed the diets supplemented with 0.15% and 0.20% CPP diet compared with the levels observed in the control crayfish. These results showed that dietary CPP supplementation greatly improved the growth, immunity and antioxidant capacities of crayfish, and according to the observed results, 0.15%-0.2% is the recommended optimal level of CPP dietary supplementation for crayfish.

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.

Effects of aerial exposure on oxidative stress, antioxidant and non-specific immune responses of juvenile sea cucumber Apostichopus japonicus under low temperature

Desiccation is a commonly stressful situation experienced by sea cucumber during transportation without/less water. The present study was conducted to investigate the effects of aerial exposure on the survival, oxidative damage, antioxidant capacity, immune-related response and gene expression of Apostichopus japonicus at different low temperatures. After acclimation, sea cucumbers were randomly divided into 3 groups, which were exposed to 5 °C, 10 °C and 15 °C in the closed laboratory condition, respectively. Each group has three parallel replicates. During the experiment, coelomic fluid and respiratory tree of A. japonicus were sampled at the time points of 0, 3, 6, 12, 24 and 48 h post-desiccation for further analysis. The results showed that the survival rates of sea cucumber significantly decreased as time prolonged, and those of 5 °C at 6-48 h of desiccation were significantly higher than 15 °C. Most oxidative damage parameters (e.g., O₂^- production, MDA, LPO and PC contents) significant increased after 6-12 h of desiccation. Antioxidant enzyme activities and T-AOC in coelomic fluid firstly increased and then decreased during aerial exposure, indicating that sea cucumber could adjust antioxidant defense to reduce the concentrations of ROS and MDA as a strategy for protecting organisms from oxidative damage in the early stage (0-6 h) of desiccation. The relative expression levels of Hsp90 and Hsp70 mRNA in respiratory tree of sea cucumber exhibited similar rise-fall trends with antioxidant parameters, while immune enzyme activities of ACP, AKP, LSZ and T-NOS, and gene expression of TLR, Rel and p105 all significantly decreased as time prolonged. Overall, low temperature postponed the process of ROS formation and the depression of antioxidant and non-specific immune responses of sea cucumber within a certain extent, which implied that it might play a positive role in improvement of desiccation tolerance. This study not only contribute to better understand the adaption mechanisms of A. japonicus to desiccation stress, but also provide valuable information for sea cucumber culture and transportation.

Immune response to acute heat stress in the intestine of the red swamp crayfish, Procambarus clarkii

High temperature is an important environmental factor that affects the survival and immunity of aquatic animals. The intestine of crustaceans is their first line of defense, and the physiological homeostasis of this organ can be influenced by high temperature stress. The red swamp crayfish Procambarus clarkii is an important commercial aquaculture species in China, but little is known about its intestinal immune response to acute heat stress. In this study, we investigated the intestinal immune response of P. clarkii individuals that were assigned to the control (25 °C) and heat stress (35 °C) groups. Biochemical assays were conducted for the oxidative stress parameters ·O₂^- generation capacity, lipid peroxide content, and malondialdehyde content; the activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase; and the activities of the immunity-related enzymes alkaline phosphatase, acid phosphatase, and lysozyme. The relative expression level of the antioxidant genes heat shock protein 70 (hsp70), ferritin (fer), and metallothione (met) was examined by RT-PCR. Based on the data obtained, all the parameters tended to increase, peak and then decrease with time, and were significantly different between the two groups (P < 0.05). These findings reveal that acute heat stress adversely affects the antioxidant status and immune function in the P. clarkii intestine. They lay the groundwork for future studies on the effect of rising water temperatures on immune function and survival of this species.

Effects of hesperidin on the growth performance, antioxidant capacity, immune responses and disease resistance of red swamp crayfish (Procambarus clarkii)

We evaluated the effects of hesperidin on the nonspecific immunity, antioxidant capacity and growth performance of red swamp crayfish (Procambarus clarkii). A total of 900 healthy crayfish were randomly divided into six groups: the control group (fed the basal diet) and the HES25, HES50, HES75, HES100 and HES150 groups, which were fed the basal diet supplemented with 25, 50, 75, 100 and 150 mg kg^-1 hesperidin, respectively. The feeding experiment lasted 8 weeks. The results indicated that compared with the control group, the crayfish groups supplemented with 50-150 mg kg^-1 hesperidin had a decreased feed conversion ratio (FCR) and increased final body weight (FBW), specific growth rate (SGR) and weight gain (WG) (P < 0.05). The protein carbonyl content (PCC), reactive oxygen species (ROS) level and malondialdehyde (MDA) level in the hepatopancreas and hemocytes were significantly lower, while the total antioxidant capacity (T-AOC), glutathione peroxidase (GPx) activity, and superoxide dismutase (SOD) activity were significantly higher in the crayfish groups supplemented with 50-150 mg kg^-1 hesperidin than in the control group. Supplementation with 50-150 mg kg^-1 hesperidin significantly increased the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), lysozyme (LZM), and phenoloxidase (PO) compared with the control group (P < 0.05); upregulated the mRNA expression of cyclophilin A (CypA), extracellular copper-zinc superoxide dismutase (ecCuZnSOD), GPxs, crustin, astacidin, Toll3 and heat shock protein 70 (HSP70) (P < 0.05); and decreased crayfish mortality following white spot syndrome virus (WSSV) infection. These findings indicate that dietary hesperidin supplementation at an optimum dose of 50-150 mg kg^-1 may effectively improve nonspecific immunity, antioxidant capacity and growth performance in crayfish.

Effects of dietary Pediococcus acidilactici GY2 single or combined with Saccharomyces cerevisiae or/and β-glucan on the growth, innate immunity response and disease resistance of Macrobrachium rosenbergii

One Pediococcus acidilactici strain, named PA-GY2 was isolated from the gut of cultured Macrobrachium rosenbergii. In order to better examine the potential scope and applicability of this strain in M. rosenbergii culture, based on the control diet, four experimental diets containing single or combined immunostimulants were produced by supplementing with yeast (Saccharomyces cerevisiae, SC) or/and β-glucan (G), then fed to the prawns (6.70 g ± 0.74) in five groups, which were named as group C (control group), P (PA-GY2), PS (PA-GY2 + SC, 1:1), PG (PA-GY2 + G) and PGS (PA-GY2 + SC + G), respectively. After a 60-day feeding trial, growth performance, feed utilization, immune response and disease resistance of prawns were evaluated in the present study. Results indicated that (1) The growth performance of the prawns in group PS and PGS were significantly improved. The prawns in group PGS presented the lowest feed coefficiency (FC), while prawns in group C presented the highest FC. (2) The protease activity was significantly improved by dietary immunostimulants supplementation, meanwhile, prawns in the group PS presented the highest lipase activity. (3) The highest total hemocyte count and respiratory burst activity were found in the group P and PG, respectively. The phagocytic index of the prawns in the group C was significantly lower than those in group P and PGS. (4) Dietary PA-GY2 single or combined with SC or/and β-glucan increased the immune related genes expression, including some antibacterial and antioxidant enzymes, while decreased the tumor necrosis factor-α gene expression, which led to the decreased cumulative mortality rate of prawns during the Aeromonas hydrophila challenge test. Based on the results of growth performance, digestive enzymes activity and immune response of M. rosenbergii, PA-GY2 supplementation, single or combined with SC or/and β-glucan could be suggested as promising immunostimulants in prawns farming.

Effects of palytoxins extracted from Ostreopsis ovata on the oxidative stress and immune responses in Pacific white shrimp Litopenaeus vannamei

Palytoxins (PLTXs) are a group of complex and poisonous marine natural products that are toxic to marine life and even human beings. In the present study, the oxidative stress and immune response in the hepatopancreas and gills of Litopenaeus vannamei were assessed for 72 h after injection with PLTX extracts. Chemical and physiological parameters, e.g., the respiratory burst (O₂^-), activities of antioxidant enzymes, oxidative damage to lipids, carbonylation of proteins, and immune gene mRNA expression levels, were analysed. The results showed that the PLTX extract was not fatal to the shrimp but could reduce their mobility. The O₂^- levels in the gills gradually increased after exposure to PLTX extracts and were significantly higher than those in the control from 6 to 72 h. The malondialdehyde content, lipid peroxidation, protein carbonyl levels, and total antioxidant capacity in the gills all peaked at 12 h. At the same time, the gills were loosely connected, there was a clear disintegration of the epithelial tissue, and the stratum corneum disappeared after 12 h. In addition, compared to those in the control group, the PLTX extract treatment increased the O₂^- content, malondialdehyde content, lipid peroxidation, and protein carbonyl levels from 12 to 72 h, 24-48 h, 12-24 h, and 12-72 h after injection in the hepatopancreas of the shrimp, respectively. Both the Crustin and Toll gene expression levels significantly increased in the hepatopancreas compared to those in the control 6-72 h after injection of the toxin. In parallel, the expression levels of the manganese superoxide dismutase gene gradually decreased from 6 to 48 h and returned to normal levels after 72 h. Interestingly, the total antioxidant capacity also significantly increased compared to that in the control from 6 to 72 h. Our results indicate that although PLTX extracts cause lipid peroxidation and carbonylation of proteins in hepatopancreatic cells, leading to their damage, they did not cause a decrease in the total antioxidant capacity of the hepatopancreas.

Transcriptome analysis of hemocytes from the white shrimp Litopenaeus vannamei with the injection of dopamine

As a crucial neuroendocrine-immune factor, dopamine (DA) could regulate the immune system of Litopenaeus vannamei. To understand the immune mechanisms and regulatory pathways of DA in L. vannamei, the transcriptome analysis of hemocytes of L. vannamei with injection of DA (10^-6 mol/shrimp) at 3 and 12 h were performed in this study. Moreover, quantitative real-time PCR (qPCR) method was applied to validate the accuracy of transcriptome sequencing and analyze the expression pattern of candidate differentially expressed genes (DEGs) at different time points (0, 3, 6, 12, and 24 h) after DA injection. The results showed that a total of 51382 unigenes with a N50 length of 2341 bp were generated. And 1397 and 457 DEGs were obtained by comparative transcriptome at 3 and 12h respectively. Moreover, the results of functional annotation and enriched pathway showed that the DEGs were involved in phagosome (ko04145), lysosome (ko04142), Endocytosis (ko04144), and NOD-like receptor signaling pathway (ko04621). Besides, the Pearson's correlation coefficient (R) between transcriptome sequencing and qPCR was 0.845, which confirmed the reliability of the transcriptome sequencing results and the accuracy of assembly. Furthermore, the expression pattern of 15 candidate DEGs, containing 9 up-regulated and 6 down-regulated DEGs at 3 h, indicated the regulation of DA in physiological functions especially in the immune system. Therefore, these results revealed that DA induced the expressions of membrane receptors or proteins, activated intracellular signaling pathways, regulated cellular and humoral immune systems, controlled antioxidation and apoptosis, and was involved in the regulation of neuroendocrine system. These findings are helpful to promote the understanding on the effects of biogenic amines on physiological functions and regulatory networks of crustacean, and offer a substantial material and foundation for researching the immune response of crustacean.

Evaluation on the antiviral activity of genipin against white spot syndrome virus in crayfish

White spot syndrome virus (WSSV) is a serious epidemic pathogen of crustaceans and cause severe economic losses to aquaculture. However, no commercial drugs presently available to control WSSV infection. Genipin (GN) is a bioactive compound extracted from the fruit of Gardenia jasminoides and exhibits potential antiviral activity. In the study, the antiviral activity of GN against WSSV was investigated in crayfish Procambarus clarkii and in shrimp Litopenaeus vannamei. In vitro antiviral test showed that GN could inhibit WSSV replication in crayfish and in shrimp, and the highest inhibition on WSSV was over 99% when treatment with 50 mg/kg of GN for 24 h. In vivo antiviral test proved that GN could be used to treat and prevent WSSV infection. GN could also effectively protect crayfish from WSSV infection by reducing the mortality rate of WSSV-infected crayfish. Moreover, GN attenuated the WSSV-induced oxidative stress and inflammatory by upregulation the expression of antioxidant-related genes and downregulation the expression of inflammatory-related genes, respectively. Mechanically, GN inhibited WSSV replication at least via decreasing STAT (signal transducer and activator of transcription) gene expression to block WSSV immediate-early gene ie1 transcription. Additionally, the inhibition of BI-1 (Bax inhibitor-1) gene expression also played an important role in the suppression of WSSV infection. In conclusion, GN represented a potential therapeutic and preventive agent to block WSSV infection.

Silencing of HIF-1 in WSSV-infected white shrimp: Effect on viral load and antioxidant enzymes

Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor that induces genes involved in glucose metabolism. HIF-1 is formed by a regulatory α-subunit (HIF-1α) and a constitutive β-subunit (HIF-1β). The white spot syndrome virus (WSSV) induces a shift in glucose metabolism and oxidative stress. HIF-1α is associated with the induction of metabolic changes in tissues of WSSV-infected shrimp. However, the contributions of HIF-1 to viral load and antioxidant responses in WSSV-infected shrimp have been not examined. In this study, the effect of HIF-1 silencing on viral load and the expression and activity of antioxidant enzymes (superoxide dismutase-SOD, glutathione S-transferase-GST, and catalase) along with oxidative damage (lipid peroxidation and protein carbonyl) in tissues of white shrimp infected with the WSSV were studied. The viral load increased in hepatopancreas and muscle after WSSV infection, and the accumulative mortality was of 100% at 72 h post-infection. The expression and activity of SOD, catalase, and GST decreased in each tissue evaluated after WSSV infection. Protein carbonyl concentrations increased in each tissue after WSSV infection, while lipid peroxidation increased in hepatopancreas, but not in muscle. Silencing of HIF-1α decreased the WSSV viral load in hepatopancreas and muscle of infected shrimp along with shrimp mortality. Silencing of HIF-1α ameliorated the antioxidant response in a tissue-specific manner, which translated to a decrease in oxidative damage. These results suggest that HIF-1 is essential for restoring the antioxidant response, which counters the oxidative injury associated with WSSV infection.

Molecular characterization and functional analysis of two phospholipid hydroperoxide isoforms from Larimichthys crocea under Vibrio parahaemolyticus challenge

Glutathione peroxidases family is a key role in the antioxidant system in oxybiotic organisms for cell redox homeostasis. One of their members, phospholipid hydroperoxide glutathione peroxidase (GPx4) have unique monomeric structure and can directly react with complex lipid and membrane-bound peroxides under the presence of glutathione(GSH). In this paper, two complete GPx4 cDNAs (designated as LcGPx4a and LcGPx4b) from Larimichthys crocea are identified by rapid amplification of cDNA ends. The cDNA of LcGPx4a was consisted of a 5'-untranslated region (UTR) of 258 bp, a 3'-UTR of 330 bp, and an open reading frame (ORF) of 561 bp encoding 186 amino acid (aa) polypeptides. And the full-length sequence of LcGPx4b was 1164 bp with a 5'-UTR of 34 bp, a 3'-UTR of 551 bp and an ORF of 576 bp encoding a polypeptide of 191 aa residues with a predicted signal peptide of 15 aa. The characteristic selenocysteine insertion (SECIS) sequence was detected in the 3'UTR of the two sequences with 78 bp in length. The conserved active site of selenocysteine (Sec) encoded by TGA was also identified and formed a tetrad functional structure with glutamine, tryptophan, and asparagine in LcGPx4a and LcGPx4b. Two signature site motifs ("LRILAFPSNQFGNQEPG" and "LRILGFPCNQFGGQEPG") were both conserved in the deduced amino acid of LcGPx4a and LcGPx4b. The genomic structure analysis revealed that the two sequences both had 7 exons and 6 introns, and the Sec opal codon and SECIS element were located at the third and seventh exons, respectively. LcGPx4a and LcGPx4b both have a wide distribution in 9 tissues with various relative expression levels and a highest expression pattern in the liver. Under Vibrio parahaemolyticus challenge, their relative expression levels were altered in the liver, spleen, kidney, and head kidney but with different magnitudes and response time. LcGPx4a and LcGPx4b showed a significantly up-regulated trend in the spleen during experimental period. Above results suggested that LcGPx4a and LcGPx4b were two conserved immune molecules and might play a role in the immune response of fish with a tissue-depemdent manners.

The oxidative stress and antioxidant responses of Litopenaeus vannamei to low temperature and air exposure

Low temperature and air exposure were the key attributes for waterless transportation of fish and shrimp. In order to investigate the oxidative stress and antioxidant responses of the live shrimp Litopenaeus vannamei in the mimic waterless transportation, live shrimp were cooled at 13 °C for 3 min, stored in oxygen at 15 °C for 12 h, and then revived in water at 25 °C. The survival rate of shrimp under this waterless transportation system was over 86.67%. The ultrastructure of hepatopancreas cells were observed while activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione peroxidase (GSH-Px), antisuperoxide anion free radicals (ASAFR), total antioxidant capacity (TAOC), reactive oxygen species (ROS) production, content of malondialdehyde (MDA) and relative mRNA expressions of CAT and GSH-Px in the hemolymph and hepatopancreas were determined. Slight distortions of some organelles in hepatopancreas cells was reversible upon the shrimp revived from the cold shock. The activities of SOD, POD, CAT, GSH-Px, TAOC, ROS production and relative mRNA expressions of CAT and GSH-Px increased following the cold shock and reached peak levels after 3 or 6 h of storage, and then decreased gradually. There was no significant difference between the fresh and the revived shrimp in SOD, POD, GSH-Px, TAOC, ROS, MDA and relative mRNA expressions of CAT and GSH-Px. The oxidative stress and antioxidant responses were tissue-specific because hepatopancreas seemed to have a greater ability to defend against organelle damage and was more sensitive to stress than hemolymph based on the results of SOD activity, MDA content and GSH-Px mRNA expression. These results revealed that low temperature and air exposure caused significant oxidative and antioxidant responses, but did not lead to irreversible damages in this waterless system.

Identification and characterization of two selenium-dependent glutathione peroxidase 1 isoforms from Larimichthys crocea

Glutathione peroxidases, a vital family of antioxidant enzymes in oxybiotic organisms, are involved in anti-pathogen immune response. In this study, two complete selenium-dependent glutathione peroxidase 1 cDNAs (designated as LcGPx1a and LcGPx1b) were obtained from the large yellow croaker Larimichthys crocea by rapid amplification of cDNA ends. The full-length sequence of LcGPx1a was 917 bp with a 5'-untranslated region (UTR) of 52 bp, a 3'-UTR of 289 bp, and an open reading frame of 576 bp encoding 191 amino acid (aa) polypeptides. The cDNA of LcGPx1b was composed of 884 bp with a 5'-UTR of 59 bp, a 3'-UTR of 258 bp, and an open reading frame of 567 bp encoding 188 aa polypeptides. The conserved selenocysteine insertion sequence was detected in the 3'-UTR of both isoforms, which can classify types I and II. Protein sequence analysis revealed that both isoforms included a selenocysteine encoded by an opal codon (TGA) and formed the functioning tetrad site with glutamine, tryptophan, and asparagine. Three conservative motifs, including one active site motif ("GKVVLIENVASLUGTT") and two signature site motifs ("LVILGVPCNQFGHQENC" and "V(A/S)WNFEKFLI"), were conserved both in sequence and location. Multiple alignments revealed that they exhibited a high level of identities with GPx1 from other organisms, especially in the abovementioned conserved amino acid sequence motifs. Tissue expression analysis indicated that LcGPx1a and LcGPx1b had a wide distribution in nine tissues with various abundances. The transcript level of LcGPx1a was not significantly different among the nine tissues, whereas that of LcGPx1b was higher in the kidney and head kidney than in the other tissues. After Vibrio parahaemolyticus stimulation, the expression levels of LcGPx1a and LcGPx1b were unanimously altered in the liver, spleen, kidney, and head kidney but with different magnitudes and response time. LcGPx1a and LcGPx1b showed distinct expression trends in the liver, where LcGPx1b was induced and LcGPx1a was depressed in response to pathogen infection. These results indicate that LcGPx1a and LcGPx1b display functional diversities and play crucial roles in mediating the immune response of fish.

Transcriptomic and morphological analyses of Litopenaeus vannamei intestinal barrier in response to Vibrio paraheamolyticus infection reveals immune response signatures and structural disruption

The white shrimp Litopenaeus vannamei has been greatly impacted by Vibrio infection. In this study, we investigated the intestinal barrier response of L vannamei following challenge with Vibrio parahaemolyticus E1, by examining morphological changes and transcriptome expression levels. A total of 16,4420 unigenes were obtained from RNAseq data after quality control and assembly, and 4646 differentially expressed genes (DEGs) were identified following Vibrio challenge, of which 2469 unigenes were significantly up-regulated and 2177 were significantly down-regulated. DEGs were determined to be involved in various physical, chemical and immunological intestinal barrier functions, including peritrophin, cytoskeleton and cell junction, pattern recognition receptors, antimicrobial peptide and immune signaling pathways, serine protease/protease inhibitor and prophenoloxidase system, apoptosis and phagocytosis, and antioxidant systems. Fifteen DEGs were randomly selected for validation by real-time quantitative PCR (RT-qPCR) and showed results consistent with the RNA-seq data. Intestinal epithelial cell morphology was also affected by Vibrio challenge, showing epithelial detachment, nuclear pyknosis, and destruction of cell junctions. These results improve our current understanding of the intestinal barrier function in the shrimp response to bacterial infection.

Transcriptome, antioxidant enzyme activity and histopathology analysis of hepatopancreas from the white shrimp Litopenaeus vannamei fed with aflatoxin B1(AFB1)

Aflatoxin produced by Aspergillus flavus or Aspergillus parasiticus fungi during grain and feed processing and storage. Aflatoxins cause severe health problems reducing the yield and profitability of shrimp cultures. We sought to understand the interaction between shrimp immunity and aflatoxin B1 (AFB1), analyzing transcriptome expression, antioxidant enzyme activity, and histological features of the hepatopancreas of shrimp fed with AFB1. From over 4 million high-quality reads, de novo unigene assembly produced 103,644 fully annotated genes. A total of 1024 genes were differentially expressed in shrimp fed with AFB1, being involved in functions, such as peroxidase metabolism, signal transduction, transcriptional control, apoptosis, proteolysis, endocytosis, and cell adhesion and cell junction. Upon AFB1 challenge, there were severe histological alterations in shrimp hepatopancreas. AFB1 challenge increased the activity of several antioxidant enzymes. Our data contribute to improve the current understanding of host-AFB1 interaction, providing an abundant source for identification of novel genes.

Identification of ecdysteroid receptor-mediated signaling pathways in the hepatopancreas of the red swamp crayfish, Procambarus clarkii

The hepatopancreas of crustaceans plays an important role in lipid and carbohydrate metabolism, digestion of food, and biogenesis. In this study, the hepatopancreas transcriptome from the red crayfish Procambarus clarkii was characterized for the first time using high-throughput sequencing, producing approximately 41.4 million reads were obtained. After de novo assembly, 57,363 unigenes with an average length of 725bp were identified, Gene Ontology analysis categorized 22,580 as being involved in biological processes, among which metabolic process and cellular process groups were the most highly enriched. A total of 8034 unigenes were assigned to 223 metabolic pathways following mapping against the Kyoto encyclopedia of genes and genomes (KEGG) database. Ecdysteroid receptor (EcR)-mediated signaling pathways were investigated using digital gene expression (DGE) analysis following RNA interference targeting the EcR. A total of 529 differentially expressed genes (DEGs) were identified, including 322 downregulated and 207 upregulated unigenes. Of these, 445 (84.12%) were annotated successfully by alignment with known sequences, many of which were related to catalytic activity and binding functional categories. Using KEGG enrichment analysis, 183 DEGs were clustered into 78 pathways, and six significantly enriched pathways were predicted. The expression patterns of candidate genes identified by real-time PCR were consistent with the DGE results.

Antioxidant enzymes and their role in phoxim and carbaryl stress in Caenorhabditis elegans

Pesticide exposure can induce oxidative stress and cause changes to antioxidant enzymes in living organisms. In the present study, the effects of phoxim (an organophosphorus insecticide) and carbaryl (a carbamate insecticide) on antioxidant enzyme activity and gene expression were investigated in the model organism Caenorhabditis elegans. The results show that phoxim exposure can induce superoxide dismutase (SOD) and catalase (CAT) activities and decrease glutathione peroxidase (GPx) activity at lower concentrations. The expression levels of sod-3, sod-5, ctl-1, gpx-6, and gpx-8 were up-regulated after treatment with phoxim. The mRNA expression levels of sod-5, ctl-1 and gpx-6 were increased approximately 70-, 170- and 130-fold, respectively, in the 0.25mM treatment group compared to the control group. Carbaryl exposure decreased SOD activity and induced CAT and GPx activities. The addition of carbaryl up-regulated the expression of sod-5, ctl-1, ctl-3 and gpx-8. Specifically, ctl-1 expression increased approximately 10-fold, and gpx-8 expression increased <30-fold in the 0.5mM treatment group relative to the control group. The transcript level of sod-5 increased >20-fold, and ctl-3 increased approximately 10-fold in the 1mM treatment group. The functions of the antioxidant enzymes during oxidative stress caused by the two insecticides were investigated using deletion mutants. The LC₅₀ values phoxim for the of sod-3 (tm760), sod-5 (tm1146), ctl-1 (ok1242), ctl-3 (ok2042) and gpx-8 (tm2108) mutant strains were lower than those observed for the N2 strain. The LC₅₀ values of carbaryl for the ctl-1 (ok1242), ctl-3 (ok2042) and gpx-6 (tm2535) deletion mutant strains decreased in comparison to the N2 strain. The results suggest that these two insecticides caused oxidative stress and changed altered the antioxidant enzyme activities and their gene expressions in C. elegans. The sod-3, sod-5, ctl-1, ctl-3, gpx-6, and gpx-8 encoding enzymes may play roles in defending cells from oxidative stress caused by these two insecticides.

Effect of the dietary probiotic Clostridium butyricum on growth, intestine antioxidant capacity and resistance to high temperature stress in kuruma shrimp Marsupenaeus japonicus

A 56-day feeding trial followed by an acute high temperature stress test were performed to evaluate the effect of dietary probiotic Clostridium butyricum (CB) on growth performance and intestine antioxidant capacity of kuruma shrimp Marsupenaeus japonicus. Shrimp were randomly allocated in 9 tanks (30 shrimp per tank) and triplicate tanks were fed with diets containing different levels of C. butyricum (1×10⁹ cfu/g): 0mgg^-1 feed (Control), 100mgg^-1 feed (CB-100), 200mgg^-1 feed (CB-200) as treatment groups. The results indicated that dietary supplementation of C. butyricum increased the growth performance and decreased the feed conversion rate (FCR) of shrimp in the CB-100 group. HE stain showed that C. butyricum increased the intestine epithelium height of M. japonicus. C. butyricum supplemented in diets decreased·O₂^- generation capacity and malondialdehyde (MDA) content, and increased total antioxidant capacity (T-AOC), catalase (CAT) and peroxidase (POD) activity and the expression level of heat shock protein 70 (hsp70) and metallothionein (mt) gene in intestine of shrimp cultured under normal condition for 56 d, while no significant changes in glutathione peroxidase (GPx) activity and ferritin gene expression level. After shrimp exposed to high temperature stress 48h, the lower level of·O₂^- generation capacity and MDA content, and the higher level survival, activities of T-AOC, CAT, GPx and POD, as well as hsp70, ferritin and mt gene expression level were found in intestine of two C. butyricum groups. These results revealed that C. butyricum could improve the growth performance, increase intestine antioxidant capacity of M. japonicus against high temperature stress, and could be a potential feed additive in shrimp aquaculture.

Intestine oxidative stress and immune response to sulfide stress in Pacific white shrimp Litopenaeus vannamei

The effects of sulfide stress on oxidative stress and immune response in intestine of Pacific white shrimp Litopenaeus vannamei were evaluated in the present study. Oxidative stress parameters, immune enzymes activity and immune gene mRNA expression level were detected in intestine of L. vannamei after the exposure of 5.0 mg/L sulfide stress 72 h. The duration of sulfide stress influenced the shrimp survival, and the cumulative mortality rate was 30.0% and 33.3% at 48 h and 72 h respectively. HE staining showed that sulfide stress caused the intestine tissue damage symptoms. Compared with the control group, after exposed to sulfide stress, the content of lipid peroxidation (LPO), malondialdehyde (MDA) and ROS production (·O₂^- generation capacity) increased. Total antioxidant capacity (T-AOC) activity increased at 6 h and decreased at 48 h. Superoxide dismutase (SOD) activity increased in the entire experiment. Inducible nitric oxide synthase (iNOS) activity and nitric oxide (NO) content increased to the highest at 6 h and 12 h respectively, and both decreased at 48 h. The relative mRNA expression level of heat shock protein 70 (HSP70) gene decreased at 6 h and increased to the highest at 48 h. The relative mRNA expression level of hypoxia inducible factor 1α (HIF-1α) gene increased at 12 h and decreased to a lower level at 72 h. The relative mRNA expression level of Toll and immune deficiency (Imd) gene increased to the highest at 12 h and 24 h respectively, and both decreased at 48 h. These results revealed that sulfide stress could induce oxidative stress and immune response via confusion of immune enzymes activity and gene expression level in intestine of L. vannamei.

Effect of desiccation on oxidative stress and antioxidant response of the black tiger shrimp Penaeus monodon

In the present study, the oxidative stress and antioxidant response in hepatopancreas of the black tiger shrimp Penaeus monodon under desiccation stress were studied, such as activities of antioxidant enzymes (SOD, CAT, GPx and POD), oxidative damage to lipid and protein which indexed by contents of LPO, MDA, protein carbonyl (PC) and ROS production, and the expression of HSP70 and ferritin gene. The duration of desiccation significantly influenced the shrimp survival, and the mortality rates were 10% and 55.0% after desiccation 0.5 h and 3 h, respectively. Compared with the control group, after exposed to desiccation stress, the content of LPO, MDA, PC and ROS production in hepatopancreas increased significantly. SOD, CAT and POD activity in hepatopancreas increased significantly at 0.5 h, but decreased markedly at 1 h. GPx activity in hepatopancreas increased significantly at 0.5 h and 1 h, then decreased significantly at 3 h. The transcript levels of HSP70 and ferritin gene in hepatopancreas increased significantly at 1 h. HE staining showed that desiccation induced damage symptoms in hepatopancreas of P. monodon. These results revealed that desiccation could induce oxidative stress and antioxidant response via confusion of antioxidant enzymes activity and gene transcript level in hepatopancreas of P. monodon, and the time of shrimp under desiccation should lower than 0.5 h.

Accumulation and detoxification dynamics of microcystin-LR and antioxidant responses in male red swamp crayfish Procambarus clarkii

MC-LR is one of major microcystin isoforms with potent hepatotoxicity. In the present study, we aim to: 1) explore the dynamics of MC-LR accumulation and elimination in different tissues of male red swamp crayfish Procambarus clarkii; 2) reveal the mechanisms underlying hepatic antioxidation and detoxification. In the semi-static toxicity tests under the water temperature of 25±2°C, P. clarkii were exposed to 0.1, 1, 10 and 100μg/L MC-LR for 7days for accumulation and subsequently relocated to freshwater for another 7days to depurate MC-LR. MC-LR was measured in the hepatopancreas, intestine, abdominal muscle and gill by HPLC. The enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST), content of glutathione (GSH), and transcripts of Mn-sod, cat, gpx1, Mu-gst, heat shock protein90 (hsp90), hsp70 and hsp60 in hepatopancreas were detected. The results showed that P. clarkii accumulated more MC-LR in intestine, and less in abdominal muscle and gill during accumulation period and eliminated the toxin more quickly in gill and abdominal muscle, and comparatively slowly in intestine during depuration period. The fast increase of SOD and CAT activities at early stage, subsequent decrease at later stage of accumulation period and then fast increase during depuration period were partially consistent with the transcriptional changes of their respective genes. GPx was activated by longer MC-LR exposure and gpx1 mRNA expression showed uncoordinated regulation pattern compared with its enzyme. Hsp genes were up-regulated when P. clarkii was exposed to MC-LR.

Molecular cloning, characterization, and expression analysis of p53 from the oriental river prawn, Macrobrachium nipponense, in response to hypoxia

The tumor suppressor gene p53 plays a critical role in safeguarding the integrity of the genome in mammalian cells. It acts as a sequence-specific transcription factor. Once p53 is activated by a variety of cellular stresses, it transactivates downstream target genes and regulates the cell cycle and apoptosis. However, little is known about the functions of the p53 pathway in prawns in response to hypoxia. In this study, the cDNA of p53 from the oriental river prawn, Macrobrachium nipponense, (Mnp53) was cloned using a combination of homology cloning and rapid amplification of cDNA ends. The full-length cDNA of Mnp53 has 2130 bp, including an open reading frame of 1125 bp that encodes a polypeptide of 374 amino acids with a predicted molecular weight of 41.9 kDa and a theoretical isoelectric point of 6.9. Quantitative real-time (qRT)-PCR assays revealed that Mnp53 was ubiquitously expressed in all examined tissues, but at high levels in the hepatopancreas. In addition, we studied respiratory bursts and reactive oxygen species (ROS) production in the hepatopancreas of M. nipponense. Our results suggest that oxidative stress occurred in prawns in response to hypoxia and that apoptosis was associated with an increase in caspase-3 mRNA expression. qRT-PCR and western blot results confirmed that hypoxic stress induced the upregulation of Mnp53 at mRNA and protein levels. Furthermore, immunohistochemistry showed remarkable changes in immunopositive staining after the same hypoxic treatment. These results suggest that hypoxia-induced oxidative stress may cause apoptosis and cooperatively stimulate the expression of Mnp53.

Six Hours after Infection, the Metabolic Changes Induced by WSSV Neutralize the Host's Oxidative Stress Defenses

Levels of intracellular ROS (reactive oxygen species) were significantly increased in hemocytes collected from WSSV-infected shrimp within the first 30–120 min after infection. Measurement of the NADPH/NADP⁺ and GSH/GSSG ratios revealed that after a significant imbalance toward the oxidized forms at 2 hpi, redox equilibrium was subsequently restored. Meanwhile, high levels of lactic acid production, elevated NADH/NAD⁺ ratios, and metabolic changes in the glycolysis pathway show that the Warburg effect was triggered by the virus. The timing of these changes suggests that WSSV uses this metabolic shift into aerobic glycolysis to counteract the high levels of ROS produced in response to viral infection. We further show that if the Warburg effect is inhibited by chemical inhibition of the PI3K-Akt-mTOR signaling pathway, or if the pentose phosphate pathway is chemically inhibited, then in both cases, the production of intracellular ROS is sustained. We conclude that WSSV uses the PI3K-Akt-mTOR-regulated Warburg effect to restore host redox balance and to counter the ROS produced by the host in response to WSSV infection. We also found that pyruvate kinase activity was inhibited by WSSV. This inhibition is likely to increase the availability of the raw materials essential for WSSV gene expression and replication.

Molecular characterization of a novel nitric oxide synthase gene from Portunus trituberculatus and the roles of NO/O2(-)- generating and antioxidant systems in host immune responses to Hematodinium

Increasing evidences have established that the nitric oxide synthase (NOS) and NADPH oxidase (NOX) play important roles in host defense system by catalyzing the production of nitrogen oxide (NO) and superoxide anions (O2(-)), respectively. While, there are limited studies to explore the roles of NOS/NOX enzymes in crustacean immunity, and no studies as yet were attempted to elucidate their functions in host immune responses to parasites. In the present study, we cloned a full-length cDNA of NOS and two partial cDNA fragments of NOX and GPx from the economic valuable crab Portunus trituberculatus. The full-length cDNA of NOS was 4002 bp in length that encoded 1203 amino acids containing motifs of the NOS protein and conserved domains. The phylogenetic analysis showed that the NOS protein sequence was clustered together with those of crustacean species in the phylogenetic tree. All of the three novel genes showed high mRNA transcripts in the immune-related tissues (e.g. hemocytes, hepatopancreas) of P. trituberculatus. Striking fluctuation in the transcripts of the critical NO/O2(-)- generating/scavenging related genes (NOS, NOX, CuZnSOD, CAT, GPx) as well as in the enzymatic activities of NOS, NOX, SOD, CAT and GPx were observed in the hemocytes and hepatopancreas of P. trituberculatus post challenged with the parasitic dinoflagellate Hematodinium, indicating that the NO/O2(-)- generating and the antioxidant systems played vital roles in the crustacean innate immunity against the parasitic intrusion. The results indicated a novel respect of the host-parasite interaction between the crab host and the parasitic dinoflagellate Hematodinium.

Effect of desiccation and resubmersion on the oxidative stress response of the kuruma shrimp Marsupenaeus japonicus

In the present study, the oxidative stress response in hepatopancreas of Marsupenaeus japonicus to desiccation stress and resubmersed in seawater were studied, such as respiratory burst, ROS production ( [Formula: see text] ), activities of antioxidant enzymes (CAT, GPx, SOD, POD and GST) and oxidative damage to lipid and protein (indexed by contents of MDA). The duration of desiccation significantly influenced shrimp survival, and the mortality rates were 37.5% and 87.5% after desiccation 5 h and 10 h, respectively. After desiccation stress 3 h, the respiratory burst, ROS production, and the activity of SOD and CAT were up-regulated significantly. The activity of GPx and POD, and the content of MDA decreased significantly at 0.5 h and 1 h, and then increased significantly at 3 h. But GST activity was no significant change after desiccation. During the resubmersion period, most of the antioxidant enzymes activities could recover to the control level at 24 h, but a small quantity of the oxidative stress still existed in tissues. HE staining showed that desiccation stress induced damage symptoms in hepatopancreas of M. japonicus. These results revealed that desiccation influenced the antioxidative status and caused oxidative stress and tissue damage via confusion of antioxidant enzymes in M. japonicus, but the oxidative stress could be eliminated within a certain range after the shrimps were resubmersed in seawater.

Identification of functional genes involved in Cd(2+) response of Chinese surf clam (Mactra chinensis) through transcriptome sequencing

The Chinese surf clam Mactra chinensis is an economically important bivalve species in the coastal waters of Liaoning and Shandong Province, China. In this study, we carried out transcriptome sequencing to develop molecular resources for M. chinensis and conducted an acute test of Cd(2+) stimulation through quantitative real-time PCR (qRT-PCR) to analyze the relative expression of six functional genes. A total of 100,839 transcripts and 56,712 unigenes were obtained from 39.9 million filtered reads and 21,305 unigenes were annotated by hitting against NCBI database. According to the results of qRT-PCR, heat shock protein 22 (Hsp22) and cytochrome P450 (CYP450(2C31)) were inhibited in the low concentration, and induced in the high concentration of Cd(2+); thioredoxin peroxidase (TPx-A) was at normal level in low concentration, but induced in high concentration of Cd(2+); glutathione peroxidase A (GPA), glutathione peroxidase 1 (GPA1) and Mn superoxide dismutase gene (MnSOD) were down-regulated when exposed to any treatment groups. Expression levels of the six functional genes following Cd(2+) exposure indicated that these genes were linked to environmental stress. Moreover, the present work enriched the molecule genetic data of M. chinensis.

The effect of banana (Musa acuminata) peels hot-water extract on the immunity and resistance of giant freshwater prawn, Macrobrachium rosenbergii via dietary administration for a long term: Activity and gene transcription

The non-specific immune parameters, disease resistance and immune genes expressions in Macrobrachium rosenbergii were evaluated at 120 days of post feeding the diets containing the extracts of banana, Musa acuminate, fruit's peel (banana peels extract, BPE) at 0, 1.0, 3.0 and 6.0 g kg(-1). Results showed that prawns fed with a diet containing BPE at the level of 1.0, 3.0 and 6.0 g kg(-1) for 120 days had a significantly higher survival rate (30.0%, 40.0% and 56.7%, respectively) than those fed with the control diet after challenge with Lactococcus garvieae for 144 h, and the respective relative survival percentages were 22.2%, 33.3%, and 51.9%, respectively. Dietary BPE supplementation at 3.0 and/or 6.0 g kg(-1) for 120 days showed a significant increase total haemocyte count (THC), granular cell (GC), superoxide dismutase (SOD) activity, phenoloxidase (PO) activity, transglutaminase (TG) activity, and phagocytic activity and clearance efficiency to L. garvieae infection, and meanwhile, the significant decrease in haemolymph clotting times and respiratory bursts (RBs) per haemocyte of prawns were revealed. Furthermore, the mRNA expressions of prophenoloxidase (proPO), lipopolysaccharide and β-1,3-glucan binding protein (LGBP), peroxinectin (PE), transglutaminase (TG), and crustin (CT) were significantly increased. We therefore recommend that BPE can be used as an immunomodulator for prawns through dietary administration at 6.0 g kg(-1) for a long term (over 120 days) to modify immune responses and genes expression following the enhanced resistance against pathogens.

Oxidative stress response of the black tiger shrimp Penaeus monodon to Vibrio parahaemolyticus challenge

Vibrio parahaemolyticus is a virulent pathogen that affects shrimp aquaculture. Reactive oxygen species are produced by the immune system that defends the host against foreign microorganisms. In the present study, the oxidative stress response in hepatopancreas and gills of Penaeus monodon to V. parahaemolyticus challenge were studied, such as respiratory burst, ROS production (·O2(-) and ·OH), activities of antioxidant enzymes (CAT, GPx, SOD, POD and GST) and oxidative damage to lipid and protein (indexed by contents of MDA). Compared with the control group, after V. parahaemolyticus challenge, respiratory burst and ROS production were up-regulated significantly. GPx and POD activity increased significantly in hepatopancreas and gills of the shrimps at 12 h, but CAT activity decreased markedly at 12 h and 24 h. SOD and GST activity in hepatopancreas of the shrimps increased significantly at 1.5 h, but decreased markedly at 12 h-48 h. MDA content increased significantly after 6 h-24 h challenge. HE staining showed that V. parahaemolyticus challenge induced damage symptoms in hepatopancreas of P. monodon. Our study revealed that V. parahaemolyticus influenced the antioxidative status and caused oxidative stress and tissue damage via confusion of antioxidant enzymes in P. monodon.

Two variants of selenium-dependent glutathione peroxidase from the disk abalone Haliotis discus discus: Molecular characterization and immune responses to bacterial and viral stresses

Glutathione peroxidase (GPx) is an essential member of the antioxidant systems of living organisms and may be involved in immune defense against pathogenic invasion. In the current study, two selenium-dependent glutathione peroxidases (AbSeGPxs) that shared 54.3% identity were identified from the disk abalone Haliotis discus discus. The open reading frames (ORFs) of AbSeGPx-a and AbSeGPx-b coded for 222 and 220 amino acids, respectively, with a characteristic selenocysteine residue encoded by an opal stop codon (TGA). The conserved selenocysteine insertion sequence (SECIS) element was predicted in the 3' untranslated region (UTR) of both isoforms, and they were found to form two stem-loop structures. Amino acid comparison and phylogenetic studies revealed that the AbSeGPxs were closely related to those in other mollusk species and were evolutionarily distinct from those of other taxonomic groups. The SYBR Green qPCR was employed in investigating the transcripts of AbSeGPxs. The expression of AbSeGPxs mRNA was examined in different embryonic developmental stages and differential expression patterns for AbSeGPx-a and AbSeGPx-b were noted. Meanwhile, the highest expression of AbSeGPxs was detected in the hepatopancreas of healthy adult animals. Next, transcriptional levels were profiled in hemocytes of adults to determine the immune responses of AbSeGPxs to microbial infections. The results revealed the significant up-regulation of AbSeGPx-a in a time-dependent manner after bacterial (Listeria monocytogenes and Vibrio parahaemolyticus) and viral (viral hemorrhagic septicemia virus) infections. Consequently, these findings indicate that AbSeGPx-a and AbSeGPx-b might be involved in the embryonic development of disk abalone and the regulation of immune defense system of adult animals.

Dietary supplement of banana (Musa acuminata) peels hot-water extract to enhance the growth, anti-hypothermal stress, immunity and disease resistance of the giant freshwater prawn, Macrobrachium rosenbergii

In the present study, Macrobrachium rosenbergii were fed with diets containing extracts of banana, Musa acuminate, fruit's peel (banana peels extract, BPE) at 0, 1.0, 3.0 and 6.0 g kg(-1). The non-specific immune parameters, disease resistance and anti-hypothermal stress were evaluated at 2, 4, 8, 16 and 32 days of post feeding. Also, we demonstrated the percent weight gain (PWG), percent length gain (PLG), feeding efficiency (FE), and survival rate of giant freshwater prawn at 30, 60, 90, and 120 days of post feeding. The PWG, PLG, FE and survival rate of prawns fed at 0, 1.0, 3.0 and 6.0 g kg(-1) BPE-containing diets after 120 days were 69.5%, 75.4%, 77.8% and 83.3%; 21.8%, 23.6%, 27.8% and 33.9%; 0.60, 0.72, 0.75 and 0.90; and 55.4%, 62.2%, 62.3% and 75.3%, respectively. After 32 days of post feeding, a significant increase in total haemocyte count (THC), different haemocyte count (DHC), respiratory bursts (RBs), superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, phenoloxidase (PO) activity and transglutaminase (TG) activity, and meanwhile, a decreased haemolymph coagulation time was observed. Furthermore, phagocytic activity and clearance efficiency of prawns against Lactococcus garvieae infection were significantly increased. Prawns challenged with L. garvieae after 32 days of feeding at 1.0, 3.0 and 6.0 g kg(-1) had a significantly higher survival rate (33.3%, 40.0% and 56.7%) than those fed with the control diet. Subsequently, hypothermal (14 °C) stress was 43.4%, 50.0% and 50.0%, respectively. Altogether, we therefore recommend the dietary BPE administration at 6.0 g kg(-1) promotes growth, anti-hypothermal stress, and enhance immunity and resistance against L. garvieae in M. rosenbergii.

Double-dose β-glucan treatment in WSSV-challenged shrimp reduces viral replication but causes mortality possibly due to excessive ROS production

In our research efforts to reduce the impact of white spot syndrome virus (WSSV) disease outbreaks in shrimp aquaculture, we studied the effect of β-glucan administration to activate the prophenoloxidase (proPO) enzymatic cascade prior to WSSV challenge. Injection of a single dose of β-glucan (5 μg/g) prior to WSSV challenge resulted in activation of the proPO system and reduced shrimp mortality (25-50%) when compared to controls (100%). By contrast, no significant reduction was observed using yellow head virus (YHV) in a similar protocol. We subsequently hypothesized that administration of a second dose of β-glucan after WSSV challenge might reduce shrimp mortality further. Surprisingly, the opposite occurred, and mortality of the WSSV-infected shrimp increased to 100% after the second β-glucan dose. Both immunofluorescence and RT-PCR assays revealed low WSSV levels in hemocytes of shrimp collected after the second dose of β-glucan administration, suggesting that the cause of increased mortality was unlikely to be increased WSSV replication. We found from measured phenoloxidase acitivity (PO) and H2O2 production that the higher mortality may have resulted from a combination of WSSV infection plus over-production of reactive oxygen species (ROS) stimulated by two doses of β-glucan. Thus, caution may be prudent in continuous or prolonged activation of the shrimp immune system by β-glucan administration lest it exacerbate shrimp mortality in the event of WSSV infection.

Effects of hot-water extract of banana (Musa acuminata) fruit's peel on the antibacterial activity, and anti-hypothermal stress, immune responses and disease resistance of the giant freshwater prawn, Macrobrachium rosenbegii

The hot-extracts isolated from fruit's peel of banana, Musa acuminata, was evaluated on the antibacterial activity to pathogens from aquatic animals, and immunostimulating potential, disease resistance and anti-hypothermal stress in giant freshwater prawn, Macrobrachium rosenbergii through injection administration. The banana peel extract (BPE) showed good activity against 1 Gram-positive and 3 Gram-negative pathogens, including Lactococcus garvieae, Photobacteria damsella, Vibrio alginolyticus and Vibrio parahemolyticus especially in prawn pathogen of L. garvieae strain, which were carried out by a disk diffusion method. Prawn received BPE via injection administration at 1-6 μg (g prawn)(-1) significantly increased total haemocyte count (THC), hyaline cell (HC), granular cell (GC), phenoloxidase (PO) activity and phagocytic activity against L. garvieae from 3 to 6 days, and significantly increased clearance efficiency against L. garvieae and a significantly decreased coagulation time of prawn from 1 to 6 days. Prawn injected with BPE at 6.0 μg (g prawn)(-1) for 6 days showed significantly increased superoxide dismutase (SOD) activity, but significantly decreased respiratory bursts (RBs) of per haemocyte. Survival rates of M. rosenbergii injected with BPE at concentrations of 1, 3 and 6 μg (g prawn)(-1) were significantly higher than those injected with saline control after challenge with L. garvieae for 4-6 days, and the respective relative survival percentages of prawn were 28.6%, 38.1%, and 47.8%, respectively at 6 days. The sublethal time of prawns that had received saline and BPE at 1, 3 and 6 μg (g prawn)(-1) for 6 days and then were transferred from 28 °C to 14 °C were 69.4, 79.8, 83.6, and 90.2 h, respectively. It was concluded that the BPE can be used as the bacteriostat, and immunostimulant and physiological regulator for prawn through injection administration to enhance immunity, physiological responses, and resistance against L. garvieae.

Expression profiles of selenium dependent glutathione peroxidase and glutathione S-transferase from Exopalaemon carinicauda in response to Vibrio anguillarum and WSSV challenge

A selenium-dependent glutathione peroxidase cDNA was obtained from the ridgetail white prawn Exopalaemon carinicauda (EcGPx) by rapid amplification of cDNA ends (RACE) methods. The full-length cDNA of EcGPx was 946 bp, which contains a 5'-untranslated region (UTR) of 105 bp, 3'-UTR of 280 bp with a poly (A) tail, an open reading frame (ORF) of 561 bp, encoding a 186 amino-acid polypeptide with the predicted molecular weight of 21.35 kDa and estimated isoelectric point of 7.65. It involves a putative selenocysteine (U39) residue which is encoded by an opal codon, (220)TGA(222), and forms an active site with residues Q73 and W141. Sequence analysis revealed that a GPx signature motif 2 ((63)LAFPCNQF(70)), an extra active site motif ((151)WNFEKF(156)), two putative N-glycosylation site ((75)NNT(77) and (107)NGS(109)), and two arginine residues (R89 and R167) were observed in the EcGPx sequence. Comparison of amino acid sequences showed that white shrimp GPx is more closely related to GPx1 and GPx2 subgroups. Quantitative real-time RT-PCR analysis indicated that two glutathione antioxidant enzymes of E. carinicauda, glutathione peroxidase (designated EcGPx) and glutathione S-transferase (designated EcGST) were widely expressed in all the tested tissues, but showed different expression patterns. After Vibrio anguillarum and WSSV challenge, EcGPx and EcGST transcripts both in hemocytes and hepatopancreas increased in the first 6 h and 3 h, respectively. The results suggested that EcGPx and EcGST might be associated with the immune defenses to V. anguillarum and WSSV in E. carinicauda.

Effects of dietary administration of water hyacinth (Eichhornia crassipes) extracts on the immune responses and disease resistance of giant freshwater prawn, Macrobrachium rosenbergii

The hot-water extract of Eichhornia crassipes leaves (ECE) was produced and incorporated into the diet of the prawn, Macrobrachium rosenbergii, as an immunostimulant. Survival rates of prawn against Lactococcus garvieae, and its immune parameters including the total haemocyte count (THC), different haemocyte count (DHC), phenoloxidase (PO) activity, respiratory bursts (RBs), superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, transglutaminase (TG) activity, haemolymph coagulation time, and phagocytic activity and clearance efficiency against L. garvieae by M. rosenbergii were determined when prawn (23.0 ± 2.8 g) were fed ECE-containing diets at 0, 1.0, 2.0 and 3.0 g kg(-1). Prawn fed a diet containing ECE at 2.0 and 3.0 g kg(-1) for 12 days showed significantly increased THC, HC, GC, PO activity, RBs, SOD activity, GPx activity, and TG activity, and a significantly decreased coagulation time. The phagocytic activity and clearance efficiency against L. garvieae of prawn fed the ECE-containing diets at 1.0, 2.0, and 3.0 g kg(-1) were significantly higher than those of prawn fed the control diet at 3-12 days. Survival rates of M. rosenbergii fed the diet containing ECE at concentrations of 2 and 3 g kg(-1) were significantly higher than those fed the control diet after challenge with L. garvieae for 48-144 h. The relative percentage survival of prawn fed the 1.0, 2.0, and 3.0 g kg(-1) ECE-containing diets for 12 days were 17.5%, 39.1%, and 52.2%. It was concluded that the ECE can be used as an immunostimulant for prawn through dietary administration to enhance immune responses and resistance of M. rosenbergii against L. garvieae.

Cloning and functional analysis of glutathione peroxidase gene in red swamp crayfish Procambarus clarkii

Glutathione peroxidases (GPxs) are key enzymes in the antioxidant defense systems of living organisms, including crustaceans. The red swamp crayfish Procambarus clarkii is the most commonly farmed freshwater crayfish in Chinese inland nowadays due to its commercial value. However, high stocking density has resulted in adverse effects in growth performance and health. To investigate the function of GPxs in immune defense of the crayfish, we cloned and characterized a full length GPx (PcGPx) from P. clarkii by a reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The 931 bp PcGPx cDNA contains a 38 bp 5'-untranslated region (UTR), a 519 bp coding sequence (CDS) and a 375 bp 3'-UTR with a selenocysteine insertion sequence (SECIS). The PcGPx was predicted to encode 172 amino acids, and its putative molecular mass was 20.9 kDa with a pI of 4.37. A selenocysteine (Sec) encoded by the unusual stop codon, TGA, was in the protein coding region. Phylogenetic analysis showed that PcGPx clustered with the GPxs from the penaeid shrimp Metapenaeus ensis and Caenorhabditis elegans, sharing much higher similarity with vertebrate GPx1 and GPx2 than with GPx3 and GPx5. Quantitative RT-PCR revealed that PcGPx was extremely highly expressed in ovary and early embryos. In addition, the levels of PcGPx mRNA and reactive oxygen species (ROS) significantly increased after challenge with gram-negative Vibrio harveyi, gram-positive Staphyloccocus aureus or white spot syndrome virus (WSSV). These results suggest that PcGPx may play important roles not only in immune defense, but also in oogenesis in the crayfish.

Discovery of immune molecules and their crucial functions in shrimp immunity

Several immune-related molecules in penaeid shrimps have been discovered, most of these via the analysis of expressed sequence tag libraries, microarray studies and proteomic approaches. These immune molecules include antimicrobial peptides, serine proteinases and inhibitors, phenoloxidases, oxidative enzymes, clottable protein, pattern recognition proteins, lectins, Toll receptors, and other humoral factors that might participate in the innate immune system of shrimps. These molecules have mainly been found in the hemolymph and hemocytes, which are the main sites where immune reactions take place, while some are found in other immune organs/tissues, such as the lymphoid organs, gills and intestines. Although the participation of some of these immune molecules in the shrimp innate immune defense against invading pathogens has been demonstrated, the functions of many molecules remain unclear. This review summarizes the current status of our knowledge concerning the discovery and functional characterization of the immune molecules in penaeid shrimps.

Selenium-dependent glutathione peroxidase gene expression during gonad development and its response to LPS and H₂O₂ challenge in Scylla paramamosain

A selenium-dependent glutathione peroxidase cDNA was obtained from green mud crab Scylla paramamosain (SpGPx) by homology PCR technique and rapid amplification of cDNA ends (RACE) methods. The 1135 bp full-length cDNA contains a 9 bp 5'-untranslated region (UTR), an open reading frame (ORF) of 564 bp encoded a deduced protein of 187 amino acids (aa), and a 562 bp 3'-UTR with a 100 bp conserved eukaryotic selenocysteine insertion sequence (SECIS). It involves a putative selenocysteine (Sec⁴⁰, or U⁴⁰) residue which is encoded by an opal codon, ¹²⁷TGA¹²⁹, and forms an active site with residues Q⁷⁴ and W¹⁴². Sequence characterization revealed that SpGPx contain a characteristic GPx signature motif 2 (⁶⁴LAFPCNQF⁷¹), an active site motif (¹⁵²WNFEKF¹⁵⁷), a potential N-glycosylation site (⁷⁶NTT⁷⁸), and two residues (R⁹⁰ and R¹⁶⁸) which contribute to the electrostatic architecture by directing the glutathione donor substrate. Multiple sequence alignment and phylogenetic analysis showed that SpGPx share a high level of identities and closer relationship with other selected invertebrate GPxs and vertebrate GPx1 and GPx2. Molecular modelling analysis results also supported these observations. Real time quantitative PCR analysis revealed that SpGPx was constitutively expressed in 10 selected tissues, and its expression level in gill and testis was higher than that in the other tissues (p < 0.05). The SpGPx expression increased and then declined during ovarian and testicular development implying thatnscrpits yowed that SpGPx might play an important role in gonad development by protecting them from oxidative stress. The expression of SpGPx mRNA was induced by lipopolysaccharide (LPS) and hydrogen peroxide (H₂O₂) in hepatopancreas and haemocytes. The results suggested that SpGPx was implicated in the immune response induced by LPS and H₂O₂.

Potential relationship among three antioxidant enzymes in eliminating hydrogen peroxide in penaeid shrimp

Antioxidant enzymes, such as glutathione peroxidase (GPx), catalase (CAT), and peroxiredoxin (Prx), are essential components in cells to eliminate excessive reactive oxygen species such as hydrogen peroxide (H(2)O(2)). GPx, CAT, and Prx genes have been reported in penaeid shrimp, and they showed different expression profiles at transcription or protein level when shrimps were challenged by microbes. In order to learn the relationship among the above three genes in their function, GPx, CAT, and Prx transcripts were analyzed, and the variation of GPx and CAT enzyme activity was detected when shrimp was injected with H(2)O(2) or one antioxidant enzyme gene was silenced in shrimp by double-strand RNA injection. The results indicated that there existed some relationships among three antioxidant enzyme genes, CAT, GPx, and Prx in shrimp at transcriptional level. The transcription of CAT and GPx could be directly induced by H(2)O(2) injection, while the transcription of Prx cannot be induced by H(2)O(2). Decreased transcription level of CAT or GPx could lead to increased transcription of the other two genes, which suggested that there existed some compensation among these three antioxidant enzyme genes. These data can help us to understand the roles of antioxidant enzymes in crustacean.