Molecular characterization and function of a PTEN gene from Litopenaeus vannamei after Vibrio alginolyticus challenge

Identifying the function of the PI3K-AKT pathway during the pathogenic infection of Macrobrachium rosenbergii

The phosphoinositide-3-kinase/protein kinase b (PI3K-Akt) pathway is a signalling pathway based on protein phosphorylation and can be activated by a wide range of factors. To investigate the function of the PI3K-AKT signalling pathway in antibacterial immunity, we analysed the gene expression level of three key factors (PI3K, AKT and FoxO) and innate immune factors in immune tissues at different time points after Vibrio parahaemolyticus and Staphylococcus aureus infection. Tissues analysis showed that PI3K, AKT, and FoxO were expressed at high levels in the intestinal, hemocytes and hepatopancreas. Moreover, the expression levels of PI3K, AKT and FoxO can be regulated postinfection by different pathogens. In hemocytes and the intestine, V. parahaemolyticus infection was found to regulate the levels of PI3K, AKT, and FoxO more rapidly; however, an S. aureus infection regulated the levels of these factors more rapidly in the hepatopancreas and gills. Analysis showed that V. parahaemolyticus and S. aureus infection caused changes in the gene expression level of crustin, caspase 3 and NF-κB. Therefore, PI3K-AKT regulates the downstream immune pathway differentially in different immune tissues and participates in the regulation of cell apoptosis and the inflammatory response by activating caspase and NF-κB, respectively, following infection with V. parahaemolyticus and S. aureus.

Preliminary study on toxicological mechanism of golden cuttlefish (Sepia esculenta) larvae exposed to cd

BACKGROUND

Cadmium (Cd) flows into the ocean with industrial and agricultural pollution and significantly affects the growth and development of economic cephalopods such as Sepia esculenta, Amphioctopus fangsiao, and Loligo japonica. As of now, the reasons why Cd affects the growth and development of S. esculenta are not yet clear.

RESULTS

In this study, transcriptome and four oxidation and toxicity indicators are used to analyze the toxicological mechanism of Cd-exposed S. esculenta larvae. Indicator results indicate that Cd induces oxidative stress and metal toxicity. Functional enrichment analysis results suggest that larval ion transport, cell adhesion, and some digestion and absorption processes are inhibited, and the cell function is damaged. Comprehensive analysis of protein-protein interaction network and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to explore S. esculenta larval toxicological mechanisms, and we find that among the 20 identified key genes, 14 genes are associated with neurotoxicity. Most of them are down-regulated and enriched to the neuroactive ligand-receptor interaction signaling pathway, suggesting that larval nervous system might be destroyed, and the growth, development, and movement process are significantly affected after Cd exposure.

CONCLUSIONS

S. esculenta larvae suffered severe oxidative damage after Cd exposure, which may inhibit digestion and absorption functions, and disrupt the stability of the nervous system. Our results lay a function for understanding larval toxicological mechanisms exposed to heavy metals, promoting the development of invertebrate environmental toxicology, and providing theoretical support for S. esculenta artificial culture.

Andrographis paniculata improves growth and non-specific immunity of shrimp Litopenaeus vannamei, and protects it from Vibrio alginolyticus by reducing oxidative stress and apoptosis

Andrographis paniculata (AP) is a traditional medicinal plant with many pharmacological activities, including anti-inflammatory, antimicrobial, immunity stimulation and so on. Several studies have reported that AP plays a strong role in promoting the immune system of aquatic animals to resist several pathogens. In the present study, we investigate the effects of a diet containing AP on the immune responses, growth, and the resistance to Vibrio alginolyticus (V. alginolyticus) in Litopenaeus vannamei (L. vannamei). Four diets were formulated by adding AP at the dosage of 0% (Control), 0.25%, 0.5%, and 1% in the basal diet, respectively. Each diet was randomly fed to one group with three replicates of shrimps in a 28-day feeding trial. The results showed that dietary AP improved the growth performance and non-specific immune function of shrimps. To investigate the effect of AP on disease resistance of L. vannamei, shrimps fed with diet containing AP were challenged with V. alginolyticus. Compared with the control group, the shrimps fed diet containing AP showed significantly higher survival. Furthermore, the hepatopancreas injury in the shrimp fed with AP was less than control group at 6 h after V. alginolyticus infection. However, no difference was observed in the degree of hepatopancreas injury between AP groups and control group at 12 h and 24 h after V. alginolyticus infection. Based on this result, the samples at 6 h after V. alginolyticus infection was selected for subsequent detection. Reactive oxygen species (ROS) accumulation in hemocytes and O₂^- production in hepatopancreas caused by V. alginolyticus infection was significantly reduced after feeding a diet containing 0.25% and 0.5% AP (p < 0.05). In addition, we found that feeding AP significantly up-regulated the expression of pro-apoptotic genes (Bax, Caspase 3, p53) and down-regulated the expression of anti-apoptotic genes (Bcl-2) in hepatopancreas after V. alginolyticus infection. In conclusion, AP promote the growth and immunity of L. vannamei, and protects shrimps against V. alginolyticus by regulating the oxidative damage and apoptosis. These results provide useful information regarding the effects of AP extracts as a shrimp feed additive for sustainable shrimp culture.

Andrographolide promote the growth and immunity of Litopenaeus vannamei, and protects shrimps against Vibrio alginolyticus by regulating inflammation and apoptosis via a ROS-JNK dependent pathway

Vibrio alginolyticus (V. alginolyticus) is one of the major pathogens causing mass mortality of shrimps worldwide, affecting energy metabolism, immune response and development of shrimps. In the context of the prohibition of antibiotics, it is necessary to develop a drug that can protect shrimp from V. alginolyticus. Andrographolide (hereinafter called Andr), a traditional drug used in Chinese medicine, which possesses diverse biological effects including anti-bacteria, antioxidant, immune regulation. In this study, we investigated the effect of Andr on growth, immunity, and resistance to V. alginolyticus infection of Litopenaeus vannamei (L. vannamei) and elucidate the underlying molecular mechanisms. Four diets were formulated by adding Andr at the dosage of 0 g/kg (Control), 0.5 g/kg, 1 g/kg, and 2 g/kg in the basal diet, respectively. Each diet was randomly fed to one group with three replicates of shrimps in a 4-week feeding trial. The results showed that dietary Andr improved the growth performance and non-specific immune function of shrimps. L. vannamei fed with Andr diets showed lower mortality after being challenged by V. alginolyticus. After 6 h of V. alginolyticus infection, reactive oxygen species (ROS) production, tissue injury, apoptosis, expression of inflammatory factors (IL-1 β and TNFα) and apoptosis-related genes (Bax, caspase3 and p53) were increased in hemocytes and hepatopancreas, while feeding diet with 0.5 g/kg Andr could inhibit the increase. Considering that JNK are important mediators of apoptosis, we examined the influence of Andr on JNK activity during V. alginolyticus infection. We found that Andr inhibited JNK activation induced by V. alginolyticus infection on L. vannamei. The ROS scavenger N-acetyl-l-cysteine (NAC) suppressed V. alginolyticus-induced inflammation and apoptosis, suggesting that ROS play an important role in V. alginolyticus-induced inflammation and apoptosis. Treated cells with JNK specific activator anisomycin, the inflammation and apoptosis inhibited by Andr were counteracted. Collectively, Andr promote the growth and immunity of L. vannamei, and protects shrimps against V. alginolyticus by regulating inflammation and apoptosis via a ROS-JNK dependent pathway. These results improve the understanding of the pathogenesis of V. alginolyticus infection and provide clues to the development of effective drugs against V. alginolyticus.

A Litopenaeus vannamei p70S6K gene is involved in the antioxidative and apoptosis under low temperature

p70S6K is involved in cellular response, such as tumor metastases, the immune response and tissue repair in vertebrates. The role of p70S6K in these physiological processes in crustaceans remains, however, unknown. In this study, the Lvp70S6K was identified, containing a 5' UTR of 294 bp, an ORF of 1494 bp ad a 3' UTR of 211 bp, encoding 497 amino acids with a theoretical molecular weight of 70 kDa and an estimated isoelectric point of (pI) of 5.16. The multiple alignment found that Lvp70S6K was highly homologous with other invertebrates. Lvp70S6K mRNA was detected in all the tested tissues and the Lvp70S6K expression levels was significantly down-regulated and reached the lowest level (0.44-fold, p < 0.01) at 1.5 h after low temperature stress. The subcellular localization of Lvp70S6K could be detected in cytoplasm. ROS production was significantly up-regulation (1.19-fold, p < 0.01), total hemocyte count (THC) was significantly down-regulation (0.22-fold, p < 0.01), apoptosis rate was markedly increased (1.09-fold, p < 0.01), apoptosis-related genes of LvPDCD4 (1.61-fold, p < 0.01) and LvCyt.C (1.23-fold, p < 0.01) were up-regulated, and anti-apoptotic gene of LvBcl-2 (0.69-fold, p < 0.01), LvIAP1 (0.68-fold, p < 0.01) and LvIAP2 (0.45-fold, p < 0.01) were decreased after low temperature stress in hemolymph of Lvp70S6K-silenced shrimp at 1.5 h. Silencing of LvPTEN significantly increased Lvp70S6K, LvPI3K, LvAKT and LvmTOR expression. In summary, these results indicated that Lvp70S6K play a crucial role in oxidative and apoptosis, which was able to negatively regulate by PTEN.

miR-19a Is Involved In Progression And Malignancy Of Anaplastic Thyroid Cancer Cells

Background

MicroRNAs (miRNAs) are endogenous, single-stranded, non-coding RNAs acting as negative regulators of gene expression involved in a number of physiological processes. MiRNAs' expression is commonly dysregulated in many types of human tumor diseases and cancers, including thyroid cancers, and is often involved in tumor initiation and progression. miR-19a, a member of miR-17-92 cluster, has been demonstrated to promote cell growth in anaplastic thyroid cancer (ATC), the most advanced and aggressive thyroid cancer.

Purpose

In this work, we investigate the potential contribution of miR-19a in thyroid cancer cells poor prognosis and de-differentiation.

Methods

We directly modulated the expression of miR-19a in papillary (PTC) and anaplastic thyroid carcinoma cell lines through transfection of specific miR-19a mimic or inhibitor. Further, we performed gene expression analysis of specific genes to evaluate miR-19a association with cell cycle, differentiation, and poor prognosis.

Results

Our data indicate that miR-19a overexpression in PTC cells significantly promotes cell growth, decreases the expression of differentiation genes and activates poor prognosis genes. Its inhibition in ATC cells reduces cell proliferation and the expression of genes related to poor prognosis but does not affect differentiation.

Conclusion

Our findings reveal the existence of functional associations between miR-19a expression and thyroid cancer progression and malignancy suggesting miR-19a as a novel candidate therapeutic target for ATC.

miRNAs induced by white spot syndrome virus involve in immunity pathways in shrimp Litopenaeus vannamei

White shrimp Litopenaeus vannamei are widely cultured in the world and white spot syndrome virus (WSSV) led to huge economic losses in the shrimp industry every year. In the present study, miRNAs involved in the response of shrimp L. vannamei to WSSV infection were obtained through the Illumina HiSeq 2500 high-throughput next-generation sequencing technique. A total number of 7 known miRNAs and 54 putative novel miRNAs were obtained. Among them, 14 DEMs were identified in the shrimp infected with WSSV. The putative target genes of these DEMs were related to host immune response or signaling pathways, indicating the importance of miRNAs in shrimp against WSSV infection. The results will provide information for further research on shrimp response to virus infection and contribute to the development of new strategies for effective protection against WSSV infections.

Comparative proteomic investigation of Marsupenaeus japonicus hepatopancreas challenged with Vibrio parahaemolyticus and white spot syndrome virus

This study aimed to use isobaric tags (IBTs) to investigate the immune response of the hepatopancreas of Marsupenaeus japonicas infected with Vibrio parahaemolyticus or white spot syndrome virus (WSSV). Liquid chromatography-tandem mass spectrometry and protein sequencing identified 1005 proteins. Among them, 109 proteins were upregulated and 94 were downregulated after V. parahaemolyticus infection. After WSSV infection, 130 proteins were identified as differentially abundant, including 88 that were upregulated and 42 were downregulated. Fifty-four proteins were identified as differentially abundant after both V. parahaemolyticus and WSSV infection. A number of proteins related to cytoskeletal processes, including actin and myosin, and apoptosis-related proteins were upregulated in shrimp after V. parahaemolyticus and WSSV infection, indicating that phagocytosis and apoptosis may be involved in the response to in V. parahaemolyticus or WSSV infection. Quantitative real-time PCR was carried out to verify the reliability of the proteomic data. These data provide a basis to characterize the immunity-related processes of shrimp in response to infection with WSSV or V. parahaemolyticus.

Full-length transcriptome analysis of Litopenaeus vannamei reveals transcript variants involved in the innate immune system

To better understand the immune system of shrimp, this study combined PacBio isoform sequencing (Iso-Seq) and Illumina paired-end short reads sequencing methods to discover full-length immune-related molecules of the Pacific white shrimp, Litopenaeus vannamei. A total of 72,648 nonredundant full-length transcripts (unigenes) were generated with an average length of 2545 bp from five main tissues, including the hepatopancreas, cardiac stomach, heart, muscle, and pyloric stomach. These unigenes exhibited a high annotation rate (62,164, 85.57%) when compared against NR, NT, Swiss-Prot, Pfam, GO, KEGG and COG databases. A total of 7544 putative long noncoding RNAs (lncRNAs) were detected and 1164 nonredundant full-length transcripts (449 UniTransModels) participated in the alternative splicing (AS) events. Importantly, a total of 5279 nonredundant full-length unigenes were successfully identified, which were involved in the innate immune system, including 9 immune-related processes, 19 immune-related pathways and 10 other immune-related systems. We also found wide transcript variants, which increased the number and function complexity of immune molecules; for example, toll-like receptors (TLRs) and interferon regulatory factors (IRFs). The 480 differentially expressed genes (DEGs) were significantly higher or tissue-specific expression patterns in the hepatopancreas compared with that in other four tested tissues (FDR <0.05). Furthermore, the expression levels of six selected immune-related DEGs and putative IRFs were validated using real-time PCR technology, substantiating the reliability of the PacBio Iso-seq results. In conclusion, our results provide new genetic resources of long-read full-length transcripts data and information for identifying immune-related genes, which are an invaluable transcriptomic resource as genomic reference, especially for further exploration of the innate immune and defense mechanisms of shrimp.

The role of delta-1-pyrroline-5-carboxylate dehydrogenase (P5CDh) in the Pacific white shrimp (Litopenaeus vannamei) during biotic and abiotic stress

Proline (Pro) metabolism is intimately associated with stress adaptation. The catabolism of Pro includes two dehydrogenation reactions catalyzed by proline dehydrogenase (ProDH) and Δ¹-pyrroline-5-carboxylate dehydrogenase (P5CDh). P5CDh is a mitochondrial matrix NAD⁺-dependent dehydrogenase that is critical in preventing P5C-Pro intensive cycling and avoiding ROS production from electron run-off. Little is known about the roles of P5CDh in invertebrates, however. We cloned the P5CDh sequence in the Pacific white shrimp, Litopenaeus vannamei, and found that LvP5CDh is expressed predominantly in pleopod, hepatopancreas and gill. Subcellular localization analysis revealed that LvP5CDh protein was mainly found in the cytoplasm. In addition, overexpressing LvP5CDh in cells reduced ROS formation and inhibited apoptosis induced by LC₅₀ Cd²⁺. Shrimp were exposed to various stress factors including infection with Vibrio alginolyticus, (½ LC₅₀ and LC₅₀) Cd²⁺, acid (pH 5.6) and alkali stress (pH 9.3). Both biotic and abiotic stress resulted in increased LvP5CDh expression and Pro accumulation; V. alginolyticus infection, pH 9.3 and LC₅₀ Cd²⁺ stress apparently stimulated the Glu pathway of Pro synthesis, while pH 5.6 and ½ LC₅₀ Cd²⁺ stress promoted the Orn pathway of Pro synthesis. Silencing of Lvp53 in shrimp attenuated LvP5CDh expression during Cd²⁺ stress, but had no effect on LvP5CDh mRNA levels if no Cd²⁺ stress was imposed. Our study contributes to the functional characterization of LvP5CDh in biotic and abiotic stress and reveals it to protect against ROS generation, damage to the cell, including the mitochondria, and apoptosis. Thus, LvP5CDh plays a critical role in immune defense and antioxidant responses.

WSSV-host interaction: Host response and immune evasion

As invertebrates, shrimps rely on multiple innate defense reactions, including humoral immunity and cellular immunity to recognize and eliminate various invaders, such as viruses. White spot syndrome virus (WSSV) causes the most prevalent and devastating viral disease in penaeid shrimps, which are the most widely cultured species in the coastal waters worldwide. In the last couple of decades, studies about WSSV implicate a dual role of the immune system in protecting shrimps against the infection; these studies also explore on the pathogenesis of WSSV infection. Herein, we review our current knowledge of the innate immune responses of shrimps to WSSV, as well as the molecular mechanisms used by this virus to evade host immune responses or actively subvert them for its own benefit. Deciphering the interactions between WSSV and the shrimp host is paramount to understanding the mechanisms that regulate the balance between immune-mediated protection and pathogenesis during viral infection and to the development of a safe and effective WSSV defensive strategy.

MiR-19a Overexpression in FTC-133 Cell Line Induces a More De-Differentiated and Aggressive Phenotype

In recent years, microRNAs (miRNAs) have received increasing attention for their important role in tumor initiation and progression. MiRNAs are a class of endogenous small non-coding RNAs that negatively regulate the expression of several oncogenes or tumor suppressor genes. MiR-19a, a component of the oncogenic miR-17-92 cluster, has been reported to be highly expressed only in anaplastic thyroid cancer, the most undifferentiated, aggressive and lethal form of thyroid neoplasia. In this work, we evaluated the putative contribution of miR-19a in de-differentiation and aggressiveness of thyroid tumors. To this aim, we induced miR-19a expression in the well-differentiated follicular thyroid cancer cell line and evaluated proliferation, apoptosis and gene expression profile of cancer cells. Our results showed that miR-19a overexpression stimulates cell proliferation and alters the expression profile of genes related to thyroid cell differentiation and aggressiveness. These findings not only suggest that miR-19a has a possible involvement in de-differentiation and malignancy, but also that it could represent an important prognostic indicator and a good therapeutic target for the most aggressive thyroid cancer.

Molecular characterization and function analysis of a nucleotide excision repair gene Rad23 from Litopenaeus vannamei after Vibrio alginolyticus challenge

Nucleotide excision repair (NER) removes many different types of DNA lesions, and NER related host factors are reported to aid recovery steps during viral integration. Here, we report the identification and characterization of a DNA repair gene Rad23 from Litopenaeus vannamei and explore its role in innate immunity of crustaceans. LvRad23 contains a1149 bp open reading frame (ORF) which encodes a 382 amino acids protein with predicted theoretical isoelectric point of 4.21. LvRad23 was ubiquitously expressed in the muscle, eyestalk, gill, stomach, heart, legs, intestine, and hepatopancreas in order from high to low and LvRad23 protein was showed to be located in the cytoplasm of Drosophila S2 cells. The homology analysis showed that it has a high sequence homology with Rad23 protein from Marsupenaeus japonicus. Vibrio alginolyticus challenge induced a remarkable up-regulation of LvRad23 mRNA in hepatopancreas. Knocking down LvRad23can interfere the NER pathway by down regulating the expression of replication protein A (RPA) and proliferating cell nuclear antigen (PCNA). However it didn't cause any significant difference on total hemocyte count (THC) between LvRad23-silenced and non-silenced group.LvRad23-silenced then challenge with V. alginolyticus inducing high level of reactive oxygen species (ROS) and DNA damage in hemolymph. As well as decreased THC, which seriously diminished the innate immune system of L. vannamei. Meanwhile, the NER pathway was reactived by enhancing the expression of LvRad23 and promoting the production of LvPCNA to resist apoptosis and maintain proliferation of hemolymph cells in the later stage. Our results suggest that LvRad23 plays a vital role in shrimp specific immune response to V. alginolytcus through its participation in NER pathway.

Identifying the function of LvPI3K during the pathogenic infection of Litopenaeus vannamei by Vibrio alginolyticus

It is well known that PI3K regulates various processes in mammalian cells by generating a secondary messenger that later activates AKT. However, its innate immune function in crustaceans remains unclear. We report the characterization of Litopenaeus vannamei PI3K (LvPI3K) for investigating how PI3K participates in the innate immunity of crustaceans. Full-length LvPI3K cDNA was 3357 bp long, with a 3222 bp open reading frame (ORF) that encodes a putative protein of 1292 amino acids. The PI3K catalytic domain (PI3Kc) of LvPI3K was found to be rather conserved when the PI3Ks from other species were analyzed. The LvPI3K protein was shown to be localized to the cytoplasm of Drosophila S2 cells, while LvPI3K mRNA was ubiquitously expressed in healthy L. vannamei, with the highest expression found in hemolymph. A dual luciferase reporter gene assay demonstrated that LvPI3K overexpression activated the promoter of antibacterial peptide LvPEN4 in a dose-dependent manner. However, the addition of PDTC, a specific inhibitor of NF-κB, suppressed the LvPI3K-induced LvPEN4 promoter activation. Moreover, Vibrio alginolyticus challenge induced a rapid up-regulation of LvPI3K expression. Further experiments showed that LvPI3K silencing in shrimp challenged with V. alginolyticus significantly increased Vibrio number, ROS production and DNA damage in the hemolymph, as well as significantly decreased total hemocyte count. The mRNA levels of certain molecules related to LvPI3K signaling, such as LvAKT and LvPEN4, also decreased following LvPI3K silencing. Taken together, these results suggest that LvPI3K regulates the downstream signal component LvPEN4 and functions in V. alginolyticus resistance.

Molecular cloning, characterization and function of a germinal center kinase MST4 gene from Litopenaeus vannamei in response to Vibrio alginolyticus challenge in TLR-TRAF6 signaling pathway

The serine/threonine protein kinase MST4 plays multiple roles in the regulation of signaling pathways that govern cellular processes including mitosis, migration, homeostasis, polarity, proliferation, differentiation and apoptosis. Here we report the identification and characterization of the full-length sequence of LvMST4 from the shrimp L. vannamei, and investigations into its role in the shrimp's immune response to infection by the pathogenic bacterium Vibrio alginolyticus. Subcellular localization assays demonstrated the enzyme's presence in the shrimp's cytoplasm, and tissue-specific expression analysis revealed that it is expressed ubiquitously but at different levels in different tissues. Infection with V. alginolyticus increased LvMST4 expression and induced a rapid response via the TLR-TRAF6 signaling pathway, causing a decline in the total hemocyte count (THC) and an increase in respiratory burst (RB) activity. In non-infected shrimp, RNAi silencing of LvMST4 with dsRNA had no significant effect on THC but seemed to activate the TRAF6-MKK6-p38 pathway and reduced RB activity. In shrimp challenged with V. alginolyticus, LvMST4 silencing reduced bacterial clearance and increased the initial upregulation of LvTRAF6 while reducing the expression of LvMKK6 and Lvp38. LvMST4 silencing also slightly reduced the THC but caused pronounced increases in RB activity and cumulative mortality. These findings suggest that LvMST4 contributes to antimicrobial responses via the TLR-TRAF6 signal pathway, and helps maintain immunological homeostasis in L. vannamei.

Identification and characterization of a laccase from Litopenaeus vannamei involved in anti-bacterial host defense

Phenoloxidases (POs) are a family of enzymes including tyrosinases, catecholases and laccases, which play an important role in immune defences of various invertebrates. Whether or not laccase exists in shrimp and its function is still poorly understood. In this study, a laccase (LvLac) was cloned and identified from Litopenaeus vannamei for the first time. The full length of LvLac is 3406 bp, including a 2034 bp open reading frame (ORF) coding for a putative protein of 677 amino acids with a signal peptide of 33 aa. LvLac contains three Cu-oxidase domains with copper binding centers formed by 10 histidines, one cysteine and one methionine, respectively. Phylogenetic analysis revealed that LvLac was close to insects laccase 1 family. LvLac expression was most abundant in heart and the crude LvLac protein could catalyze the oxidation of hydroquinone. Real-time PCR showed that LvLac expression was responsive to Vibrio parahaemolyticus, Micrococcus lysodeikticus and white spot syndrome virus (WSSV) infection. Knockdown of LvLac enhanced the sensitivity of shrimps to V. parahaemolyticus and M. lysodeikticus challenge, suggesting that LvLac may play a positive role against bacterial pathogens.

Molecular characterization and function of the Prohibitin2 gene in Litopenaeus vannamei responses to Vibrio alginolyticus

Prohibitin2 (PHB2), a potential tumor suppressor protein, plays important roles in inhibition of cell cycle progression, transcriptional regulation, apoptosis and the mitochondrial respiratory chain. To explore its potential roles in crustaceans' immune responses we have identified and characterized LvPHB2, a 891 bp gene encoding a 297 amino acids protein in the shrimp Litopenaeus vannamei. Expression analyses showed that LvPHB2 is expressed in all examined tissues, and largely present in cytoplasm, correlating with its known anti-oxidation function in mitochondria. Luciferase reporter assays showed that over-expression of LvPHB2 could activate the p53 pathway, indicating that it might participate in apoptosis regulation. Quantitative real-time PCR revealed that infection with Vibrio alginolyticus induces its up-regulation in hepatopancreas. Moreover, RNAi knock-down of LvPHB2 in vivo raises mortality rates of L. vannamei infected by V. alginolyticus, and affects expression of STAT3, Caspase3 and p53 genes. We found significantly higher reactive oxygen species production, DNA damage and apoptosis rates in LvPHB2-silenced shrimp challenged with V. alginolyticus than in controls injected with a Green Fluorescent Protein-silencing construct. Our results suggest that LvPHB2 plays a vital role in shrimp responses to V. alginolyticus infection through its participation in regulation of oxidants and apoptosis.

Shrimp with knockdown of LvSOCS2, a negative feedback loop regulator of JAK/STAT pathway in Litopenaeus vannamei, exhibit enhanced resistance against WSSV

JAK/STAT pathway is one of cytokine signaling pathways and mediates diversity immune responses to protect host from viral infection. In this study, LvSOCS2, a member of suppressor of cytokine signaling (SOCS) families, has been cloned and identified from Litopenaeus vannamei. The full length of LvSOCS2 is 1601 bp, including an 1194 bp open reading frame (ORF) coding for a putative protein of 397 amino acids with a calculated molecular weight of ∼42.3 kDa. LvSOCS2 expression was most abundant in gills and could respond to the challenge of LPS, Vibrio parahaemolyticus, Staphhylococcus aureus, Poly (I: C) and white spot syndrome virus (WSSV). There are several STAT binding motifs presented in the proximal promoter region of LvSOCS2 and its expression was induced by LvJAK or LvSTAT protein in a dose dependent manner, suggesting LvSOCS2 could be the transcriptional target gene of JAK/STAT pathway. Moreover, the transcription of DmVir-1, a read out of the activation of JAK/STAT pathway in Drosophila, was promoted by LvJAK but inhibited by LvSOCS2, indicating that LvSOCS2 could be a negative regulator in this pathway and thus can form a negative feedback loop. Our previous study indicated that shrimp JAK/STAT pathway played a positive role against WSSV. In this study, RNAi-mediated knockdown of LvSOCS2 shrimps showed lower susceptibility to WSSV infection and caused lessened virus loads, which further demonstrated that the JAK/STAT pathway could function as an anti-viral immunity in shrimp.