Regulation of lactate dehydrogenase in response to WSSV infection in the shrimp Litopenaeus vannamei

OsLdh7, a rice lactate dehydrogenase, confers stress resilience in rice under cadmium stress through NAD+/NADH regulation

Lactate dehydrogenase (Ldh, EC 1.1.1.27), an oxidoreductase enzyme catalyses the interconversion of pyruvate to L-lactate and vice-versa with concomitant oxidation and reduction of NADH and NAD+. The enzyme functions as a ROS sensor and mitigates stress response by maintaining NAD+/NADH homeostasis. In this study, we delineated the role of the Ldh enzyme in imparting cadmium stress tolerance in rice. Previously, we identified a putatively active Ldh in rice (OsLdh7) through insilico modelling. Biochemical characterization of the OsLdh7 enzyme revealed it to be optimally active at pH 6.6 in the forward direction and pH 9 in the reverse direction. Overexpression of OsLdh7 in rice cv. IR64, increased tolerance of the transgenic lines to cadmium stress compared to the wild type (WT) at both seedling and reproductive stages. The transgenic lines showed increased enzyme activity in the reverse direction under cadmium stress, attributed to elevated cytosolic pH resulting from increased calcium concentration. This increased NADH content is highly essential for functioning of the ROS scavenging enzymes, RbohD and MPK6. qPCR analysis revealed that the overexpression lines had increased transcript abundance of these genes indicating an effective ROS scavenging mechanism. Additionally, the overexpression lines showed an efficient cadmium sequestration mechanism compared to the WT by increasing the transcript levels of the vacuolar transporters of cadmium as well as total phytochelatin content. Thus, our findings indicated OsLdh7 imparts cadmium stress tolerance in rice through a two-pronged approach by mitigating ROS and sequestering cadmium ions, highlighting its potential for crop improvement programs.

HIF-1-mediated regulation of LDH gene unravels key insights into MCDV-1 pathogenesis in mud crabs Scylla paramamosain

Hypoxia-inducible factors -1 (HIF-1) is a crucial transcription factor that regulates the expression of glycolytic genes. Our previous study proved that the Mud crab dicistrovirus-1 (MCDV-1) can induce aerobic glycolysis that favors viral replication in mud crab Scylla paramamosain. However, the role of HIF-1 on key glycolytic genes during the MCDV-1 infection has not been examined. In this study, the intricate interplay between HIF-1 and the key glycolysis enzyme, lactate dehydrogenase (LDH), was investigated after MCDV-1 infection. The expression of LDH was significant increased after MCDV-1 infection. Additionally, the expression of HIF-1α was upregulated following MCDV-1 infection, potentially attributed to the downregulation of prolyl hydroxylase domains 2 expression. Subsequent examination of the SpLDH promoter identified the presence of hypoxia response elements (HREs), serving as binding sites for HIF-1α. Intriguingly, experimental evidence demonstrated that SpHIF-1α actively promotes SpLDH transcription through these HREs. To further elucidate the functional significance of SpHIF-1α, targeted silencing was employed, resulting in a substantial reduction in SpLDH expression, activity, and lactate concentrations in MCDV-1-infected mud crabs. Notably, SpHIF-1α-silenced mud crabs exhibited higher survival rates and lower viral loads in hepatopancreas tissues following MCDV-1 infection. These results highlight the critical role of SpHIF-1α in MCDV-1 pathogenesis by regulating LDH gene dynamics, providing valuable insights into the molecular mechanisms underlying the virus-host interaction.

Role of HIF in fish inflammation

The hypoxia-inducing factor (HIF) is a central transcription factor in cellular oxygen sensing and regulation. It is common that the inflammation always appears in many diseases, like infectious diseases in fishes, and the inflammation is often accompanied by hypoxia, as a hallmark of inflammation. Besides coordinating cellular responses to low oxygen, HIF-mediated hypoxia signaling pathway is also crucial for immune responses such as the regulations of innate immune cell phenotype and function, as well as metabolic reprogramming under the inflammation. However, the understanding of the molecular mechanisms by which HIFs regulate the inflammatory response in fish is still very limited. Here, we review the characteristics of HIF as well as its roles in innate immune cells and the infections caused by bacteria and viruses. The regulatory effects of HIF on the metabolic reprogramming of innate immune cells are also discussed and the future research directions are outlooked. This paper will serve as a reference for elucidating the molecular mechanism of HIF regulating inflammation and identifying treatment strategies to target HIF for fish disease.

G6PDH as a key immunometabolic and redox trigger in arthropods

The enzyme glucose-6-phosphate dehydrogenase (G6PDH) plays crucial roles in glucose homeostasis and the pentose phosphate pathway (PPP), being also involved in redox metabolism. The PPP is an important metabolic pathway that produces ribose and nicotinamide adenine dinucleotide phosphate (NADPH), which are essential for several physiologic and biochemical processes, such as the synthesis of fatty acids and nucleic acids. As a rate-limiting step in PPP, G6PDH is a highly conserved enzyme and its deficiency can lead to severe consequences for the organism, in particular for cell growth. Insufficient G6PDH activity can lead to cell growth arrest, impaired embryonic development, as well as a reduction in insulin sensitivity, inflammation, diabetes, and hypertension. While research on G6PDH and PPP has historically focused on mammalian models, particularly human disorders, recent studies have shed light on the regulation of this enzyme in arthropods, where new functions were discovered. This review will discuss the role of arthropod G6PDH in regulating redox homeostasis and immunometabolism and explore potential avenues for further research on this enzyme in various metabolic adaptations.

Background factors predicting the occurrence of herpes zoster in atopic dermatitis patients treated with upadacitinib

Upadacitinib, an oral Janus kinase 1 inhibitor approved for treating atopic dermatitis (AD), can cause adverse events such as herpes zoster (HZ) and acne. We aimed to identify background factors predicting the occurrence of HZ and acne during upadacitinib treatment in patients with AD. From August 2021 to December 2022, 112 Japanese patients with moderate-to-severe AD (aged ≥12 years) were treated with upadacitinib 15 mg/day (78 patients) or 30 mg/day (34 patients) plus topical corticosteroids or delgocitinib limited to head and neck for 3-9 months. AD patients with the occurrence of HZ during upadacitinib treatment had higher incidences for history of HZ and of bronchial asthma than those without in the upadacitinib 15 mg, 30 mg, and whole groups. AD patients with occurrence of HZ had higher pretreatment values of lactate dehydrogenase and eczema area and severity index on head and neck compared to those without in the upadacitinib 15 mg and whole groups. Logistic regression analysis revealed that history of HZ was associated with the occurrence of HZ in the upadacitinib 15 mg and whole groups. The proportion of underage patients (<18 years) was higher in patients with occurrence of acne compared to those without in the upadacitinib 30 mg group, but no significant differences were found in the other background factors between the two patient populations. History of HZ may predict the occurrence of HZ during upadacitinib treatment in patients with AD.

Copper exposure does not alter the ability of intertidal sea cucumber Cucumaria miniata to tolerate emersion during low tide

Intertidal animals experience cycles of tidal emersion from water and are vulnerable to copper (Cu) exposure due to anthropogenic toxicant input into marine waters. Both emersion and Cu toxicity can cause damage to physiological processes like aerobic metabolism, ammonia excretion, and osmoregulation, but the interactions of the combination of these two stressors on marine invertebrates are understudied. Mixed effects of 96 h of low and high Cu exposure (20 and 200 μg/L) followed by 6 h of tidal emersion were evaluated on the intertidal sea cucumber Cucumaria miniata. The respiratory tree accumulated the highest concentrations of Cu, followed by the introvert retractor muscle, body wall, and coelomic fluid. Emersion affected accumulation of Cu, perhaps by inhibiting excretion. 200 μg/L of Cu increased lactate production in the respiratory tree, indicative of damaged aerobic metabolism. Cu diminished ammonia excretion, but emersion increased oxygen uptake and ammonia excretion upon re-immersion. The combination of the two stressors did not have any interactive effects on metabolism or ammonia excretion. Neither Cu exposure nor emersion altered ion (sodium, potassium, calcium, magnesium) content of the coelomic fluid. Overall, results of this study suggest that Cu exposure does not alter C. miniata's high tolerance to emersion, and some potential strategies that this species uses to overcome environmental stress are illuminated.

Effects of tributyltin (TBT) on the intermediate metabolism of the crab Callinectes sapidus

This study investigated if the exposure to tributyltin (TBT), a chemical used worldwide in boat antifouling paints, could result in metabolic disturbances in the blue crab Callinectes sapidus. After the exposure to TBT 100 or 1000 ng.L^-1 for 48 and 96 h, hemolymph and tissues were collected to determine the concentration of metabolites and lipid peroxidation. The levels of glucose, lactate, cholesterol, and triglycerides in the hemolymph were not affected by TBT exposure. Hemolymph protein and heart glycogen increased in the crabs exposed to TBT 1000 for 96 h. Anterior gills protein and lipoperoxidation decreased after 96 h in all groups. These results suggest that C. sapidus can maintain energy homeostasis when challenged by the TBT exposure for 48 h and that metabolic alterations initiate after 96 h.

Biochemical, metabolic, and immune responses of mud crab (Scylla paramamosain) after mud crab reovirus infection

Mud crab reovirus (MCRV) is a serious pathogen that leads to large economic losses in the mud crab farming. However, the molecular mechanism of the immune response after MCRV infection is unclear. In the present study, physiological, transcriptomic, and metabolomic responses after MCRV infection were investigated. The results showed that MCRV infection could increase lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase activities. MCRV infection decreased antioxidant enzyme activity levels, induced oxidative stress, and caused severe histological damage. Transcriptome analysis identified 416 differentially expressed genes, including 354 up-regulated and 62 down-regulated genes. The detoxification, immune response, and metabolic processes-related genes were found. The results showed that two key pathways including phagocytosis and apoptosis played important roles in response to MCRV infection. The combination of transcriptomic and metabolomic analyses showed that related metabolic pathways, such as glycolysis, citrate cycle, lipid, and amino acid metabolism were also significantly disrupted. Moreover, the biosynthesis of unsaturated fatty acids was activated in response to MCRV infection. This study provided a novel insight into the understanding of cellular mechanisms in crustaceans against viral invasion.

White Spot Syndrome Virus Triggers a Glycolytic Pathway in Shrimp Immune Cells (Hemocytes) to Benefit Its Replication

White spot syndrome virus (WSSV) is the causative agent of a shrimp disease that inflicts in huge economic losses in shrimp-farming industry. WSSV triggers aerobic glycolysis in shrimp immune cells (hemocytes), but how this virus regulates glycolytic enzymes or pathway is yet to be characterized. Therefore, mRNA levels and activity of four important glycolytic enzymes, Hexokinase (HK), Phosphofructokinase (PFK), Pyruvate kinase (PK), and Lactate dehydrogenase (LDH), were measured in WSSV-infected shrimp hemocytes. Gene expression of HK and PFK, but not LDH or PK, was increased at the viral genome replication stage (12 hpi); furthermore, activity of these enzymes, except HK, was concurrently increased. However, there was no increased enzyme activity at the viral late stage (24 hpi). In vivo dsRNA silencing and glycolysis disruption by 2-DG further confirmed the role of glycolysis in virus replication. Based on tracing studies using stable isotope labeled glucose, glycolysis was activated at the viral genome replication stage, but not at the viral late stage. This study demonstrated that WSSV enhanced glycolysis by activating glycolytic enzyme at the viral genome replication stage, providing energy and biomolecules for virus replication.

Metabolomic Investigation of Ultraviolet Ray-Inactivated White Spot Syndrome Virus-Induced Trained Immunity in Marsupenaeus japonicus

Trained immunity is driven by metabolism and epigenetics in innate immune cells in mammals. The phenomenon of trained immunity has been identified in invertebrates, including shrimp, but the underlying mechanisms remain unclear. To elucidate mechanisms of trained immunity in shrimp, the metabolomic changes in hemolymph of Marsupenaeus japonicus trained by the UV-inactivated white spot syndrome virus (UV-WSSV) were analyzed using tandem gas chromatography–mass/mass spectrometry. The metabolomic profiles of shrimp trained with UV-WSSV followed WSSV infection showed significant differences comparison with the control groups, PBS injection followed WSSV infection. 16 differential metabolites in total of 154 metabolites were identified, including D-fructose-6-phosphate, D-glucose-6-phosphate, and D-fructose-6-phosphate, and metabolic pathways, glycolysis, pentose phosphate pathway, and AMPK signaling pathway were enriched in the UV-WSSV trained groups. Further study found that histone monomethylation and trimethylation at H3K4 (H3K4me1 and H3K4me3) were involved in the trained immunity. Our data suggest that the UV-WSSV induced trained immunity leads to metabolism reprogramming in the shrimp and provide insights for WSSV control in shrimp aquaculture.

Characterization of phosphofructokinase (PFK) from mud crab Scylla paramamosain and its role in mud crab dicistrovirus-1 proliferation

Phosphofructokinase (PFK), the key enzyme of glycolysis, can catalyze the irreversible transphosphorylation of fructose-6-phosphate forming fructose-1, 6-biphosphate. In the present study, a PFK gene from the mud crab Scylla paramamosain, named SpPFK, was cloned and characterized. The full length of SpPFK contained a 5'untranslated region (UTR) of 249 bp, an open reading frame of 2,859 bp, and a 3'UTR of 1,248 bp. The mRNA of SpPFK was highly expressed in the gill, followed by the hemocytes and muscle. The expression of SpPFK was significantly up-regulated after mud crab dicistrovirus-1 (MCDV-1) infection. Knocking down SpPFK in vivo by RNA interference significantly reduced the expression of lactate dehydrogenase after MCDV-1 infection. Furthermore, silencing of SpPFK in vivo increased the survival rate of mud crabs and decreased the MCDV-1 copies in the gill and hepatopancreas after MCDV-1 infection. All these results suggested that SpPFK could play an important role in the process of MCDV-1 proliferation in mud crab.

Combination of serum lactate dehydrogenase and sex is predictive of severe disease in patients with COVID-19

Elevated serum lactate dehydrogenase (LDH) was commonly reported in COVID-19 patients. However, the relationship between LDH and the incidence of severe cases has not been characterized in those patients.We retrospectively analyzed the characteristics of patients from a designated isolation medical center for COVID-19 patients diagnosed from February 6 to March 1. Variables accessed within 48 hours on admission were compared between patients with and without the severe disease. Logistic model analyses were performed to examine the prognostic value of LDH for predicting severe disease.52 (28.6%) patients later developed severe disease. Comparing to non-severe cases, severe cases had a higher level of serum LDH (321.85 ± 186.24 vs 647.35 ± 424.26, P < .001), neutrophils (5.42 ± 3.26 vs 9.19 ± 6.33, P < .001), and C-reactive protein (38.63 ± 43.14 vs 83.20 ± 51.01, P < .001). The patients with severe disease tended to be male (44.6% vs 80.8%, P < .001), lower level of serum albumin (31.41 ± 6.20 vs 27.18 ± 5.74, P < .001), and SpO2 (96.30 ± 2.75 vs 92.37 ± 8.29, P < .001). In the multivariate analysis model, LDH and sex remained independent risk factors for severe disease. The serum LDH predicted severe cases with an area under the curve (AUC) of 0.7999. A combination of serum LDH and sex predicted severe cases with an AUC of 0.849. A combination of serum LDH accessed on admission and sex had a better predictive performance than the serum LDH (P = .0238).Serum LDH on admission combined with sex is independently associated with severe disease in COVID-19.

Comparative Transcriptome Analysis of Litopenaeus vannamei Reveals That Triosephosphate Isomerase-Like Genes Play an Important Role During Decapod Iridescent Virus 1 Infection

Decapod iridescent virus 1 (DIV1) results in severe economic losses in shrimp aquaculture. However, little is known about the physiological effect of DIV1 infection on the host. In this study, we found that the lethal dose 50 of DIV1-infected Litopenaeus vannamei after 48, 72, 96, and 156 h were 4.86 × 10⁶, 5.07 × 10⁵, 2.13 × 10⁵, and 2.38 × 10⁴ copies/μg DNA, respectively. In order to investigate the mechanisms of DIV1 infection, a comparative transcriptome analysis of hemocytes from L. vannamei, infected or not with DIV1, was conducted. The BUSCO analysis showed that the transcriptome was with high completeness (complete single-copy BUSCOs: 57.3%, complete duplicated BUSCOs: 41.1%, fragmentation: 0.8%, missing: 0.8%). A total of 168,854 unigenes were assembled, with an average length of 601 bp. Based on homology searches, Kyoto Encyclopedia of Genes and Genomes (KEGG), gene ontology (GO), and cluster of orthologous groups of proteins (KOG) analysis, 62,270 (36.88%) unigenes were annotated. Among them, 1,112 differentially expressed genes (DEGs) were identified, of which 889 genes were up-regulated and 223 genes were down-regulated after DIV1 infection. These genes were mainly annotated to the major metabolic processes such as fructose and mannose metabolism, carbon metabolism, and inositol phosphate metabolism. Among these metabolic pathways, the triosephosphate isomerase (TPI) family was the most eye-catching DEG as it participates in several metabolic processes. Three types of TPI, LvTPI-like, LvTPI-Blike, and LvTPI-Blike1, were obtained for gene silencing by RNA interference. The results showed that LvTPI-like and LvTPI-Blike1 silencing caused a high mortality rate among L. vannamei. However, LvTPI-like and LvTPI-Blike silencing reduced DIV1 replication in DIV1-infected L. vannamei. All the results indicated that TPI-like genes play an important role during DIV1 infection, which provides valuable insight into the infection mechanism of DIV1 in shrimp and may aid in preventing viral diseases in shrimp culture.

Expression of lactate dehydrogenase is induced during hypoxia via HIF-1 in the mud crab Scylla paramamosain

Lactate dehydrogenase (LDH) is a key enzyme involved in anaerobic metabolism in most organisms. In the present study, we determined the structure and function of LDH sequence in Scylla paramamosain (SpLDH) by gene cloning, expression and RNA interference techniques in order to explore the genetic characteristics of LDH and its relationship with HIF-1 during hypoxia. The full-length cDNA was 1453 bp with an open reading frame (ORF) of 996 bp, and encoded a polypeptide of 332 amino acids. Homology analysis showed that the SpLDH gene is highly similar to arthropods. The SpLDH transcript increased after hypoxia in all tested tissues. The silencing of HIF-1 blocked the increase in LDH mRNA and activity, which were induced by hypoxia in gill and muscle tissues. Our results indicated that SpLDH expression was regulated transcriptionally by HIF-1.

Accelerated Metabolite Levels of Aerobic Glycolysis and the Pentose Phosphate Pathway Are Required for Efficient Replication of Infectious Spleen and Kidney Necrosis Virus in Chinese Perch Brain Cells

Glucose is a main carbon and energy source for virus proliferation and is usually involved in the glycolysis, pentose phosphate pathway (PPP), and tricarboxylic acid cycle (TCA cycle) pathways. In this study, we investigated the roles of glucose-related metabolic pathways during the replication of infectious spleen and kidney necrosis virus (ISKNV), which has caused serious economic losses in the cultured Chinese perch (Siniperca chuatsi) industry. We found that ISKNV infection enhanced the metabolic pathways of the PPP and the TCA cycle at the early stage of the ISKNV infection cycle and enhanced the glycolysis pathway at the late stage of the ISKNV infection cycle though the comprehensive analysis of transcriptomics, proteomics, and metabolomics. The advanced results proved that ISKNV replication induced upregulation of aerobic glycolysis at the late stage of ISKNV infection cycle and aerobic glycolysis were required for ISKNV multiplication. In addition, the PPP, providing nucleotide biosynthesis, was also required for ISKNV multiplication. However, the TCA cycle involving glucose was not important and necessary for ISKNV multiplication. The results reported here provide new insights into viral pathogenesis mechanism of metabolic shift, as well as antiviral treatment strategies.

Identification and functional analysis of the Mandarin fish (Siniperca chuatsi) hypoxia-inducible factor-1α involved in the immune response

Mandarin fish (Siniperca chuatsi) is a popular cultured freshwater fish species due to its high market value in China. With increasing density of breeding, mandarin fish is often cultured under low environmental oxygen concentrations (hypoxia). In this study, the relative expression levels of hypoxia response element (HRE)-luciferase reporter and the HIF signaling pathway downstream genes (scldha, scvegf, and scglut-1) were significantly increased by hypoxic stress, thereby indicating that mandarin fish has an HIF signaling pathway. The mandarin fish HIF-1α (scHIF-1α) was also characterized. Multiple sequence alignments showed that scHIF-1α presented similar architectures to other known vertebrates. Subcellular localization analysis showed that scHIF-1α was mainly located in the nucleus of the mandarin fish fry-1 (MFF-1) cells. The role of scHIF-1α in the regulation of the HIF signaling pathway was confirmed. Overexpression of scHIF-1α could induce the HIF signaling pathway, whereas knockdown of scHIF-1α inhibited the activity of the HIF-1 signaling pathway. Tissue distribution analysis showed that schif-1α was significantly highly expressed in the blood, heart, and liver, which indicated that the main function of scHIF-1α was closely related to the circulatory system. Furthermore, scHIF-1α expression was significantly induced by poly I:C, poly dG:dC or PMA, thereby indicating that scHIF-1α was involved in the immune response. HIF-1α plays an important role in pathogen infections in mammals, but its role in fish is rarely investigated. Overexpression of scHIF-1α could inhibit MRV and SCRV infections, whereas knockdown of scHIF-1α could promote such infections. Those results suggested that scHIF-1α played an important role in fish virus infection. Our study will help understand the hypoxia associated with the outbreaks of aquatic viral disease.

Hypoxia inducible factor -1 regulates WSSV-induced glycolytic genes in the white shrimp Litopenaeus vannamei

Hypoxia-inducible factor -1 (HIF-1) is a transcriptional factor that regulates the expression of several glycolytic genes. The white spot syndrome virus (WSSV) induces a shift in glycolysis that favors viral replication in white shrimp Litopenaeus vannamei. HIF-1 is related to the pathogenesis of the WSSV infection through the induction of metabolic changes in infected white shrimp. Although the WSSV infection is associated with metabolic changes, the role of HIF-1 on key glycolytic genes during the WSSV infection has not been examined. In this work, we evaluated the effect of HIF-1α silencing on expression and activity of glycolytic enzymes (Hexokinase-HK, phosphofructokinase-PFK and pyruvate kinase-PK) along with the glucose transporter 1 (Glut1), regulatory enzymes (glucose-6-phosphate dehydrogenase-G6PDH and pyruvate dehydrogenase-PDH), and metabolic intermediates of glycolysis (glucose-6-phosphate-G6P and pyruvate). The expression of Glut1 increased in each tissue evaluated after WSSV infection, while HK, PFK and PK gene expression and enzyme activities increased in a tissue-specific manner. G6PDH activity increased during WSSV infection, and its substrate G6P decreased, while PDH activity decreased and its substrate pyruvate increased. Silencing of HIF-1α blocked the WSSV-induced Glut1 and glycolytic genes upregulation and enzyme activity in a tissue-specific manner. We conclude that HIF-1 regulates the WSSV-induced glycolysis through induction of glycolytic genes contributing to glucose metabolism in tissues of infected shrimp. Also, the inhibition, and activation of regulatory genes are likely to decrease the availability of the raw materials essential for WSSV replication and increase oxidative metabolism.

Glycogen phosphorylase of shrimp (Litopenaeus vannamei): Structure, expression and anti-WSSV function

Glycogen phosphorylase (GP, EC 2.4.1.1) catalyze the rate-limiting step in glycogenolysis in animals, forming glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. Therefore, GP plays a crucial role in carbohydrate metabolism. In the present study, the full-length cDNA sequence of GP (LvGP) was cloned from shrimp, Litopenaeus vannamei. The obtained 3242-bp LvGP cDNA sequence included a 5'-terminal untranslated region (UTR) of 48 bp, an open reading frame (ORF) of 2559 bp encoding a polypeptide of 852 amino acids (aa) and a 3'-UTR of 635 bp. The predicted LvGP protein sequence contained a typical phosphorylase domain (113-829 aa) and shared 72%-97% identities with GP from other species. Phylogenetic analysis revealed that LvGP showed the closest relationship with GP from Marsupenaeus japonicus. Tissue expression profiles showed that LvGP existed in most examined tissues, with the most predominant expression in the brain, followed by the muscles and stomach. LvGP transcripts in hepatopancreas and hemocytes were up regulated after the WSSV challenge. Furthermore, the role of LvGP in shrimp defending against WSSV infection was investigated by RNA interference (RNAi). Our findings showed that WSSV proliferation and shrimp accumulative mortality increased significantly after LvGP RNAi (P < 0.01). The glycogen, glucose, and pyruvate content decreased in GP RNAi shrimp after WSSV injection, however, the lactate and ATP concentration enhanced. Moreover, lectin and anti-lipopolysaccharide factor2 (ALF2) were induced in LvGP silencing shrimp after WSSV infection, whereas the expression levels of crustin, ALF1 and ALF3 decreased. Our results suggested that the LvGP might play a crucial role in shrimp defending against WSSV infection by regulating metabolism and affecting the anti-infectious gene expression.

Regulation of glyceraldehyde-3-phosphate dehydrogenase by hypoxia inducible factor 1 in the white shrimp Litopenaeus vannamei during hypoxia and reoxygenation

Hypoxia is a frequent source of stress in the estuarine habitat of the white shrimp Litopenaeus vannamei. During hypoxia, L. vannamei gill cells rely more heavily on anaerobic glycolysis to obtain ATP. This is mediated by transcriptional up-regulation of glycolytic enzymes including glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The hypoxia inducible factor 1 (HIF-1) is an important transcriptional activator of several glycolytic enzymes during hypoxia in diverse animals, including crustaceans. In this work, we cloned and sequenced a fragment corresponding to the 5' flank of the GAPDH gene and identified a putative HIF-1 binding site, as well as sites for other transcription factors involved in the hypoxia signaling pathway. To investigate the role of HIF-1 in GAPDH regulation, we simultaneously injected double-stranded RNA (dsRNA) into shrimp to silence HIF-1α and HIF-1β under normoxia, hypoxia, and hypoxia followed by reoxygenation, and then measured gill HIF-1α, HIF-1β expression, GAPDH expression and activity, and glucose and lactate concentrations at 0, 3, 24 and 48 h. During normoxia, HIF-1 silencing induced up-regulation of GAPDH transcripts and activity, suggesting that expression is down-regulated via HIF-1 under these conditions. In contrast, HIF-1 silencing during hypoxia abolished the increases in GAPDH expression and activity, glucose and lactate concentrations. Finally, HIF-1 silencing during hypoxia-reoxygenation prevented the increase in GAPDH expression, however, those changes were not reflected in GAPDH activity and lactate accumulation. Altogether, these results indicate that GAPDH and glycolysis are transcriptionally regulated by HIF-1 in gills of white shrimp.

White spot syndrome virus (WSSV) infection impacts intestinal microbiota composition and function in Litopenaeus vannamei

Intestinal microbiota homeostasis is crucial to the health of host. Pathogen invasion results in dynamics of microbiota composition and structure, disrupting their function in maintaining host health. WSSV is the most prevalent viral pathogen and is able to cause extremely high mortality in Litopenaeus vannamei. However, the changes of intestinal microbiota induced by WSSV are yet to be elucidated. In this study, we analyzed and compared the microbiota of healthy and WSSV-challenged shrimp intestines. Though the richness and diversity of microbiota was barely affected by WSSV, the abundance of predominant phyla like Proteobacteria and Fusobacteria were upregulated significantly, while Bacteroidetes and Tenericutes were significantly decreased in WSSV-infected shrimps. At the genus level, significant increase was observed in Photobacterium, Propionigenium and Arcobacter, as well as significant decrease in Candidatus Bacilloplasma and Flavobacterium in WSSV-infected shrimps. Additionally, metagenomic predictions by PICRUSt suggested that the altered microbiota was mainly related to metabolism, human diseases, genetic information processing, environmental information processing and cellular processes. These results suggested that the invasion of WSSV could impact intestinal microbiota composition and function in L. vannamei.

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.