Molecular cloning and characterization of a peroxiredoxin gene from the mole cricket, Gryllotalpa orientalis

Peroxiredoxin-2 gene in Antheraea pernyi modulates immune functions and protect DNA damage

Peroxiredoxins have been shown to protect insects from oxidative damage and to play a role in the immune system. In the present study, we cloned and characterized the Antheraea pernyi peroxiredoxin 2 (ApPrx-2) gene, then assessed its functional roles. The ApPrx-2 gene has a 687 bp open reading frame that encodes a protein with 288 amino acid residues. Quantitative real-time PCR analysis revealed that the mRNA levels of ApPrx-2 were highest in the hemocytes. Immune challenge assay revealed that ApPrx-2 transcription could be induced after microbial challenge. A DNA cleavage assay employing recombinant ApPrx-2 protein and a metal-catalyzed oxidation system showed that rApPrx-2 protein could protect supercoiled DNA against oxidative stress. The protein antioxidant activity of rApPrx-2 was examined, and it was found that rApPrx-2 exhibited a high level of antioxidant activity by removing H2O2. In addition, ApPrx-2 knockdown larvae had higher H2O2 levels and a lower survival rate when compared to controls. Interestingly, the antibacterial activity was significantly higher in ApPrx-2 depleted larvae compared with control. Overall, our findings indicate that ApPrx-2 may be involved in a range of physiological functions of A. pernyi, as it protects supercoiled DNA from oxidative stress and regulates antibacterial activity.

Environmental mercury exposure and selenium-associated biomarkers of antioxidant status at molecular and biochemical level. A short-term intervention study

Mercury (Hg) is a potent toxicant. In the field of public health a chronic-low-level environmental Hg exposure resulting from fish consumption in general population is still being discussed. The objective of the study was to assess the influence of real Hg exposure on biomarkers of selenium (Se) status and selected biomarkers of pro-oxidant/anti-oxidant effects in healthy men (n = 67) who participated in the short-term intervention study consisting in daily fish consumption for two weeks. The analysis included Se level, Se-associated antioxidants at molecular (profile of 7 genes encoding selected proteins related to antioxidant defense) and biochemical levels (Se-dependent glutathione peroxidases activities and plasma selenoprotein P concentration). A pro-oxidant/anti-oxidant balance was explored using a biomarker of plasma lipid peroxidation and total antioxidant activity. The study revealed significant correlations (p < 0.05) between the biomarkers of exposure to Hg, Se level and Se-dependent antioxidants. Even though the risk of adverse effects of Hg for volunteers was substantially low, biomarkers of Hg altered levels of circulation selenoproteins and their genes expression. Changes in genes expression during study differed between the main enzymes involved in two systems: downregulation of thioredoxin reductase1 and upregulation of glutathione peroxidases. Hg exposure caused imbalance between the biomarkers of pro-oxidant/anti-oxidant effects.

Peroxiredoxin 1 from cuttlefish (Sepiella maindroni): Molecular characterization of development and its immune response against Vibrio alginolyticus

The aim of this work was constructive to understand the function of peroxiredoxin (PRDX) family member Peroxiredoxin 1 in Sepiella maindroni (SmPrx1) through molecular mechanisms of reproduction, embryonic development and immune responses to Vibrio alginolyticus. The full-length cDNA of SmPrx1 was of 1062 bp, contains a 5' untranslated region (UTR) of 79bp, a 3' UTR of 359 bp, an open reading frame of 624 bp encoding 207 amino acids. The conserved peroxidase catalytic center "FYPLDFTFVCPTEI" and "GEVCPA" were observed in the sequence of SmPrx1; this indicated that it was a member of 2-Cys Prx. Quantitative real-time (qRT)-PCR assays revealed that SmPrx1 was ubiquitously expressed in all examined tissues, muscle, ink sac, liver, ovary, testis, intestine, gill and totally blood cells, and showed high levels in testis. SmPrx1 mRNA was ubiquitously detected in all tested tissues, and the expression was comparatively high in testis, hemocyte, liver and ovary. Moreover, the SmPrx1 gene transcript was detected at all five stages of embryonic development phases that were respectively the zygote stage, the pre-embryonic stage, the organogenesis stage, the morphological integrity stage, the pre-hatching stage. The general tendency of expression was gradually increased and rapidly decreased. High expressed in progenitive tissues and embryonic development exhibit the proliferation-associated protein characterization like in mammal. The expression levels of SmPrx1 in liver and hemocytes grew swiftly and quickly reached peak value after Vibrio alginolyticus challenge. As hours passed by, the expression level began to reduce and resumed to normal levels after 48 h. The antioxidant activity and peroxidase activity of SmPrx1 were 6.17 U/mg. The results showed that the recombined protein of SmPrx1 had antioxidant activity and was the importance part of the antioxidant system in Sepiella maindroni. This study provides useful information to help further understand the functional mechanism of Prx 1 in marine cephalopod immunity.

Differential expression of CuZnSOD gene under low temperature stress in noble scallop Chlamys nobilis with different carotenoid content

The noble scallop Chlamys nobilis belongs to a warm-water mollusk and has been cultured in the sea of southern China since 1980s'. However, accidents of massive mortality have often occurred during the winter, and one of the reasons could be accumulation of harmful reactive oxygen species caused by lower temperature. Carotenoids are well known for their anti-oxidant function. To investigate whether carotenoids do play a role in mollusks' antioxidant defense system under lower temperature stress, an acute lower temperature experiment was conducted by using two types of scallops: the orange with higher carotenoids content and the brown with lower carotenoids content. Their CuZnSOD gene was cloned, mRNA expression levels were determined, and SOD activity and carotenoids content were measured. The complete CuZnSOD cDNA consists of 1078 nucleotides with an open reading frame encoding 154 amino acid residues, which has high identity with that of its sister species Chlamys farreri. The mRNA expression levels in both the mantle and gill from the orange scallops were significantly higher (P < 0.05) than that of the brown ones, but the result was the opposite in the blood. SOD activity in the mantle and gill from the orange scallops was significantly higher than (P < 0.05) that from the brown ones. Further, significantly positive correlations were found among CuZnSOD gene transcript levels, SOD activity and total carotenoids content in the orange scallops. The present results suggested that carotenoids could play roles in antioxidant defense system by upregulating gene expression under lower temperature stress in the noble scallop.

Predicting and Understanding the Enzymatic Inhibition of Human Peroxiredoxin 5 by 4-Substituted Pyrocatechols by Combining Funnel Metadynamics, Solution NMR, and Steady-State Kinetics

Funnel metadynamics is a kind of computational simulation used to enhance the sampling of protein-ligand binding events in solution. By characterization of the binding interaction events, an estimated absolute binding free energy can be calculated. Nuclear magnetic resonance and funnel metadynamics were used to evaluate the binding of pyrocatechol derivatives (catechol, 4-methylcatechol, and 4-tert-butylcatechol) to human peroxiredoxin 5. Human peroxiredoxins are peroxidases involved in cellular peroxide homeostasis. Recently, overexpressed or suppressed peroxiredoxin levels have been linked to various diseases. Here, the catechol derivatives were found to be inhibitors against human peroxiredoxin 5 through a partial mixed type noncompetitive mechanism. Funnel metadynamics provided a microscopic model for interpreting the inhibition mechanism. Correlations were observed between the inhibition constants and the absolute binding free energy. Overall, this study showcases the fact that funnel metadynamics simulations can be employed as a preliminary approach to gain an in-depth understanding of potential enzyme inhibitors.

Comparative Analyses of Cu-Zn Superoxide Dismutase (SOD1) and Thioredoxin Reductase (TrxR) at the mRNA Level between Apis mellifera L. and Apis cerana F. (Hymenoptera: Apidae) Under Stress Conditions

This study compared stress-induced expression of Cu-Zn superoxide dismutase (SOD1) and thioredoxin reductase (TrxR) genes in the European honeybee Apis mellifera L. and Asian honeybee Apis cerana F. Expression of both SOD1 and TrxR rapidly increased up to 5 h after exposure to cold (4 °C) or heat (37 °C) treatment and then gradually decreased, with a stronger effect induced by cold stress in A. mellifera compared with A. cerana. Injection of stress-inducing substances (methyl viologen, [MV] and H2O2) also increased SOD1 and TrxR expression in both A. mellifera and A. cerana, and this effect was more pronounced with MV than H2O2. Additionally, we heterologously expressed the A. mellifera and A. cerana SOD1 and TrxR proteins in an Escherichia coli expression system, and detection by SDS-PAGE, confirmed by Western blotting using anti-His tag antibodies, revealed bands at 16 and 60 kDa, respectively. Our results show that the expression patterns of SOD1 and TrxR differ between A. mellifera and A. cerana under conditions of low or high temperature as well as oxidative stress.

Molecular characterization and functional analysis of a peroxiredoxin 1 cDNA from golden pompano (Trachinotus ovatus)

Peroxiredoxin 1 (Prx 1) is an important antioxidant protein that can protect organisms against the toxicity of reactive oxygen species. In this study, a full-length Prx 1 cDNA sequence (ToPrx 1) was identified from golden pompano (Trachinotus ovatus). The ToPrx 1 cDNA was 1049 base pairs (bp) long and contained a 5'-untranslated region (UTR) of 127 nucleotides, a 3'-UTR of 328 nucleotides, and a 594 bp open reading frame (ORF) encoding a 197 amino acid polypeptide. The ToPrx 1 protein showed strong homology (79-91%) with Prx 1 proteins from other species and contained the conserved Prx domain and the signature of the peroxidase catalytic center. Phylogenetic analysis revealed that ToPrx 1 was in the fish Prx 1 subgroup, which suggests that ToPrx 1 could belong to the 2-Cys Prx subgroup. ToPrx 1 mRNA was ubiquitously detected in all tested tissues, and its expression was comparatively high in the fin, spleen, kidney, intestine, eye, gill, and blood. The expression levels of ToPrx 1 mRNA were significantly up-regulated in liver, spleen, kidney, and intestine of golden pompano injected with Photobacterium damselae. The recombinant ToPrx 1 protein (rToPrx 1) was expressed and purified through affinity chromatography and refolded successfully using ion-exchange chromatography. The antioxidant activity assay of rToPrx 1 showed that it could reduce insulin in the presence of dithiothreitol, which suggests that the antioxidant function of rToPrx 1 is thiol dependent. This study provides useful information to help further understand the functional mechanism of Prx 1 in marine fish immunity.

Expression, purification and characterization of an atypical 2-Cys peroxiredoxin from the silkworm, Bombyx mori

Peroxiredoxins (Prxs) play important roles in protecting organisms against damage caused by reactive oxygen species (ROS). In this study, we cloned a cDNA of Bombyx mori peroxiredoxin 5 (BmPrx5), which contained a 565-bp open reading frame for a 188-residue protein. Sequence analysis indicated that BmPrx5 belongs to the atypical 2-Cys peroxiredoxin family. Recombinant BmPrx5 purified from Escherichia coli showed antioxidant activity that removes H2 O2 and protects DNA from oxidative damage. Quantitative real-time PCR showed that the level of BmPrx5 mRNA in haemocytes increased early and decreased by 24 h after injection of H2 O2 whereas, in the fat body, the transcript level decreased at 6 h and increased at 12 h. Pseudomonas aeruginosa and Staphylococcus aureus infection resulted in higher levels of H2 O2 in the haemolymph and of BmPrx5 mRNA in haemocytes at 8 h postinfection. These data suggest that BmPrx5 acts as an antioxidant enzyme to protect the silkworm from oxidative damage induced by bacterial infection. Further study is needed to elucidate the exact role of BmPrx5 in the silkworm immune system.

Mitochondrial peroxiredoxin 3 (Prx3) from rock bream (Oplegnathus fasciatus): immune responses and role of recombinant Prx3 in protecting cells from hydrogen peroxide induced oxidative stress

Pathogenic infections and environmental factors cause a variety of stresses in fish including oxidative stress by rapid elevation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Transcriptional activation and expression of antioxidant enzymes are essential for reducing the oxidative stress. In this study, we present the molecular characterization, immune responses and ROS scavenging activity of mitochondrial peroxiredoxin 3 from Oplegnathus fasciatus (RbPrx3). Coding sequence (CDS) of RbPrx3 contains 248 amino acids polypeptide which consists of highly conserved peroxiredoxin super family domain and two cysteine residues. Pairwise sequence comparison revealed that RbPrx3 has the greatest identity (94.8%) to Sparus aurata Prx3. Transcriptional analysis of RbPrx3 indicated the ubiquitously expressed mRNA in wide array of organs showing the highest expression in the liver of rock bream. Upon immune challenge of Edwardsiella tarda, Streptococcus iniae, rock bream iridovirus (RBIV) and lipopolysaccharide (LPS), RbPrx3 mRNA level was up-regulated in immunocompetent liver tissues compared to unchallenged fish. Purified recombinant RbPrx3 treated THP-1 cells showed higher survival rate against H(2)O(2) induced oxidative stress and significantly reduced the level of intracellular ROS. Overall results from our study suggest that RbPrx3 may be involved in broader functions such as regulating oxidative stresses by scavenging ROS and activating immune responses in rock bream.

Comparative study of two thioredoxins from common cutworm (Spodoptera litura): cloning, expression, and functional characterization

Thioredoxins (Trxs) are a ubiquitous family of antioxidant enzymes that are involved in protecting organisms against various oxidative stresses. Here, we cloned and characterized two thioredoxins, named SlTrx1 and SlTrx2, from the common cutworm Spodoptera litura. SlTrx1 and SlTrx2, respectively, consist of 988 and 606 bp full-length cDNA with 318 and 447 bp open reading frames encoding 106 and 149 amino acid residues. Furthermore, the N-terminal region of SlTrx2 contains a predicted mitochondrial localization signal (33 amino acids). A phylogenetic relationship analysis revealed that SlTrx1 is in the cytosolic thioredoxin Trx1 cluster, whereas SlTrx2 is in the mitochondrial thioredoxin Trx2 cluster. Recombinant SlTrx1 (14 kDa) and SlTrx2 (16 kDa), expressed in baculovirus-infected insect Sf9 cells, demonstrated insulin disulfide reductase activity at the same optimum temperature and pH value of 35 °C and 7.0, respectively, in vitro. During S. litura development, we found that SlTrx1 and SlTrx2 had similar transcript expression patterns and were constitutively expressed in the epidermis, fat body, and midgut, with the highest expression occurring in the sixth-instar larval stage in the epidermis and midgut. In addition, both SlTrx1 and SlTrx2 mRNA were up-regulated in S. litura after injection with H2O2, cumene hydroperoxide, indoxacarb, and metaflumizone. These results suggest that SlTrx1 and SlTrx2 function as potent antioxidant enzymes, and provide a molecular basis for the roles SlTrx1 and SlTrx2 during development and the oxidative stress response of S. litura.

Molecular characterization, immune response against white spot syndrome virus infection of peroxiredoxin 4 in Fenneropenaeus chinensis and its antioxidant activity

Peroxiredoxins (Prx) are a family of antioxidant proteins and perform important functions in intracellular signal transduction. Here, we report a Prx gene from Chinese shrimp Fenneropenaeus chinensis. The full-length cDNA of FcPrx gene contained an open reading frame of 735 bp encoding a polypeptide of 275 amino acids. The molecular mass of the deduced amino acid of FcPrx is 27445.43 Da with an estimated pI of 5.71. Sequence comparison showed that the FcPrx shares high identities with Prx IVs and it was named FcPrx4. A real-Time PCR (qRT-PCR) assay was developed to assess the mRNA expression of FcPrx4 in different tissues and temporal expression in hemocytes and hepatopancreas of F. chinensis challenged by white spot syndrome virus (WSSV). Transcripts of FcPrx4 can be detected in all tissues examined. The expression of FcPrx4 showed significant up-regulation in shrimp hemocytes and hepatopancreas after artificial infection with WSSV. A fusion protein containing FcPrx4 was produced in vitro and was confirmed by Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) assay. And activity analysis indicated that the recombinant FcPrx4 proteins can reduce H2O2 in the presence of dithiothreitol.

Molecular cloning, expression and oxidative stress response of a mitochondrial thioredoxin peroxidase gene (AccTpx-3) from Apis cerana cerana

Thioredoxin peroxidase (Tpxs) plays an important role in maintaining redox homeostasis and in protecting organisms from the accumulation of toxic reactive oxygen species (ROS). Here, we isolated a mitochondrial thioredoxin peroxidase gene from Apis cerana cerana, AccTpx-3. The open reading frame (ORF) of AccTpx-3 is 729 bp in length and encodes a predicted protein of 242 amino acids, 27.084 kDa and an isoelectric point of 8.70. Furthermore, the 980 bp 5' flanking region was cloned, and the transcription factor binding sites were predicted. A quantitative RT-PCR (Q-PCR) analysis indicated that AccTpx-3 was expressed higher in muscle than other tissues, with its highest expression occurring on the fourth day of the larval stage, followed by the fifteenth day of the adult stage. Moreover, the expression of the AccTpx-3 transcript was upregulated by such abiotic stresses as 4°C, 42°C, H(2)O(2), cyhalothrin, acaricide and phoxime treatments. In contrast, AccTpx-3 transcription was downregulated by other abiotic stresses, including 16°C, 25°C, ultraviolet light and HgCl(2). Recombinant AccTpx-3 protein acted as a potent antioxidant that resisted paraquat-induced oxidative stress and protected DNA from oxidative damage. Taken together, these results suggest that the AccTpx-3 protein is an antioxidant enzyme that may protect organisms from oxidative stress.

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.

Immunological role of thiol-dependent peroxiredoxin gene in Macrobrachium rosenbergii

In this study, we have reported a full length of peroxiredoxin (designated MrPrdx) gene, identified from the transcriptome of freshwater prawn Macrobrachium rosenbergii. The complete gene sequence of the MrPrdx is 940 base pairs in length, and encodes 186 amino acids. MrPrdx contains a long thioredoxin domain in the amino acid sequence between 34 and 186. The gene expressions of MrPrdx in healthy and the infectious hypodermal and hematopoietic necrosis virus (IHHNV) challenged M. rosenbergii were examined using quantitative real time polymerase chain reaction. MrPrdx is highly expressed in all the other tissues of M. rosenbergii considered for analysis and the highest in gills. The expression is strongly up-regulated in gills after IHHNV infection. To understand MrPrdx functional properties, the recombinant MrPrdx protein was expressed in Escherichia coli BL21 (DE3) and purified. A peroxidise activity assay was conducted using recombinant MrPrdx protein at different concentrations. This peroxidises activity showed that the recombinant MrPrdx is a thiol-dependant protein. Additionally, this result showed that recombinant MrPrdx protein, as a secretory protein can remove H₂O₂ and protect DNA damage. This finding leads a possible way to propose the recombinant MrPrdx protein as an effective medicine for reactive oxygen species (ROS) related diseases.

Molecular Cloning and Sequence Analysis of Peroxiredoxin cDNA from American White Shrimp (Litopenaeus vannamei)

Peroxiredoxin (Prx) is an antioxidant protein, which protects organisms against various oxidative stresses. In this study, we isolated Peroxiredoxin cDNA from the muscle tissues of American white shrimp, Litopenaeus vannamei, using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The full-length cDNA consists of 962-bp, which includes a 49-bp 5′-untranslated region (UTR), a 316-bp 3′-untranslated region, and a 597-bp open reading frame (ORF) encoding 198 amino acids. The signal peptide sequence was not found in this cDNA. We aligned the deduced amino acid sequence with the known amino acid sequences of Fenneropenaeus indicus, Fenneropenaeus chinensis, Marsupenaeus japonicus, Scylla serrata, Drosophila melanogaster, Bos taurus, Branchiostoma belcheri, Anoplopoma fimbria, and Rattus norvegicus, and the sequence similarities scores were found to be 97%, 96%, 95%, 83%, 72%, 70%, 80%, 81%, and 75%, respectively. We also found 2-cysteine (Cys) residues in this peroxiredoxin sequence. The RT-PCR analysis revealed that the peroxiredoxin mRNA was expressed in the gills, hepatopancreas, muscles, intestine, and hemocytes. Studies using this newly cloned peroxiredoxin gene from Litopenaeus vannamei will add to the existing knowledge base on the physiological role of peroxiredoxin in shrimp species.

Microarray expression profiling of Spodoptera litura in response to oxidative stress

To examine the expression profile of oxidative stress responsive genes in Spodoptera litura, we constructed a cDNA library from S. litura injected with hydrogen peroxide (H(2)O(2)). Using a microarray chip composed of 2,964 cDNAs, we screened gene expression at 1, 3, 5, 7, and 9 h post H(2)O(2) injection. Data were clustered into 15 groups of genes that behave similarly across each time course. Seventy-three genes were identified as being at least twofold up- or downregulated after treatment with H(2)O(2) in S. litura. We constructed expressed sequence tags (ESTs) for genes that changed at least twofold after treatment with H(2)O(2) . The functional classification of these ESTs based on Gene Ontology showed that the ESTs are rich in genes involved in oxidoreductase activity (5.7%), defense (14.3%), cellular process (22.9%), and development (17.1%).

Molecular characterization and oxidative stress response of an intracellular Cu/Zn superoxide dismutase (CuZnSOD) of the whitefly, Bemisia tabaci

Superoxide dismutases (SODs) are important for the survival of insects under environmental and biological stresses; however, little attention has been devoted to the functional characterization of SODs in whitefly. In this study, an intracellular copper/zinc superoxide dismutase of whitefly (Bemisia tabaci) (Bt-CuZnSOD) was cloned. Sequence analysis indicated that the full length cDNA of Bt-CuZnSOD is of 907 bp with a 471 bp open reading frame encoding 157 amino acids. The deduced amino acid sequence shares common consensus patterns with the CuZnSODs of various vertebrate and invertebrate animals. Phylogenetic analysis revealed that Bt-CuZnSOD is grouped together with intracellular CuZnSODs. Bt-CuZnSOD was then over-expressed in E. coli and purified using GST purification system. The enzymatic activity of purified Bt-CuZnSOD was assayed under various temperatures. When whiteflies were exposed to low (4°C) and high (40°C) temperatures, the in vivo activity of Bt-CuZnSOD was significantly increased. Furthermore, we measured the activities of several antioxidant enzymes, including SOD, catalase and peroxidase, in the whitefly after transferring the whitefly from cotton to tobacco (an unfavorable host plant). We found that the activity of SOD increased rapidly on tobacco plant. Taken together, these results suggest that the Bt-CuZnSOD plays a major role in protecting the whitefly against various stress conditions.

Molecular cloning and characterization of a thioredoxin peroxidase gene from Apis cerana cerana

Thioredoxin peroxidases (Tpxs) play important roles in protecting organisms against the toxicity of reactive oxygen species (ROS) and regulating intracellular signal transduction. In the present study, we cloned the full cDNA of Tpx1 encoding a 195-amino acid protein from Apis cerana cerana (Acc). Based on the genomic DNA sequence, a 1442-bp 5'-flanking region was obtained, and the putative transcription factor binding sites were predicted. Quantitative PCR analysis showed that AccTpx1 was highly expressed in thorax and that the AccTpx1 transcript reached its highest level in two-week-old adult worker honeybees. Moreover, expression of the AccTpx1 transcript was increased by various abiotic stresses, such as ultraviolet light, HgCl(2) , and insecticide treatments. In addition, the recombinant AccTpx1 protein exhibited antioxidant activity; it removed hydrogen peroxide and protected DNA. These results suggest that AccTpx1 plays an important role in protecting honeybees from oxidative injury and may act in extending the lifespan of them.

Reactive oxygen species scavenging by catalase is important for female Lutzomyia longipalpis fecundity and mortality

The phlebotomine sand fly Lutzomyia longipalpis is the most important vector of American visceral leishmaniasis (AVL), the disseminated and most serious form of the disease in Central and South America. In the natural environment, most female L. longipalpis are thought to survive for less than 10 days and will feed on blood only once or twice during their lifetime. Successful transmission of parasites occurs when a Leishmania-infected female sand fly feeds on a new host. Knowledge of factors affecting sand fly longevity that lead to a reduction in lifespan could result in a decrease in parasite transmission. Catalase has been found to play a major role in survival and fecundity in many insect species. It is a strong antioxidant enzyme that breaks down toxic reactive oxygen species (ROS). Ovarian catalase was found to accumulate in the developing sand fly oocyte from 12 to 48 hours after blood feeding. Catalase expression in ovaries as well as oocyte numbers was found to decrease with age. This reduction was not found in flies when fed on the antioxidant ascorbic acid in the sugar meal, a condition that increased mortality and activation of the prophenoloxidase cascade. RNA interference was used to silence catalase gene expression in female Lu. longipalpis. Depletion of catalase led to a significant increase of mortality and a reduction in the number of developing oocytes produced after blood feeding. These results demonstrate the central role that catalase and ROS play in the longevity and fecundity of phlebotomine sand flies.

Molecular cloning, characterization and expression analysis of peroxiredoxin 6 from disk abalone Haliotis discus discus and the antioxidant activity of its recombinant protein

Peroxiredoxins (Prxs) play an important role against various oxidative stresses and intra-cellular signal transduction. Peroxiredoxin 6 (PrxVI) was identified from the disk abalone Haliotis discus discus cDNA library and named HdPrxVI. The full length cDNA of HdPrxVI was 1457 bp with a 654 bp open reading frame (ORF) encoding 218 amino acids. The predicted molecular mass and estimated isoelectric point (pI) of HdPrxVI were 24 kDa and 7.3, respectively. The deduced amino acid sequence demonstrated the greatest degree (72.4%) of identity with Crassostrea gigas PrxVI. The conserved peroxidase catalytic center (42PVCTTE47) with a conserved cysteine residue (Cys44) and a catalytic center for PLA2 activity (27GGSWA31) were observed in the sequence, indicating that it is a member of 1-Cys Prx. Real time PCR results revealed that HdPrxVI mRNA is constitutively expressed in all tissues in a tissue-specific manner. During exposure to haemorrhagic septicaemia virus (VHSV), HdPrxVI mRNA transcription was down-regulated in the gill, suggesting that the abalone responded to the viral infection quickly, and HdPrxVI played a physiological role against virus-induced oxidative stress. The purified recombinant HdPrxVI, together with dithiothreitol (DTT), was shown to scavenge H2O2 in human leukemia THP-1 cells and provided protection against H2O2-induced apoptosis.

Molecular cloning and characterization of peroxiredoxin 6 from Chinese mitten crab Eriocheir sinensis

Peroxiredoxin is a superfamily of antioxidative proteins that play important roles in protecting organisms against the toxicity of reactive oxygen species (ROS). In this study, the full-length cDNA encoding peroxiredoxin 6 (designated EsPrx6) was cloned from Chinese mitten crab Eriocheir sinensis by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EsPrx6 was of 1076 bp, containing a 5' untranslated region (UTR) of 69 bp, a 3' UTR of 347 bp with a poly (A) tail, and an open reading frame (ORF) of 660 bp encoding a polypeptide of 219 amino acids with the predicted molecular weight of 24 kDa. The conserved Prx domain, AhpC domain and the signature of peroxidase catalytic center identified in EsPrx6 strongly suggested that EsPrx6 belonged to the 1-Cys Prx subgroup. Quantitative real-time RT-PCR was employed to assess the mRNA expression of EsPrx6 in various tissues and its temporal expression in haemocytes of crabs challenged with Listonella anguillarum. The mRNA transcript of EsPrx6 could be detected in all the examined tissues with highest expression level in hepatopancreas. The expression level of EsPrx6 in haemocytes was down-regulated after bacterial challenge and significantly decreased compared to the control group at 12h. As time progressed, the expression level began to increase but did not recover to the original level during the experiment. The results suggested the involvement of EsPrx6 in responses against bacterial infection and further highlighted its functional importance in the immune system of E. sinensis.

Comparative study of two thioredoxin peroxidases from disk abalone (Haliotis discus discus): cloning, recombinant protein purification, characterization of antioxidant activities and expression analysis

Thioredoxin peroxidase (TPx), also named peroxiredoxin (Prx), is an important peroxidase, which can protect organisms against various oxidative stresses. Two TPxs were isolated from a disk abalone (Haliotis discus discus) cDNA library, named as AbTPx1 and AbTPx2, respectively. AbTPx1 and AbTPx2 consist of 1315 and 1045 bp full-length cDNA with 753 and 597 bp open reading frames encoding 251 and 199 amino acids, respectively. The TPx signature motif 1 (FYPLDFTFVCPTEI) and motif 2 (GEVCPA) were conserved in both AbTPx1 and AbTPx2 amino acid sequences. Purified recombinant abalone TPx fusion proteins catalyzed the reduction of H2O2 and butyl hydroperoxide in peroxidase assays. Furthermore, both AbTPx fusion proteins were shown to protect super-coiled DNA from damage by metal-catalyzed oxidation (MCO) in vitro. Escherichia coli cells transformed with AbTPx1 and AbTPx2 coding sequences in pMAL-c2x showed resistance to H2O2 at 0.8 mM concentration by in vivo H2O2 tolerance assay. AbTPx1 and AbTPx2 mRNA were constitutively expressed in gill, mantle, abductor muscle and digestive tract in a tissue specific manner. Additionally, both TPxs mRNA were up-regulated in gill and digestive tract tissues against H2O2 at 3h post injection. The results indicate that AbTPx1 and AbTPx2 gene expressions are induced by oxidative stress and their respective proteins function in the detoxification of different ROS molecules to maintain efficient antioxidant defense in disk abalone.

A peroxiredoxin from kuruma shrimp, Marsupenaeus japonicus, inhibited by peptidoglycan

Crustaceans rely on both the cellular and humoral responses of their innate immune system for protection against invading pathogens. Peroxiredoxins (Prx) are a family of anti-oxidant proteins that protect aerobic organisms against oxidative damage by reactive oxygen species (ROS). Although it is ubiquitously found in all organisms, it has not been studied thoroughly in crustaceans. Here, we report a Prx from the crustacean kuruma shrimp, Marsupenaeus japonicus (mjPrx). This crustacean Prx has a full-length cDNA of 659 bp encoding for 198 putative amino acids. It has no signal peptide and is composed of 4 cysteine residues. Based on the conservation of these residues, particularly the N- and C-terminal cysteines, conserved protein domains and on phylogenetic analysis, mjPrx was found to belong to the 2-Cys Prx subgroup. The mjPrx gene is constitutively expressed in heart, hemocyte and lymphoid tissues, and is down-regulated in heart and lymphoid tissues by peptidoglycan (PG) treatment.

Peroxiredoxin 6 gene: a new physiological and genetic indicator of multiple environmental stress response in Pacific oyster Crassostrea gigas

Peroxiredoxin 6 is a 1-cysteine peroxiredoxin involved in antioxidant processes. We characterised the full-length cDNA and genomic sequence of the gene encoding peroxiredoxin 6 (CgPrx6) in the Pacific oyster, Crassostrea gigas. A phylogenetic analysis of Prx6 sequences showed that the CgPrx6 segregates between vertebrate and invertebrate groups. We analysed the expression of mRNA coding for CgPrx6 using RT-PCR in gills and digestive gland of oysters sampled in different contaminated and reference estuaries of the Atlantic French coast. We also studied CgPrx6 exon 6 polymorphism by PCR-SSCP in the same populations. Our results showed that CgPrx6 gene expression was highly regulated in the estuaries showing differential contamination levels, as expression increased with pollution level. Polymorphism analysis revealed no significant allelic frequency variations between populations. However, heterozygote deficiency seems to occur in the most contaminated estuaries, suggesting a potential selective effect of environmental stress on heterozygote frequency. Finally, the use of CgPrx6 as a possible marker to monitor stress exposure in disturbed ecosystems is discussed.

Molecular cloning, expression of a peroxiredoxin gene in Chinese shrimp Fenneropenaeus chinensis and the antioxidant activity of its recombinant protein

Peroxiredoxin (Prx) is known to be an antioxidant protein that protects the organisms against various oxidative stresses and functions in intracellular signal transduction. A Prx gene was firstly isolated in the crustacean, Chinese shrimp Fenneropenaeus chinensis. The full-length cDNA consists of 942bp with a 594bp open reading frame, encoding 198 amino acids. The molecular mass of the deduced amino acid is 22041.17Da with an estimated pI of 5.17. Sequence comparison showed that Prx of F. chinensis shares 76%, 73% and 72% identity with that of Aedes aegypti, Branchiostoma belcheri tsingtaunese and Drosophila melanogaster, respectively. Northern blot analysis revealed the presence of Prx transcripts of F. chinensis in all tissues examined. Real-time PCR analysis indicated that the Prx showed different expression profiles in shrimp hemocytes and hepatopancreas after artificial infection with Vibrio anguillarum. In addition, a fusion protein containing Prx was produced in vitro. LC-ESI-MS analysis showed that four peptide fragments of the recombinant protein were identical to the corresponding sequence of F. chinensis Prx. And the purified recombinant proteins were shown to reduce H(2)O(2) in the presence of dithiothreitol.

Thioredoxin from the silkworm, Bombyx mori: cDNA sequence, expression, and functional characterization

A thioredoxin (Trx) gene was cloned from the silkworm, Bombyx mori. The B. mori Trx (BmTrx) cDNA contains an open reading frame of 318 bp encoding 106 amino acid residues with a conserved active site (CGPC). Northern blot analysis revealed the presence of BmTrx transcripts in all tissues examined. The cDNA encoding BmTrx was expressed as a 12-kDa polypeptide in baculovirus-infected insect Sf9 cells. The recombinant BmTrx proved to be biologically active, using an insulin reduction assay, and was also able to activate thioredoxin peroxidase from B. mori. When H2O2 or paraquat was injected into the body cavity of B. mori larvae, BmTrx mRNA expression was upregulated in the fat body tissue. In addition, the expression levels of BmTrx mRNA in the fat body were greatly increased when B. mori larvae were exposed to low or high temperatures, or injected with microorganisms. These results suggest that BmTrx possibly protects against oxidative stress caused by extreme temperatures and microbial infection as well as by intracellularly generated reactive oxygen species during metabolism.

Bombus ignitus Cu,Zn superoxide dismutase (SOD1): cDNA cloning, gene structure, and up-regulation in response to paraquat, temperature stress, or lipopolysaccharide stimulation

A Cu,Zn superoxide dismutase (SOD1) gene was cloned from the bumblebee, Bombus ignitus. The SOD1 gene of B. ignitus spans 1,317 bp and consists of three introns and four exons encoding 151 amino acid residues. The B. ignitus SOD1 (BiSOD1) possesses the typical metal-binding ligands of six histidines and one aspartic acid common to SOD1s. The deduced amino acid sequence of the BiSOD1 cDNA showed 82% identity to Apis mellifera SOD1 and 68-64% to SOD1 sequences from other insects. Northern blot analysis revealed the presence of BiSOD1 transcripts in all tissues examined. When paraquat (methyl viologen), a free radical-inducing agent, was injected into the body cavity of B. ignitus workers, BiSOD1 mRNA expression was up-regulated in the fat body. In addition, the expression levels of BiSOD1 mRNA in the fat body significantly increased when B. ignitus workers were exposed to low (4 degrees C) or high (37 degrees C) temperatures, or injected with lipopolysaccharide (LPS), which suggests that BiSOD1 possibly protects against oxidative stress caused by extreme temperatures and bacterial infection.

Molecular cloning and characterization of ATX1 cDNA from the mole cricket, Gryllotalpa orientalis

To search for an insect homologue of antioxidant protein 1 (ATX1), a mole cricket, Gryllotalpa orientalis, cDNA library was screened and a cDNA clone, which encodes a 73 amino acid polypeptide with a predicted molecular mass of 8.0 kDa and pI of 5.68, was isolated. The G. orientalis ATX1 (GoATX1) cDNA features both a MTCXXC copper-binding site in the N-terminus and a KTGK lysine-rich region in the C-terminus. The deduced amino acid sequence of the GoATX1 cDNA showed 63% identity to Drosophila melanogaster ATX1 and 55% to Ixodes pacificus ATX1. Northern blot analysis revealed the presence of GoATX1 transcripts in midgut, fat body, and epidermis. When H2O2 was injected into the body cavity of G. orientalis adult, GoATX1 mRNA expression was up-regulated in the fat body tissue. Fat body expression level of GoATX1 mRNA in the fat body was increased following exposure to low (4 degrees C) and high (37 degrees C) temperatures, suggesting that GoATX1 plays a protective role against oxidative stress caused by temperature shock. This is the first report about a functional role of insect ATX1 in antioxidant defense.

Cloning and characterization of the Cu,Zn superoxide dismutase (SOD1) cDNA from the mole cricket, Gryllotalpa orientalis

A Cu,Zn superoxide dismutase (SOD1) cDNA was cloned from the mole cricket, Gryllotalpa orientalis. The G. orientalis SOD1 (GoSOD1) cDNA contains an open reading frame of 462 bp encoding 154 amino acid polypeptide with a predicted molecular mass of 15.8 kDa and pI of 6.1, and possesses the typical metal binding ligands of six histidines and one aspartic acid common to SOD1s. The deduced amino acid sequence of the GoSOD1 cDNA showed 75% identity to Lasius niger SOD1, 73% to Apis mellifera SOD1, and 70-68% to SOD1 sequences from other insects. Northern blot analysis revealed the presence of GoSOD1 transcripts in all tissues examined. The expression level of GoATX1 mRNA in the fat body was induced when G. orientalis adult was exposed at low (4 degrees C) and high (37 degrees C) temperatures, suggesting that the GoSOD1 seems to play a protective role against oxidative stress caused by temperature shock.