cDNA cloning, characterization and gene expression of nitric oxide synthase from the silkworm, Bombyx mori

Molecular mechanism of the NOS/NOX regulation of antibacterial activity in Eriocheir sinensis

To elucidate the role of nitric oxide synthase (NOS), which produces the free radical nitric oxide (NO), and nicotinamide adenine dinucleotide phosphate oxidase (NOX), which produces the superoxide anion (O2-), in the innate immunity of Eriocheir sinensis, the full lengths of the NOS and NOX genes were cloned via rapid amplification of the cDNA ends and then expressed in the prokaryotic form to obtain the recombinant proteins, NOS-HIS and NOX-HIS. Through bacterial binding and stimulation experiments, the molecular mechanisms of NOS and NOX in the innate immunity of E. sinensis were explored. Based on the results, NOS and NOX were 5900 bp and 4504 bp long, respectively, and were evolutionarily conserved. Quantitative real-time PCR revealed that NOS and NOX were expressed in all studied tissues, and both were expressed in the highest amounts in hemocytes. NOS-HIS and NOX-HIS could bind to bacteria with different binding powers; their binding ability to gram-positive bacteria was higher than that of binding to gram-negative bacteria. After stimulation with Aeromonas hydrophila, NOS expression was significantly up-regulated at 3, 6, and 48 h, and NOX expression was significantly down-regulated at 3, 12, 24, and 48 h. After bacterial stimulation, the NOS enzyme activity in the serum of E. sinensis was also significantly up-regulated at 6 and 48 h, and the NOX enzyme activity was significantly down-regulated at 12 and 48 h, aligning with the gene expression trend. Moreover, the related free radical molecules, NO, O2-, and H2O2, tended to decrease after bacterial stimulation. Overall, the gene expression and enzyme activity of NOS and NOX had been changed respectively, and the contents of a series of free radical molecules (NO, O2- and H2O2) were induced in E. sinensis after bacterial stimulation, which then exert antibacterial immunity.

Effects of L-arginine on Nitric Oxide Synthesis and Larval Metamorphosis of Mytilus coruscus

To investigate the regulatory functions of L-arginine and nitric oxide (NO) on Mytilus coruscus metamorphosis, M. coruscus larvae were exposed to an inhibitor of nitric oxide synthase (NOS), aminoguanidine hemisulfate (AGH), and a substrate for NO synthesis, L-arginine. We observed that NO levels showed a significant increase, and this trend continued with L-arginine treatment. When NOS activity was inhibited, the larvae could not synthesize NO, and metamorphosis was not inhibited even in the presence of L-arginine. On transfecting pediveliger larvae with NOS siRNA followed by L-arginine exposure, we found that the larvae did not produce NO and that the larval metamorphosis rate was significantly increased, suggesting that L-arginine regulates M. coruscus larval metamorphosis by promoting NO synthesis. Our findings improve our understanding of the effects of marine environmental factors on larval metamorphosis of mollusks.

Exploring the Mystery of the Tetrahydrobiopterin Synthetic Defect Lethal Mutant leml from Birth to Death in the Silkworm Bombyx mori

Tetrahydrobiopterin (BH4) is a vital coenzyme for several enzymes involved in diverse enzymatic reactions in animals, and BH4 deficiency can lead to metabolic and neurological disorders due to dysfunction in its metabolism. In the silkworm natural homozygous mutant lem^l, the key enzyme sepiapterin reductase (BmSPR) in the de novo synthesis pathway of BH4 is inactivated, resulting in severe deficiency of BH4 synthesis. However, it is not known why the lem^l larvae can survive to the second-instar stage and which pathways lead to their death when BH4 is deficient. Here, we quantified BH4 and found that the fertilized eggs contained large amounts of BH4 transferred from the mother to the offspring, maintaining its normal development in the embryo and the first instar. Subsequently, we investigated the multiple pathways in which BH4 is involved as a cofactor. The results showed that BH4 deficiency in silkworms blocked the melanin synthesis pathway, caused an insufficient degree of epidermal sclerosis, disordered tyrosine metabolism, and damaged mitochondria. On the other hand, BH4 deficiency led to the uncoupling of nitric oxide synthase (BmNOS), a reduced NO production, and a significantly reduced fat in fat body catalyzation by phospholipase A2, resulting in an impaired immune system. Meanwhile, the uncoupling of BmNOS increased the O₂⁻ content, damaged the DNA, and caused the apoptosis of the body cells. Taken together, BH4 is critical for the life and death of lem^l mutants. This study lays a foundation for the further exploration of lepidopteran insects and provides an important basis for the treatment of human BH4 deficiency-related diseases.

CTL10 has multiple functions in the innate immune responses of the silkworm, Bombyx mori

Insect C-type lectins (CTLs) play crucial roles in modulating the humoral and cellular immune responses. In the domesticated silkworm Bombyx mori L., BmCTL10 gene encodes an immulectin containing two carbohydrate recognition domains (CRDs). The phylogenetic analysis showed that BmCTL10 didn't cluster with other immulectin homologs in B. mori. BmCTL10 was mainly expressed in second to fifth instar larvae, wandering stage larvae, prepupa, and adults. In naïve fifth instar larvae, BmCTL10 was predominantly expressed in the fat body and epidermis. In second instar larvae, the topical application of Beauveria bassiana by immersion caused down-regulation of BmCTL10. The intra-hemocoel injection of E. coli, S. aureus, B. bassiana, and 20-hydroxyecdysone in fifth instar larvae caused tissue and time-specific inductions. The recombinant protein (rBmCTL10) can bind to larval hemocytes and various pathogen-associated molecular patterns to enhance hemocyte-mediated nodulation, phagocytosis, and encapsulation. rBmCTL10 caused significant upregulation of most antimicrobial peptides and nitric oxide synthase 1 in hemocytes in vivo. Yeast two-hybrid demonstrated that integrin β3 and β4 subunits can interact with BmCTL10. Furthermore, only CRD2 can interact with the β3, while both CRD1 and CRD2 can interact with the β4. Taken together, this study showed that BmCTL10 has multiple functions in the innate immune responses of B. mori and two integrin β subunits are their potential receptors.

Nitric oxide plays a crucial role in midgut immunity under microsporidian infection in Antheraea pernyi

The insect gut participates in initial local immune responses by producing reactive oxygen and nitrogen species as well as anti-microbial peptides to resist pathogenic invasions. Nitric oxide (NO), a signaling and an immune effector molecule synthesized by the enzyme NO synthase (NOS), mediates an early step of the signal transduction pathway. In this study, we evaluated NO levels after Nosema pernyi infection in Antheraea pernyi gut. NOS activity was higher in the microsporidia-infected gut of A. pernyi than in that of control. Three NOS-related genes were cloned, and their spatio-temporal expression patterns were evaluated. ApNOS2 was expressed quickly in the midgut after N. pernyi infection. Sodium nitroprusside, dihydrate (SNP), or Nω-_L-nitro-arginine methyl ester, hydrochloride (_L-NAME), altered the NO content in A. pernyi midgut. Anti-microbial peptides (AMPs) in the groups exposed to N. pernyi plus SNP and N. pernyi plus _L-NAME exhibited higher and lower expression, respectively, relative to the control. These results indicate that microsporidia infection triggers short-term activation of NO and NOS genes in the A. pernyi gut that is downregulated after 24 h. Notably, infection rates can be influenced by a NOS inhibitor. Furthermore, NO can be induced by pathogens. Similarly, NO content in the A. pernyi gut also influences AMPs in humoral immunity and some immune-related genes. Our results suggest that nitric oxide plays a vital role in A. pernyi gut immunity.

Storage of Carotenoids in Crustaceans as an Adaptation to Modulate Immunopathology and Optimize Immunological and Life-History Strategies

Why do some invertebrates store so much carotenoids in their tissues? Storage of carotenoids may not simply be passive and dependent on their environmental availability, as storage variation exists at various taxonomic scales, including among individuals within species. While the strong antioxidant and sometimes immune-stimulating properties of carotenoids may be beneficial enough to cause the evolution of features improving their assimilation and storage, they may also have fitness downsides explaining why massive carotenoid storage is not universal. Here, the functional and ecological implications of carotenoid storage for the evolution of invertebrate innate immune defenses are examined, especially in crustaceans, which massively store carotenoids for unclear reasons. Three testable hypotheses about the role of carotenoid storage in immunological (resistance and tolerance) and life-history strategies (with a focus on aging) are proposed, which may ultimately explain the storage of large amounts of these pigments in a context of host-pathogen interactions.

Immune Defenses of a Beneficial Pest: The Mealworm Beetle, Tenebrio molitor

The mealworm beetle, Tenebrio molitor, is currently considered as a pest when infesting stored grains or grain products. However, mealworms are now being promoted as a beneficial insect because their high nutrient content makes them a viable food source and because they are capable of degrading polystyrene and plastic waste. These attributes make T. molitor attractive for mass rearing, which may promote disease transmission within the insect colonies. Disease resistance is of paramount importance for both the control and the culture of mealworms, and several biotic and abiotic environmental factors affect the success of their anti-parasitic defenses, both positively and negatively. After providing a detailed description of T. molitor’s anti-parasitic defenses, we review the main biotic and abiotic environmental factors that alter their presentation, and we discuss their implications for the purpose of controlling the development and health of this insect.

Nitric Oxide and the Neuroendocrine Control of the Osmotic Stress Response in Teleosts

The involvement of nitric oxide (NO) in the modulation of teleost osmoresponsive circuits is suggested by the facts that NO synthase enzymes are expressed in the neurosecretory systems and may be regulated by osmotic stimuli. The present paper is an overview on the research suggesting a role for NO in the central modulation of hormone release in the hypothalamo-neurohypophysial and the caudal neurosecretory systems of teleosts during the osmotic stress response. Active NOS enzymes are constitutively expressed by the magnocellular and parvocellular hypophysiotropic neurons and the caudal neurosecretory neurons of teleosts. Moreover, their expression may be regulated in response to the osmotic challenge. Available data suggests that the regulatory role of NO appeared early during vertebrate phylogeny and the neuroendocrine modulation by NO is conservative. Nonetheless, NO seems to have opposite effects in fish compared to mammals. Indeed, NO exerts excitatory effects on the electrical activity of the caudal neurosecretory neurons, influencing the amount of peptides released from the urophysis, while it inhibits hormone release from the magnocellular neurons in mammals.

Immune responses to bacterial and fungal infections in the silkworm, Bombyx mori

The silkworm Bombyx mori, an economically important insect that is usually reared indoors, is susceptible to various pathogens, including bacteria, fungi, viruses, and microsporidia. As with other insects, the silkworm lacks an adaptive immune system and relies solely on innate immunity to defend itself against infection. Compared to other intensively studied insects, such as the fruit fly and tobacco hornworm, the principal immune pathways in the silkworm remain unclear. In this article, we review the literature concerning silkworm immune responses to bacteria and fungi and present our perspectives on future research into silkworm immunity.

Detection of Nitric Oxide via Electronic Paramagnetic Resonance in Mollusks

Electronic paramagnetic resonance (EPR) is an appropriate tool to identify free radicals formed in tissues under normal as well as stressful conditions. Since nitric oxide (NO) as a free radical has paramagnetic properties it can be detected by EPR. The use of spin traps highly improves the sensitivity allowing NO identification, detection and quantification at room temperature in vitro and in vivo conditions. NO production in animals is almost exclusively associated to an enzyme family known as Nitric Oxide Synthases (NOSs). The digestive glands of mollusks are a major target for oxidative disruption related to environmental stress. A simple EPR-methodology to asses both, the presence of NO and its rate of generation in tissues from different mollusk species, is reported here.

A dietary carotenoid reduces immunopathology and enhances longevity through an immune depressive effect in an insect model

Immunopathology corresponds to self-damage of the inflammatory response, resulting from oxidizing molecules produced when the immune system is activated. Immunopathology often contributes to age-related diseases and is believed to accelerate ageing. Prevention of immunopathology relies on endogenous antioxidant enzymes and the consumption of dietary antioxidants, including carotenoids such as astaxanthin. Astaxanthin currently raises considerable interest as a powerful antioxidant and for its potential in alleviating age-related diseases. Current in vitro and short-term in vivo studies provide promising results about immune-stimulating and antioxidant properties of astaxanthin. However, to what extent dietary supplementation with astaxanthin can prevent long-term adverse effects of immunopathology on longevity is unknown so far. Here, using the mealworm beetle, Tenebrio molitor, as biological model we tested the effect of lifetime dietary supplementation with astaxanthin on longevity when exposed to early life inflammation. While supplementation with astaxanthin was found to lessen immunopathology cost on larval survival and insect longevity, it was also found to reduce immunity, growth rate and the survival of non immune-challenged larvae. This study therefore reveals that astaxanthin prevents immunopathology through an immune depressive effect and can have adverse consequences on growth.

Success in the acquisition of Bombyx mori sperm motility is influenced by the extracellular production of nitric oxide (NO) in the presence of seminal fluid nitric oxide synthase (NOS)

A trypsin-like protease called initiatorin is known to initiate sperm motility in the silkworm, Bombyx mori, but little is known about the signaling events leading to sperm flagellar beating. The aim of this study was to investigate whether this mechanism of sperm motility activation involves the signaling transmitter nitric oxide (NO). NO is produced from the amino acid L-arginine by the enzyme action of nitric oxide synthase (NOS; EC 1.14.13.39). Simple treatment of quiescent sperm with an NO donor (SNAP or NOC7) in vitro did not lead to activation of motility. Nevertheless, initiatorin- or trypsin-induced motility was blocked by pretreatment of sperm with either the NOS inhibitor L-NAME or NO scavenger carboxy-PTIO. These observations suggested that NO may play important physiological roles in the acquisition of sperm motility under the in vitro condition used here. Then, we investigated whether NO synthesis would occur in the spermatophore, a capsule containing spermatozoa that is created by the contents of various male reproductive glands and is the site of sperm maturation. The amounts of NO₂^- and NO₃^-, stable metabolites of NO, reached maximum values after enclosure in the spermatophore, a time when apyrene spermatozoa acquire vigorous motility. Moreover, RT-PCR and Western blotting analyses of NOS indicated that it is abundantly expressed in glandula (g.) lacteola of the virgin male ejaculatory duct, from which it is secreted to the seminal fluid and transferred to the female during mating. Previous studies demonstrated that free L-arginine is supplied de novo by a specific proteolytic reaction in which initiatorin participates during spermatophore formation (Osanai et al., 1987c). Based on these results, it can be presumed that the mixing of seminal fluid contents from each male reproductive organ during ejaculation induced NO production outside of the spermatid, and exogenous NO stimulated a signaling pathway involved in the activation of silkworm apyrene sperm.

Differential sensitivity to infections and antimicrobial peptide-mediated immune response in four silkworm strains with different geographical origin

The domesticated silkworm Bombyx mori has an innate immune system, whose main effectors are the antimicrobial peptides (AMPs). Silkworm strains are commonly grouped into four geographical types (Japanese, Chinese, European and Tropical) and are generally characterised by a variable susceptibility to infections. To clarify the genetic and molecular mechanisms on which the different responses to infections are based, we exposed one silkworm strain for each geographical area to oral infections with the silkworm pathogens Enterococcus mundtii or Serratia marcescens. We detected a differential susceptibility to both bacteria, with the European strain displaying the lowest sensitivity to E. mundtii and the Indian one to S. marcescens. We found that all the strains were able to activate the AMP response against E. mundtii. However, the highest tolerance of the European strain appeared to be related to the specific composition of its AMP cocktail, containing more effective variants such as a peculiar Cecropin B6 isoform. The resistance of the Indian strain to S. marcescens seemed to be associated with its prompt capability to activate the systemic transcription of AMPs. These data suggest that B. mori strains with distinct genetic backgrounds employ different strategies to counteract bacterial infections, whose efficacy appears to be pathogen-dependent.

Nitric oxide synthase during early embryonic development in silkworm Bombyx mori: Gene expression, enzyme activity, and tissue distribution

To elucidate the mechanism for embryonic diapause or the breakdown of diapause in Bombyx mori, we biochemically analyzed nitric oxide synthase (NOS) during the embryogenesis of B. mori. The gene expression and enzyme activity of B. mori NOS (BmNOS) were examined in diapause, non-diapause, and HCl-treated diapause eggs. In the case of HCl-treated diapause eggs, the gene expression and enzyme activity of BmNOS were induced by HCl treatment. However, in the case of diapause and non-diapause eggs during embryogenesis, changes in the BmNOS activity and gene expressions did not coincide except 48-60 h after oviposition in diapause eggs. The results imply that changes in BmNOS activity during the embryogenesis of diapause and non-diapause eggs are regulated not only at the level of transcription but also post-transcription. The distribution and localization of BmNOS were also investigated with an immunohistochemical technique using antibodies against the universal NOS; the localization of BmNOS was observed mainly in the cytoplasm of yolk cells in diapause eggs and HCl-treated diapause eggs. These data suggest that BmNOS has an important role in the early embryonic development of the B. mori.

Midgut immune responses induced by bacterial infection in the silkworm, Bombyx mori

Insect gut epithelial cells produce reactive oxygen species (ROS) and antimicrobial peptides (AMPs) to protect hosts from pathogenic microorganisms. In this study, we evaluate the pathogenicity of Pseudomonas aeruginosa and Bacillus bombysepticus in the silkworm, Bombyx mori. Survival curves show that B. bombysepticus is deadly when larval silkworms are infected orally. Bacterial infection caused intestinal hydrogen peroxide (H2O2) and nitric oxide (NO) levels to increase significantly by 8 and 16 h post-infection (hpi), respectively. Real-time quantitative polymerase chain reaction (qPCR) analysis shows that the transcription levels of dual oxidase (Duox) and catalase (CAT) are highly up-regulated by P. aeruginosa infection at 8 hpi. P. aeruginosa infection induced nitric oxide synthase 2 (NOS2) expression at 16 hpi, which contributes to the generation of NO. mRNA levels of AMP genes, specifically Glovorin 2 and Glovorin 3, which obviously increase during the early infection stage. These results indicate that invading bacteria elevate intestinal ROS and NO levels and induce AMP gene transcription, which contributes to intestinal immune defense.

Transcriptome profiling during a natural host-parasite interaction

BACKGROUND

Infection outcome in some coevolving host-pathogens is characterised by host-pathogen genetic interactions, where particular host genotypes are susceptible only to a subset of pathogen genotypes. To identify candidate genes responsible for the infection status of the host, we exposed a Daphnia magna host genotype to two bacterial strains of Pasteuria ramosa, one of which results in infection, while the other does not. At three time points (four, eight and 12 h) post pathogen exposure, we sequenced the complete transcriptome of the hosts using RNA-Seq (Illumina).

RESULTS

We observed a rapid and transient response to pathogen treatment. Specifically, at the four-hour time point, eight genes were differentially expressed. At the eight-hour time point, a single gene was differentially expressed in the resistant combination only, and no genes were differentially expressed at the 12-h time point.

CONCLUSIONS

We found that pathogen-associated transcriptional activity is greatest soon after exposure. Genome-wide resistant combinations were more likely to show upregulation of genes, while susceptible combinations were more likely to be downregulated, relative to controls. Our results also provide several novel candidate genes that may play a pivotal role in determining infection outcomes.

Nitric oxide participates in the toxicity of Bacillus thuringiensis Cry1Ab toxin to kill Manduca sexta larvae

Nitric oxide (NO) produced by the nitric oxide synthase (NOS) enzyme is a reactive oxygen molecule widely considered as important participant in the immune system of different organisms to confront microbial infections. In insects the NO molecule has also been implicated in immune response against microbial pathogens. Bacillus thuringiensis (Bt) is an insect-pathogenic bacterium that produces insecticidal proteins such as Cry toxins. These proteins kill insects because they form pores in the larval-midgut cells. Here we show that intoxication of Manduca sexta larvae with Cry1Ab activates expression of NOS with a corresponding increase in NO. This effect is not observed with a non-toxic mutant toxin Cry1Ab-E129K that is affected in pore formation. The increased production of NO triggered by intoxication with LC50 dose of Cry1Ab toxin is not associated with higher expression of antimicrobial peptides. NO participates in Cry1Ab toxicity since inhibition of NOS by selective l-NAME inhibitor prevented NO production and resulted in reduced mortality of the larvae. The fact that mortality was not completely abolished by L-NAME indicates that other processes participate in toxin action and induction of NO production upon Cry1Ab toxin administration accounts only for a part of the toxicity of this protein to M. sexta larvae.

Injury and immune response: applying the danger theory to mosquitoes

The insect immune response can be activated by the recognition of both non-self and molecular by-products of tissue damage. Since pathogens and tissue damage usually arise at the same time during infection, the specific mechanisms of the immune response to microorganisms, and to tissue damage have not been unraveled. Consequently, some aspects of damage caused by microorganisms in vector-borne arthropods have been neglected. We herein reassess the Anopheles-Plasmodium interaction, incorporating Matzinger's danger/damage hypothesis and George Salt's injury assumptions. The invasive forms of the parasite cross the peritrophic matrix and midgut epithelia to reach the basal lamina and differentiate into an oocyst. The sporozoites produced in the oocyst are released into the hemolymph, and from there enter the salivary gland. During parasite development, wounds to midgut tissue and the basement membrane are produced. We describe the response of the different compartments where the parasite interacts with the mosquito. In the midgut, the response includes the expression of antimicrobial peptides, production of reactive oxygen species, and possible activation of midgut regenerative cells. In the basal membrane, wound repair mainly involves the production of molecules and the recruitment of hemocytes. We discuss the susceptibility to damage in tissues, and how the place and degree of damage may influence the differential response and the expression of damage associated molecular patterns (DAMPs). Knowledge about damage caused by parasites may lead to a deeper understanding of the relevance of tissue damage and the immune response it generates, as well as the origins and progression of infection in this insect-parasite interaction.

An evolutionarily ancient NO synthase (NOS) in shrimp

Nitric oxide (NO) is a well known essential molecule that is involved in multiple functions such as neuron transduction, cardiac disease, immune responses, etc.; nitric oxide synthase (NOS) is a critical enzyme that catalyzes the synthesis of it. A very few crustacean NOS molecules were biochemically characterized so far. In the present study, we cloned and characterized a NOS cDNA from haemocytes of tiger shrimp (Penaeus monodon) (PmNOS). The full-length of PmNOS cDNA contained 3997 bp, including a 5'UTR of 249 bp, ORF of 3582 bp and a 3'UTR of 166 bp. The putative peptide was 1193 amino acid residues in length, with an estimated molecular weight of 134.7 kDa and pI 6.7. Structurally, PmNOS contained oxygenase and reductase domains at N-terminal and C-terminal, respectively, and connected with a calmodulin binding motif. The deduced amino acid sequence of PmNOS shared 98% identical to the Chinese shrimp (Fenneropenaeus chinensis) NOS. Phylogenetically, PmNOS clustered with invertebrate NOS, but not clustered with iNOS, eNOS or nNOS found in vertebrates. PmNOS mRNA was expressed in many tissues or organs including thoracic and ventral nerves, midgut, gill, eyestalk, haemocytes, subcuticular epithelium and heart, but not found in hepatopancreas, muscle and lymphoid organ. But there was no significant difference in PmNOS mRNA expression after stimulation with LPS either by different concentration or time course or against CpG-ODN 2006. The enzyme activities of rPmNOS or crude homogenates from different tissues were detected, and were shown its highest activity in thoracic and ventral nerves, moderate in midgut and haemocytes but the lowest activity were seen in muscle. The addition of NOS antibody against NADPH binding domain leads to less activity which suggested that NADPH was an essential cofactor for PmNOS catalytic activity. The calcium dependency of PmNOS was ascertained using calmodulin inhibitor, Trifluroperazine. To confirm the population of haemocyte which produce NOS, the florescence test was assayed, and it implicated that the production of NO was catalyzed by subset of granulocytic NOS. Since the MW range, inducible/noninducible transcript, calcium-dependent activity and tissue distribution, we suggest that PmNOS may recognize as an ancient NOS evolutionarily.

Role of nitric oxide-detoxifying enzymes in the virulence of Pseudomonas aeruginosa against the silkworm, Bombyx mori

Pseudomonas aeruginosa has two nitric oxide (NO)-detoxification enzymes, NO reductase and flavohemoglobin, which catalyze the reduction and oxygenation of NO respectively. In this study, the NO reductase-deficient mutant showed decreased virulence against the silkworm Bombyx mori, but the flavohemoglobin-deficient mutant did not, indicating that NO-reduction is important to the full virulence of P. aeruginosa against B. mori.

Cellular, biochemical, and molecular characterization of nitric oxide synthase expressed in the nervous system of the prosobranch Stramonita haemastoma (Gastropoda, Neogastropoda)

Nitric oxide synthase (NOS) has been characterized in several opistobranchs and pulmonates but it was much less investigated in prosobranchs, which include more than 20,000 species and account for most of the gastropod diversity. Therefore, new data from this large group are needed for a better knowledge of the molecular evolution of NOS enzymes in molluscs. This study focused on NOS expressed in the nervous system of the prosobranch neogastropod Stramonita haemastoma. In this study we report compelling evidence on the expression of a constitutive Ca(2+) /CaM-dependent neuronal NOS in the central and peripheral nervous system. The prevailing neuronal localization of NADPHd activity was demonstrated by NADPHd histochemistry in both central and peripheral nervous system structures. L-arginine/citrulline assays suggested that Stramonita NOS is a constitutive enzyme which is both cytosolic and membrane-bound. Molecular cloning of the full-length Stramonita NOS (Sh-NOS) by reverse-transcription polymerase chain reaction (RT-PCR) followed by 5' and 3' RACE showed that Sh-NOS is a protein of 1,517 amino acids, containing a PDZ domain at the N-terminus and sharing similar regulatory domains to the mammalian neuronal NOS (nNOS). Regional expression of the Sh-NOS gene was evaluated by RT-PCR. This analysis showed different expression levels in the nerve ring, the osphradium, the cephalic tentacles, the buccal tissues, and the foot, whereas NOS expression was not found in the salivary glands and the gland of Leiblein. The present data provide a solid background for further studies addressing the specific functions of NO in neogastropods.

Defense role of the cocoon in the silk worm Bombyx mori L

Silk from the domesticated silk worm Bombyx mori procures foreign body response naturally, so it has been utilized as a biomaterial for decades. In India the prime focus of the sericulture industry is to improve silk production with high quality silk. Naturally, the silk worm builds its cocoon not only with silk proteins, but also with antimicrobial proteins to avoid infection since the cocoon is non-motile and non-feeding. The aim of the present study is to elucidate the antimicrobial proteins that persist in the cocoon of the silk worm Bombyx mori. At the pupal stage, the silk worm cocoon shell extract was prepared from the day of pupation (P0) to the day of natural rupture of the cocoon for the eclosion of moth (NR). Using the cocoon shell extract a microbial susceptibility test was performed by the disc diffusion method against the microbes Escherchia coli, Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae. The development of a zone of inhibition against the microbes confirmed the presence of antimicrobial/immunogenic activity of the cocoon shell extract. For further analysis, the cocoon shell extract was subjected to 7-15% sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE). The protein profile of the cocoon extract revealed the coomassie blue stained bands resolved from the 150-15 kDa molecular range. Interestingly, a polypeptide localized at around 29 kDa showed remarkable expressional changes during the development of pupa. To characterize the 29 kDa protein, it was eluted from the gel, digested with trypsin and analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The trypsin-digested peptide peaks were analyzed through MASCOT and peptides were matched with the NCBI nr database. The peptides were very well matched with the 18 wheeler protein, which is reported to be responsible for innate immunity, belonging to the Toll family in insects and responsible for cellular mediated immunity.

L-arginine enhances immunity to parasitoids in Drosophila melanogaster and increases NO production in lamellocytes

Drosophila melanogaster was used as a model system to explore the link between nutrition and immunity, and to investigate the role of nitric oxide (NO) in enhancing immunity following dietary enhancement with L-arginine. First, we show that adding L-arginine to the food medium increases the ability of D. melanogaster larvae to encapsulate the eggs of the parasitoid Asobara tabida. Secondly, we show that the increase in immunity is specific to L-arginine, and not to an enhanced calorific content, and that immunity decreases when larvae are fed food with added L-NAME, an inhibitor of nitric oxide synthase. Finally, we show that parasitised larvae fed L-arginine have increased haemocyte numbers, and that the lamellocytes (haemocytes which play a key role in encapsulation) show evidence of an increased production of NO. These results suggest that NO plays a key role in immunity and that the effect of NO is mostly targeted via the lamellocytes.

Pathogen and host factors are needed to provoke a systemic host response to gastrointestinal infection of Drosophila larvae by Candida albicans

Candida albicans systemic dissemination in immunocompromised patients is thought to develop from initial gastrointestinal (GI) colonisation. It is unclear what components of the innate immune system are necessary for preventing C. albicans dissemination from the GI tract, but studies in mice have indicated that both neutropenia and GI mucosal damage are crucial for allowing widespread invasive C. albicans disease. Mouse models, however, provide limited applicability to genome-wide screens for pathogen or host factors - factors that might influence systemic dissemination following GI colonisation. For this reason we developed a Drosophila model to study intestinal infection by Candida. We found that commensal flora aided host survival following GI infection. Candida provoked extensive JNK-mediated death of gut cells and induced antimicrobial peptide expression in the fat body. From the side of the host, nitric oxide and blood cells influenced systemic antimicrobial responses. The secretion of SAP4 and SAP6 (secreted aspartyl proteases) from Candida was also essential for activating systemic Toll-dependent immunity.

A calcium-insensitive attenuated nitrosative stress response contributes significantly in the radioresistance of Sf9 insect cells

Lepidopteran insects/insect cells display 50-100 times higher radioresistance than humans, and are evolutionarily closest to mammals amongst all radioresistant organisms known. Compared to mammalian cells, Lepidopteran cells (TN-368, Sf9) display more efficient antioxidant system and DNA repair and suffer considerably less radiation-induced DNA/cytogenetic damage and apoptosis. Recent studies indicate that a considerably lower radiation-induced oxidative stress may significantly reduce macromolecular damage in Lepidopteran cells. Since nitrosative stress contributes in radiation-induced cellular damage, we investigated its nature in the γ-irradiated Sf9 cells (derived from Spodoptera frugiperda; order Lepidoptera; family Noctuidae) and compared with BMG-1 human cell line having significant NOS expression. Radiation induced considerably less ROS/RNS in Sf9 cells, which remained unchanged on treatment with NOS inhibitor l-NMMA. Surprisingly, growth of Sf9 cultures or irradiation could not induce NO or its metabolites, indicating negligible basal/radiation-induced NOS activity that remained unchanged even after supplementation with arginine. Cytosolic calcium release following high-dose (1000-2000Gy at 61.1cGys(-1)) γ-irradiation or H(2)O(2) (250μM) treatment also failed to generate NO in Sf9 cells having high constitutive levels of calmodulin, whereas BMG-1 cells displayed considerable calcium-dependent NO generation even following 10Gy dose. These results strongly imply the lack of calcium-mediated NOS activity in Sf9 cells. Addition of exogenous NO from GSH-NO caused considerable increase in radiation-induced apoptosis, indicating significant contribution of constitutively attenuated nitrosative stress response into the radioresistance of Lepidopteran cells. Our study demonstrates for the first time that a calcium-insensitive, attenuated nitrosative stress response may contribute significantly in the unusual radioresistance displayed by Lepidopteran insect cells.

Iron and nitrosative metabolism in the Antarctic mollusc Laternula elliptica

The objective of this work was to study Fe distribution, and oxidative and nitrosative metabolism in Laternula elliptica for physiological analysis and interspecific comparisons. Lipid peroxidation, superoxide dismutase and catalase activity and total Fe content were estimated in the digestive glands (DG) of L. elliptica. The labile Fe pool (LIP) represents the amount of cellular Fe responsible for catalyzing radical-dependent reactions. LIP assessed by the calcein assay, represents 3.5% of the total Fe in L. elliptica. Experimental isolation of ferritin (Ft) was performed. Subunit analyses of the protein by SDS-polyacrilamide gel electrophoresis indicated that the protein was composed of 20.6kDa protein subunits, consistent with the horse spleen Ft and the molecular weight markers, however, a higher molecular mass subunit could appear. The identity of the protein was confirmed by Western blot analysis. The nitrate+nitrite content was 73±7pmol/mg fresh mass (FW). The nitric oxide (NO) content in DG homogenates, assessed by electronic paramagnetic resonance (EPR) spin trapping measurements using the NO trap sodium-N-methyl-D-glucamine dithiocarbamate-Fe at room temperature, was 30±2pmol/mg FW. Nitric oxide synthase-like activity (1.50±0.09pmol/mg FW min) was assessed by measuring NO production by EPR in the presence of L-arginine (L-A) and NADPH. This activity was significantly inhibited by L-A analogs such as Nω-nitro-L-arginine methyl ester hydrochloride (-77%) and Nω-nitro-L-arginine (-62%), or by the lack of added L-A (-55%). The data presented here documented the physiological presence of labile Fe, Ft and highly reactive nitrogen species, and are the first evidence that support the hypothesis that NO being generated in L. elliptica might contribute to restrict oxidative damage by a close link with Fe metabolism.

The effect of nitric oxide and hydrogen peroxide in the activation of the systemic immune response of Anopheles albimanus infected with Plasmodium berghei

The expression of genes encoding the antimicrobial peptides (AMPs) attacin, cecropin and gambicin, as well as the effects of NO and H(2)O(2) on their expression was investigated in midguts and fat bodies of Anopheles albimanus during the midgut infection with Plasmodium berghei. Midgut infection induced an increase in the expression of the three AMPs in both tissues; while NO and H(2)O(2) were present in haemolymph. Treatment with L-NAME and vitamin C reduced the effect of P. berghei infection on the AMP's expression, and exogenous NO and H(2)O(2) induced their expression in the mosquito fat body. The induction of AMPs in abdominal tissues, while the malaria parasites are in the mosquito midgut, suggests communication between the midgut epithelial cells and the abdominal tissue which has not yet had direct contact with the parasites. Free radical production in mosquito midgut and haemolymph during Plasmodium infection and their inductive effect on AMPs in abdominal tissues indicates the possible participation of these radicals in mediating a systemic immune response in this mosquito.

Evolution of the nitric oxide synthase family in metazoans

Nitric oxide (NO) is essential to many physiological functions and operates in several signaling pathways. It is not understood how and when the different isoforms of nitric oxide synthase (NOS), the enzyme responsible for NO production, evolved in metazoans. This study investigates the number and structure of metazoan NOS enzymes by genome data mining and direct cloning of Nos genes from the lamprey. In total, 181 NOS proteins are analyzed from 33 invertebrate and 63 vertebrate species. Comparisons among protein and gene structures, combined with phylogenetic and syntenic studies, provide novel insights into how NOS isoforms arose and diverged. Protein domains and gene organization--that is, intron positions and phases--of animal NOS are remarkably conserved across all lineages, even in fast-evolving species. Phylogenetic and syntenic analyses support the view that a proto-NOS isoform was recurrently duplicated in different lineages, acquiring new structural configurations through gains and losses of protein motifs. We propose that in vertebrates a first duplication took place after the agnathan-gnathostome split followed by a paralog loss. A second duplication occurred during early tetrapod evolution, giving rise to the three isoforms--I, II, and III--in current mammals. Overall, NOS family evolution was the result of multiple gene and genome duplication events together with changes in protein architecture.

Molecular cloning and characterization of the nitric oxide synthase gene from kuruma shrimp, Marsupenaeus japonicus

Nitric oxide (NO) signaling is involved in many physiological processes in vertebrates and invertebrates. In crustaceans, nitric oxide synthase (NOS) plays a significant role in the regulation of the nervous system and in innate immunity. Here, we describe the entire cDNA sequence (4616 bp) of the kuruma shrimp Marsupenaeus japonicus NOS (Mj NOS) generated using the reverse transcriptase-polymerase chain reaction (RT-PCR) and 5'- and 3'- rapid amplification PCRs of cDNA ends from brain and gill mRNAs. The open reading frame of Mj NOS encoded a protein of 1187 amino acids with an estimated mass of 134 kDa, and had an 82.3% sequence homology with the NOS gene of the land crab Gecarcinus lateralis. Highly conserved amino acid sequences in heme and tetrahydrobiopterin were observed in the oxygenase domain. FMN, FAD and NADPH were found in the reductase domain. Mj NOS mRNA was constitutively expressed in the brain, gill, intestine, thoracic ganglion and testis of the kuruma shrimp. When Vibrio penaeicida was injected into the kuruma shrimp, Mj NOS was expressed in the brain, gill, heart, lymphoid organ, intestine and thoracic ganglion. Mj NOS expression in the gill reached its peak 12 h and decreased to its normal level 24 h after V. penaeicida injection.

An ancient immunity gene duplication in Daphnia magna: RNA expression and sequence analysis of two nitric oxide synthase genes

NO (nitric oxide) is a highly reactive free radical gas thought to play a major role in the invertebrate immune response by harming pathogens and limiting their growth. Here we report on studies of nitric oxide synthase (NOS) genes in the crustacean Daphnia, one of the few non-insect arthropod models used to study host-pathogen interactions. While the NOS gene is found as a single copy in other invertebrates, we found two copies (NOS1 and NOS2), which a phylogenetic reconstruction showed to be the result of an ancient duplication event. Both genes bear features commonly found in invertebrate NOS, however, the two genes differ in their rate of evolution, intraspecific polymorphism and expression level. We tested whether the more rapid evolution of NOS2 could be due to positive selection, but found the rate of amino-acid substitutions between Daphnia species to be compatible with a neutral model. To associate NOS or NO activity with infection, we performed infection experiments with Daphnia magna and one of its natural pathogens (the bacterium Pasteuria ramosa). In one set of experimental infections, we supplemented D. magna with L-arginine, the NOS substrate, or with L-NAME, a NOS antagonist, and found this to result in lower and higher infection levels, respectively, which is at least compatible with the notion that NO may aid defence against Pasteuria. A second experiment indicated that NOS transcription does not increase following exposure to Pasteuria. Thus, the function of NOS in Daphnia immunity remains uncertain, but the pattern of gene duplication and subsequent divergence suggests evolution via neo- or subfunctionalization.

Induced nitric oxide synthesis in the gut of Manduca sexta protects against oral infection by the bacterial pathogen Photorhabdus luminescens

Injecting the insect pathogenic bacterium Photorhabdus luminescens into the blood system of the model lepidopteran insect Manduca sexta induces nitric oxide synthase (NOS) expression in the fat body and blood cells (haemocytes), whereas following oral ingestion of bacteria NOS expression is limited to the gut. We used RNA interference to knock-down expression of NOS throughout the insect. Preventing NOS induction in this way adversely affected the survival of orally infected insects and caused a significant increase in the number of bacteria crossing into the haemolymph. By contrast, knock-down of NOS had no effect on the mortality rate of insects infected with P. luminescens by injection. Pharmacological inhibition of NOS decreased both nitric oxide (NO) levels in the gut wall and survival of orally infected insects, whereas elevation of gut wall NO using an NO donor increased survival of NOS silenced caterpillars. Together, our results imply that induced synthesis of NO is important in mediating insect immune defence against the pathogen by inhibiting transfer of bacteria across the gut wall.

The components of the Daphnia pulex immune system as revealed by complete genome sequencing

Background

Branchiopod crustaceans in the genus Daphnia are key model organisms for investigating interactions between genes and the environment. One major theme of research on Daphnia species has been the evolution of resistance to pathogens and parasites, but lack of knowledge of the Daphnia immune system has limited the study of immune responses. Here we provide a survey of the immune-related genome of D. pulex, derived from the newly completed genome sequence. Genes likely to be involved in innate immune responses were identified by comparison to homologues from other arthropods. For each candidate, the gene model was refined, and we conducted an analysis of sequence divergence from homologues from other taxa.

Results and conclusion

We found that some immune pathways, in particular the TOLL pathway, are fairly well conserved between insects and Daphnia, while other elements, in particular antimicrobial peptides, could not be recovered from the genome sequence. We also found considerable variation in gene family copy number when comparing Daphnia to insects and present phylogenetic analyses to shed light on the evolution of a range of conserved immune gene families.

Nitric oxide synthase (NOS) in the Japanese fireflies Luciola lateralis and Luciola cruciata

Species-specific flash patterns in firefly species are important for the investigation of the evolution of Lampyridae. Since nitric oxide synthase (NOS) is one of the key enzymes controlling flash patterns, we determined the cDNA sequences of NOS in the Japanese fireflies Luciola lateralis and L. cruciata. The identity of the NOS sequences was very high between these 2 species. Firefly NOS also exhibited a high identity with those of other insect species, and the cofactor-binding domains were particularly well conserved. Many negatively selected sites were detected throughout the NOS sequences; however, no positive selection was detected. The phylogenetic relationship of insect NOS was different from that of the general classification system, although the lineages corresponded to the major recognized taxonomic groups.

Nitric oxide-cyclic guanosine monophosphate signaling in the local circuit of the cricket abdominal nervous system

The distribution of potential nitric oxide (NO) donor neurons and NO-responsive target neurons was revealed in the terminal abdominal ganglion (TAG) of the cricket. The expression of nitric oxide synthase (NOS) in the nervous system was examined by Western blotting using universal nitric oxide synthase (uNOS) antibody that gave about a 130 kDa protein band. Immunohistochemistry using the uNOS antibody detected neurons whose cell bodies are located at the lateral region of the TAG. These neurons expanded their neuronal branches into the dorsal-median region or the dorsal-lateral region of the TAG. NADPH-diaphorase histochemistry was performed to confirm the distribution of NOS-containing neurons. The distributions of cell bodies and stained neuronal branches were similar to those revealed by uNOS immunohistochemistry. NO-induced cGMP immunohistochemistry was performed to reveal NO-responsive target neurons. Most of the cell bodies stained by immunohistochemistry appeared at the dorsal side of the TAG. At the dorsal-median region, some unpaired neuronal cell bodies were strongly stained. Some efferent neurons whose axon innervate into each nerve root were strongly stained. The generation of NO in the TAG was detected by NO electrode. We found that NO is generally produced to maintain a basal concentration of 70 nM. Hemoglobin scavenged released NO from the ganglion. The concentration of NO was partly recovered when hemoglobin was replaced by normal saline. Application of 10 microM L-arginine that is a substrate of NOS increased NO release by approximately 10 nM. Furthermore, an excitatory neurotransmitter acetylcholine (ACh) also increased NO generation by approximately 40-50 nM in concentration in addition to the basal level of 70 nM. Optical imaging with fluorescent NO-indicator demonstrated that ACh-induced enhancement of NO release was transiently observed in the outer-edge region of TAG, where cell bodies of NOS-immunoreactive neurons were located. These results suggest that ACh accelerates NO production via neuronal events activated by ACh in the TAG.

Role of nitric oxide synthase in insect cell radioresistance: an in-silico analysis

Previous studies on various insect cell lines have displayed very high radioresistance in Lepidoptera (butterflies and moths) as compared to mammals as well as other orders of Insecta including Diptera. Since NOS is known to modulate cellular radiation sensitivity, we carried out in silico analysis of Lepidopteran NOS and compared its structural and functional features including the sequence homology, predicted tertiary structure, post-translational phosphorylation and intracellular localization with the other species. Our study demonstrates that Lepidopteran NOS, while carrying significant sequence homology with mammalian nNOS, has structural/ functional features that may enhance resistance to radiation and other stress agents. A higher phosphorylation score of Lepidopteran NOS (0.885+/-0.02 as against 0.694+/-0.094 of mammalian NOS; predicted using Net Phos 2.0) was observed at many well-conserved phosphorylation sites, which may reduce NOS activation by stress agents including radiation. Further, the primarily cytoplasmic localization of Lepidopteran NOS (score 23 against 10 of mammalian NOS, derived using WoLFPSORT), aided by higher phosphorylation scores as well as sequence-driven cytoplasmic localizing signals, may significantly reduce amplification of extraneous oxidative damage. Based on these findings, we hypothesize that a primarily cytosolic and less responsive NOS could significantly contribute to radioresistance of Lepidopteran insects as well as their cultured cell lines.

Positional cloning of a Bombyx wingless locus flugellos (fl) reveals a crucial role for fringe that is specific for wing morphogenesis

Mutations at the flügellos (fl) locus in Bombyx mori produce wingless pupae and moths because of the repressed response of wing discs to ecdysteroid. Four recessive fl alleles occurred spontaneously and were mapped at 13.0 of the silkworm genetic linkage group 10. By positional cloning, we confirmed that the gene responsible for fl is fringe (fng) encoding Fng glycosyltransferase, which is involved in regulating the Notch signaling pathway. In four different fl alleles, we detected a large deletion of the fng gene in fl(k) and nonsense mutations in fl, fl(o), and fl(n). In the wild-type (WT) silkworm, fng is expressed actively in the wing discs, brain, and reproductive organs from the fourth to final instars but barely in the other tissues tested. In situ hybridization showed that fng mRNA is expressed in the dorsal layer of the WT wing discs. The wingless (wg) mRNA, a downstream marker of Fng-mediated Notch signaling, is localized at the dorsoventral boundary in the WT wing discs but repressed markedly in the fl wing discs. Although null mutants of Drosophila fng result in postembryonic lethality, loss of fng function in Bombyx affects only wing morphogenesis, suggesting different essential roles for fng in tissue differentiation among insects.

Distribution and characterization of nitric oxide synthase in the nervous system of Triatoma infestans (Insecta: Heteroptera)

The biochemical characterization of nitric oxide synthase (NOS) and its distribution in the central nervous system (CNS) were studied in the heteropteran bug Triatoma infestans. NOS-like immunoreactivity was found in the brain, subesophageal ganglion, and thoracic ganglia by using immunocytochemistry. In the protocerebrum, NOS-immunoreactive (IR) somata were detected in the anterior, lateral, and posterior soma rinds. In the optic lobe, numerous immunostained somata were observed at the level of the first optic chiasma, around the lobula, and in the proximal optic lobe. In the deutocerebrum, NOS-IR perikarya were mainly observed in the lateral soma rind, surrounding the sensory glomeruli, and a few cell bodies were seen in association with the antennal mechanosensory and motor neuropil. No immunostaining could be detected in the antennal nerve. The subesophageal and prothoracic ganglia contained scattered immunostained cell bodies. NOS-IR somata were present in all the neuromeres of the posterior ganglion. Western blotting showed that a universal NOS antiserum recognized a band at 134 kDa, in agreement with the expected molecular weight of the protein. Analysis of the kinetics of nitric oxide production revealed a fully active enzyme in tissue samples of the CNS of T. infestans.

Changes in mitochondrial electron transport chain activity during insect metamorphosis

The midgut of the tobacco hornworm (Manduca sexta) is a highly aerobic tissue that is destroyed by programmed cell death during larval-pupal metamorphosis. The death of the epithelium begins after commitment to pupation, and the oxygen consumption of isolated midgut mitochondria decreases soon after commitment. To assess the role of the electron transport chain in this decline in mitochondrial function, the maximal activities of complexes I-IV of the respiratory chain were measured in isolated midgut mitochondria. Whereas there were no developmental changes in the activity of complex I or III, activities of complexes II and IV [cytochrome c oxidase (COX)] were higher in mitochondria from precommitment than postcommitment larvae. This finding is consistent with a higher rate of succinate oxidation in mitochondria isolated from precommitment larvae and reveals that the metamorphic decline in mitochondrial respiration is due to the targeted destruction or inactivation of specific sites within the mitochondria, rather than the indiscriminate destruction of the organelles. The COX turnover number (e- x s(-1) x cytochrome aa3(-1)) was greater for the enzyme from precommitment than postcommitment larvae, indicating a change in the enzyme structure and/or its lipid environment during the early stages of metamorphosis. The turnover number of COX in the intact mitochondria (in organello COX) was also lower in postcommitment larvae. In addition to changes in the protein or membrane phospholipids, the metamorphic decline in this rate constant may be a result of the observed loss of endogenous cytochrome c.

Nitric oxide: an antiparasitic molecule of invertebrates

Since Furchgott, Ignarro and Murad won the Nobel prize in 1998 for their work on the role of nitric oxide (NO) as a signaling molecule, many reports have shown the seemingly limitless range of body functions controlled by this compound. In vertebrates, the role of NO as a defense against infection caused by viruses, bacteria, and protozoan and metazoan parasites has been known for several years. New evidence, however, shows that NO is also important in defending invertebrates against parasites. This discovery is a breakthrough in the understanding of how the invertebrate immune system works, and it has implications for the emerging field of invertebrate ecological immunology.

Expression of one isoform of GTP cyclohydrolase I coincides with the larval black markings of the swallowtail butterfly, Papilio xuthus

The larva of the swallowtail butterfly Papilio xuthus changes its body markings during the fourth ecdysis. We found that stage-specific cuticular black markings are mainly regulated by co-localization of two melanin synthesis enzymes; tyrosine hydroxylase (TH) and dopa decarboxylase (DDC). TH converts tyrosine to dihydroxyphenylalanine (dopa), and tyrosine itself is converted from phenylalanine by phenylalanine hydroxylase (PAH). Guanosine triphosphate cyclohydrolase I (GTPCHI) is essential for the synthesis of tetrahydrobiopterin (BH4) that is a cofactor of TH and PAH. In this report, we found that a GTPCHI inhibitor prevents pigmentation in cultured integuments, suggesting that the GTPCHI activity is also involved in cuticle pigmentation. We have cloned GTPCHI and PAH cDNAs from P. xuthus and investigated their spatial expression patterns in epidermis by whole-mount in situ hybridization. There are two isoforms of GTPCHI in larval epidermis (GTPCHIa and GTPCHIb). GTPCHIa is expressed at the black markings of the subsequent instar, similar to TH, whereas GTPCHIb is expressed uniformly, similar to PAH. This suggests that the region-specific expression of GTPCHIa supplies sufficient BH(4) reinforcing the TH activity in black marking area. Our results imply that larval markings are regulated by not only melanin synthesis enzymes but also the cofactor supplying enzyme.

Nitric oxide production in blowfly hemolymph after yeast inoculation

Although insects lack the adaptive immune response of the mammalians, they manifest effective innate immune responses that include both cellular and humoral components. Cellular responses are mediated by hemocytes and humoral responses include the activation of proteolytic cascades that initiate many events, including NO production. In this work, we determined NO production in Chrysomya megacephala hemolymph and hemocytes after yeast inoculation. Assays were performed with non-infected controls (NIL), saline-injected larvae (SIL) or larvae injected with Saccharomyces cerevisiae (YIL). The hemolymph of injected groups was collected 0.5, 1, 2, 4, 12, 24 or 48h post-injection. NO levels in SIL were comparable to those measured in NIL until 12h, which might be considered the basal production, increasing at 24 and 48h post-injection, probably in response to the increased larval fragility after cuticle rupture. YIL exhibited significantly higher levels of NO than were found in other groups, peaking at 24h. l-NAME and EDTA caused a significant reduction of NO production in YIL at this time, suggesting the activity of a Ca(2+)-dependent NOS. Plasmatocytes and granular cells phagocytosed the yeasts. Plasmatocytes initiated the nodule formation and granular cells were the only hemocyte type to produce NO. These results permit us to conclude that yeasts induced augmented NO production in C. megacephala hemolymph and granular cells are the hemocyte type involved with the generation of this molecule.

Nitric oxide synthase in the nervous system and ink gland of the cuttlefish Sepia officinalis: molecular cloning and expression

Nitric oxide (NO) signaling is involved in numerous physiological processes in mollusks, e.g., learning and memory, feeding behavior, neural development, and defence response. We report the first molecular cloning of NOS mRNA from a cephalopod, the cuttlefish Sepia officinalis (SoNOS). SoNOS was cloned using a strategy that involves hybridization of degenerate PCR primers to highly conserved NOS regions, combined with RACE procedure. Two splicing variants of SoNOS, differing by 18 nucleotides, were found in the nervous system and the ink gland of Sepia. In situ hybridization shows that SoNOS is expressed in the immature and mature cells of the ink gland and in the regions of the nervous system that are related to the ink defence system.

Plasmodium berghei ookinetes induce nitric oxide production in Anopheles pseudopunctipennis midguts cultured in vitro

The Anopheles pseudopunctipennis nitric oxide synthase gene (ApNOS) was identified and its partial sequence showed high homology with NOS from A. stephensi, A. gambiae (putative sequence), and Drosophila melanogaster. ApNOS was mainly expressed in male and female adult mosquitoes and was induced by a blood meal. Nitric oxide (NO) was produced by in vitro-cultured mosquito midguts inoculated by enema with Plasmodium berghei ookinetes, Saccharomyces cerevisiae, Gram-positive bacteria (Micrococcus luteus), but not with Gram-negative bacteria (Klebsiella pneumoniae, Escherichia coli or Serratia marcescens). Dihydroxyphenylalanine (L-DOPA) oxidation induced the generation of NO in midguts in vitro, and hydrogen peroxide generated during its oxidation induced ApNOS expression. P. berghei ookinetes exposed in vitro to L-DOPA and sodium nitroprusside (a NO generator) were killed. These observations demonstrate that reactive oxygen and nitrogen intermediates constitute a part of the cytotoxic arsenal employed by Anopheles mosquitoes against microbial pathogens and Plasmodium ookinetes.

A crustacean nitric oxide synthase expressed in nerve ganglia, Y-organ,gill and gonad of the tropical land crab,Gecarcinus lateralis

NO signaling is involved in many physiological processes in invertebrates. In crustaceans, it plays a role in the regulation of the nervous system and muscle contraction. Nested reverse transcription-polymerase chain reaction(RT-PCR) and 5′ and 3′ rapid amplification of cDNA ends (RACE) PCR generated a full-length cDNA sequence (3982 bp) of land crab NO synthase(Gl-NOS) from molting gland (Y-organ) and thoracic ganglion mRNA. The open reading frame encoded a protein of 1199 amino acids with an estimated mass of 135 624 Da. Gl-NOS had the highest sequence identity with insect NOS. The amino acid sequences for binding heme and tetrahydrobiopterin in the oxygenase domain, binding calmodulin and binding FMN, FAD and NADPH in the reductase domain were highly conserved. Gl-NOS had single amino acid differences in all three highly conserved FAD-binding sequences, which distinguished it from other NOS sequences. RT-PCR showed that the Gl-NOS mRNA was present in testis,ovary, gill, eyestalk neural ganglia, thoracic ganglion and Y-organ. NOS mRNA varied between preparations of Y-organ, thoracic ganglion and gill, while NOS mRNA was at consistently high levels in the ovary, testis and eyestalk ganglia. Immunohistochemistry confirmed that the Gl-NOS protein was expressed in Y-organ, ovary and gill. These results suggest that NOS has functions in addition to neuromodulation in adults, such as regulating or modulating ecdysteroid synthesis in the Y-organ.

Nitric oxide production by carpet shell clam (Ruditapes decussatus) hemocytes

We have demonstrated that carpet shell clam (Ruditapes decussatus) hemocytes produce nitric oxide (NO) in response to zymosan or bacterial lipopolysaccharide (LPS). This NO production was partially inhibited by the NO synthase inhibitor, N-omega-nitro-L-arginine (L-NAME). The capability of clam hemocytes to produce NO in response to the bacterial pathogen Vibrio tapetis was also studied. Incubation with bacteria induced a significant NO production by clam hemocytes, even though exogenous NO only slightly decreased the growth of V. tapetis. The effect of exogenous NO on the capability of clam hemocytes to phagocytose labeled Escherichia coli was studied using two different NO donors S-nitroso-N-acetyl-penicillamine (SNAP), and diethylenetriamine NO adduct (DETA/NO). Exogenous NO did not increase hemocyte phagocytosis, indicating that NO does not mediate phagocytosis in this species. These results are in accordance to those observed in other mollusk species, in which NO was independent of phagocytosis and constitutes an alternative method of killing invading pathogens.