Serine proteases as mediators of mosquito immune responses

Pathogen-associated molecular patterns (PAMPs) derived from Leishmania and bacteria increase gene expression of antimicrobial peptides and gut surface proteins in sand flies

The interaction between pathogens and vectors' physiology can impact parasite transmission. Studying this interaction at the molecular level can help in developing control strategies. We study leishmaniases, diseases caused by Leishmania parasites transmitted by sand fly vectors, posing a significant global public health concern. Lipophosphoglycan (LPG), the major surface glycoconjugate of Leishmania, has been described to have several roles throughout the parasite's life cycle, both in the insect and vertebrate hosts. In addition, the sand fly midgut possesses a rich microbiota expressing lipopolysaccharides (LPS). However, the effect of LPG and LPS on the gene expression of sand fly midgut proteins or immunity effectors has not yet been documented. We experimentally fed Lutzomyia longipalpis and Phlebotomus papatasi sand flies with blood containing purified LPG from Leishmania infantum, Leishmania major, or LPS from Escherichia coli. The effect on the expression of genes encoding gut proteins galectin and mucin, digestive enzymes trypsin and chymotrypsin, and antimicrobial peptides (AMPs) attacin and defensins was assessed by quantitative PCR (qPCR). The gene expression of a mucin-like protein in L. longipalpis was increased by L. infantum LPG and E. coli LPS. The gene expression of a galectin was increased in L. longipalpis by L. major LPG, and in P. papatasi by E. coli LPS. Nevertheless, the gene expression of trypsins and chymotrypsins did not significantly change. On the other hand, both L. infantum and L. major LPG significantly enhanced expression of the AMP attacin in both sand fly species and defensin in L. longipalpis. In addition, E. coli LPS increased the expression of attacin and defensin in L. longipalpis. Our study showed that Leishmania LPG and E. coli LPS differentially modulate the expression of sand fly genes involved in gut maintenance and defence. This suggests that the glycoconjugates from microbiota or Leishmania may increase the vector's immune response and the gene expression of a gut coating protein in a permissive vector.

Knockdown of Anopheles dirus far upstream element-binding protein gene lower oocyst numbers of Plasmodium vivax

The modulation of gene expression levels of Anopheles dirus on Plasmodium vivax infection at the ookinete and oocyst stages was previously reported. In the present study, several upregulated An. dirus genes were selected based on their high expression levels and subcellular locations to examine their roles in P. vivax infection. Five An. dirus genes-carboxylesterase, cuticular protein RR-2 family, far upstream element-binding protein, kraken, and peptidase212-were knocked down by dsRNA feeding using dsRNA-lacZ as a control. The dsRNA-fed mosquitoes were later challenged by P. vivax-infected blood, and the oocyst numbers were determined. The expression of these five genes was examined in many organs of both male and female mosquitoes. The results showed that the decreased expression level of the far upstream element-binding protein gene could lower the oocyst numbers, whereas the others showed no effect on P. vivax infection. The expression levels of these genes in ovaries were found, and in many organs, they were similar between male and female mosquitoes. The reduction of these five gene expressions did not affect the lifespan of the mosquitoes. In addition, the malaria box compound, MMV000634, demonstrated the lowest binding energy to the far upstream element-binding protein using virtual screening. This protein might be a target to block malaria transmission.

De novo assembly and annotation of the Amblyomma hebraeum tick midgut transcriptome response to Ehrlichia ruminantium infection

The South African bont tick Amblyomma hebraeum is a hematophagous vector for the heartwater disease pathogen Ehrlichia ruminantium in southern Africa. During feeding, the tick's enterocytes express proteins that perform vital functions in blood digestion, including proteins that may be involved in E. ruminantium acquisition, colonization or immunity. To delineate the molecular mechanism of midgut response to E. ruminantium infection, we performed comparative analyses of midgut transcriptomes of E. ruminantium infected engorged A. hebraeum nymphs, and infected adult male and female ticks with their corresponding matched uninfected controls, before and during feeding. A total of 102,036 unigenes were annotated in public databases and their expression levels analyzed for engorged nymphs as well as unfed and partly-fed adult ticks. There were 2,025 differentially expressed genes (DEGs) in midguts, of which 1,225 unigenes were up-regulated and 800 unigenes were down-regulated in the midguts of infected ticks. Annotation of DEGs revealed an increase in metabolic and cellular processes among E. ruminantium infected ticks. Notably, among the infected ticks, there was up-regulation in the expression of genes involved in tick immunity, histone proteins and oxidative stress responses. We also observed up-regulation of glycoproteins that E. ruminantium could potentially use as docking sites for host cell entry. Insights uncovered in this study offer a platform for further investigations into the molecular interaction between E. ruminantium and A. hebraeum.

Enhanced locomotor behaviour is mediated by activation of tyrosine hydroxylase in the silkworm brain

Animal behaviour regulation is a complex process involving many factors, and the nervous system is an essential factor in this process. In many species, pathogens can alter host behaviour by affecting the host's nervous system. An interesting example is that the silkworm shows enhanced locomotor behaviour after being infected with the nucleopolyhedrosis virus. In this study, we analysed the transcriptome of the silkworm brain at different time points after infection and found that various genes related to behaviour regulation changed after infection. In-depth analysis showed that the tyrosine hydroxylase gene might be a key candidate gene, and the content of dopamine, its downstream metabolite, increased significantly in the brain of silkworms infected with the virus. After the injection of tyrosine hydroxylase inhibitor into the infected silkworm, the dopamine content in the silkworm brain decreased and the locomotor behaviour caused by the virus was blocked successfully. These results confirm that tyrosine hydroxylase is involved in regulating enhanced locomotor behaviour after virus infection in silkworms. Furthermore, the tyrosine hydroxylase gene was specifically overexpressed in the brain of the silkworm, and the transgenic silkworm was enhanced in locomotor behaviour and foraging behaviour. These results suggest that the tyrosine hydroxylase gene plays a vital role in regulating insect behaviour.

Trypsin, the Major Proteolytic Enzyme for Blood Digestion in the Mosquito Midgut

When a female mosquito takes a blood meal, proteolytic activity surges in the midgut. Trypsin-like serine proteases are the major endoproteolytic enzyme induced by feeding in mosquitoes. The mosquito midgut lacks trypsin activity before the blood meal, but in most anautogenous mosquitoes, trypsin activity increases continuously up to 30 h after feeding and subsequently returns to baseline levels by 60 h. Trypsin activity in mosquitoes is restricted entirely to the posterior midgut lumen, where blood is stored and digested. Trypsin enzyme activity can be quantitatively measured using the artificial Nα-benzoyl-DL-arginine 4-nitroanilide hydrochloride substrate, a method described in our associated protocol.

Cloning and functional analysis of a trypsin-like serine protease from Pinctada fucata martensii

Trypsin-like serine proteases (TLSs) play various roles in dietary protein digestion, hemolymph coagulation, antimicrobial peptide synthesis, and, in particular, the rapid immune pathways activated in response to pathogen detection. The cultured pearl industry, of which Pinctada fucata martensii is one of the most important species, is plagued by disease, thus leading to large economic losses. Herein, the molecular mechanisms underlying the innate immune response of P.f. martensii were explored. First, immune effector molecules from the P.f. martensii genome were screened and a TLS-like gene encoding a protein with a trypsin domain, herein designated as PmTLS, was identified. A multi-sequence alignment indicated a low sequence homology between PmTLS and other mollusk TLS-like proteins. Furthermore, a neighbor-joining phylogenetic analysis indicated that PmTLS has the closest genetic relationship to a Crassostrea gigas TLS. Additionally, real-time quantitative PCR (qPCR) analysis showed that PmTLS mRNA is constitutively expressed in all of the 6 examined P.f. martensii tissues, with significantly higher expression noted in hemocytes relative to the other tissues examined (p < 0.05). P.f. martensii samples were then challenged with various pathogen-associated molecular patterns (PAMPs), including lipopolysaccharide, peptidoglycan, and polyinosinic acid. In the challenge groups, PmTLS was significantly upregulated in hemocytes at 48 h post-challenge when compared to the unchallenged controls. Furthermore, treatment with recombinant PmTLS (rPmTLS) also significantly inhibited the growth of most of the examined gram-negative bacteria tested in vitro (p < 0.05), but it had little effect on the growth of the examined gram-positive bacteria. When examining morphological changes via transmission electron microscopy, rPmTLS treated bacteria exhibited morphological changes such as plasma wall separation. Thus, rPmTLS appears to play a bactericidal role by destroying bacterial cell membranes or cell walls, which subsequently leads to a release of the cellular contents and cell death. The findings presented herein have enabled further characterization of the immune defense mechanisms in P.f. martensii and may lead to improved disease control methods for the pearl cultivation industry.

Characterization and functional analysis of a clip domain serine protease (MncSP) and its alternative transcript (MncSP-isoform) from Macrobrachium nipponense

Clip domain serine protease (cSPs) play an important role in the innate immune defense of crustaceans. In this study, a clip domain serine protease (MncSP) and its alternative transcript (MncSP-isoform) were identified from Macrobrachium nipponense. The full-length cDNA sequences of MncSP and MncSP-isoform were 2447 and 2351 bp with open reading frames comprising 1497 and 1401 bp nucleotides and encoding 498 and 466 amino acids, respectively. The genome of MncSP had 10 exons and 9 introns. MncSP contained all 10 exons, whereas MncSP-isoform lacked the second exon. MncSP and MncSP-isoform contained a signal peptide, a clip domain, and a Tryp_SPc domain. Phylogenetic tree analysis showed that MncSP and MncSP-isoform clustered with cSPs from Palaemonidae. MncSP and MncSP-isoform were widely distributed in hemocytes, heart, hepatopancreas, gills, stomach, and intestine. The expression profiles of MncSP and MncSP-isoform in the hemocytes of M. nipponense changed after simulation by Vibrio parahaemolyticus or Staphylococcus aureus. The RNAi of MncSP could inhibit the expression of antimicrobial peptides (AMPs), including crustins and anti-lipopolysaccharide factors. Phenoloxidase activity was also down-regulated in MncSP-silenced prawns. This study indicated that MncSP participated in the synthesis of AMPs and the activation of prophenoloxidase.

Diapause differentially modulates the transcriptomes of fat body and flight muscle in the Colorado potato beetle

Many temperate insects, such as the Colorado potato beetle, enter diapause in winter, during which they arrest their development, suppress their metabolic rate and have high stress tolerance. Diapause phenotypes can be transcriptionally regulated, however many studies to date report only whole animal gene expression rather than tissue-specific processes during diapause. We used RNA-seq to measure gene expression in fat body and flight muscle of diapausing and non-diapausing beetles. We used differential expression and GO enrichment analyses to evaluate longstanding hypotheses about the mechanisms that drive arrested development, changes in energy metabolism, and increased stress tolerance during diapause. We found evidence of G2/M cell cycle arrest, juvenile hormone catabolism, increased antioxidant metabolism, epigenetic modification, transposable element regulation, and cytoskeletal remodeling in both the fat body and flight muscle of diapausing beetles. Beetles differentially modulated the fat body and flight muscle transcriptomes during diapause with fat body playing a larger role in the hypoxia response and immunity, whereas flight muscle had higher abundance of transcripts related to the chaperone response and proteostasis. Our transcriptome provides evidence for distinct roles and responses of fat body and flight muscle during diapause in the Colorado potato beetle, and we provide testable hypotheses for biological processes that appear to drive diapause phenotypes in insects.

Comparative transcriptome analysis reveals a potential mechanism for host nutritional manipulation after parasitization by Leptopilina boulardi

Parasitoids have been extensively found to manipulate nutrient amounts of their hosts to benefit their own development and survival, but the underlying mechanisms are largely unknown. Leptopilina boulardi (Hymenoptera: Figitidae) is a larval-pupal endoparasitoid wasp of Drosophila melanogaster whose survival relies on the nutrients provided by its Drosophila host. Here, we used RNA-seq to compare the gene expression levels of the host midgut at 24 h and 48 h post L. boulardi parasitization. We obtained 95 and 191 differentially expressed genes (DEGs) in the parasitized host midgut at 24 h and 48 h post L. boulardi parasitization, respectively. A KEGG analysis revealed that several metabolic pathways were significantly enriched in the upregulated DEGs, and these pathways included "starch and sucrose metabolism" and "galactose metabolism". A functional annotation analysis showed that four classes of genes involved in carbohydrate digestion process had increased expression levels in the midgut post L.boulardi parasitization than nonparasitized groups: glucosidase, mannosidase, chitinase and amylase. Genes involved in protein digestion process were also found among the DEGs, and most of these genes, which belonged to the metallopeptidase and serine-type endopeptidase families, were found at higher expression levels in the parasitized host midgut comparing with nonparasitized hosts. Moreover, some immune genes, particularly those involved in the Toll and Imd pathways, also exhibited high expression levels after L.boulardi parasitization. Our study provides large-scale transcriptome data and identifies sets of DEGs between parasitized and nonparasitized host midgut tissues at 24 h and 48 h post L. boulardi parasitization. These resources help improve our understanding of how parasitoid infection affects the nutrient components in the hosts.

A trypsin-like serine protease domain of masquerade gene in crayfish Procambarus clarkii could activate prophenoloxidase and inhibit bacterial growth

Masquerade (Mas) is a secreted trypsin-like serine protease (SPs) and involved in immune response in some arthropods. However, according to previous studies, Mas presents different functional activities. In the present study, the functional mechanisms of Mas in crayfish Procambarus clarkii immune defense were studied. A fragment cDNA sequence of PcMas was identified and characterized. From the structural analysis, it contains a trypsin-like serine protease domain. The highest expression level of PcMas was detected in hepatopancreas. The infection of A. hydrophila could induce the expression of PcMas, while the WSSV infection did not cause changes in the expression of PcMas. Through the prokaryotic expression system, the PcMas protein was expressed in E. coli. It was verified that PcMas can bind to bacteria in vitro and inhibit the growth of the bacteria. By dsRNA interference with the expression of PcMas, the decrease expression of PcMas led to a decrease in the activity of phenoloxidase in hemolymph and an increase of mortality caused by A. hydrophila infection. The injection of recombinant protein can enhance the activity of phenoloxidase and reduce mortality caused by A. hydrophila infections. Therefore, the present study confirmed that PcMas could improve the body's immune response to eliminate bacterial pathogens by binding with bacteria and activating the prophenoloxidase system. The results will enrich the molecular mechanisms of crustaceans immune defense.

Parent of origin gene expression in the bumblebee, Bombus terrestris, supports Haig's kinship theory for the evolution of genomic imprinting

Genomic imprinting is the differential expression alleles in diploid individuals, with the expression being dependent on the sex of the parent from which it was inherited. Haig's kinship theory hypothesizes that genomic imprinting is due to an evolutionary conflict of interest between alleles from the mother and father. In social insects, it has been suggested that genomic imprinting should be widespread. One recent study identified parent-of-origin expression in honey bees and found evidence supporting the kinship theory. However, little is known about genomic imprinting in insects and multiple theoretical predictions must be tested to avoid single-study confirmation bias. We, therefore, tested for parent-of-origin expression in a primitively eusocial bee. We found equal numbers of maternally and paternally biased expressed genes. The most highly biased genes were maternally expressed, offering support for the kinship theory. We also found low conservation of potentially imprinted genes with the honey bee, suggesting rapid evolution of genomic imprinting in Hymenoptera.

Glucose transporter GLUT1 influences Plasmodium berghei infection in Anopheles stephensi

Background

Sugar-feeding provides energy for mosquitoes. Facilitated glucose transporters (GLUTs) are responsible for the uptake of glucose in animals. However, knowledge of GLUTs function in Anopheles spp. is limited.

Methods

Phylogenetic analysis of GLUTs in Anopheles stephensi was performed by the maximum likelihood and Bayesian inference methods. The spatial and temporal expression patterns of four Asteglut genes were analyzed by qPCR. The function of Asteglut1 was examined using a dsRNA-mediated RNA interference method. Transcriptome analysis was used to investigate the global influence of Asteglut1 on mosquito physiology.

Results

We identified 4 glut genes, Asteglut1, Asteglutx, Asteglut3 and Asteglut4 in An. stephensi. Asteglut1, Asteglut3 and Asteglut4 were mainly expressed in the midgut. Plasmodium berghei infection differentially regulated the expression of Asteglut genes with significant downregulation of Asteglut1 and Asteglut4, while upregulation of Asteglutx. Only knocking-down Asteglut1 facilitated Plasmodium berghei infection in An. stephensi. This might be due to the accumulation of glucose prior to blood-feeding in dsAsteglut1-treated mosquitoes. Our transcriptome analysis revealed that knockdown of Asteglut1 differentially regulated expression of genes associated with multiple functional clusters, especially those related to detoxification and immunity. The dysregulation of multiple pathways might contribute to the increased P. berghei infection.

Conclusions

Our study shows that Asteglut1 participates in defense against P. berghei in An. stephensi. The regulation of Asteglut1 on vector competence might through modulating multiple biological processes, such as detoxification and immunity.

Insights into the Gryllus bimaculatus Immune-Related Transcriptomic Profiling to Combat Naturally Invading Pathogens

Natural pathogen pressure is an important factor that shapes the host immune defense mechanism. The current study primarily aimed to explore the molecular basis of the natural immune defense mechanism of a sporadic pest, Gryllus bimaculatus, during swarming by constructing cDNA libraries of the female mid-gut, male mid-gut, testes, and ovaries. The Illumina HiSeq platform generated an average of 7.9 G, 11.77 G, 10.07 G, and 10.07 G bases of outputs from the male mid-gut, female mid-gut, testes, and ovaries and libraries, respectively. The transcriptome of two-spotted field crickets was assembled into 233,172 UniGenes, which yielded approximately 163.58 million reads. On the other hand, there were 43,055 genes in common that were shared among all the biological samples. Gene Ontology analysis successfully annotated 492 immune-related genes, which comprised mainly Pattern Recognition Receptors (62 genes), Signal modulators (57 genes), Signal transduction (214 genes), Effectors (36 genes), and another immune-related 123 genes. In summary, the identified wide range of immune-related genes from G. bimaculatus indicates the existence of a sophisticated and specialized broad spectrum immune mechanism against invading pathogens, which provides, for the first time, insights into the molecular mechanism of disease resistance among two-spotted field crickets.

In vitro shared transcriptomic responses of Aedes aegypti to arboviral infections: example of dengue and Rift Valley fever viruses

Background

Arthropod borne virus infections are the cause of severe emerging diseases. Among the diseases due to arboviruses, dengue (DEN) and Rift Valley fever (RVF) are in the top ten in the list of diseases responsible of severe human cases worldwide. Understanding the effects of viral infection on gene expression in competent vectors is a challenge for the development of early diagnostic tools and may enable researchers and policy makers to better anticipate outbreaks in the next future.

Methods

In this study, alterations in gene expression across the entire Aedes aegypti genome during infection with DENV and RVFV were investigated in vitro at two time points of infection, the early phase (24 h) and the late phase (6 days) of infection using the RNA sequencing approach

Results

A total of 10 upregulated genes that share a similar expression profile during infection with both viruses at early and late phases of infection were identified. Family B and D clip-domain serine proteases (CLIP) were clearly overrepresented as well as C-type lectins and transferrin.

Conclusions

Our data highlight the presence of 10 viral genes upregulated in Ae. aegypti during infection. They may also be targeted in the case of the development of broad-spectrum anti-viral diagnostic tools focusing the mosquito vectors rather than the mammalian hosts as they may predict the emergence of outbreaks.

Genome of the webworm Hyphantria cunea unveils genetic adaptations supporting its rapid invasion and spread

BACKGROUND

The fall webworm Hyphantria cunea is an invasive and polyphagous defoliator pest that feeds on nearly any type of deciduous tree worldwide. The silk web of H. cunea aids its aggregating behavior, provides thermal regulation and is regarded as one of causes for its rapid spread. In addition, both chemosensory and detoxification genes are vital for host adaptation in insects.

RESULTS

Here, a high-quality genome of H. cunea was obtained. Silk-web-related genes were identified from the genome, and successful silencing of the silk protein gene HcunFib-H resulted in a significant decrease in silk web shelter production. The CAFE analysis showed that some chemosensory and detoxification gene families, such as CSPs, CCEs, GSTs and UGTs, were expanded. A transcriptome analysis using the newly sequenced H. cunea genome showed that most chemosensory genes were specifically expressed in the antennae, while most detoxification genes were highly expressed during the feeding peak. Moreover, we found that many nutrient-related genes and one detoxification gene, HcunP450 (CYP306A1), were under significant positive selection, suggesting a crucial role of these genes in host adaptation in H. cunea. At the metagenomic level, several microbial communities in H. cunea gut and their metabolic pathways might be beneficial to H. cunea for nutrient metabolism and detoxification, and might also contribute to its host adaptation.

CONCLUSIONS

These findings explain the host and environmental adaptations of H. cunea at the genetic level and provide partial evidence for the cause of its rapid invasion and potential gene targets for innovative pest management strategies.

Immune transcriptome analysis in predatory beetles reveals two cecropin genes overexpressed in mandibles

The great complexity and variety of the innate immune system and the production of antimicrobial peptides in insects is correlated with their evolutionary success and adaptation to different environments. Tiger beetles are an example of non-pest species with a cosmopolitan distribution, but the immune system is barely known and its study could provide useful information about the humoral immunity of predatory insects. Suppression subtractive hybridization (SSH) was performed in Calomera littoralis beetles to obtain a screening of those genes that were overexpressed after an injection with Escherichia coli lipopolysaccharide (LPS). Several genes were identified to be related to immune defense. Among those genes, two members of the cecropin antimicrobial peptides were characterized and identified as CliCec-A and CliCec-B2. Both protein sequences showed cecropin characteristics including 37 and 38 residue mature peptides, composed by two α-helices structures with amphipathic and hydrophobic nature, as shown in their predicted three-dimensional structure. Chemically synthesized CliCec-B2 confirmed cecropin antimicrobial activity against some Gram (+) and Gram (-) bacteria, but not against yeast. Expression of both cecropin genes was assessed by qPCR and showed increases after a LPS injection and highlighted their overexpression in adult beetle mandibles, which could be related to their alimentary habits.

Effects of two juvenile hormone analogue insecticides, fenoxycarb and methoprene, on Neocaridina davidi

Juvenile hormone analogue (JHA) insecticides are endocrine disrupters that interfere with hormonal action in insects by mimicking their juvenile hormones (JH). As the structure and functions of methyl farnesoate in crustaceans are similar to those of JH in insects, exogenous JHA insecticides could have adverse effects on the development and reproduction of crustaceans. This study examined the toxic effects of two JHA insecticides, fenoxycarb and methoprene, on a freshwater shrimp model of cherry shrimp, Neocaridina davidi. Both insecticides had detrimental effects on cherry shrimp, but fenoxycarb was more toxic than methoprene. Chronic exposure to these insecticides reduced the shrimp's body length and molting frequency. Based on transcriptome annotations for N. davidi, we identified important gene homologues that were active in both insect JH biosynthetic and degradative pathways as well as JH and ecdysteroid signaling pathways. Chronic treatments with JHAs had significant effects on these genes in N. davidi. Our transcriptomic analysis showed that genes involved in the pathways related to cuticle development, serine protease activity, and carbohydrate, peptide and lipid metabolic processes were differentially expressed in shrimp exposed to JHAs. These results demonstrate the toxicity of fenoxycarb and methoprene to freshwater crustaceans and indicate the need to monitor the use of JHA insecticides.

Regulation of the Larval Transcriptome of Diatraea saccharalis (Lepidoptera: Crambidae) by Maternal and Other Factors of the Parasitoid Cotesia flavipes (Hymenoptera: Braconidae)

Koinobiont endoparasitoid wasps regulate the host's physiology to their own benefit during their growth and development, using maternal, immature and/or derived-tissue weaponry. The tools used to subdue the wasps' hosts interfere directly with host transcription activity. The broad range of host tissues and pathways affected impedes our overall understanding of the host-regulation process during parasitoid development. Next-generation sequencing and de novo transcriptomes are helpful approaches to broad questions, including in non-model organisms. In the present study, we used Illumina sequencing to assemble a de novo reference transcriptome of the sugarcane borer Diatraea saccharalis, to investigate the regulation of host gene expression by the larval endoparasitoid Cotesia flavipes. We obtained 174,809,358 reads and assembled 144,116 transcripts, of which 44,325 were putatively identified as lepidopteran genes and represented a substantial number of pathways that are well described in other lepidopteran species. Comparative transcriptome analyses of unparasitized versus parasitized larvae identified 1,432 transcripts of D. saccharalis that were up-regulated under parasitization by C. flavipes, while 1,027 transcripts were down-regulated. Comparison of the transcriptomes of unparasitized and pseudoparasitized D. saccharalis larvae led to the identification of 1,253 up-regulated transcripts and 972 down-regulated transcripts in the pseudoparasitized larvae. Analysis of the differentially expressed transcripts showed that C. flavipes regulated several pathways, including the Ca+2 transduction signaling pathway, glycolysis/gluconeogenesis, chitin metabolism, and hormone biosynthesis and degradation, as well as the immune system, allowing us to identify key target genes involved in the metabolism and development of D. saccharalis.

Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes

BACKGROUND

Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity.

RESULTS

Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges.

CONCLUSIONS

Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.

Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes

BACKGROUND

Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity.

RESULTS

Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges.

CONCLUSIONS

Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.

Bioinformatic analysis suggests potential mechanisms underlying parasitoid venom evolution and function

Hymenopteran parasitoid wasps are a diverse collection of species that infect arthropod hosts and use factors found in their venoms to manipulate host immune responses, physiology, and behaviour. Whole parasitoid venoms have been profiled using proteomic approaches, and here we present a bioinformatic characterization of the venom protein content from Ganaspis sp. 1, a parasitoid that infects flies of the genus Drosophila. We find evidence that diverse evolutionary processes including multifunctionalization, co-option, gene duplication, and horizontal gene transfer may be acting in concert to drive venom gene evolution in Ganaspis sp.1. One major role of parasitoid wasp venom is host immune evasion. We previously demonstrated that Ganaspis sp. 1 venom inhibits immune cell activation in infected Drosophila melanogaster hosts, and our current analysis has uncovered additional predicted virulence functions. Overall, this analysis represents an important step towards understanding the composition and activity of parasitoid wasp venoms.

Transcriptomic analysis reveals insights into deep-sea adaptations of the dominant species, Shinkaia crosnieri (Crustacea: Decapoda: Anomura), inhabiting both hydrothermal vents and cold seeps

Background

Hydrothermal vents and cold seeps are typical deep-sea chemosynthetically-driven ecosystems that allow high abundance of specialized macro-benthos. To gather knowledge about the genetic basis of adaptation to these extreme environments, species shared between different habitats, especially for the dominant species, are of particular interest. The galatheid squat lobster, Shinkaia crosnieri Baba and Williams, 1998, is one of the few dominant species inhabiting both deep-sea hydrothermal vents and cold seeps. In this study, we performed transcriptome analyses of S. crosnieri collected from the Iheya North hydrothermal vent (HV) and a cold seep in the South China Sea (CS) to provide insights into how this species has evolved to thrive in different deep-sea chemosynthetic ecosystems.

Results

We analyzed 5347 orthologs between HV and CS to identify genes under positive selection through the maximum likelihood approach. A total of 82 genes were identified to be positively selected and covered diverse functional categories, potentially indicating their importance for S. crosnieri to cope with environmental heterogeneity between deep-sea vents and seeps. Among 39,806 annotated unigenes, a large number of differentially expressed genes (DEGs) were identified between HV and CS, including 339 and 206 genes significantly up-regulated in HV and CS, respectively. Most of the DEGs associated with stress response and immunity were up-regulated in HV, possibly allowing S. crosnieri to increase its capability to manage more environmental stresses in the hydrothermal vents.

Conclusions

We provide the first comprehensive transcriptomic resource for the deep-sea squat lobster, S. crosnieri, inhabiting both hydrothermal vents and cold seeps. A number of stress response and immune-related genes were positively selected and/or differentially expressed, potentially indicating their important roles for S. crosnieri to thrive in both deep-sea vents and cold seeps. Our results indicated that genetic adaptation of S. crosnieri to different deep-sea chemosynthetic environments might be mediated by adaptive evolution of functional genes related to stress response and immunity, and alterations in their gene expression that lead to different stress resistance. However, further work is required to test these proposed hypotheses. All results can constitute important baseline data for further studies towards elucidating the adaptive mechanisms in deep-sea crustaceans.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5753-7) contains supplementary material, which is available to authorized users.

Comparative Proteomics of Peritrophic Matrix Provides an Insight into its Role in Cry1Ac Resistance of Cotton Bollworm Helicoverpa armigera

Crystalline (Cry) proteins from Bacillus thuringiensis (Bt) are widely used in sprays and transgenic crops to control insect pests, but the evolution of insect resistance threatens their long-term use. Different resistance mechanisms have been identified, but some have not been completely elucidated. Here, the transcriptome of the midgut and proteome of the peritrophic matrix (PM) were comparatively analyzed to identify potential mechanism of resistance to Cry1Ac in laboratory-selected strain XJ10 of Helicoverpa armigera. This strain had a 146-fold resistance to Cry1Ac protoxin and 45-fold resistance to Cry1Ac activated toxin compared with XJ strain. The mRNA and protein levels for several trypsin genes were downregulated in XJ10 compared to the susceptible strain XJ. Furthermore, 215 proteins of the PM were identified, and nearly all had corresponding mRNAs in the midgut. These results provide new insights that the PM may participate in Bt resistance.

Transcriptome-wide responses of adult melon thrips (Thrips palmi) associated with capsicum chlorosis virus infection

Thrips palmi is a widely distributed major agricultural pest in the tropics and subtropics, causing significant losses in cucurbit and solanaceous crops through feeding damage and transmission of tospoviruses. Thrips palmi is a vector of capsicum chlorosis virus (CaCV) in Australia. The present understanding of transmission biology and potential effects of CaCV on T. palmi is limited. To gain insights into molecular responses to CaCV infection, we performed RNA-Seq to identify thrips transcripts that are differentially-abundant during virus infection of adults. De-novo assembly of the transcriptome generated from whole bodies of T. palmi adults generated 166,445 contigs, of which ~24% contained a predicted open reading frame. We identified 1,389 differentially-expressed (DE) transcripts, with comparable numbers up- (708) and down-regulated (681) in virus-exposed thrips compared to non-exposed thrips. Approximately 59% of these DE transcripts had significant matches to NCBI non-redundant proteins (Blastx) and Blast2GO identified provisional functional categories among the up-regulated transcripts in virus-exposed thrips including innate immune response-related genes, salivary gland and/or gut-associated genes and vitellogenin genes. The majority of the immune-related proteins are known to serve functions in lysosome activity and melanisation in insects. Most of the up-regulated oral and extra-oral digestion-associated genes appear to be involved in digestion of proteins, lipids and plant cell wall components which may indirectly enhance the likelihood or frequency of virus transmission or may be involved in the regulation of host defence responses. Most of the down-regulated transcripts fell into the gene ontology functional category of 'structural constituent of cuticle'. Comparison to DE genes responsive to tomato spotted wilt virus in Frankliniella occidentalis indicates conservation of some thrips molecular responses to infection by different tospoviruses. This study assembled the first transcriptome in the genus Thrips and provides important data to broaden our understanding of networks of molecular interactions between thrips and tospoviruses.

Improved reference genome of Aedes aegypti informs arbovirus vector control

Female Aedes aegypti mosquitoes infect more than 400 million people each year with dangerous viral pathogens including dengue, yellow fever, Zika and chikungunya. Progress in understanding the biology of mosquitoes and developing the tools to fight them has been slowed by the lack of a high-quality genome assembly. Here we combine diverse technologies to produce the markedly improved, fully re-annotated AaegL5 genome assembly, and demonstrate how it accelerates mosquito science. We anchored physical and cytogenetic maps, doubled the number of known chemosensory ionotropic receptors that guide mosquitoes to human hosts and egg-laying sites, provided further insight into the size and composition of the sex-determining M locus, and revealed copy-number variation among glutathione S-transferase genes that are important for insecticide resistance. Using high-resolution quantitative trait locus and population genomic analyses, we mapped new candidates for dengue vector competence and insecticide resistance. AaegL5 will catalyse new biological insights and intervention strategies to fight this deadly disease vector.

An improved, fully re-annotated Aedes aegypti genome assembly (AaegL5) provides insights into the sex-determining M locus, chemosensory systems that help mosquitoes to hunt humans and loci involved in insecticide resistance and will help to generate intervention strategies to fight this deadly disease vector.

Applying microarray-based technique to study and analyze silkworm (Bombyx mori) transcriptomic response to long-term high iron diet

To investigate the biological processes affected by long-term iron supplementation, newly hatched silkworms were exposed to high iron mulberry diet (10 and 100 ppm) and its effect on silkworm transcriptom was determined. The results showed that the silkworm was responsive to iron by increasing iron concentration and ferritin levels in the hemolymph and by regulating the expression of many other genes. A total of 523 and 326 differentially expressed genes were identified in 10 and 100 ppm Fe group compared to the control, respectively. Of these genes, 249 were shared between in both the 10 ppm and 100 ppm Fe group, including 152 up-regulated and 97 down-regulated genes. These shared genes included 19 known Fe regulated, 24 immune-related, 12 serine proteases and serine proteases homologs, 41 cuticular and cuticle genes. Ten genes (carboxypeptidases A, serine protease homologs 85, fibrohexamerin/P25, transferrin, sex-specific storage-protein 2, fungal protease inhibitor F, insect intestinal mucin, peptidoglycan recognition protein B, cuticle protein CPH45, unknown gene) were involved in the regulation of iron overload responses.

Evaluation of Aedes aegypti (Diptera: Culicidae) Life Table Attributes Upon Chikungunya Virus Replication Reveals Impact on Egg-Laying Pathways

Arthropod-borne virus disease cycles constitute interactions among three primary players-the host, the vector, and the virus-in which the virus needs to interact with the host and the vector to establish its survival. While in the host, some arboviruses replicate aggressively, resulting in host pathogenicity, and manifest as a disease condition. These viruses more often utilize the vectors as reservoirs before they are transmitted to the host and therefore do not amplify to as large titers as they do in the hosts. In spite of this, the vector undergoes stress and activates several of its defense systems, resulting in alterations in its physiology. The present study was undertaken to evaluate the physiological changes that the mosquito vector Aedes aegypti (L.) (Diptera: Culicidae) undergoes during the replication of an arbovirus, Chikungunya virus (CHIKV). After the mosquitoes were infected with CHIKV, dissemination of the virus into various tissues and physiological parameters such as fecundity, vector mortality, egg laying, survival rate, overall fitness were monitored throughout the lifespan of the mosquitoes. Our study reveals that there is a fitness cost to the mosquitoes due to the infection of CHIKV. This fitness cost is manifested as higher mortality and low survival rate of the CHIKV-infected mosquitoes. Further evaluation revealed that the egg-laying pathway was affected, resulting in lower number of eggs. Expression analysis of six transcripts in the egg-laying pathway revealed that these transcripts were downregulated during the gonotrophic cycles in CHIKV-infected mosquitoes as compared to normal blood-fed mosquitoes.

Proteome-wide analysis of Anopheles culicifacies mosquito midgut: new insights into the mechanism of refractoriness

BACKGROUND

Midgut invasion, a major bottleneck for malaria parasites transmission is considered as a potential target for vector-parasite interaction studies. New intervention strategies are required to explore the midgut proteins and their potential role in refractoriness for malaria control in Anopheles mosquitoes. To better understand the midgut functional proteins of An. culicifacies susceptible and refractory species, proteomic approaches coupled with bioinformatics analysis is an effective means in order to understand the mechanism of refractoriness. In the present study, an integrated in solution- in gel trypsin digestion approach, along with Isobaric tag for relative and absolute quantitation (iTRAQ)-Liquid chromatography/Mass spectrometry (LC/MS/MS) and data mining were performed to identify the proteomic profile and differentially expressed proteins in Anopheles culicifacies susceptible species A and refractory species B.

RESULTS

Shot gun proteomics approaches led to the identification of 80 proteins in An. culicifacies susceptible species A and 92 in refractory species B and catalogue was prepared. iTRAQ based proteomic analysis identified 48 differentially expressed proteins from total 130 proteins. Of these, 41 were downregulated and 7 were upregulated in refractory species B in comparison to susceptible species A. We report that the altered midgut proteins identified in naturally refractory mosquitoes are involved in oxidative phosphorylation, antioxidant and proteolysis process that may suggest their role in parasite growth inhibition. Furthermore, real time polymerase chain reaction (PCR) analysis of few proteins indicated higher expression of iTRAQ upregulated protein in refractory species than susceptible species.

CONCLUSION

This study elucidates the first proteome of the midguts of An. culicifacies sibling species that attempts to analyze unique proteogenomic interactions to provide insights for better understanding of the mechanism of refractoriness. Functional implications of these upregulated proteins in refractory species may reflect the phenotypic characteristics of the mosquitoes and will improve our understandings of blood meal digestion process, parasite vector interactions and proteomes of other vectors of human diseases for development of novel vector control strategies.

Identification of a clip domain serine proteinase involved in immune defense in Chinese mitten crab Eriocheir sinensis

Clip-domain serine proteinase is an important serine proteinase family involved in many biological processes, which is only found in invertebrates. In the present study, the full-length cDNA of a clip domain serine proteinase (designed as EsCDSP) gene was cloned from Chinese mitten crab Eriocheir sinensis using rapid amplification of cDNA ends (RACE) technique. It was of 1488 bp with an open reading frame (ORF) of 1134 bp encoding a polypeptide of 377 amino acids. There were a signal peptide, a clip domain, and a Tryp_SPc domain in the deduced amino acid sequence of EsCDSP. Highly conserved cysteine residues were identified in the clip domain and Tryp_SPc domain. EsCDSP shared similarities of 40%-61% with CDSPs from Penaeus monodon (ACP19562.1), Scylla paramamosain (CCW43200.1), Drosophila melanogaster (NP_649734.2) and Delia antiqua (AAW57295.1). It was clustered with other CDSPs from crabs in the phylogenetic tree. EsCDSP transcript was highly expressed in hemocytes and it could response to the stimulations of Vibro anguillarum and Pichia pastoris. rEsCDSP could activate proPO system and significantly increase the PO activity of HLS. In addition, rEsCDSP could bond to Aeromonas hydrophila, Vibro anguillarum and Vibro alginolyticus, and reduced the mortality rate causing by pathogen infection. All the results suggested that EsCDSP was an important immune response participator involved in activation of the proPO system of crab.

Caste-, sex-, and age-dependent expression of immune-related genes in a Japanese subterranean termite, Reticulitermes speratus

Insects protect themselves from microbial infections through innate immune responses, including pathogen recognition, phagocytosis, the activation of proteolytic cascades, and the synthesis of antimicrobial peptides. Termites, eusocial insects inhabiting microbe-rich wood, live in closely-related family groups that are susceptible to shared pathogen infections. To resist pathogenic infection, termite families have evolved diverse immune adaptations at both individual and societal levels, and a strategy of trade-offs between reproduction and immunity has been suggested. Although termite immune-inducible genes have been identified, few studies have investigated the differential expression of these genes between reproductive and neuter castes, and between sexes in each caste. In this study, we compared the expression levels of immune-related genes among castes, sexes, and ages in a Japanese subterranean termite, Reticulitermes speratus. Using RNA-seq, we found 197 immune-related genes, including 40 pattern recognition proteins, 97 signalling proteins, 60 effectors. Among these genes, 174 showed differential expression among castes. Comparing expression levels between males and females in each caste, we found sexually dimorphic expression of immune-related genes not only in reproductive castes, but also in neuter castes. Moreover, we identified age-related differential expression of 162 genes in male and/or female reproductives. In addition, although R. speratus is known to use the antibacterial peptide C-type lysozyme as an egg recognition pheromone, we determined that R. speratus has not only C-type, but also P-type and I-type lysozymes, as well as other termite species. Our transcriptomic analyses revealed immune response plasticity among all castes, and sex-biased expression of immune genes even in neuter castes, suggesting a sexual division of labor in the immune system of R. speratus. This study heightens the understanding of the evolution of antimicrobial strategies in eusocial insects, and of sexual roles in insect societies as a whole.

RNA-sequence analysis of gene expression from honeybees (Apis mellifera) infected with Nosema ceranae

Honeybees (Apis mellifera) are constantly subjected to many biotic stressors including parasites. This study examined honeybees infected with Nosema ceranae (N. ceranae). N. ceranae infection increases the bees energy requirements and may contribute to their decreased survival. RNA-seq was used to investigate gene expression at days 5, 10 and 15 Post Infection (P.I) with N. ceranae. The expression levels of genes, isoforms, alternative transcription start sites (TSS) and differential promoter usage revealed a complex pattern of transcriptional and post-transcriptional gene regulation suggesting that bees use a range of tactics to cope with the stress of N. ceranae infection. N. ceranae infection may cause reduced immune function in the bees by: (i)disturbing the host amino acids metabolism (ii) down-regulating expression of antimicrobial peptides (iii) down-regulation of cuticle coatings and (iv) down-regulation of odorant binding proteins.

Molecular characterization of firefly nuptial gifts: a multi-omics approach sheds light on postcopulatory sexual selection

Postcopulatory sexual selection is recognized as a key driver of reproductive trait evolution, including the machinery required to produce endogenous nuptial gifts. Despite the importance of such gifts, the molecular composition of the non-gametic components of male ejaculates and their interactions with female reproductive tracts remain poorly understood. During mating, male Photinus fireflies transfer to females a spermatophore gift manufactured by multiple reproductive glands. Here we combined transcriptomics of both male and female reproductive glands with proteomics and metabolomics to better understand the synthesis, composition and fate of the spermatophore in the common Eastern firefly, Photinus pyralis. Our transcriptome of male glands revealed up-regulation of proteases that may enhance male fertilization success and activate female immune response. Using bottom-up proteomics we identified 208 functionally annotated proteins that males transfer to the female in their spermatophore. Targeted metabolomic analysis also provided the first evidence that Photinus nuptial gifts contain lucibufagin, a firefly defensive toxin. The reproductive tracts of female fireflies showed increased gene expression for several proteases that may be involved in egg production. This study offers new insights into the molecular composition of male spermatophores, and extends our understanding of how nuptial gifts may mediate postcopulatory interactions between the sexes.

Transcriptome Analysis of the Midgut of the Chinese Oak Silkworm Antheraea pernyi Infected with Antheraea pernyi Nucleopolyhedrovirus

The Antheraea pernyi nucleopolyhedrovirus (ApNPV) is an exclusive pathogen of A. pernyi. The intense interactions between ApNPV and A. pernyi cause a series of physiological and pathological changes to A. pernyi. However, no detailed report exists regarding the molecular mechanisms underlying the interactions between ApNPV and A. pernyi. In this study, four cDNA libraries of the A. pernyi midgut, including two ApNPV-infected groups and two control groups, were constructed for transcriptomic analysis to provide new clues regarding the molecular mechanisms that underlie these interactions. The transcriptome of the A. pernyi midgut was de novo assembled using the Trinity platform because of the lack of a genome resource for A. pernyi. Compared with the controls, a total of 5,172 differentially expressed genes (DEGs) were identified, including 2,183 up-regulated and 2,989 down-regulated candidates, of which 2,965 and 911 DEGs were classified into different GO categories and KEGG pathways, respectively. The DEGs involved in A. pernyi innate immunity were classified into several categories, including heat-shock proteins, apoptosis-related proteins, serpins, serine proteases and cytochrome P450s. Our results suggested that these genes were related to the immune response of the A. pernyi midgut to ApNPV infection via their essential roles in regulating a variety of physiological processes. Our results may serve as a basis for future research not only on the molecular mechanisms of ApNPV invasion but also on the anti-ApNPV mechanism of A. pernyi.

Chemical proteomic analysis of the potential toxicological mechanisms of microcystin-RR in zebrafish (Danio rerio) liver

Microcystins (MCs) are common toxins produced by freshwater cyanobacteria, and they represent a potential health risk to aquatic organisms and animals, including humans. Specific inhibition of protein phosphatases 1 and 2A is considered the typical mechanism of MCs toxicity, but the exact mechanism has not been fully elucidated. To further our understanding of the toxicological mechanisms induced by MCs, this study is the first to use a chemical proteomic approach to screen proteins that exhibit special interactions with MC-arginine-arginine (MC-RR) from zebrafish (Danio rerio) liver. Seventeen proteins were identified via affinity blocking test. Integration of the results of previous studies and this study revealed that these proteins play a crucial role in various toxic phenomena of liver induced by MCs, such as the disruption of cytoskeleton assembly, oxidative stress, and metabolic disorder. Moreover, in addition to inhibition of protein phosphate activity, the overall toxicity of MCs was simultaneously modulated by the distribution of MCs in cells and their interactions with other target proteins. These results provide new insight into the mechanisms of hepatotoxicity induced by MCs. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1206-1216, 2016.

Towards a Proteomic Catalogue and Differential Annotation of Salivary Gland Proteins in Blood Fed Malaria Vector Anopheles culicifacies by Mass Spectrometry

In order to understand the importance of functional proteins in mosquito behavior, following blood meal, a baseline proteomic dataset is essential for providing insights into the physiology of blood feeding. Therefore, in this study as first step, in solution and 1-D electrophoresis digestion approach combined with tandem mass spectrometry (nano LC-MS/MS) and computational bioinformatics for data mining was used to prepare a baseline proteomic catalogue of salivary gland proteins of sugar fed An. culicifacies mosquitoes. A total of 106 proteins were identified and analyzed by SEQUEST algorithm against mosquito protein database from Uniprot/NCBI. Importantly, D7r1, D7r2, D7r4, salivary apyrase, anti-platelet protein, calreticulin, antigen 5 family proteins were identified and grouped on the basis of biological and functional roles. Secondly, differential protein expression and annotations between salivary glands of sugar fed vs blood fed mosquitoes was analyzed using 2-Delectrophoresis combined with MALDI-TOF mass spectrometry. The alterations in the differential expression of total 38 proteins was observed out of which 29 proteins like beclin-1, phosphorylating proteins, heme oxygenase 1, ferritin, apoptotic proteins, coagulation and immunity like, serine proteases, serpins, c-type lectin and protein in regulation of blood feeding behavior were found to be up regulated while 9 proteins related to blood feeding, juvenile hormone epoxide hydrolase ii, odorant binding proteins and energy metabolic enzymes were found to be down regulated. To our knowledge, this study provides a first time baseline proteomic dataset and functional annotations of An. culicifacies salivary gland proteins that may be involved during the blood feeding. Identification of differential salivary proteins between sugar fed and blood fed mosquitoes and their plausible role may provide insights into the physiological processes associated with feeding behavior and sporozoite transmission during the process of blood feeding.

IDENTIFICATION AND MOLECULAR CHARACTERIZATION OF TWO SERINE PROTEASES AND THEIR POTENTIAL INVOLVEMENT IN PROPHENOLOXIDASE ACTIVATION IN Plutella xylostella

The proteolytic activation of prophenoloxidase (proPO) is a humoral defense mechanism in insects and crustaceans. Phenoloxidase (PO) is produced as an inactive precursor namely, proPO and is activated via specific proteolytic cleavage by proPO-activating proteinase. The current research reports two novel serine proteinase genes (PxSP1-768 bp and PxSP2-816 bp) from Plutella xylostella, encoding 255 and 271 amino acid residues, respectively. Tissue distribution analyses by semiquantitative reverse transcription-PCR (RT-PCR) revealed the resultant genes to be primarily expressed in the hemocytes, while quantitative-RT-PCR (qRT-PCR) assay showed that transcription level of PxSP1 and PxSP2 increased significantly after injection of the fungal pathogen Beauveria bassiana. Purified recombinant fusion proteins of PxSP2 and PxSP1 were injected to New Zealand white rabbits and polyclonal antibodies were generated with the titers of 1:12,800. After silencing the expression of PxSP2 by RNAi, the PO activity decreased significantly. The results show that PxSP2 is involved in prophenoloxidase activation in P. xylostella.

Comparative Transcriptomics Reveals Key Gene Expression Differences between Diapausing and Non-Diapausing Adults of Culex pipiens

Diapause is a critical eco-physiological adaptation for winter survival in the West Nile Virus vector, Culex pipiens, but little is known about the molecular mechanisms that distinguish diapause from non-diapause in this important mosquito species. We used Illumina RNA-seq to simultaneously identify and quantify relative transcript levels in diapausing and non-diapausing adult females. Among 65,623,095 read pairs, we identified 41 genes with significantly different transcript abundances between these two groups. Transcriptome divergences between these two phenotypes include genes related to juvenile hormone synthesis, anaerobic metabolism, innate immunity and cold tolerance.

Identification of Genes Putatively Involved in Chitin Metabolism and Insecticide Detoxification in the Rice Leaf Folder (Cnaphalocrocis medinalis) Larvae through Transcriptomic Analysis

The rice leaf roller (Cnaphalocrocis medinalis) is one of the most destructive agricultural pests. Due to its migratory behavior, it is difficult to control worldwide. To date, little is known about major genes of C. medinalis involved in chitin metabolism and insecticide detoxification. In order to obtain a comprehensive genome dataset of C. medinalis, we conducted de novo transcriptome sequencing which focused on the major feeding stage of fourth-instar larvae, and our work revealed useful information on chitin metabolism and insecticide detoxification and target genes of C. medinalis. We acquired 29,367,797 Illumina reads and assembled these reads into 63,174 unigenes with an average length of 753 bp. Among these unigenes, 31,810 were annotated against the National Center for Biotechnology Information non-redundant (NCBI nr) protein database, resulting in 24,246, 8669 and 18,176 assigned to Swiss-Prot, clusters of orthologous group (COG), and gene ontology (GO), respectively. We were able to map 10,043 unigenes into 285 pathways using the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG). Specifically, 16 genes, including five chitin deacetylases, two chitin synthases, five chitinases and four other related enzymes, were identified to be putatively involved in chitin biosynthesis and degradation, whereas 360 genes, including cytochrome P450s, glutathione S-transferases, esterases, and acetylcholinesterases, were found to be potentially involved in insecticide detoxification or as insecticide targets. The reliability of the transcriptome data was determined by reverse transcription quantitative PCR (RT-qPCR) for the selected genes. Our data serves as a new and valuable sequence resource for genomic studies on C. medinalis. The findings should improve our understanding of C. medinalis genetics and contribute to management of this important agricultural pest.

Profiling of proteins and proteases in the products of the salivary gland, digestive tract and excretions from larvae of the camel nasal botfly, Cephalopina titillator (Clark)

Proteins and proteolytic activities in the contents of the salivary gland (SGc), digestive tract (DTc) and excretory-secretory products (ESP) from larvae of the camel nasal botfly Cephalopina titillator were separated electrophoretically, and characterized. The protein profiles of the different samples were qualitatively quite similar in the larval stages L2 and L3. Zymogram analysis of proteases in the samples indicated that the digestive tract contained a greater variety of proteases than the salivary gland or the excretory-secretory products. They are mainly serine proteases. Proteases of ESP and DTc (especially of 3rd instar) contain trypsin- and chymotrypsin-like serine proteases, while the serine proteases of SGc are not of the trypsin- or chemotrypsin-type.

A novel single WAP domain-containing protein isoform with antibacterial relevance in Litopenaeus vannamei

Single WAP domain (SWD)-containing protein is a small protein containing a whey acidic protein (WAP) domain at the C-terminal region. SWD-containing protein exhibits structural similarity to the family of serine proteinase inhibitors. As of this writing, some SWD domain-containing proteins have been identified in crustaceans, and their functions included antibacterial and anti-proteinase activities. We identified a SWD protein isoform gene in Litopenaeus vanname (Lv-SWDi). Very high sequence similarity was found between Lv-SWDi and Lv-SWD. Results of time-course analysis for the gene expression profile showed that Lv-SWDi could produce a rapid feedback and an obvious upregulation at 12 h after Vibrio injection. Endogenous Lv-SWDi protein was obviously upregulated, and the highest expression level was reached at 24 h after Vibrio injection. The purified rLv-SWDi could directly bind to Gram-positive and Gram-negative bacteria. Results of the proteinase inhibitory assay also showed that rLv-SWDi could inhibit secretory protease activity from Bacillus subtilis. Lv-SWDi is a part of an important immunity-relevant gene and may serve important functions in defense against bacteria.

Expression of active trypsin-like serine peptidases in the midgut of sugar-feeding female Anopheles aquasalis

BACKGROUND

Anopheles aquasalis is a dipteran of the family Culicidae that is widely distributed in the coastal regions of South and Central America. This species acts as a vector of Plasmodium vivax, an important etiological agent of malaria, which represents a serious public health problem. In mosquitoes, trypsin-like serine proteases are important in blood meal digestion, immune responses and reproductive functions. The study of peptidases expressed in the mosquito midgut is essential to understanding the mechanisms of parasite-host interaction and the physiological process of nutrient digestion.

METHODS

Our study aimed to identify and characterize the proteolytic activities in the midgut of sugar-fed An. aquasalis females using zymographic analyses (substrate-SDS-PAGE), in-solution assays and mass spectrometry.

RESULTS

Here, we used a zymographic analysis to further biochemically characterize the proteolytic profile of the midgut of sugar-feeding An. aquasalis females. The trypsin peptidases migrated between ~17 and ~76 kDa and displayed higher proteolytic activities between pH 7.5 and 10 and at temperatures between 37 °C and 50 °C. Four putative trypsin-like serine peptidases were identified using mass spectrometry and data mining. The molecular masses of these peptidases were similar to those observed using zymography, which suggested that these peptidases could be responsible for some of the observed proteolytic bands.

CONCLUSIONS

Taken together, our results contribute to the gene annotation of the unknown genome of this species, to the tissue location of these peptidases, and to the functional prediction of these crucial enzymes, which all impact further studies of this species.

Examination of the genetic basis for sexual dimorphism in the Aedes aegypti (dengue vector mosquito) pupal brain

Background

Most animal species exhibit sexually dimorphic behaviors, many of which are linked to reproduction. A number of these behaviors, including blood feeding in female mosquitoes, contribute to the global spread of vector-borne illnesses. However, knowledge concerning the genetic basis of sexually dimorphic traits is limited in any organism, including mosquitoes, especially with respect to differences in the developing nervous system.

Methods

Custom microarrays were used to examine global differences in female vs. male gene expression in the developing pupal head of the dengue vector mosquito, Aedes aegypti. The spatial expression patterns of a subset of differentially expressed transcripts were examined in the developing female vs. male pupal brain through in situ hybridization experiments. Small interfering RNA (siRNA)-mediated knockdown studies were used to assess the putative role of Doublesex, a terminal component of the sex determination pathway, in the regulation of sex-specific gene expression observed in the developing pupal brain.

Results

Transcripts (2,527), many of which were linked to proteolysis, the proteasome, metabolism, catabolic, and biosynthetic processes, ion transport, cell growth, and proliferation, were found to be differentially expressed in A. aegypti female vs. male pupal heads. Analysis of the spatial expression patterns for a subset of dimorphically expressed genes in the pupal brain validated the data set and also facilitated the identification of brain regions with dimorphic gene expression. In many cases, dimorphic gene expression localized to the optic lobe. Sex-specific differences in gene expression were also detected in the antennal lobe and mushroom body. siRNA-mediated gene targeting experiments demonstrated that Doublesex, a transcription factor with consensus binding sites located adjacent to many dimorphically expressed transcripts that function in neural development, is required for regulation of sex-specific gene expression in the developing A. aegypti brain.

Conclusions

These studies revealed sex-specific gene expression profiles in the developing A. aegypti pupal head and identified Doublesex as a key regulator of sexually dimorphic gene expression during mosquito neural development.

Molecular cloning, characterization and expression analysis of trypsin-like serine protease from triangle-shell pearl mussel (Hyriopsis cumingii)

Trypsin-like serine protease (TLS) is ubiquitous in animals and plays a number of diverse roles, including dietary protein digestion, hemolymph coagulation, antimicrobial activity and immune responses, among others. This study reports the isolation of a 1048 bp full-length cDNA sequence of TLS from triangle-shell pearl mussel (Hyriopsis cumingii), including a 12 bp 5' UTR (untranslated region), a 172 bp 3' UTR, and an open reading frame (ORF) of 864 bp by rapid amplification of cDNA ends (RACE). Bioinformatic analysis shows that the gene belongs to the trypsin-like serine protease superfamily, and contains a 15 residues N-terminal signal peptide and a conserved C-terminal domain. In comparison to other serine proteases, the catalytic triad were identified as His-98, Asp-149, and Ser-240. Quantitative real-time PCR (qPCR) showed a broad expression of the TLS gene in ten tested tissues. Time-course expression analysis demonstrated that the expression level of the TLS mRNA was significantly up-regulated in eight tested tissues (liver, intestine, gill, heart, axe foot, adductor muscle, kidney and gonad), but down-regulated in mantle and stomach after Aeromonas hydrophila injection. This is one of the results indicate that TLS may be involved in innate defense reactions against A. hydrophila in triangle-shell pearl mussel.

Immunity-related genes in Ixodes scapularis--perspectives from genome information

Ixodes scapularis, commonly known as the deer tick, transmits a wide array of human and animal pathogens including Borrelia burgdorferi. Despite substantial advances in our understanding of immunity in model arthropods, including other disease vectors, precisely how I. scapularis immunity functions and influences persistence of invading pathogens remains largely unknown. This review provides a comprehensive analysis of the recently sequenced I. scapularis genome for the occurrence of immune-related genes and related pathways. We will also discuss the potential influence of immunity-related genes on the persistence of tick-borne pathogens with an emphasis on the Lyme disease pathogen B. burgdorferi. Further enhancement of our knowledge of tick immune responses is critical to understanding the molecular basis of the persistence of tick-borne pathogens and development of novel interventions against the relevant infections.

The midgut of Aedes albopictus females expresses active trypsin-like serine peptidases

Background

Aedes albopictus is widely distributed across tropical and sub-tropical regions and is associated with the transmission of several arboviruses. Although this species is increasingly relevant to public health due its ability to successfully colonize both urban and rural habitats, favoring the dispersion of viral infections, little is known about its biochemical traits, with all assumptions made based on studies of A. aegypti. In previous studies we characterized the peptidase profile of pre-imaginal stages of A. albopictus and we reported the first proteomic analysis of the midgut from sugar-fed females of this insect species.

Methods

In the present work, we further analyzed the peptidase expression in the midgut of sugar-fed females using 1DE-substrate gel zymography, two-dimensional electrophoresis (2DE), mass spectrometry (MS), and protein identification based on similarity.

Results

The combination of zymography, in solution assays using fluorescent substrates and 2DE-MS/MS allowed us to identify the active serine peptidase “fingerprint” in the midgut of A. albopictus females. Zymographic analysis revealed a proteolytic profile composed of at least 13 bands ranging from ~25 to 250 kDa, which were identified as trypsin-like serine peptidases by using specific inhibitors of this class of enzymes. Concomitant use of the fluorogenic substrate Z-Phe-Arg-AMC and trypsin-like serine protease inhibitors corroborated the zymographic findings. Our proteomic approach allowed the identification of two different trypsin-like serine peptidases and one chymotrypsin in protein spots of the alkaline region in 2DE map of the A. albopictus female midgut. Identification of these protein coding genes was achieved by similarity to the A. aegypti genome sequences using Mascot and OMSSA search engines.

Conclusion

These results allowed us to detect, identify and characterize the expression of active trypsin-like serine peptidases in the midgut of sugar-fed A. albopictus females. In addition, proteomic analysis allowed us to confidently assign the expression of two trypsin genes and one chymotrypsin gene to the midgut of this mosquito. These results contribute to the gene annotation in this species of unknown genome and represent a small but important step toward the protein-level functional and localization assignment of trypsin-like serine peptidase genes in the Aedes genus.

Fighting a losing battle: vigorous immune response countered by pathogen suppression of host defenses in the chytridiomycosis-susceptible frog Atelopus zeteki

The emergence of the disease chytridiomycosis caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) has been implicated in dramatic global amphibian declines. Although many species have undergone catastrophic declines and/or extinctions, others appear to be unaffected or persist at reduced frequencies after Bd outbreaks. The reasons behind this variance in disease outcomes are poorly understood: differences in host immune responses have been proposed, yet previous studies suggest a lack of robust immune responses to Bd in susceptible species. Here, we sequenced transcriptomes from clutch-mates of a highly susceptible amphibian, Atelopus zeteki, with different infection histories. We found significant changes in expression of numerous genes involved in innate and inflammatory responses in infected frogs despite high susceptibility to chytridiomycosis. We show evidence of acquired immune responses generated against Bd, including increased expression of immunoglobulins and major histocompatibility complex genes. In addition, fungal-killing genes had significantly greater expression in frogs previously exposed to Bd compared with Bd-naïve frogs, including chitinase and serine-type proteases. However, our results appear to confirm recent in vitro evidence of immune suppression by Bd, demonstrated by decreased expression of lymphocyte genes in the spleen of infected compared with control frogs. We propose susceptibility to chytridiomycosis is not due to lack of Bd-specific immune responses but instead is caused by failure of those responses to be effective. Ineffective immune pathway activation and timing of antibody production are discussed as potential mechanisms. However, in light of our findings, suppression of key immune responses by Bd is likely an important factor in the lethality of this fungus.

Increasing transcriptome response of serpins during the ontogenetic stages in the salmon louse Caligus rogercresseyi (Copepoda: Caligidae)

Serine protease inhibitors, or serpins, target serine proteases, and are important regulators of intra- and extracellular proteolysis. For parasite survival, parasite-derived protease inhibitors have been suggested to play essential roles in evading the host's immune system and protecting against exogenous host proteases. The aim of this work was to identify serpins via high throughput transcriptome sequencing and elucidate their potential functions during the lifecycle of the salmon louse Caligus rogercresseyi. Eleven putative, partial serpin sequences in the C. rogercresseyi transcriptome were identified and denoted as Cr-serpins 1 to 11. Comparative analysis of the deduced serpin-like amino acid sequences revealed a highly conserved reactive center loop region. Interestingly, P1 residues suggest putative functions involved with the trypsin/subtilisin, elastase, or subtilisin inhibitors, which evidenced increasing gene expression profiles from the copepodid to adult stage in C. rogercresseyi. Concerning this, Cr-serpin 10 was mainly expressed in the copepodid stage, while Cr-serpins 3, 4, 5, and 11 were mostly expressed in chalimus and adult stages. These results suggest that serpins could be involved in evading the immune response of the host fish. The identification of these serpins furthers the understanding of the immune system in this important ectoparasite species.

PmPPAF is a pro-phenoloxidase activating factor involved in innate immunity response of the shrimp Penaeus monodon

One of the major steps in the innate immune response of shrimp includes the activation of serine proteinases of the pro-phenoloxidase pathway by the prophenoloxidase activation enzyme (PPAF). In this study, the cDNA encoding a serine proteinase homologue (SPH) with prophenoloxidase activating activity of Penaeus monodon (PmPPAF) was cloned and characterized. PmPPAF cDNA consists of 1444 nucleotides encoding a protein with 394 amino acid residues. The estimated molecular weight of PmPPAF is 43.5 kDa with an isoelectric point of 5.19. PmPPAF consists of a signal peptide, a CLIP domain and a carboxyl-terminal trypsin-like serine protease domain. It is highly similar to the masquerade-like protein 2A (61% similarity) of the crayfish Pacifastacus leniusculus, other serine proteases (42.9-67% identity) of P. monodon, and the PPAF of the crab (61% similarity). Unlike other SPH of P. monodon, which express mainly in the hemocytes, PmPPAF transcripts were detected in the hemocytes, eyestalk, hypodermis, gill, swimming leg and brain. Similar to the crab PPAF, PmPPAF transcript level is high in shrimp at the premolt stages and PmPPAF expression is up-regulated in shrimp infected with white spot syndrome virus (WSSV). Gene silencing of PmPPAF decreased expression of a prophenoloxidase-like gene and injection of Anti-PmPPAF antibody causes a decrease in PO activity. Taken together, these results provided evidence that PmPPAF is a serine proteinase homologue, and is involved in the pro-PO activation pathway of the shrimp innate immune system.

Mechanisms relevant to the enhanced virulence of a dihydroxynaphthalene-melanin metabolically engineered entomopathogen

The entomopathogenic fungus Metarhizium anisopliae MA05-169 is a transformant strain that has been metabolically engineered to express dihydroxynaphthalene-melanin biosynthesis genes. In contrast to the wild type strain, the transformant displays a greater resistance to environmental stress and a higher virulence toward target insect host. However, the underlying mechanisms for these characteristics remain unclear; hence experiments were initiated to explore the possible mechanism(s) through physiological and molecular approaches. Although both transformant and wild type strains could infect and share the same insect host range, the former germinated faster and produced more appressoria than the latter, both in vivo and in vitro. The transformant showed a significantly shorter median lethal time (LT₅₀) when infecting the diamondback moth (Plutella xylostella) and the striped flea beetle (Phyllotreta striolata), than the wild type. Additionally, the transformant was more tolerant to reactive oxygen species (ROS), produced 40-fold more orthosporin and notably overexpressed the transcripts of the pathogenicity-relevant hydrolytic enzymes (chitinase, protease, and phospholipase) genes in vivo. In contrast, appressorium turgor pressure and destruxin A content were slightly decreased compared to the wild type. The transformant's high anti-stress tolerance, its high virulence against five important insect pests (cowpea aphid Aphis craccivora, diamondback moth Pl. xylostella, striped flea beetle Ph. striolata, and silverleaf whitefly Bemisia argentifolii) and its capacity to colonize the root system are key properties for its potential bio-control field application.