Mosquito cathepsin B-like protease involved in embryonic degradation of vitellin is produced as a latent extraovarian precursor

Maternal lipid mobilization is essential for embryonic development in the malaria vector Anopheles gambiae

Lipid metabolism is an essential component in reproductive physiology. While lipid mobilization has been implicated in the growth of Plasmodium falciparum malaria parasites in their Anopheles vectors, the role of this process in the reproductive biology of these mosquitoes remains elusive. Here, we show that impairing lipolysis in Anopheles gambiae, the major malaria vector, leads to embryonic lethality. Embryos derived from females in which we silenced the triglyceride lipase AgTL2 or the lipid storage droplet AgLSD1 develop normally during early embryogenesis but fail to hatch due to severely impaired metabolism. Embryonic lethality is efficiently recapitulated by exposing adult females to broad-spectrum lipase inhibitors prior to blood feeding, unveiling lipolysis as a potential target for inducing mosquito sterility. Our findings provide mechanistic insights into the importance of maternal lipid mobilization in embryonic health that may inform studies on human reproduction.

Fibroinase plays a vital role in silk gland degeneration by regulating autophagy and apoptosis in the silkworm, Bombyx mori

The silkworm is an incredibly valuable insect that produces silk through its silk gland. Within this organ, Fibroinase has been identified and named due to its ability to fibroin degradation. The expression of Fibroinase in the silk gland significantly increases during the larval-pupal stage, which might be associated with the degeneration of the silk gland. In this study, Fibroinase was overexpressed and knocked down specifically both in the middle and posterior silk glands, respectively, using transgenic technology. The investigation of silk gland development in these transgenic silkworms showed that Fibroinase plays a direct role in accelerating silk gland degeneration. The staining analyses performed in the silk glands of transgenic silkworms suggest that Fibroinase is involved in the processes of autophagy and apoptosis during silk gland degeneration. Further experiments demonstrated that Fibroinase, acting as a lysosomal regulator, negatively regulates autophagy via the mTOR (mechanistic target of rapamycin) pathway. Moreover, during apoptosis, Fibroinase could activate Caspase3 by increasing the activity of BmCaspase1, ultimately accelerating the apoptosis process. These findings enhance our understanding of the physiological role of Fibroinase in promoting silk gland degeneration, which plays a role in breaking down proteins in the silk gland and coordinating the regulation of autophagy and apoptosis.

Structural Characterization and Physiological Role of Bombyx mori Fibroinase in the Silk Gland Development

Silkworm is a highly valuable insect that produces silk through secretion by a silk gland. Within this gland, a type of cathepsin L protease called Fibroinase was identified as an enzyme for hydrolyzing the primary components of silk, including fibroin and sericin. Here, we determined the crystal structure of Fibroinase fromBombyx mori at a resolution of 1.56 Å. Comparative structural analysis revealed that Fibroinase adopted a similar structural pattern with papain-type cathepsin, consisting of an N-terminal domain and a C-terminal domain. The interface between the domains forms a substrate-binding cleft, where the E64 inhibitor noncovalently binds in a novel manner. Additionally, computational simulations combined with biochemical analysis allowed us to define the binding mode and inhibition mechanism of physiological inhibitor Bombyx cysteine protease inhibitor (BCPI) with Fibroinase. Moreover, the expression profiles and RNA interference of Fibroinase indicated its critical role in removing silk proteins in the silk gland lumen and the destruction of silk gland tissue during the larval-pupal metamorphosis. These findings enhance our understanding of the structural and biochemical features of Fibroinase and its inhibitors, while also providing evidence for the physiological role of Fibroinase in silk gland development.

mosGILT controls innate immunity and germ cell development in Anopheles gambiae

Gene-edited mosquitoes lacking a gamma-interferon-inducible lysosomal thiol reductase-like protein, namely (mosGILTnull) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILTnull Anopheles gambiae was therefore compared to wild type (WT) mosquitoes by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILTnull A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg, an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILTnull mosquitoes. These results provide a crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

Gene silencing of cathepsins B and L using CTV-based, plant-mediated RNAi interferes with ovarial development in Asian citrus psyllid (ACP), Diaphorina citri

Diaphorina citri Kuwayama (Hemiptera: Liviidae) is a vector of the bacteria Candidatus Liberibacter americanus (CLam) and Candidatus Liberibacter asiaticus (CLas), which are phloem-restricted and associated with the most important and destructive worldwide citrus disease, Huanglongbing (HLB). Currently, no cure for HLB has been described. Therefore, measures have focused on reducing D. citri populations. In these insects, cathepsin B (DCcathB) and L (DCcathL) enzymes play an important role in digestion, and are involved in embryogenesis, immune defense, and ecdysis. In this study, we used a CTV-based vector to deliver dsRNA (CTV-dsRNA) into Citrus macrophylla plants targeting DCcathB and DCcathL genes in D. citri that fed on the phloem of these CTV-RNAi infected plants. Subsequently, we evaluated expression of DCcathB and DCcathL genes as well as the Vitellogenin (Vg) gene by RT-qPCR in D. citri fed on CTV-dsRNA occurring in plant phloem. It was found that a defective phenotype in D. citri females as a result of knockdown of DCcathB and DCcathL genes mediated by CTV dsRNA. These results showed that Psyllids fed on plants treated with the CTV-dsRNA exhibited downregulation of the Vg gene, one of the most important genes associated with embryogenic and female development, which was associated with dsRNA-mediated silencing of the two cathepsin genes. Based on our findings, a CTV-based strategy for delivering RNAi via plants that targets DCcathB and DCcathL genes may represent a suitable avenue for development of dsRNA-based tools to manage D. citri that limits the spread of HLB.

Anopheles gambiae mosGILT regulates innate immune genes and zpg expression

Gene-edited mosquitoes lacking a g amma-interferon-inducible lysosomal thiol reductase-like protein, namely ( mosGILT null ) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILT null A. gambiae was therefore compared to wild type (WT) by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILT null A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg , an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILT null mosquitoes. These results provide the crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

Functional characterization of maternally accumulated hydrolases in the mature oocytes of the vector Rhodnius prolixus reveals a new protein phosphatase essential for the activation of the yolk mobilization and embryo development

Yolk biogenesis and consumption have been well conserved in oviparous animals throughout evolution. Most egg-laying animals store yolk proteins within the oocytes' yolk granules (Ygs). Following fertilization, the Ygs participate in controlled pathways of yolk breakdown to support the developing embryo's anabolic metabolism. While the unfolding of the yolk degradation program is a crucial process for successful development in many species, the molecular mechanisms responsible for yolk mobilization are still mysterious and have mostly not been explored. Here, we investigate the functional role of the oocyte maternally accumulated mRNAs of a protein phosphatase (PP501) and two aspartic proteases (cathepsin-D 405, CD405 and cathepsin-D 352, CD352) in the yolk degradation and reproduction of the insect vector of Chagas disease Rhodnius prolixus. We found that PP501 and CD352 are highly expressed in the vitellogenic ovary when compared to the other organs of the adult insect. Parental RNAi silencing of PP501 resulted in a drastic reduction in oviposition and increased embryo lethality whereas the silencing of CD352 resulted only in a slight decrease in oviposition and embryo viability. To further investigate the PP501-caused high reproduction impairment, we investigated the Ygs biogenesis during oocyte maturation and the activation of the yolk degradation program at early development. We found that the Ygs biogenesis was deficient during oogenesis, as seen by flow cytometry, and that, although the PP501-silenced unviable eggs were fertilized, the Ygs acidification and acid phosphatase activity were affected, culminating in a full impairment of the yolk proteins degradation at early embryogenesis. Altogether we found that PP501 is required for the oocyte maturation and the activation of the yolk degradation, being, therefore, essential for this vector reproduction.

A comparative analysis of Aedes albopictus and Aedes aegypti subjected to diapause-inducing conditions reveals conserved and divergent aspects associated with diapause, as well as novel genes associated with its onset

Aedes albopictus and Aedes aegypti are mosquito species that are distributed worldwide and transmit diverse arboviruses of medical importance, such as those causing yellow fever, dengue, chikungunya and Zika. A. albopictus embryos may remain viable for long periods in the environment due to their ability to become dormant through quiescence or diapause, a feature that contributes to their dispersion and hinders control actions. Diapause incidence can vary among natural populations of A. albopictus, but metabolic and genetic parameters associated with its induction still need to be better defined. The present study aimed to investigate the effect of exposure to diapause-inducing conditions on several biological parameters in different populations of A. albopictus (from tropical and temperate areas) and the diapause-refractory A. aegypti (tropical and subtropical populations). As expected, only the A. albopictus populations exhibited diapause, but with a lower incidence for the population from a tropical area. Exposure to diapause-inducing conditions, however, led to a sharp reduction in fecundity for both A. albopictus and A. aegypti tropical populations, with no effect on fertility (>90%). It also led to a prolonged period as pupae for the progeny of all induced groups, with a further delay for those from temperate climates. In all those induced groups, the lipid contents in eggs and adult females were higher than in the non-induced controls, with the highest values observed for both A. albopictus groups. Three genes were selected to have their expression profile investigated: cathepsin, idgf4, and pepck. Upon exposure to diapause-inducing conditions, all three genes were upregulated in the A. albopictus embryos from the tropical region, but only idgf4 was upregulated in the temperate climate embryos. This represents a new gene associated with diapause that can be used as a target to evaluate and prevent embryonic dormancy, a possible new vector control strategy for mosquito species from temperate areas, such as A. albopictus.

Functional Role of AsAP in the Reproduction of Adelphocoris suturalis (Hemiptera: Miridae)

Adelphocoris suturalis Jakovlev (Hemiptera: Miridae) is an omnivorous agricultural pest that has severe economic impacts on a diverse range of agricultural crops. Although the targeted disruption of reproductive development among insects has been proposed as a novel control strategy for pest species, the current understanding of the physiology and molecular mechanisms of A. suturalis reproduction is very limited. In this study, we isolated a putative A. suturalisaspartic protease (AsAP) gene that is highly expressed in the fat body and ovaries of sexually mature females. The double-stranded RNA (dsRNA)-mediated knockdown of AsAP suppressed ovarian development and negatively impacted female fertility, which suggested that it plays an essential role in A. suturalis reproduction. The results of this study could help to expand our understanding of A. suturalis reproductive development and have the potential to facilitate the development of effective strategies for the better control of this pest species.

Conserved molecular pathways underlying biting in two divergent mosquito genera

Mosquitoes transmit a wide variety of devastating pathogens when they bite vertebrate hosts and feed on their blood. However, three entire mosquito genera and many individual species in other genera have evolved a nonbiting life history in which blood is not required to produce eggs. Our long-term goal is to develop novel interventions that reduce or eliminate the biting behavior in vector mosquitoes. A previous study used biting and nonbiting populations of a nonvector mosquito, Wyeomyia smithii, as a model to uncover the transcriptional basis of the evolutionary transition from a biting to a nonbiting life history. Herein, we ask whether the molecular pathways that were differentially expressed due to differences in biting behavior in W. smithii are also differentially expressed between subspecies of Culex pipiens that are obligate biting (Culex pipiens pipiens) and facultatively nonbiting (Culex pipiens molestus). Results from RNAseq of adult heads show dramatic upregulation of transcripts in the ribosomal protein pathway in biting C. pipiens, recapitulating the results in W. smithii, and implicating the ancient and highly conserved ribosome as the intersection to understanding the evolutionary and physiological basis of blood feeding in mosquitoes. Biting Culex also strongly upregulate energy production pathways, including oxidative phosphorylation and the citric acid (TCA) cycle relative to nonbiters, a distinction that was not observed in W. smithii. Amino acid metabolism pathways were enriched for differentially expressed genes in biting versus nonbiting Culex. Relative to biters, nonbiting Culex upregulated sugar metabolism and transcripts contributing to reproductive allocation (vitellogenin and cathepsins). These results provide a foundation for developing strategies to determine the natural evolutionary transition between a biting and nonbiting life history in vector mosquitoes.

The Function of Nilaparvata lugens (Hemiptera: Delphacidae) E74 and Its Interaction With βFtz-F1

Drosophila E74 is an early gene located in the polytene chromosome 74EF puff position. E74 controls the production of late genes, indicating that it plays a crucial role in this cascade model. Nilaparvata lugens E74 is closely related to Diaphorina citri, Bemisia tabaci, and Laodelphax striatellus. After downregulating E74, molting, and nymphal mortality were increased, and ovarian development was delayed. Moreover, the expression of Vg was reduced at the transcriptional level, as measured by qRT-PCR, and the content of Vg protein was reduced, as detected by Western blotting. After downregulating E74, the expression of hormone-related genes, including Tai, βFtz-F1, Met, Kr-h1, UspA, UspB, E93, and Br, was changed. The expression of E74 was significantly decreased after downregulating hormone-related genes. When the expression of E74 and βFtz-F1 was downregulated together, nymph mortality and molting mortality were higher than those when E74 or βFtz-F1 was downregulated alone. Thus, E74 probably interacts with βFtz-F1 at the genetic level. In summary, this study showed that E74 plays a crucial role in the development, metamorphosis and reproduction of N. lugens, possibly via the interaction with βFtz-F1 at the genetic level. This study provides a basis for the development of new target-based pesticides and new methods for the effective control of N. lugens.

Open questions on the functional biology of the yolk granules during embryo development

Biogenesis and consumption of the yolk are well-conserved aspects of the reproductive biology in oviparous species. Most egg-laying animals accumulate yolk proteins within the oocytes thus creating the source of nutrients and energy that will feed embryo development. Yolk accumulation drives the generation of a highly specialized oocyte cytoplasm with maternal mRNAs, ribosomes, mitochondria, and, mainly, a set of organelles collectively referred to as yolk granules (Ygs). Following fertilization, the Ygs are involved in regulated mechanisms of yolk degradation to fuel the anabolic metabolism of the growing embryo. Thus, yolk accumulation and degradation are essential processes that allow successful development in many species. Nevertheless, the molecular machinery and mechanisms dedicated to the programmed yolk mobilization throughout development are still enigmatic and remain mostly unexplored. Moreover, while the Ygs functional biology as a nutritional source for the embryo has been acknowledged, several reports have suggested that Ygs cargoes and functions go far beyond yolk storage. Evidence of the role of Ygs in gene expression, microbiota harboring, and paracrine signaling has been proposed. In this study, we summarize the current knowledge of the Ygs functional biology pointing to open questions and where further investigation is needed.

The KNRL nuclear receptor controls hydrolase-mediated vitellin breakdown during embryogenesis in the brown planthopper, Nilaparvata lugens

Vitellin (Vn) homeostasis is central to the fecundity of oviparous insects. Most studies have focused on the synthesis and transportation of Vn as a building block for developing eggs during vitellogenesis; however, less is known about how the utilization of this nutrient reserve affects embryonic development. Here, we show that the single ortholog of the knirps and knirps-like nuclear receptors, KNRL, negatively regulates Vn breakdown by suppressing the expression of hydrolase genes in the brown planthopper, Nilaparvata lugens. KNRL was highly expressed in the ovary of adult females, and knockdown of KNRL by RNA interference resulted in the acceleration of Vn breakdown and the inhibition of embryonic development. Transcriptome sequencing analysis revealed that numerous hydrolase genes, including cathepsins and trypsins were up-regulated after KNRL knockdown. At least eight of the nine significantly enriched Gene Ontology terms for the up-regulated genes were in proteolysis-related categories. The expression levels of five selected trypsin genes and the enzymatic activities of trypsin in the embryos were significantly increased after KNRL knockdown. Moreover, trypsin injection prolonged egg duration, delayed embryonic development, accelerated Vn breakdown and severely reduced egg hatchability, a pattern similar to that observed in KNRL-silenced N. lugens. These observations suggest that KNRL controls Vn breakdown in embryos via the transcriptional inhibition of hydrolases. Generally, this study provides a foundation for understanding how embryo nutrient reserves are mobilized during embryogenesis and identifies several genes and pathways that may prove valuable targets for pest control.

Transcriptome Analysis of Myzus persicae to UV-B Stress

As an environmental stress factor, ultraviolet-B (UV-B) radiation directly affects the growth and development of Myzus persicae (Sulzer) (Homoptera: Aphididae). How M. persicae responds to UV-B stress and the molecular mechanisms underlying this adaptation remain unknown. Here, we analyzed transcriptome data for M. persicae following exposure to UV-B radiation for 30 min. We identified 758 significant differentially expressed genes (DEGs) following exposure to UV-B stress, including 423 upregulated and 335 downregulated genes. In addition, enrichment analysis using the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases illustrated that these DEGs are associated with antioxidation and detoxification, metabolic and protein turnover, immune response, and stress signal transduction. Simultaneously, these DEGs are closely related to the adaptability to UV-B stress. Our research can raise awareness of the mechanisms of insect responses to UV-B stress.

Trained Immunity in Anopheles gambiae: Antibacterial Immunity Is Enhanced by Priming via Sugar Meal Supplemented With a Single Gut Symbiotic Bacterial Strain

Mosquitoes have evolved an effective innate immune system. The mosquito gut accommodates various microbes, which play a crucial role in shaping the mosquito immune system during evolution. The resident bacteria in the gut microbiota play an essential role in priming basal immunity. In this study, we show that antibacterial immunity in Anopheles gambiae can be enhanced by priming via a sugar meal supplemented with bacteria. Serratia fonticola S1 and Enterobacter sp. Ag1 are gut bacteria in mosquitoes. The intrathoracic injection of the two bacteria can result in an acute hemocoelic infection in the naïve mosquitoes with mortality of ∼40% at 24 h post-infection. However, the Enterobacter orSerratia primed mosquitoes showed a better 24 h survival upon the bacterial challenge. The priming confers the protection with a certain degree of specificity, the Enterobacter primed mosquitoes had a better survival upon the Enterobacter but not Serratia challenge, and the Serratia primed mosquitoes had a better survival upon the Serratia but not Enterobacter challenge. To understand the priming-mediated immune enhancement, the transcriptomes were characterized in the mosquitoes of priming as well as priming plus challenges. The RNA-seq was conducted to profile 10 transcriptomes including three samples of priming conditions (native microbiota, Serratia priming, and Enterobacter priming), six samples of priming plus challenges with the two bacteria, and one sample of injury control. The three priming regimes resulted in distinctive transcriptomic profiles with about 60% of genes affected by both bacteria. Upon challenges, different primed mosquitoes displayed different transcriptomic patterns in response to different bacteria. When a primed cohort was challenged with a heterogenous bacterium, more responsive genes were observed than when challenged with a homogenous bacterium. As expected, many canonical immune genes were responsive to the priming and challenge, but much more non-immune genes with various functions were also responsive in the contexts, which implies that the prior priming triggers a delicately coordinated systemic regulation that results in an enhanced immunity against the subsequent challenge. Besides the participation of typical immune pathways, the transcriptome data suggest the involvement of lysosome and metabolism in the context. Overall, this study demonstrated a trained immunity via priming with bacteria in diet.

Proteomic Polyphenism in Color Morphotypes of Diaphorina citri, Insect Vector of Citrus Greening Disease

Diaphorina citri is a vector of "Candidatus Liberibacter asiaticus" (CLas), associated with citrus greening disease. D. citri exhibit at least two color morphotypes, blue and non-blue, the latter including gray and yellow morphs. Blue morphs have a greater capacity for long-distance flight and transmit CLas less efficiently as compared to non-blue morphs. Differences in physiology and immunity between color morphs of the insect vector may influence disease epidemiology and biological control strategies. We evaluated the effect of CLas infection on color morph and sex-specific proteomic profiles of D. citri. Immunity-associated proteins were more abundant in blue morphs as compared to non-blue morphs but were upregulated at a higher magnitude in response to CLas infection in non-blue insects. To test for differences in color morph immunity, we measured two phenotypes: (1) survival of D. citri when challenged with the entomopathogenic fungus Beauveria bassiana and (2) microbial load of the surface and internal microbial communities. Non-blue color morphs showed higher mortality at four doses of B. bassinana, but no differences in microbial load were observed. Thus, color morph polyphenism is associated with two distinct proteomic immunity phenotypes in D. citri that may impact transmission of CLas and resistance to B. bassiana under some conditions.

The ecdysone-induced protein 93 is a key factor regulating gonadotrophic cycles in the adult female mosquito Aedes aegypti

Repeated blood feedings are required for adult female mosquitoes to maintain their gonadotrophic cycles, enabling them to be important pathogen carriers of human diseases. Elucidating the molecular mechanism underlying developmental switches between these mosquito gonadotrophic cycles will provide valuable insight into mosquito reproduction and could aid in the identification of targets to disrupt these cycles, thereby reducing disease transmission. We report here that the transcription factor ecdysone-induced protein 93 (E93), previously implicated in insect metamorphic transitions, plays a key role in determining the gonadotrophic cyclicity in adult females of the major arboviral vector Aedes aegypti Expression of the E93 gene in mosquitoes is down-regulated by juvenile hormone (JH) and up-regulated by 20-hydroxyecdysone (20E). We find that E93 controls Hormone Receptor 3 (HR3), the transcription factor linked to the termination of reproductive cycles. Moreover, knockdown of E93 expression via RNAi impaired fat body autophagy, suggesting that E93 governs autophagy-induced termination of vitellogenesis. E93 RNAi silencing prior to the first gonadotrophic cycle affected normal progression of the second cycle. Finally, transcriptomic analysis showed a considerable E93-dependent decline in the expression of genes involved in translation and metabolism at the end of a reproductive cycle. In conclusion, our data demonstrate that E93 acts as a crucial factor in regulating reproductive cycle switches in adult female mosquitoes.

A De Novo Transcriptomics Approach Reveals Genes Involved in Thrips Tabaci Resistance to Spinosad

The onion thrip, Thrips tabaci (Thysanoptera: Thripidae) is a major polyphagous pest that attacks a wide range of economically important crops, especially Allium species. The thrip's damage can result in yield loss of up to 60% in onions (Allium cepa). In the past few decades, thrip resistance to insecticides with various modes of actions have been documented. These include resistance to spinosad, a major active compound used against thrips, which was reported from Israel. Little is known about the molecular mechanisms underlying spinosad resistance in T. tabaci. We attempted to characterize the mechanisms involved in resistance to spinosad using quantitative transcriptomics. Susceptible (LC50 = 0.6 ppm) and resistant (LC50 = 23,258 ppm) thrip populations were collected from Israel. An additional resistant population (LC50 = 117 ppm) was selected in the laboratory from the susceptible population. De novo transcriptome analysis on the resistant and susceptible population was conducted to identify differently expressed genes (DGEs) that might be involved in the resistance against spinosad. In this analysis, 25,552 unigenes were sequenced, assembled, and functionally annotated, and more than 1500 DGEs were identified. The expression levels of candidate genes, which included cytochrome P450 and vittelogenin, were validated using quantitative RT-PCR. The cytochrome P450 expression gradually increased with the increase of the resistance. Higher expression levels of vitellogenin in the resistant populations were correlated with higher fecundity, suggesting a positive effect of the resistance on resistant populations. This research provides a novel genetic resource for onion thrips and a comprehensive molecular examination of resistant populations to spinosad. Those resources are important for future studies concerning thrips and resistance in insect pests regarding agriculture.

Transcript Assembly and Quantification by RNA-Seq Reveals Significant Differences in Gene Expression and Genetic Variants in Mosquitoes of the Culex pipiens (Diptera: Culicidae) Complex

The taxonomy of Culex pipiens complex of mosquitoes is still debated, but in North America it is generally regarded to include Culex pipiens pipiens, Culex pipiens molestus, and Culex quinquefasciatus (or Culex pipiens quinquefasciatus). Although these mosquitoes have very similar morphometry, they each have unique life strategies specifically adapted to their ecological niche. Differences include the capability for overwintering diapause, bloodmeal preference, mating behaviors, and reliance on blood meals to produce eggs. Here, we used RNA-seq transcriptome analysis to investigate the differential gene expression and nucleotide polymorphisms that may link to the divergent traits specifically between Cx. pipiens pipiens and Cx. pipiens molestus.

Proteolytic profile of larval developmental stages of Penaeus vannamei: An activity and mRNA expression approach

In arthropods, the cleavage of specific proteins by peptidases has pivotal roles in multiple physiological processes including oogenesis, immunity, nutrition, and parasitic infection. These enzymes are also key players in the larval development, and well-described triggers of molting and metamorphosis. In this work the peptidase complement throughout the larvae development of Penaeus vannamei was quantified at the transcript and activity level using qPCR and fluorogenic substrates designed to be hydrolyzed by class-specific peptidases respectively, providing a detailed identification of the proteolytic repertoire in P. vannamei larvae. Significant changes in the peptidase activity profile were observed. During the lecithotrophic naupliar instars, the dominant peptidase activity and expression derive from cysteine peptidases, suggesting that enzymes of this class hydrolyze the protein components of yolk as the primary amino acid source. At the first feeding instar, zoea, dominant serine peptidase activity was found where trypsin activity is particularly high, supporting previous observations that during zoea the breakdown of food protein is primarily enzymatic. At decapodid stages the peptidase expression and activity is more diverse indicating that a multienzyme network achieves food digestion. Our results suggest that proteolytic enzymes fulfill specific functions during P. vannamei larval development.

Examining the Role of Niemann-Pick C1 Protein in the Permissiveness of Aedes Mosquitoes to Filoviruses

Aedes mosquitoes vector many viruses with divergent characteristics, yet the criteria needed for a virus to be vectored by an arthropod remain unknown. The intracellular cholesterol transporter protein Niemann-Pick C1 (NPC1) has been identified as the necessary entry receptor for filoviruses such as Ebola and Marburg viruses. While homologues of NPC1 are observed in mosquitoes, currently no filovirus has been identified as circulating in mosquitoes. This work aimed at increasing the understanding of the mosquito vector by examining the capability of a virus to gain the ability to enter mosquito cells. We developed a model system of Aedes cells expressing human NPC1 (hNPC1) and attempted to infect these cells with recombinant vesicular stomatitis virus expressing the Ebola virus glycoprotein. As compared to the control cells, no significant increase in infection was observed in cells expressing hNPC1, demonstrating that the expression of human NPC1 alone is not sufficient to support filovirus infection, and that host factors other than NPC1 determine filovirus susceptibility of mosquito cells.

Insecticidal Activity of Artemisia vulgaris Essential Oil and Transcriptome Analysis of Tribolium castaneum in Response to Oil Exposure

Red flour beetle (Tribolium castaneum) is one of the most destructive pests of stored cereals worldwide. The essential oil (EO) of Artemisia vulgaris (mugwort) is known to be a strong toxicant that inhibits the growth, development, and reproduction of T. castaneum. However, the molecular mechanisms underlying the toxic effects of A. vulgaris EO on T. castaneum remain unclear. Here, two detoxifying enzymes, carboxylesterase (CarEs) and cytochrome oxidase P450 (CYPs), were dramatically increased in red flour beetle larvae when they were exposed to A. vulgaris EO. Further, 758 genes were differentially expressed between EO treated and control samples. Based on Gene Ontology (GO) analysis, numerous differentially expressed genes (DEGs) were enriched for terms related to the regulation of biological processes, response to stimulus, and antigen processing and presentation. Our results indicated that A. vulgaris EO disturbed the antioxidant activity in larvae and partially inhibited serine protease (SP), cathepsin (CAT), and lipase signaling pathways, thus disrupting larval development and reproduction as well as down-regulating the stress response. Moreover, these DEGs showed that A. vulgaris indirectly affected the development and reproduction of beetles by inducing the expression of genes encoding copper-zinc-superoxide dismutase (CuZnSOD), heme peroxidase (HPX), antioxidant enzymes, and transcription factors. Moreover, the majority of DEGs were mapped to the drug metabolism pathway in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Notably, the following genes were detected: 6 odorant binding proteins (OBPs), 5 chemosensory proteins (CSPs), 14 CYPs, 3 esterases (ESTs), 5 glutathione S-transferases (GSTs), 6 UDP-glucuronosyltransferases (UGTs), and 2 multidrug resistance proteins (MRPs), of which 8 CYPs, 2 ESTs, 2 GSTs, and 3 UGTs were up-regulated dramatically after exposure to A. vulgaris EO. The residual DEGs were significantly down-regulated in EO exposed larvae, implying that partial compensation of metabolism detoxification existed in treated beetles. Furthermore, A. vulgaris EO induced overexpression of OBP/CYP, and RNAi against these genes significantly increased mortality of larvae exposed to EO, providing further evidence for the involvement of OBP/CYP in EO metabolic detoxification in T. castaneum. Our results provide an overview of the transcriptomic changes in T. castaneum in response to A. vulgaris EO.

Gene expression studies and molecular characterization of a cathepsin L-like from the Asian citrus psyllid Diaphorina citri, vector of Huanglongbing

Huanglongbing (HLB) is a devastating citrus disease associated with Candidatus Liberibacter asiaticus (CLas) and is transmitted by the psyllid Diaphorina citri Kuwayama. Diaphorina citri belongs to Hemiptera order, which has cysteine peptidases as the most abundant proteolytic enzymes present in digestive tract. As cysteine peptidases are involved in different insect development processes, this class of enzymes has acquired biotechnological importance. In this context, we identified a cathepsin L-like (DCcathL1) from the Diaphorina citri transcriptome database and expressed the enzyme in E. coli. Quantitative real-time RT-PCR was conducted to determine DCcathL1 gene expression in different parts and developmental phases of the insect. We observed that DCcathL1 expression in the gut was 2.59 and 2.87-fold higher than in the head and carcass, respectively. Furthermore, DCcathL1 expression was greater in eggs than in nymphs and adults, suggesting a putative role of the enzyme in the embryonic development. In addition, enzymatic inhibitory activity using four recombinant Citrus cystatins were performed. Among them, CsinCPI-2 was the strongest DCcathL1 inhibitor with a Ki value of 0.005 nM. Our results may contribute in the development of strategies for D. citri control, such as silencing the DCcathL1 gene and the use of transgenic plants that overexpress peptidase inhibitors.

Levels of the endosymbiont Rickettsia in the whitefly Bemisia tabaci are influenced by the expression of vitellogenin

Bacterial endosymbionts play essential roles in the biology of their arthropod hosts by interacting with internal factors in the host. The whitefly Bemisia tabaci is a worldwide agricultural pest and a supervector for more than 100 plant viruses. Like many other arthropods, Be. tabaci harbours a primary endosymbiont, Porteira aleyrodidarum, and an array of secondary endosymbionts that coexist with Portiera inside bacteriocyte cells. Unlike all of the other secondary symbionts that infect Be. tabaci, Rickettsia has been shown to be an exception by infecting insect organs and not colocalizing with Portiera, and has been shown to significantly impact the insect biology and its interactions with the environment. Little is known about the molecular interactions that underlie insect-symbiont interactions in general, and particularly Be. tabaci-Rickettsia interactions. Here we performed transcriptomic analysis and identified vitellogenin as an important protein that influences the levels of Rickettsia in Be. tabaci. Vitellogenin expression levels were lower in whole insects, but higher in midguts of Rickettsia-infected insects. Immunocapture-PCR assay showed interaction between vitellogenin and Rickettsia, whereas silencing of vitellogenin resulted in nearly complete disappearance of Rickettsia from midguts. Altogether, these results suggest that vitellogenin plays an important role in influencing the levels of Rickettsia in Be. tabaci.

Transcriptome of Tetranychus urticae embryos reveals insights into Wolbachia-induced cytoplasmic incompatibility

The endosymbiont Wolbachia is known for manipulating host reproduction in selfish ways. However, the molecular mechanisms have not yet been investigated in embryos. Here, we found that Wolbachia had no effect on the number of deposited eggs in Tetranychus urticae Koch (Acari: Tetranychidae) but caused two types of reproductive manipulation: killing uninfected female embryos via cytoplasmic incompatibility (CI) and increasing the hatching ratio of infected female embryos. RNA sequencing analyses showed that 145 genes were differentially expressed between Wolbachia-infected (WI) and Wolbachia-uninfected (WU) embryos. Wolbachia infection down-regulated messenger RNA (mRNA) expression of glutathione S-transferase that could buffer oxidative stress. In addition, 1613 and 294 genes were identified as CI-specific up-/down-regulated genes. Compared to WU and WI embryos, embryos of CI cross strongly expressed genes involved in transcription, translation, tissue morphogenesis, DNA damage and mRNA surveillance. In contrast, most of the genes associated with energy production and metabolism were down-regulated in the CI embryos compared to the WU and WI embryos, which provides some clues as to the cause of death of CI embryos. These results identify several genes that could be candidates for explaining Wolbachia-induced CI. Our data form a basis to help elucidate the molecular consequences of CI in embryos.

The first characterization of a cystatin and a cathepsin L-like peptidase from Aedes aegypti and their possible role in DENV infection by the modulation of apoptosis

Recently, a salivary gland transcriptome study demonstrated that the transcripts of a putative cystatin gene (SeqID AAEL013287; Aacystatins) from Aedes aegypti were increased in DENV2-infected mosquitoes and that silencing of the Aacystatin gene resulted in an increase in DENV titres. In this work, Aacystatin was biochemically characterized; the purified recombinant inhibitor was able to inhibit typical cysteine proteases with a Ki in the nM range. Pulldown assays using Aag2 cell extracts identified a cathepsin L-like peptidase (AaCatL) as a possible target of Aacystatin. Purified recombinant AaCatL had an optimal pH of 5.0 and displayed a preference for Leu, Val and Phe residues at P2, which is common for other cathepsin L-like peptidases. Transcription analysis of Aacystatin and AaCatL in the salivary glands and midgut of DENV2-infected mosquitoes revealed a negative correlation between DENV2 titres and levels of the inhibitor and peptidase, suggesting their involvement in DENV2-mosquito interactions. Considering that apoptosis may play an important role during viral infections, the possible involvement of Aacystatin in staurosporine-induced apoptosis in Aag2 cells was investigated; the results showed higher expression of the inhibitor in treated cells; moreover, pre incubation with rAacystatin was able to increase Aag2 cell viability.

Fat body-specific vitellogenin expression regulates host-seeking behaviour in the mosquito Aedes albopictus

The high vector competence of mosquitoes is intrinsically linked to their reproductive strategy because females need a vertebrate blood meal to develop large batches of eggs. However, the molecular mechanisms and pathways regulating mosquito host-seeking behaviour are largely unknown. Here, we test whether host-seeking behaviour may be linked to the female's energy reserves, with low energy levels triggering the search for a nutrient-rich blood meal. Our results demonstrate that sugar feeding delays host-seeking behaviour in the invasive tiger mosquito Aedes albopictus, but the levels of energy reserves do not correlate with changes in host-seeking behaviour. Using tissue-specific gene expression analyses, we show for the first time, to our knowledge, that sugar feeding alone induces a transient up-regulation of several vitellogenesis-related genes in the female fat body, resembling the transcriptional response after a blood meal. Specifically, high expression levels of a vitellogenin gene (Vg-2) correlated with the lowest host-seeking activity of sugar-fed females. Knocking down the Vg-2 gene via RNA interference (RNAi) restored host-seeking behaviour in these females, firmly establishing that Vg-2 gene expression has a pivotal role in regulating host-seeking behaviour in young Ae. albopictus females. The identification of a molecular mechanism regulating host-seeking behaviour in mosquitoes could pave the way for novel vector control strategies aiming to reduce the biting activity of mosquitoes. From an evolutionary perspective, this is the first demonstration of vitellogenin genes controlling feeding-related behaviours in nonsocial insects, while vitellogenins are known to regulate caste-specific foraging and brood-care behaviours in eusocial insects. Hence, this work confirms the key role of vitellogenin in controlling feeding-related behaviours in distantly related insect orders, suggesting that this function could be more ubiquitous than previously thought.

Cathepsin L-a novel cysteine protease from Haemaphysalis flava Neumann, 1897

Ixodid ticks are ectoparasites responsible for the transmission of a large number of bacterial, viral, and protozoan pathogens to animals and humans. As long-term blood-pool feeders, the digestion of host blood is critical to their development as well as to the establishment of the sexual cycle of hemoparasites such as Babesia parasites, the agents of human and animal babesiosis. Previous studies have demonstrated that cysteine proteases are involved in blood digestion, embryogenesis, and pathogen transmission in other species of ticks, but their characteristics and functions are still unidentified in Haemaphysalis flava. Here, we describe the characterization of a cysteine protease HfCL from H. flava. We show that HfCL belongs to the L-like papain family of proteases, exhibits high expression in nymphs and adults, and localizes to both the midgut and salivary glands. Biochemical assays using purified recombinant enzyme reveal that rHfCL can hydrolyze the fluorogenic substrate Z-phe-Arg-MCA with optimal activity detected at pH 6. Furthermore, the short-term growth assay indicates that rHfCL can inhibit the intraerythrocytic development of Babesia microti and Babesia gibsoni in vitro.

Blood-induced differential gene expression in Anopheles dirus evaluated using RNA sequencing

Malaria parasites are transmitted through blood feeding by female Anopheline mosquitoes. Unveiling the blood-feeding process will improve understanding of vector biology. Anopheles dirus (Diptera: Culicidae) is one of the primary malaria vectors in the Greater Mekong Subregion, the epicentre of malaria drug resistance. In this study, differential gene expression between sugar- and blood-fed An. dirus was investigated by RNA sequencing (RNA-seq). A total of 589 transcripts were found to be upregulated and 703 transcripts downregulated as a result of blood feeding. Transcriptional differences were found in genes involved in blood digestion, peritrophic matrix formation, oogenesis and vitellogenesis. The expression levels of several genes were validated by quantitative reverse transcription polymerase chain reaction. The present results provide better understanding of An. dirus biology in relation to its blood feeding.

DmCatD, a cathepsin D-like peptidase of the hematophagous insect Dipetalogaster maxima (Hemiptera: Reduviidae): Purification, bioinformatic analyses and the significance of its interaction with lipophorin in the internalization by developing oocytes

DmCatD, a cathepsin D-like peptidase of the hematophagous insect Dipetalogaster maxima, is synthesized by the fat body and the ovary and functions as yolk protein precursor. Functionally, DmCatD is involved in vitellin proteolysis. In this work, we purified and sequenced DmCatD, performed bioinformatic analyses and investigated the events involved in its targeting and storage in developing oocytes. By ion exchange and gel filtration chromatography, DmCatD was purified from egg homogenates and its identity was confirmed by mass spectrometry. Approximately 73% of the full-length transcript was sequenced. The phylogeny indicated that DmCatD has features which suggest its distancing from "classical" cathepsins D. Bioinformatic analyses using a chimeric construct were employed to predict post-translational modifications. Structural modeling showed that DmCatD exhibited the expected folding for this type of enzyme, and an active site with conserved architecture. The interaction between DmCatD and lipophorin in the hemolymph was demonstrated by co-immunoprecipitation. Colocalization of both proteins in developing oocyte membranes and yolk bodies was detected by immunofluorescence. Docking assays favoring the interaction DmCatD-lipophorin were carried out after modeling lipophorin of a related triatomine species. Our results suggest that lipophorin acts as a carrier for DmCatD to facilitate its further internalization by the oocytes. The mechanisms involved in the uptake of peptidases within the oocytes of insects have not been reported. This is the first experimental work supporting the interaction between cathepsin D and lipophorin in an insect species, enabling us to propose a pathway for its targeting and storage in developing oocytes.

Cathepsin L-like protease can regulate the process of metamorphosis and fat body dissociation in Antheraea pernyi

Cathepsins are a group of protease, located in lysosome and play a vital role in physiological process. Here, we reported cathepsin L-like protease (Ap-cathL), which contained an open reading frame of 1155 bp and encoding 385 amino acid residues protein. The I29 inhibitor domain and peptidase C1A (clan CA of cysteine proteases, papain family C1 subfamily) putative conserved domains were detected in Ap-cathL. Quantitative real-time PCR (qRT-PCR) analysis revealed that Ap-cathL highly expressed in the fat body and midgut. The high expression during the molting stage, pupal stage and following 20E (20-hydroxyecdysone) treatment indicated that it maybe involved in the process of molting and metamorphosis. In addition, depletion of Ap-cathL influenced the expression of apoptosis pathway related genes. The protease inhibitor and RNA interference experiments showed that Ap-cathL was involved in the fat body dissociation of A. pernyi. These results suggest that Ap-cathL may involve in the process of metamorphosis and fat body dissociation of A. pernyi.

Active subsite properties, subsite residues and targeting to lysosomes or midgut lumen of cathepsins L from the beetle Tenebrio molitor

Cathepsins L are the major digestive peptidases in the beetle Tenebrio molitor. Two digestive cathepsins L (TmCAL2 and TmCAL3) from it had their 3D structures solved. The aim of this paper was to study in details TmCAL3 specificity and properties and relate them to its 3D structure. Recombinant TmCAL3 was assayed with 64 oligopeptides with different amino acid replacements in positions P2, P1, P1' and P2'. Results showed that TmCAL3 S2 specificity differs from the human enzyme and that its specificities also explain why on autoactivation two propeptide residues remain in the enzyme. Data on free energy of binding and of activation showed that S1 and S2' are mainly involved in substrate binding, S1' acts in substrate binding and catalysis, whereas S2 is implied mainly in catalysis. Enzyme subsite residues were identified by docking with the same oligopeptide used for kinetics. The subsite hydrophobicities were calculated from the efficiency of hydrolysis of different amino acid replacements in the peptide and from docking data. The results were closer for S1 and S2' than for S1' and S2, indicating that the residue subsites that were more involved in transition state binding are different from those binding the substrate seen in docking. Besides TmCAL1-3, there are nine other cathepsins L, most of them more expressed at midgut. They are supposed to be directed to lysosomes by a Drosophila-like Lerp receptor and/or motifs in their prodomains. The mannose 6-phosphate lysosomal sorting machinery is absent from T. molitor transcriptome. Cathepsin L direction to midgut contents seems to depend on overexpression.

Response to Blood Meal in the Fat Body of Anopheles stephensi Using Quantitative Proteomics: Toward New Vector Control Strategies Against Malaria

Malaria remains a grand challenge for disruptive innovation in global health therapeutics and diagnostics. Anopheles stephensi is one of the major vectors of malaria in Asia. Vector and transmission control are key focus areas in the fight against malaria, a field of postgenomics research where proteomics can play a substantive role. Moreover, to identify novel strategies to control the vector population, it is necessary to understand the vector life processes at a global and molecular scale. In this context, fat body is a vital organ required for vitellogenesis, vector immunity, vector physiology, and vector-parasite interaction. Given its central role in energy metabolism, vitellogenesis, and immune function, the proteome profile of the fat body and the impact of blood meal (BM) ingestion on the protein abundances of this vital organ have not been investigated so far. Therefore, using a proteomics approach, we identified the proteins expressed in the fat body of An. stephensi and their differential expression in response to BM ingestion. In all, we identified 3,218 proteins in the fat body using high-resolution mass spectrometry, of which 483 were found to be differentially expressed in response to the BM ingestion. Bioinformatics analysis of these proteins underscored their role in amino acid metabolism, vitellogenesis, lipid transport, signal peptide processing, mosquito immunity, and oxidation-reduction processes. Interestingly, we identified five novel genes, which were found to be differentially expressed upon BM ingestion. Proteins that exhibited altered expression in the present study are potential targets for vector control strategies and development of transmission blocking vaccines in the fight against malaria.

Vector competence and innate immune responses to dengue virus infection in selected laboratory and field-collected Stegomyia aegypti (= Aedes aegypti)

Control of dengue virus (DenV) transmission, primarily based on strategies to reduce populations of the principle vector Stegomya aegypti (= Aedes aegypti) (Diptera: Culicidae), is difficult to sustain over time. Other potential strategies aim to manipulate characteristics such as vector competence (VC), the innate capacity of the vector to transmit the virus. Previous studies have identified genetic factors, including differential expression of apoptosis-related genes, associated with the refractory and susceptible phenotypes in selected strains of S. aegypti from Cali, Colombia. The present study was designed to evaluate the variability of VC in selected strains against different DenV serotypes and to determine whether field-collected mosquitoes respond similarly to selected laboratory strains in terms of enhanced or reduced expression of apoptosis-related genes. Vector competence differed between strains, but did not differ in response to different DenV serotypes. Differences in VC were observed among mosquitoes collected from different localities in Cali. The overexpression of the pro-apoptosis genes, caspase 16 and Aedronc, was conserved in field-collected refractory mosquitoes and the selected laboratory refractory strain. The results suggest that the apoptosis response is conserved among all refractory mosquitoes to inhibit the development of all DenV serotypes.

Proteases of haematophagous arthropod vectors are involved in blood-feeding, yolk formation and immunity - a review

Ticks, triatomines, mosquitoes and sand flies comprise a large number of haematophagous arthropods considered vectors of human infectious diseases. While consuming blood to obtain the nutrients necessary to carry on life functions, these insects can transmit pathogenic microorganisms to the vertebrate host. Among the molecules related to the blood-feeding habit, proteases play an essential role. In this review, we provide a panorama of proteases from arthropod vectors involved in haematophagy, in digestion, in egg development and in immunity. As these molecules act in central biological processes, proteases from haematophagous vectors of infectious diseases may influence vector competence to transmit pathogens to their prey, and thus could be valuable targets for vectorial control.

Transgenic Expression of a Viral Cystatin Gene CpBV-CST1 in Tobacco Confers Insect Resistance

A viral gene, CpBV-CST1, was identified from a polydnavirus Cotesia plutellae bracovirus (CpBV). Its protein product was significantly toxic to lepidopteran insects. This study generated a transgenic tobacco plant expressing CpBV-CST1 Expression of transgene CpBV-CST1 was confirmed in T1 generation (second generation after transgenesis) in both mRNA and protein levels. Young larvae of Spodoptera exigua (Hübner) suffered high mortalities after feeding on transgenic tobacco. All 10 T1 transgenic tobacco plants had no significant variation in speed-to-kill. In order to further explore insect resistance of these transgenic tobaccos, bioassays were performed by assessing antixenosis and antibiosis. S. exigua larvae significantly avoided T1 plants in a choice test. Larvae fed with T1 plant exhibited significant decrease in protease activity in the midgut due to consuming CpBV-CST1 protein produced by the transgenic plant. Furthermore, the transgenic tobacco exhibited similar insect resistance to other tobacco-infesting insects, including a leaf-feeding insect, Helicoverpa assulta, and a sap-feeding insect, Myzus persicae These results demonstrate that a viral cystatin gene can be used to develop insect-resistant transgenic plant, suggesting a prospective possibility of expanding the current transgenic approach to high-valued crops.

Next Generation Sequencing Identifies Five Major Classes of Potentially Therapeutic Enzymes Secreted by Lucilia sericata Medical Maggots

Lucilia sericata larvae are used as an alternative treatment for recalcitrant and chronic wounds. Their excretions/secretions contain molecules that facilitate tissue debridement, disinfect, or accelerate wound healing and have therefore been recognized as a potential source of novel therapeutic compounds. Among the substances present in excretions/secretions various peptidase activities promoting the wound healing processes have been detected but the peptidases responsible for these activities remain mostly unidentified. To explore these enzymes we applied next generation sequencing to analyze the transcriptomes of different maggot tissues (salivary glands, gut, and crop) associated with the production of excretions/secretions and/or with digestion as well as the rest of the larval body. As a result we obtained more than 123.8 million paired-end reads, which were assembled de novo using Trinity and Oases assemblers, yielding 41,421 contigs with an N50 contig length of 2.22 kb and a total length of 67.79 Mb. BLASTp analysis against the MEROPS database identified 1729 contigs in 577 clusters encoding five peptidase classes (serine, cysteine, aspartic, threonine, and metallopeptidases), which were assigned to 26 clans, 48 families, and 185 peptidase species. The individual enzymes were differentially expressed among maggot tissues and included peptidase activities related to the therapeutic effects of maggot excretions/secretions.

Characterization of a Recombinant Cathepsin B-Like Cysteine Peptidase from Diaphorina citri Kuwayama (Hemiptera: Liviidae): A Putative Target for Control of Citrus Huanglongbing

Huanglonbing (HLB) is one of the most destructive disease affecting citrus plants. The causal agent is associated with the phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas) and the psyllid Diaphorina citri, vector of disease, that transmits the bacterium associated with HLB. The control of disease can be achieved by suppressing either the bacterium or the vector. Among the control strategies for HLB disease, one of the widely used consists in controlling the enzymes of the disease vector, Diaphorina citri. The insect Diaphorina citri belongs to the order Hemiptera, which frequently have cysteine peptidases in the gut. The importance of this class of enzymes led us to search for enzymes in the D. citri transcriptome for the establishment of alternatives strategies for HLB control. In this study, we reported the identification and characterization of a cathepsin B-like cysteine peptidase from D. citri (DCcathB). DCcathB was recombinantly expressed in Pichia pastoris, presenting a molecular mass of approximately 50 kDa. The enzyme hydrolyzed the fluorogenic substrate Z-F-R-AMC (Km = 23.5 μM) and the selective substrate for cathepsin B, Z-R-R-AMC (Km = 6.13 μM). The recombinant enzyme was inhibited by the cysteine protease inhibitors E64 (IC50 = 0.014 μM) and CaneCPI-4 (Ki = 0.05 nM) and by the selective cathepsin B inhibitor CA-074 (IC50 = 0.095 nM). RT-qPCR analysis revealed that the expression of the DCcathB in nymph and adult was approximately 9-fold greater than in egg. Moreover, the expression of this enzyme in the gut was 175-fold and 3333-fold higher than in the remaining tissues and in the head, respectively, suggesting that DCcathB can be a target for HLB control.

Cathepsin B Cysteine Proteinase is Essential for the Development and Pathogenesis of the Plant Parasitic Nematode Radopholus similis

Radopholus similis is an important plant parasitic nematode which severely harms many crops. Cathepsin B is present in a wide variety of organisms, and plays an important role in many parasites. Understanding cathepsin B of R. similis would allow us to find new targets and approaches for its control. In this study, we found that Rs-cb-1 mRNA was expressed in esophageal glands, intestines and gonads of females, testes of males, juveniles and eggs in R. similis. Rs-cb-1 expression was the highest in females, followed by juveniles and eggs, and was the lowest in males. The maximal enzyme activity of Rs-CB-1 was detected at pH 6.0 and 40 °C. Silencing of Rs-cb-1 using in vitro RNAi (Soaking with dsRNA in vitro) not only significantly inhibited the development and hatching of R. similis, but also greatly reduced its pathogenicity. Using in planta RNAi, we confirmed that Rs-cb-1 expression in nematodes were significantly suppressed and the resistance to R. similis was significantly improved in T2 generation transgenic tobacco plants expressing Rs-cb-1 dsRNA. The genetic effects of in planta RNAi-induced gene silencing could be maintained in the absence of dsRNA for at least two generations before being lost, which was not the case for the effects induced by in vitro RNAi. Overall, our results first indicate that Rs-cb-1 plays key roles in the development, hatching and pathogenesis of R. similis, and that in planta RNAi is an effective tool in studying gene function and genetic engineering of plant resistance to migratory plant parasitic nematodes.

The Role of DmCatD, a Cathepsin D-Like Peptidase, and Acid Phosphatase in the Process of Follicular Atresia in Dipetalogaster maxima (Hemiptera: Reduviidae), a Vector of Chagas' Disease

In this work, we have investigated the involvement of DmCatD, a cathepsin D-like peptidase, and acid phosphatase in the process of follicular atresia of Dipetalogaster maxima, a hematophagous insect vector of Chagas' disease. For the studies, fat bodies, ovaries and hemolymph were sampled from anautogenous females at representative days of the reproductive cycle: pre-vitellogenesis, vitellogenesis as well as early and late atresia. Real time PCR (qPCR) and western blot assays showed that DmCatD was expressed in fat bodies and ovaries at all reproductive stages, being the expression of its active form significantly higher at the atretic stages. In hemolymph samples, only the immunoreactive band compatible with pro-DmCatD was observed by western blot. Acid phosphatase activity in ovarian tissues significantly increased during follicular atresia in comparison to pre-vitellogenesis and vitellogenesis. A further enzyme characterization with inhibitors showed that the high levels of acid phosphatase activity in atretic ovaries corresponded mainly to a tyrosine phosphatase. Immunofluorescence assays demonstrated that DmCatD and tyrosine phosphatase were associated with yolk bodies in vitellogenic follicles, while in atretic stages they displayed a different cellular distribution. DmCatD and tyrosine phosphatase partially co-localized with vitellin. Moreover, their interaction was supported by FRET analysis. In vitro assays using homogenates of atretic ovaries as the enzyme source and enzyme inhibitors demonstrated that DmCatD, together with a tyrosine phosphatase, were necessary to promote the degradation of vitellin. Taken together, the results strongly suggested that both acid hydrolases play a central role in early vitellin proteolysis during the process of follicular atresia.

Expression Analysis of Cathepsin F during Embryogenesis and Early Developmental Stage in Olive Flounder (Paralichthys olivaceus)

Cathepsins are members of the multigene family of lysosomal cysteine proteinases and have regulated function in several life processes. The potential role of cathepsin F cysteine gene was expected as protease in the yolk processing mechanism during early developmental stage, but expression analysis was unknown after fertilization. The alignment analysis showed that amino acid sequence of cathepsin F from olive flounder liver expressed sequence tag (EST) homologous to cathepsin F of other known cathepsin F sequences with 87-98% identity. In this study, we examined the gene expression analysis of cathepsin F in various tissues at variety age flounder. Tissue distribution of the cathepsin F mRNA has been shown to be ubiquitous and constitutive pattern regardless of age in each group, although derived from cDNA library using liver sample. The mRNA level of cathepsin F more increased as developmental proceed during embryogenesis and early developmental stage, especially increased in the blastula, hatching stage and 3 days post hatching (dph). As a result, it may suggest that the proteolysis of yolk proteins (YPs) has been implicated as a mechanism for nutrient supply during early larval stages in olive flounder.

Cathepsin Gene Family Reveals Transcriptome Patterns Related to the Infective Stages of the Salmon Louse Caligus rogercresseyi

Cathepsins are proteases involved in the ability of parasites to overcome and/or modulate host defenses so as to complete their own lifecycle. However, the mechanisms underlying this ability of cathepsins are still poorly understood. One excellent model for identifying and exploring the molecular functions of cathepsins is the marine ectoparasitic copepod Caligus rogercresseyi that currently affects the Chilean salmon industry. Using high-throughput transcriptome sequencing, 56 cathepsin-like sequences were found distributed in five cysteine protease groups (B, F, L, Z, and S) as well as in an aspartic protease group (D). Ontogenic transcriptome analysis evidenced that L cathepsins were the most abundant during the lifecycle, while cathepsins B and K were mostly expressed in the larval stages and adult females, thus suggesting participation in the molting processes and embryonic development, respectively. Interestingly, a variety of cathepsins from groups Z, L, D, B, K, and S were upregulated in the infective stage of copepodid, corroborating the complexity of the processes involved in the parasitic success of this copepod. Putative functional roles of cathepsins were conjectured based on the differential expressions found and on roles previously described in other phylogenetically related species. Moreover, 140 single nucleotide polymorphisms (SNP) were identified in transcripts annotated for cysteine and aspartic proteases located into untranslated regions, or the coding region. This study reports for the first time the presence of cathepsin-like genes and differential expressions throughout a copepod lifecycle. The identification of cathepsins together with functional validations represents a valuable strategy for pinpointing target molecules that could be used in the development of new delousing drugs or vaccines against C. rogercresseyi.

Two cathepsins B are responsible for the yolk protein hydrolysis in Culex quinquefasciatus

Despite the established role of Culex quinquefasciatus as a vector of various neurotropic viruses, such as the Rift Valley and West Nile viruses, as well as lymphatic filariasis, little is known regarding the organism’s reproductive physiology. As in other oviparous animals, vitellogenin, the most important source of nutrients for the embryo development, is digested by intracellular proteases. Using mass spectrometry, we have identified two cathepsin B homologues partially purified by self-proteolysis of Cx. quinquefasciatus total egg extract. The transcriptional profile of these two cathepsin B homologues was determined by quantitative RT-PCR, and the enzymatic activity associated with the peptidase was determined in ovaries after female engorgement. According to the VectorBase (vectorbase.org) annotation, both cathepsin B homologues shared approximately 66% identity in their amino acid sequences. The two cathepsin B genes are expressed simultaneously in the fat body of the vitellogenic females, and enzymatic activity was detected within the ovaries, suggesting an extra-ovarian origin. Similar to the transcriptional profile of vitellogenin, cathepsin B transcripts were shown to accumulate post-blood meal and reached their highest expression at 36 h PBM. However, while vitellogenin expression decreased drastically at 48 h PBM, the expression of the cathepsins increased until 84 h PBM, at which time the females of our colony were ready for oviposition. The similarity between their transcriptional profiles strongly suggests a role for the cathepsin B homologues in vitellin degradation.

Four-way regulation of mosquito yolk protein precursor genes by juvenile hormone-, ecdysone-, nutrient-, and insulin-like peptide signaling pathways

Anautogenous mosquito females require a meal of vertebrate blood in order to initiate the production of yolk protein precursors by the fat body. Yolk protein precursor gene expression is tightly repressed in a state-of-arrest before blood meal-related signals activate it and expression levels rise rapidly. The best understood example of yolk protein precursor gene regulation is the vitellogenin-A gene (vg) of the yellow fever mosquito Aedes aegypti. Vg-A is regulated by (1) juvenile hormone signaling, (2) the ecdysone-signaling cascade, (3) the nutrient sensitive target-of-rapamycin signaling pathway, and (4) the insulin-like peptide (ILP) signaling pathway. A plethora of new studies have refined our understanding of the regulation of yolk protein precursor genes since the last review on this topic in 2005 (Attardo et al., 2005). This review summarizes the role of these four signaling pathways in the regulation of vg-A and focuses upon new findings regarding the interplay between them on an organismal level.

Core promoter regulates the expression of cathepsin B gene in the fat body of Bombyx mori

Bombyx mori cathepsin B (BmCatB) is involved in the programmed cell death of the fat body during B. mori metamorphosis. For a better understanding of the functional regulatory mechanism, the promoter region of BmCatB in the transcriptional regulation has been identified and analyzed in the present study. BmCatB promoter region performed by the 5' truncation or mutagenesis of EcREs was inserted in the pFA3Luc-A3RL double fluorescence expression vector to activate the fireflies luciferase (FLuc) gene. The results indicated that the dual-luciferase activity of BmCatB gene in the silkworm larval fat body is regulated by the length of promoter. Site-directed mutagenesis of EcRE experiment has shown that the EcREs are up-regulated significantly in the regulation of the BmCatB promoter. A 142bp region (-1165 to -1023) and EcREs are the mainly fat-body tissue-specificity related region and could function as a core promoter element.

Characterization of cysteine protease-like genes in the striped rice stem borer, Chilo suppressalis

The striped rice stem borer, Chilo suppressalis (Walker), is a major pest for rice production in China and the rest of Southeast Asia. Chemical control is the main means to alleviate losses due to this pest, which causes serious environmental pollution. An effective and environmentally friendly approach is needed for the management of the striped rice stem borer. Cysteine proteases in insects could be useful targets for pest management either through engineering plant protease inhibitors, targeting insect digestive cysteine proteases, or through RNA interference-based silencing of cysteine proteases, disrupting developmental regulation of insects. In this study, eight cysteine protease-like genes were identified and partially characterized. The genes CCO2 and CCL4 were exclusively expressed in the larval gut, and their expression was affected by the state of nutrition in the insect. The expression of CCL2, CCL3, and CCO1 was significantly affected by the type of host plant, suggesting a role in host plant – insect interactions. Our initial characterization of the striped rice stem borer cysteine protease-like genes provides a foundation for further research on this important group of genes in this major insect pest of rice.

Transcriptomic survey of the midgut of Anthonomus grandis (Coleoptera: Curculionidae)

Anthonomus grandis Boheman is a key pest in cotton crops in the New World. Its larval stage develops within the flower bud using it as food and as protection against its predators. This behavior limits the effectiveness of its control using conventional insecticide applications and biocontrol techniques. In spite of its importance, little is known about its genome sequence and, more important, its specific expression in key organs like the midgut. Total mRNA isolated from larval midguts was used for pyrosequencing. Sequence reads were assembled and annotated to generate a unigene data set. In total, 400,000 reads from A. grandis midgut with an average length of 237 bp were assembled and combined into 20,915 contigs. The assembled reads fell into 6,621 genes models. BlastX search using the NCBI-NR database showed that 3,006 unigenes had significant matches to known sequences. Gene Ontology (GO) mapping analysis evidenced that A. grandis is able to transcripts coding for proteins involved in catalytic processing of macromolecules that allows its adaptation to very different feeding source scenarios. Furthermore, transcripts encoding for proteins involved in detoxification mechanisms such as p450 genes, glutathione-S-transferase, and carboxylesterases are also expressed. This is the first report of a transcriptomic study in A. grandis and the largest set of sequence data reported for this species. These data are valuable resources to expand the knowledge of this insect group and could be used in the design of new control strategies based in molecular information.

Cathepsin B/X is secreted by Echinometra lucunter sea urchin spines, a structure rich in granular cells and toxins

Background

Echinometra lucunter is a common American sea urchin responsible for the majority of the marine accidents in Brazil. Although not lethal, these accidents are reported to be extremely painful. Recently, our group described the presence of toxins in its spines that contribute to the pathological reactions. Additionally, we have observed that the E. lucunter spines can regenerate when broken. In the present work we evaluated the enzymatic activities of sea urchin spine extracts in order to identify an enzyme that could contribute not only to the toxicity, but also participate in the spine growth and regeneration.

Results

The spine aqueous extract was tested for peptidase activity, with synthetic substrates, in the presence and absence of inhibitors and activators. For proper enzyme classification, the FRET-substrate cleavage pattern, pH-dependency activity and Western-blot analyses were performed. The spine extract was able to cleave Z-R-MCA and Abz-GIVRAK(Dnp)-OH following pre-incubation with DTT, and was inhibited by E-64. Furthermore, the double-peaked pH curve (5 and 7) and the cleavage site proportion (4:6, R↓A:A↓K) indicate the presence of both mono and dicarboxypeptidase activities. Moreover, in Western-blot analysis, the spine extract was positive for anti-cathepsin B antibody.

Conclusions

E. lucunter spines extracts presented a cysteine peptidase activity that was identified as cathepsin B/X that would participate in the remodeling and growth processes of the spine, as well as in the inflammatory response to the accident.