The accumulation of specific mRNAs following multiple blood meals in Anopheles gambiae

HM, Lee HF, Marshall JM, Dimopoulos G, James AA. Dual effector population modification gene-drive strains of the African malaria mosquitoes, Anopheles gambiae and Anopheles coluzzii

Proposed genetic approaches for reducing human malaria include population modification, which introduces genes into vector mosquitoes to reduce or prevent parasite transmission. We demonstrate the potential of Cas9/guide RNA (gRNA)-based gene-drive systems linked to dual antiparasite effector genes to spread rapidly through mosquito populations. Two strains have an autonomous gene-drive system coupled to dual anti-Plasmodium falciparum effector genes comprising single-chain variable fragment monoclonal antibodies targeting parasite ookinetes and sporozoites in the African malaria mosquitoes Anopheles gambiae (AgTP13) and Anopheles coluzzii (AcTP13). The gene-drive systems achieved full introduction within 3 to 6 mo after release in small cage trials. Life-table analyses revealed no fitness loads affecting AcTP13 gene-drive dynamics but AgTP13 males were less competitive than wild types. The effector molecules reduced significantly both parasite prevalence and infection intensities. These data supported transmission modeling of conceptual field releases in an island setting that shows meaningful epidemiological impacts at different sporozoite threshold levels (2.5 to 10 k) for human infection by reducing malaria incidence in optimal simulations by 50 to 90% within as few as 1 to 2 mo after a series of releases, and by ≥90% within 3 mo. Modeling outcomes for low sporozoite thresholds are sensitive to gene-drive system fitness loads, gametocytemia infection intensities during parasite challenges, and the formation of potentially drive-resistant genome target sites, extending the predicted times to achieve reduced incidence. TP13-based strains could be effective for malaria control strategies following validation of sporozoite transmission threshold numbers and testing field-derived parasite strains. These or similar strains are viable candidates for future field trials in a malaria-endemic region.

Vitellogenin genes are transcribed in Culex quinquefasciatus ovary

BACKGROUND

Culex quinquefasciatus, a cosmopolitan, domestic, and highly anthropophilic mosquito, is a vector of pathogenic arboviruses such as West Nile virus and Rift Valley virus, as well as lymphatic filariasis. The current knowledge on its reproductive physiology regarding vitellogenin expression in different tissues is still limited.

OBJECTIVES

In this study, we analysed the transcriptional profiles of vitellogenin genes in the fat body and ovaries of C. quinquefasciatus females during the first gonotrophic cycle.

METHODS

C. quinquefasciatus ovaries and/or fat bodies were dissected in different times during the first gonotrophic cycle and total RNA was extracted and used for reverse transcription polymerase chain reaction, quantitative real time-PCR, and in situ hybridisation.

FINDINGS

We confirmed the classical descriptions of the vitellogenic process in mosquitoes by verifying that vitellogenin genes are transcribed in the fat bodies of C. quinquefasciatus females. Using RNA in situ hybridisation approach, we showed that vitellogenin genes are also transcribed in developing ovaries, specifically by the follicle cells.

MAIN CONCLUSIONS

This is the first time that vitellogenin transcripts are observed in mosquito ovaries. Studies to determine if Vg transcripts are translated into proteins and their contribution to the reproductive success of the mosquito need to be further investigated.

Identification and transcriptional profile of Culex quinquefasciatus Say (Diptera: Culicidae) lipophorin in different stages

Lipophorin is a major hemolymph lipoprotein found in insects with a molecular native mass of 700 kDa. In mosquitoes, two different types of apolipoproteins are characterized, apolipophorin-I (ApoLp-I, ~250 kDa) and apolipophorin-II (ApoLp-II, ~80 kDa). This concentration depends on the stage of development and the age of the insects. Lipophorins are best studied in mosquitoes of the genus Aedes and Anopheles. In this study, we analyze the lipophorin sequence and show the lipophorin purification of the Culex quinquefasciatus and the transcriptional profile of the lipophorin gene in different life cycle stages. Similar amino acid composition and molecular weights are founded in three mosquitoes species lipophorins amino acid sequence. The two subunits of purified lipophorin (Apo I and Apo II) showed molecular masses of approximately 248 and 93 kDa, like that found in other mosquitoes. A gradual increase in the lipophorin expression gene was obtained during the previtellogenic period and after feeding we obtained peak expression at 24 h after feeding. With our results, we conclude that C. quinquefasciatus protein sequence has the same characteristics as those observed in other mosquitoes and that the expression of its apolipophorins is induced by blood feeding.

Molecular Characterization and Expression Analysis of the Sterol-carrier Protein-2 Fragment in Anopheles sacharovi Generations

Objective

It was aimed to characterize the sterol carrier protein-2 (SCP-2) gene in Anopheles sacharovi using molecular methods for the first time, and to reveal the expression levels of An. sacharovi in the developmental stages and female generation in different tissues such as salivary gland, midgut and adipose tissue.

Methods

The adult female An. sacharovi collected from the Sultan Sazlığı region and the development stages in the insectarium constituted the study material. cDNA isolation was performed following total RNA extraction from An. sacharovi strains. The 216 bp fragment of the SCP-2 gene was amplified with optimized primers in cDNA templates and was sequenced. Genetic characterization of the sequences was provided in silico analysis.

Results

Twelve of the SCP-2 nucleotide sequences of 14 isolates included in the sequence analysis were 100% identical and the SCP-2 sequences of the other two isolates that were homologous to each other showed a single nucleotide change at base 183. The 216 bp fragment of the SCP-2 gene region was found encoding the 72 amino acid chain. SCP-2 gene sequences clustered the isolates monophyletically on the basis of mosquito species and strains, and that Anopheles sacharovi isolates formed a subcluster together with Anopheles stephensi and Anopheles funestus within the Anopheles cluster in phylogenetic analysis. Because of q-polymerase chain reaction-mediated expression analysis, SCP-2 gene was expressed highest in adult males, followed by an adult female, ss L4, L3, L2, L1, and pupal stages, respectively. In adult female tissues, the SCP-2 gene was expressed the highest in the fat body, followed by the midgut and salivary glands, respectively.

Conclusion

SCP2, which is an important vaccine candidate or target drug site for Anopheles sacharovi with high vector potential, was firstly characterized in this study and the developmental stages and expression differences in the tissues of the mosquito were revealed.

Blood meal analysis of Anopheles vectors of simian malaria based on laboratory and field studies

Blood feeding and host-seeking behaviors of a mosquito play an imperative role in determining its vectorial capacity in transmitting pathogens. Unfortunately, limited information is available regarding blood feeding behavior of Anopheles species in Malaysia. Collection of resting Anopheles mosquitoes for blood meal analysis poses a great challenge especially for forest dwelling mosquitoes. Therefore, a laboratory-based study was conducted to evaluate the potential use of mosquitoes caught using human landing catch (HLC) for blood meal analysis, and subsequently to document blood feeding behavior of local Anopheles mosquitoes in Peninsular Malaysia. The laboratory-based experiment from this study revealed that mosquitoes caught using HLC had the potential to be used for blood meal analysis. Besides HLC, mosquitoes were also collected using manual aspirator and Mosquito Magnet. Overall, 47.4% of 321 field-caught Anopheles mosquitoes belonging to six species were positive for vertebrate host DNA in their blood meal. The most frequent blood meal source was human (45.9%) followed by wild boar (27.4%), dog (15.3%) and monkey (7.5%). Interestingly, only Anopheles cracens and Anopheles introlatus (Leucosphyrus Group) fed on monkey. This study further confirmed that members of the Leucosphyrus Group are the predominant vectors for knowlesi malaria transmission in Peninsular Malaysia mainly due to their simio-anthropophagic feeding behavior.

Lipid metabolism in insect disease vectors

More than a third of the world population is at constant risk of contracting some insect-transmitted disease, such as Dengue fever, Zika virus disease, malaria, Chagas' disease, African trypanosomiasis, and others. Independent of the life cycle of the pathogen causing the disease, the insect vector hematophagous habit is a common and crucial trait for the transmission of all these diseases. This lifestyle is unique, as hematophagous insects feed on blood, a diet that is rich in protein but relatively poor in lipids and carbohydrates, in huge amounts and low frequency. Another unique feature of these insects is that blood meal triggers essential metabolic processes, as molting and oogenesis and, in this way, regulates the expression of various genes that are involved in these events. In this paper, we review current knowledge of the physiology and biochemistry of lipid metabolism in insect disease vectors, comparing with classical models whenever possible. We address lipid digestion and absorption, hemolymphatic transport, and lipid storage by the fat body and ovary. In this context, both de novo fatty acid and triacylglycerol synthesis are discussed, including the related fatty acid activation process and the intracellular lipid binding proteins. As lipids are stored in order to be mobilized later on, e.g. for flight activity or survivorship, lipolysis and β-oxidation are also considered. All these events need to be finely regulated, and the role of hormones in this control is summarized. Finally, we also review information about infection, when vector insect physiology is affected, and there is a crosstalk between its immune system and lipid metabolism. There is not abundant information about lipid metabolism in vector insects, and significant current gaps in the field are indicated, as well as questions to be answered in the future.

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 the Anti-parasitic Factor TEP1 in the Malaria Mosquito Anopheles gambiae

Mosquitoes genetically engineered to be resistant to Plasmodium parasites represent a promising novel approach in the fight against malaria. The insect immune system itself is a source of anti-parasitic genes potentially exploitable for transgenic designs. The Anopheles gambiae thioester containing protein 1 (TEP1) is a potent anti-parasitic protein. TEP1 is secreted and circulates in the mosquito hemolymph, where its activated cleaved form binds and eliminates malaria parasites. Here we investigated whether TEP1 can be used to create malaria resistant mosquitoes. Using a GFP reporter transgene, we determined that the fat body is the main site of TEP1 expression. We generated transgenic mosquitoes that express TEP1r, a potent refractory allele of TEP1, in the fat body and examined the activity of the transgenic protein in wild-type or TEP1 mutant genetic backgrounds. Transgenic TEP1r rescued loss-of-function mutations, but did not increase parasite resistance in the presence of a wild-type susceptible allele. Consistent with previous reports, TEP1 protein expressed from the transgene in the fat body was taken up by hemocytes upon a challenge with injected bacteria. Furthermore, although maturation of transgenic TEP1 into the cleaved form was impaired in one of the TEP1 mutant lines, it was still sufficient to reduce parasite numbers and induce parasite melanization. We also report here the first use of Transcription Activator Like Effectors (TALEs) in Anopheles gambiae to stimulate expression of endogenous TEP1. We found that artificial elevation of TEP1 expression remains moderate in vivo and that enhancement of endogenous TEP1 expression did not result in increased resistance to Plasmodium. Taken together, our results reveal the difficulty of artificially influencing TEP1-mediated Plasmodium resistance, and contribute to further our understanding of the molecular mechanisms underlying mosquito resistance to Plasmodium parasites.

Unravelling the Evolution of the Allatostatin-Type A, KISS and Galanin Peptide-Receptor Gene Families in Bilaterians: Insights from Anopheles Mosquitoes

Allatostatin type A receptors (AST-ARs) are a group of G-protein coupled receptors activated by members of the FGL-amide (AST-A) peptide family that inhibit food intake and development in arthropods. Despite their physiological importance the evolution of the AST-A system is poorly described and relatively few receptors have been isolated and functionally characterised in insects. The present study provides a comprehensive analysis of the origin and comparative evolution of the AST-A system. To determine how evolution and feeding modified the function of AST-AR the duplicate receptors in Anopheles mosquitoes, were characterised. Phylogeny and gene synteny suggested that invertebrate AST-A receptors and peptide genes shared a common evolutionary origin with KISS/GAL receptors and ligands. AST-ARs and KISSR emerged from a common gene ancestor after the divergence of GALRs in the bilaterian genome. In arthropods, the AST-A system evolved through lineage-specific events and the maintenance of two receptors in the flies and mosquitoes (Diptera) was the result of a gene duplication event. Speciation of Anopheles mosquitoes affected receptor gene organisation and characterisation of AST-AR duplicates (GPRALS1 and 2) revealed that in common with other insects, the mosquito receptors were activated by insect AST-A peptides and the iCa²⁺-signalling pathway was stimulated. GPRALS1 and 2 were expressed mainly in mosquito midgut and ovaries and transcript abundance of both receptors was modified by feeding. A blood meal strongly up-regulated expression of both GPRALS in the midgut (p < 0.05) compared to glucose fed females. Based on the results we hypothesise that the AST-A system in insects shared a common origin with the vertebrate KISS system and may also share a common function as an integrator of metabolism and reproduction. Highlights: AST-A and KISS/GAL receptors and ligands shared common ancestry prior to the protostome-deuterostome divergence. Phylogeny and gene synteny revealed that AST-AR and KISSR emerged after GALR gene divergence. AST-AR genes were present in the hemichordates but were lost from the chordates. In protostomes, AST-ARs persisted and evolved through lineage-specific events and duplicated in the arthropod radiation. Diptera acquired and maintained functionally divergent duplicate AST-AR genes.

Cloning of a trypsin-like serine protease and expression patterns during Plasmodium falciparum invasion in the mosquito, Anopheles dirus (Peyton and Harrison)

Understanding specific gene regulation during responses to malaria infection is key to dissecting the mosquito defense mechanisms and host/parasite interactions. A full-length serine protease cDNA was isolated from the fat body of female Anopheles dirus, a major malaria vector in Thailand. The predicted amino acid sequence of SERF4 identifies it as a member of the serine protease family containing a single trypsin-like protease domain. Digestive trypsins function in the female mosquito midgut and are inducible in two phases in this tissue upon blood intake. However, the gene was highly upregulated in the midgut at day 3 postinfection by Plasmodium falciparum. In situ hybridization confirmed that SERF4 transcripts were located in the midgut epithelial cells rather than hemocytes or other tissues associated with the midgut. SERF4 was also strongly downregulated in the whole insects at day 16 after infection in comparison with the blood-fed control. Changes in the expression of the SERF4 gene in response to infection with this human malaria parasite suggest a role in parasite-specific innate immunity.

Development of the bi-partite Gal4-UAS system in the African malaria mosquito, Anopheles gambiae

Functional genetic analysis in Anopheles gambiae would be greatly improved by the development of a binary expression system, which would allow the more rapid and flexible characterisation of genes influencing disease transmission, including those involved in insecticide resistance, parasite interaction, host and mate seeking behaviour. The Gal4-UAS system, widely used in Drosophila melanogaster functional genetics, has been significantly modified to achieve robust application in several different species. Towards this end, previous work generated a series of modified Gal4 constructs that were up to 20 fold more active than the native gene in An. gambiae cells. To examine the Gal4-UAS system in vivo, transgenic An. gambiae driver lines carrying a modified Gal4 gene under the control of the carboxypeptidase promoter, and responder lines carrying UAS regulated luciferase and eYFP reporter genes have been created. Crossing of the Gal4 and UAS lines resulted in progeny that expressed both reporters in the expected midgut specific pattern. Although there was minor variation in reporter gene activity between the different crosses examined, the tissue specific expression pattern was consistent regardless of the genomic location of the transgene cassettes. The results show that the modified Gal4-UAS system can be used to successfully activate expression of transgenes in a robust and tissue specific manner in Anopheles gambiae. The midgut driver and dual reporter responder constructs are the first to be developed and tested successfully in transgenic An. gambiae and provide the basis for further advancement of the system in this and other insect species.

Cysteine proteases from bloodfeeding arthropod ectoparasites

Cysteine proteases have been discovered in various bloodfeeding ectoparasites. Here, we assemble the available information about the function of these peptidases and reveal their role in hematophagy and parasite development. While most of the data shed light on key proteolytic events that play a role in arthropod physiology, we also report on the association of cysteine proteases with arthropod vectorial capacity. With emphasis on ticks, specifically Ixodes ricinus, we finally propose a model about the contribution of cysteine peptidases to blood digestion and how their concerted action with other tick midgut proteases leads to the absorbance of nutrients by the midgut epithelial cells.

Genome-wide patterns of gene expression during aging in the African malaria vector Anopheles gambiae

The primary means of reducing malaria transmission is through reduction in longevity in days of the adult female stage of the Anopheles vector. However, assessing chronological age is limited to crude physiologic methods which categorize the females binomially as either very young (nulliparous) or not very young (parous). Yet the epidemiologically relevant reduction in life span falls within the latter category. Age-grading methods that delineate chronological age, using accurate molecular surrogates based upon gene expression profiles, will allow quantification of the longevity-reducing effects of vector control tools aimed at the adult, female mosquito. In this study, microarray analyses of gene expression profiles in the African malaria vector Anopheles gambiae were conducted during natural senescence of females in laboratory conditions. Results showed that detoxification-related and stress-responsive genes were up-regulated as mosquitoes aged. A total of 276 transcripts had age-dependent expression, independently of blood feeding and egg laying events. Expression of 112 (40.6%) of these transcripts increased or decreased monotonically with increasing chronologic age. Seven candidate genes for practical age assessment were tested by quantitative gene amplification in the An. gambiae G3 strain in a laboratory experiment and the Mbita strain in field enclosures set up in western Kenya under conditions closely resembling natural ones. Results were similar between experiments, indicating that senescence is marked by changes in gene expression and that chronological age can be gauged accurately and repeatedly with this method. These results indicate that the method may be suitable for accurate gauging of the age in days of field-caught, female An. gambiae.

Molecular analysis of photic inhibition of blood-feeding in Anopheles gambiae

Background

Anopheles gambiae mosquitoes exhibit an endophilic, nocturnal blood feeding behavior. Despite the importance of light as a regulator of malaria transmission, our knowledge on the molecular interactions between environmental cues, the circadian oscillators and the host seeking and feeding systems of the Anopheles mosquitoes is limited.

Results

In the present study, we show that the blood feeding behavior of mosquitoes is under circadian control and can be modulated by light pulses, both in a clock dependent and in an independent manner. Short light pulses (~2–5 min) in the dark phase can inhibit the blood-feeding propensity of mosquitoes momentarily in a clock independent manner, while longer durations of light stimulation (~1–2 h) can induce a phase advance in blood-feeding propensity in a clock dependent manner. The temporary feeding inhibition after short light pulses may reflect a masking effect of light, an unknown mechanism which is known to superimpose on the true circadian regulation. Nonetheless, the shorter light pulses resulted in the differential regulation of a variety of genes including those implicated in the circadian control, suggesting that light induced masking effects also involve clock components. Light pulses (both short and long) also regulated genes implicated in feeding as well as different physiological processes like metabolism, transport, immunity and protease digestions. RNAi-mediated gene silencing assays of the light pulse regulated circadian factors timeless, cryptochrome and three takeout homologues significantly up-regulated the mosquito's blood-feeding propensity. In contrast, gene silencing of light pulse regulated olfactory factors down-regulated the mosquito's propensity to feed on blood.

Conclusion

Our study show that the mosquito's feeding behavior is under circadian control. Long and short light pulses can induce inhibition of blood-feeding through circadian and unknown mechanisms, respectively, that involve the chemosensory system.

Anopheles gambiae males produce and transfer the vitellogenic steroid hormone 20-hydroxyecdysone to females during mating

In female insects, the steroid hormone 20-hydroxyecdysone (20E) plays a major role in activating vitellogenesis, a process required for egg development. By contrast with vertebrates, production of large amounts of hormonal steroids has not been reported in adult male insects. In the present study, we analyzed steroidogenesis in both male and female adult of the malaria mosquito Anopheles gambiae and we found that A. gambiae male mosquitoes produce high amounts of the steroid hormone 20E. Importantly, we found that male accessory glands, but not testes, are the source of 20E. Moreover, this steroid hormone is stored in male accessory glands and delivered to females during mating. These findings suggest that male 20E may not act as a true male sex steroid, but more likely as an allohormone. Our results give new insights into species-specific physiological processes that govern the reproductive success of the malaria mosquito. This could thus lead to the identification of new target genes for manipulating male and/or female reproductive success, a promising way to reduce or eliminate mosquito population and therefore to control malaria transmission.

Bloodmeal-induced differential gene expression in the disease vector Culex nigripalpus (Diptera: Culicidae)

We have characterized gene expression changes in the midgut tissue of Culex nigripalpus Theobold (Diptera: Culicidae) females, after they ingest a bloodmeal, by differential display of RNA isolated from pre- and postfeeding females. Seventy-two cDNA fragments exhibiting reproducible differences were observed. Of these, 22 showed an increase in gene expression and 50 showed a decrease in gene expression as a result of blood feeding. Eleven cDNA fragments exhibiting increased expression after a bloodmeal were cloned and sequenced. Seven of these were novel transcripts, and they did not match any sequences in GenBank. Three clones were similar to conserved proteins of unknown function from Aedes aegypti (L.) and Anopheles gambiae Giles. Here, we present the expression data on the first cDNA clones isolated from Cx. nigripalpus midgut tissue, including their molecular characterization, and we discuss their possible involvement in blood-feeding-associated processes and disease transmission.

GP35 ANOAL, an abundant acidic glycoprotein of female Anopheles albimanus saliva

Salivary glands of female mosquitoes produce proteins, not completely described yet, that participate in carbohydrate and blood feeding. Here, we report an acidic glycoprotein of 35 kDa (GP35 ANOAL) secreted in the saliva of the malaria vector mosquito Anopheles albimanus. GP35 ANOAL is produced exclusively in the distal lateral lobes of adult female salivary glands, it has a pI of 4.45 and is negatively stained by regular silver stain. An 888 bp cDNA clone encoding a predicted product of 240 amino acids has a signal peptide, potential post-translational modification sites, and a disintegrin signature RGD. The GP35 ANOAL sequence depicts high similarities with the 30 kDa saliva allergen of Aedes aegypti, 30 kDa allergen-like hypothetical proteins, and GE-rich proteins present in several Anopheles species, as well as in Ae. albopictus and Culex pipiens quinquefasciatus. The function of this protein family is still unknown.

Functional characterization of the promoter of the vitellogenin gene, AsVg1, of the malaria vector, Anopheles stephensi

Some genetic strategies for controlling transmission of mosquito-borne diseases call for the introgression of antipathogen effector genes into vector populations. Endogenous mosquito promoter and other cis-acting DNA sequences are needed to direct the expression of the effector molecules to maximize their efficacy. Vitellogenin (Vg)-encoding gene control sequences are candidates for driving tissue-, stage- and sex-specific expression of exogenous genes. One of the Anopheles stephensi Vg genes, AsVg1, was cloned and a full-length cDNA, as well as 850 base pairs adjacent to the 5'-end, were sequenced and characterized. Expression of AsVg1 is restricted to the fat body tissues of blood-fed females, and the amino acid sequence of the conceptual translation product is >85% identical to those of other anopheline Vgs. These characteristics support the conclusion that AsVg1 is a Vg-encoding gene. Functional analyses of the AsVg1 putative cis-regulatory sequences were performed using transgenic mosquitoes. The results showed that DNA fragments encompassing the 850 base pairs immediately adjacent to the 5'-end of the gene and the 3'-end untranslated region are sufficient to direct sex-, stage- and tissue-specific expression of a reporter gene. These data indicate that the AsVg1 promoter is a good candidate for controlling the expression of anti-pathogen effector molecules in this malaria vector mosquito.

Structure and expression of the lipophorin-encoding gene of the malaria vector, Anopheles gambiae

Lipophorin is the major hemolymph protein responsible for lipid transport among tissues of insects. This protein may be a lipid source for the development and reproduction of human malaria parasites in mosquitoes, and therefore could be a target to disrupt malaria parasite development in the vector. The lipophorin of Anopheles gambiae was purified by KBr gradient ultracentrifugation and showed variation in density from 1.111 to 1.143 g/ml during development. The amount and density of lipophorin increase in blood-fed females, indicating an adaptation of vitellogenic mosquitoes to an elevated rate of lipid transport to the developing eggs. The A. gambiae lipophorin gene is composed of eight exons and transcribes an mRNA that is 10,516 nucleotides in length. The predicted initial translation product is a preproapoliphorin consisting of 3332 amino acids, which is processed by proteolysis to generate two mature apolipophorins: apolipophorin-I (Mr = 280,000) and apolipophorin-II (Mr = 81,000). The gene is expressed in the fat body tissues throughout development. An elevated transcriptional activity of the lipophorin gene during vitellogenesis is consistent with the presence of putative cis-regulatory elements (GATA and ecdysone responsive elements) in its 3'-end flanking DNA sequence.

Genome-wide analysis of gene expression in adult Anopheles gambiae

With their genome sequenced, Anopheles gambiae mosquitoes now serve as a powerful tool for basic research in comparative, evolutionary and developmental biology. The knowledge generated by these studies is expected to reveal molecular targets for novel vector control and pathogen transmission blocking strategies. Comparisons of gene-expression profiles between adult male and nonblood-fed female Anopheles gambiae mosquitoes revealed that roughly 22% of the genes showed sex-dependent regulation. Blood-fed females switch the majority of their metabolism to blood digestion and egg formation within 3 h after the meal is ingested, in detriment to other activities such as flight and response to environment stimuli. Changes in gene expression are most evident during the first, second and third days after a blood meal, when as many as 50% of all genes showed significant variation in transcript accumulation. After laying the first cluster of eggs (between 72 and 96 h after the blood meal), mosquitoes return to a nongonotrophic stage, similar but not identical to that of 3-day-old nonblood-fed females. Ageing and/or the nutritional state of mosquitoes at 15 days after a blood meal is reflected by the down-regulation of approximately 5% of all genes. A full description of the large number of genes regulated at each analysed time point and each biochemical pathway or biological processes in which they are involved is not possible within the scope of this contribution. Therefore, we present descriptions of groups of genes displaying major differences in transcript accumulation during the adult mosquito life. However, a publicly available searchable database (http://www.angagepuci.bio.uci.edu/) has been made available so that detailed analyses of specific groups of genes based on their descriptions, functions or levels of gene expression variation can be performed by interested investigators according to their needs.

Starvation and diet composition affect mRNA levels of the high density-lipoprotein-β glucan binding protein in the shrimp Litopenaeus vannamei

A high density lipoprotein-beta glucan binding protein (HDL-BGBP) is synthesized in the hepatopancreas of the white shrimp Litopenaeus vannamei and secreted to the hemolymph. Recently, we reported the HDL-BGBP full length cDNA sequence and found that the predicted polypeptide is larger than the mature protein and also, that it contains a long 5'- and 3'-UTRs that may be involved in transcript level regulation. To test whether starvation and feeding may play a role in regulating HDL-BGBP mRNA levels, two different stimuli were evaluated: starvation and composition of diets. After 24 h, the steady state HDL-BGBP mRNA levels of starved shrimp decreased, suggesting that synthesis of the lipoprotein is less required in the absence of food. When shrimp were fed with diets containing different concentrations of protein and lipids, changes in HDL-BGBP mRNA levels were also detected. Shrimp fed the lower concentration of protein and lipid feed accumulated higher levels of HDL-BGBP mRNA. These results indicate that feeding influences HDL-BGBP transcript levels in the hepatopancreas.

Morphological and enzymatic analysis of the midgut of Anopheles darlingi during blood digestion

The midgut of adult female Anopheles darlingi is comprised of narrow anterior and dilated posterior regions, with a single layered epithelium composed by cuboidal digestive cells. Densely packed apical microvilli and an intricate basal labyrinth characterize each cell pole. Before blood feeding, apical cytoplasm contains numerous round granules and whorled profiles of rough endoplasmic reticulum. Engorgement causes a great distension of midgut. This provokes the flattening of digestive cells and their nuclei. Simultaneously, apical granules disappear, the whorls of endoplasmic reticulum disassemble and 3h post bloodmeal (PBM), nucleoli enlarge manyfold. An intense absorptive process takes place during the first 24 h PBM, with the formation of large glycogen inclusions, which persist after the end of the digestive process. Endoproteases activities are induced after bloodmeal and attain their maximum values between 10 and 36 h PBM. At least two different aminopeptidases seem to participate in the digestive process, with their maximum activity values at 36 and 48 h PBM, respectively. Coarse electrondense aggregates, possibly debris from digested erythrocytes, begin to appear on the luminal face of the peritrophic membrane from 18 h PBM and persist during all the digestive process, and are excreted at its end. We suggest that these aggregates could contain some kind of insoluble form of haem, in order of neutralize its toxicity.