Genome sequence of Aedes aegypti, a major arbovirus vector

Identification of odorant-binding proteins of the yellow fever mosquito Aedes aegypti: genome annotation and comparative analyses

The yellow fever mosquito Aedes aegypti is an important human health pest which vectors yellow fever and dengue viruses. Olfaction plays a crucial role in its attraction to hosts and although the molecular basis of this is not well understood it is likely that odorant-binding proteins (OBPs) are involved in the first step of molecular recognition. Based on the OBPs of Drosophila melanogaster and Anopheles gambiae we have defined sequence motifs based on OBP conserved cysteine and developed an algorithm which has allowed us to identify 66 genes encoding putative OBPs from the genome sequence and expressed sequence tags (ESTs) of Ae. aegypti. We have also identified 11 new OBP genes for An. gambiae. We have examined all of the corresponding peptide sequences for the properties of OBPs. The predicted molecular weights fall within the expected range but the predicted isoeletric points are spread over a wider range than found previously. Comparative analyses of the 66 OBP sequences of Ae. aegypti with other dipteran species reveal some mosquito-specific genes as well as conserved homologues. The genomic organisation of Ae. aegypti OBPs suggests that a rapid expansion of OBPs has occurred, probably by gene duplication. The analyses of OBP-containing regions for microsynteny indicate a very high synteny between Ae. aegypti and An. gambiae.

Aedes aegypti uses RNA interference in defense against Sindbis virus infection

Background

RNA interference (RNAi) is an important anti-viral defense mechanism. The Aedes aegypti genome encodes RNAi component orthologs, however, most populations of this mosquito are readily infected by, and subsequently transmit flaviviruses and alphaviruses. The goal of this study was to use Ae. aegypti as a model system to determine how the mosquito's anti-viral RNAi pathway interacts with recombinant Sindbis virus (SINV; family Togaviridae, genus Alphavirus).

Results

SINV (TR339-eGFP) (+) strand RNA, infectious virus titers and infection rates transiently increased in mosquitoes following dsRNA injection to cognate Ago2, Dcr2, or TSN mRNAs. Detection of SINV RNA-derived small RNAs at 2 and 7 days post-infection in non-silenced mosquitoes provided important confirmation of RNAi pathway activity. Two different recombinant SINV viruses (MRE16-eGFP and TR339-eGFP) with significant differences in infection kinetics were used to delineate vector/virus interactions in the midgut. We show virus-dependent effects on RNAi component transcript and protein levels during infection. Monitoring midgut Ago2, Dcr2, and TSN transcript levels during infection revealed that only TSN transcripts were significantly increased in midguts over blood-fed controls. Ago2 protein levels were depleted immediately following a non-infectious bloodmeal and varied during SINV infection in a virus-dependent manner.

Conclusion

We show that silencing RNAi components in Ae. aegypti results in transient increases in SINV replication. Furthermore, Ae. aegypti RNAi is active during SINV infection as indicated by production of virus-specific siRNAs. Lastly, the RNAi response varies in a virus-dependent manner. These data define important features of RNAi anti-viral defense in Ae. aegypti.

The molecular evolution of four anti-malarial immune genes in the Anopheles gambiae species complex

Background

If the insect innate immune system is to be used as a potential blocking step in transmission of malaria, then it will require targeting one or a few genes with highest relevance and ease of manipulation. The problem is to identify and manipulate those of most importance to malaria infection without the risk of decreasing the mosquito's ability to stave off infections by microbes in general. Molecular evolution methodologies and concepts can help identify such genes. Within the setting of a comparative molecular population genetic and phylogenetic framework, involving six species of the Anopheles gambiae complex, we investigated whether a set of four pre-selected immunity genes (gambicin, NOS, Rel2 and FBN9) might have evolved under selection pressure imposed by the malaria parasite.

Results

We document varying levels of polymorphism within and divergence between the species, in all four genes. Introgression and the sharing of ancestral polymorphisms, two processes that have been documented in the past, were verified in this study in all four studied genes. These processes appear to affect each gene in different ways and to different degrees. However, there is no evidence of positive selection acting on these genes.

Conclusion

Considering the results presented here in concert with previous studies, genes that interact directly with the Plasmodium parasite, and play little or no role in defense against other microbes, are probably the most likely candidates for a specific adaptive response against P. falciparum. Furthermore, since it is hard to establish direct evidence linking the adaptation of any candidate gene to P. falciparum infection, a comparative framework allowing at least an indirect link should be provided. Such a framework could be achieved, if a similar approach like the one involved here, was applied to all other anopheline complexes that transmit P. falciparum malaria.

Cross-kingdom patterns of alternative splicing and splice recognition

BACKGROUND

Variations in transcript splicing can reveal how eukaryotes recognize intronic splice sites. Retained introns (RIs) commonly appear when the intron definition (ID) mechanism of splice site recognition inconsistently identifies intron-exon boundaries, and cassette exons (CEs) are often caused by variable recognition of splice junctions by the exon definition (ED) mechanism. We have performed a comprehensive survey of alternative splicing across 42 eukaryotes to gain insight into how spliceosomal introns are recognized.

RESULTS

All eukaryotes we studied exhibit RIs, which appear more frequently than previously thought. CEs are also present in all kingdoms and most of the organisms in our analysis. We observe that the ratio of CEs to RIs varies substantially among kingdoms, while the ratio of competing 3' acceptor and competing 5' donor sites remains nearly constant. In addition, we find the ratio of CEs to RIs in each organism correlates with the length of its introns. In all 14 fungi we examined, as well as in most of the 9 protists, RIs far outnumber CEs. This differs from the trend seen in 13 multicellular animals, where CEs occur much more frequently than RIs. The six plants we analyzed exhibit intermediate proportions of CEs and RIs.

CONCLUSION

Our results suggest that most extant eukaryotes are capable of recognizing splice sites via both ID and ED, although ED is most common in multicellular animals and ID predominates in fungi and most protists.

Cloning and identification of an oxytocin/vasopressin-like receptor and its ligand from insects

More than 20 years ago, an oxytocin/vasopressin-like peptide, CLITNCPRGamide, was isolated from the locust, Locusta migratoria [Proux JP, et al. (1987) Identification of an arginine vasopressin-like diuretic hormone from Locusta migratoria. Biochem Biophys Res Commun 149:180-186]. However, no similar peptide could be identified in other insects, nor could its prohormone be cloned, or its physiological actions be established. Here, we report that the recently sequenced genome from the red flour beetle Tribolium castaneum contains a gene coding for an oxytocin/vasopressin-like peptide, identical to the locust peptide, which we named inotocin (for insect oxytocin/vasopressin-like peptide) and a gene coding for an inotocin G protein-coupled receptor (GPCR). We cloned the Tribolium inotocin preprohormone and the inotocin GPCR and expressed the GPCR in CHO cells. This GPCR is strongly activated by low concentrations of inotocin (EC(50), 5 x 10(-9) M), demonstrating that it is the inotocin receptor. Quantitative RT-PCR (qPCR) showed that in adult Tribolium, the receptor is mainly expressed in the head and much less in the hindgut and Malpighian tubules, suggesting that the inotocin/receptor couple does not play a role in water homeostasis. Surprisingly, qPCR also showed that the receptor is 30x more expressed in the first larval stages than in adult animals. The inotocin/receptor couple can also be found in the recently sequenced genome from the parasitic wasp Nasonia vitripennis but not in any other holometabolous insect with a completely sequenced genome (12 Drosophila species, the malaria mosquito Anopheles gambiae, the yellow fever mosquito Aedes aegypti, the silk worm Bombyx mori, and the honey bee Apis mellifera), suggesting that this neuropeptide system is confined to basal holometabolous insects. Furthermore, we identified an oxytocin/vasopressin-like peptide and receptor in the recently sequenced genome from the water flea Daphnia pulex (Crustacea). To our knowledge, this is the first report on the molecular cloning of an oxytocin/vasopressin-like receptor and its ligand from arthropods.

Annotation and expression profiling of apoptosis-related genes in the yellow fever mosquito, Aedes aegypti

Apoptosis has been extensively studied in Drosophila by both biochemical and genetic approaches, but there is a lack of knowledge about the mechanisms of apoptosis regulation in other insects. In mosquitoes, apoptosis occurs during Plasmodium and arbovirus infection in the midgut, suggesting that apoptosis plays a role in mosquito innate immunity. We searched the Aedes aegypti genome for apoptosis-related genes using Drosophila and Anopheles gambiae protein sequences as queries. In this study we have identified eleven caspases, three inhibitor of apoptosis (IAP) proteins, a previously unreported IAP antagonist, and orthologs of Drosophila Ark, Dnr1, and BG4 (also called dFadd). While most of these genes have been previously annotated, we have improved the annotation of several of them, and we also report the discovery of four previously unannotated apoptosis-related genes. We examined the developmental expression profile of these genes in Ae. aegypti larvae, pupae and adults, and we also studied the function of a novel IAP antagonist, IMP. Expression of IMP in mosquito cells caused apoptosis, indicating that it is a functional pro-death protein. Further characterization of these genes will help elucidate the molecular mechanisms of apoptosis regulation in Ae. aegypti.

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.

Comparative genomic analysis of the arthropod muscle myosin heavy chain genes allows ancestral gene reconstruction and reveals a new type of 'partially' processed pseudogene

BACKGROUND

Alternative splicing of mutually exclusive exons is an important mechanism for increasing protein diversity in eukaryotes. The insect Mhc (myosin heavy chain) gene produces all different muscle myosins as a result of alternative splicing in contrast to most other organisms of the Metazoa lineage, that have a family of muscle genes with each gene coding for a protein specialized for a functional niche.

RESULTS

The muscle myosin heavy chain genes of 22 species of the Arthropoda ranging from the waterflea to wasp and Drosophila have been annotated. The analysis of the gene structures allowed the reconstruction of an ancient muscle myosin heavy chain gene and showed that during evolution of the arthropods introns have mainly been lost in these genes although intron gain might have happened in a few cases. Surprisingly, the genome of Aedes aegypti contains another and that of Culex pipiens quinquefasciatus two further muscle myosin heavy chain genes, called Mhc3 and Mhc4, that contain only one variant of the corresponding alternative exons of the Mhc1 gene. Mhc3 transcription in Aedes aegypti is documented by EST data. Mhc3 and Mhc4 inserted in the Aedes and Culex genomes either by gene duplication followed by the loss of all but one variant of the alternative exons, or by incorporation of a transcript of which all other variants have been spliced out retaining the exon-intron structure. The second and more likely possibility represents a new type of a 'partially' processed pseudogene.

CONCLUSION

Based on the comparative genomic analysis of the alternatively spliced arthropod muscle myosin heavy chain genes we propose that the splicing process operates sequentially on the transcript. The process consists of the splicing of the mutually exclusive exons until one exon out of the cluster remains while retaining surrounding intronic sequence. In a second step splicing of introns takes place. A related mechanism could be responsible for the splicing of other genes containing mutually exclusive exons.

Anatomical ontologies of mosquitoes and ticks, and their web browsers in VectorBase

VectorBase, an integrated, relational database that manages genomic and other genetic/biological data pertaining to arthropod vectors of disease, has recently embarked on the construction of ontologies and controlled vocabularies (CVs). It aims, thus, at providing all necessary tools for the complete annotation of vector genomes and, in particular, the annotation of functional genomic data. This task was initiated with the development of anatomical ontologies of mosquitoes and ticks, both of which were made compliant to CARO, the common anatomy reference ontology. The ontologies are complemented by the development of novel web-based browsers that can show figures for anatomical terms, something that is especially helpful for fully illustrating the controlled vocabularies of anatomy.

The Aedes aegypti genome: a comparative perspective

The sequencing of the second mosquito genome, Aedes aegypti, in addition to Anopheles gambiae, is a major milestone that will drive molecular-level and genome-wide high-throughput studies of not only these but also other mosquito vectors of human pathogens. Here we overview the ancestry of the mosquito genes, list the major expansions of gene families that may relate to species adaptation processes, as exemplified by CYP9 cytochrome P450 genes, and discuss the conservation of chromosomal gene arrangements among the two mosquitoes and fruit fly. Many more invertebrate genomes are expected to be sequenced in the near future, including additional vectors of human pathogens (see http://www.vectorbase.org), and further comparative analyses will become increasingly refined and informative, hopefully improving our understanding of the genetic basis of phenotypical differences among these species, their vectorial capacity, and ultimately leading to the development of novel disease control strategies.

Identity and transfer of male reproductive gland proteins of the dengue vector mosquito, Aedes aegypti: potential tools for control of female feeding and reproduction

Male reproductive gland proteins (mRGPs) impact the physiology and/or behavior of mated females in a broad range of organisms. We sought to identify mRGPs of the yellow fever mosquito, Aedes aegypti, the primary vector of dengue and yellow fever viruses. Earlier studies with Ae. aegypti demonstrated that "matrone" (a partially purified male reproductive accessory gland substance) or male accessory gland fluid injected into virgin female Ae. aegypti affect female sexual refractoriness, blood feeding and digestion, flight, ovarian development, and oviposition. Using bioinformatic comparisons to Drosophila melanogaster accessory gland proteins and mass spectrometry of proteins from Ae. aegypti male accessory glands and ejaculatory ducts (AG/ED) and female reproductive tracts, we identified 63 new putative Ae. aegypti mRGPs. Twenty-one of these proteins were found in the reproductive tract of mated females but not of virgin females suggesting that they are transferred from males to females during mating. Most of the putative mRGPs fall into the same protein classes as mRGPs in other organisms, although some appear to be evolving rapidly and lack identifiable homologs in Culex pipiens, Anopheles gambiae, and D. melanogaster. Our results identify candidate male-derived molecules that may have an important influence on behavior, survival, and reproduction of female mosquitoes.

Automated eukaryotic gene structure annotation using EVidenceModeler and the Program to Assemble Spliced Alignments

EVidenceModeler (EVM) is presented as an automated eukaryotic gene structure annotation tool that reports eukaryotic gene structures as a weighted consensus of all available evidence. EVM, when combined with the Program to Assemble Spliced Alignments (PASA), yields a comprehensive, configurable annotation system that predicts protein-coding genes and alternatively spliced isoforms. Our experiments on both rice and human genome sequences demonstrate that EVM produces automated gene structure annotation approaching the quality of manual curation.

Genomic resources for invertebrate vectors of human pathogens, and the role of VectorBase

High-throughput genome sequencing techniques have now reached vector biology with an emphasis on those species that are vectors of human pathogens. The first mosquito to be sequenced was Anopheles gambiae, the vector for Plasmodium parasites that cause malaria. Further mosquitoes have followed: Aedes aegypti (yellow fever and dengue fever vector) and Culex pipiens (lymphatic filariasis and West Nile fever). Species that are currently in sequencing include the body louse Pediculus humanus (Typhus vector), the triatomine Rhodnius prolixus (Chagas disease vector) and the tick Ixodes scapularis (Lyme disease vector). The motivations for sequencing vector genomes are to further understand vector biology, with an eye on developing new control strategies (for example novel chemical attractants or repellents) or understanding the limitations of current strategies (for example the mechanism of insecticide resistance); to analyse the mechanisms driving their evolution; and to perform an exhaustive analysis of the gene repertory. The proliferation of genomic data creates the need for efficient and accessible storage. We present VectorBase, a genomic resource centre that is both involved in the annotation of vector genomes and act as a portal for access to the genomic information (http://www.vectorbase.org).

Gene expression studies in mosquitoes

Research on gene expression in mosquitoes is motivated by both basic and applied interests. Studies of genes involved in hematophagy, reproduction, olfaction, and immune responses reveal an exquisite confluence of biological adaptations that result in these highly-successful life forms. The requirement of female mosquitoes for a bloodmeal for propagation has been exploited by a wide diversity of viral, protozoan and metazoan pathogens as part of their life cycles. Identifying genes involved in host-seeking, blood feeding and digestion, reproduction, insecticide resistance and susceptibility/refractoriness to pathogen development is expected to provide the bases for the development of novel methods to control mosquito-borne diseases. Advances in mosquito transgenesis technologies, the availability of whole genome sequence information, mass sequencing and analyses of transcriptomes and RNAi techniques will assist development of these tools as well as deepen the understanding of the underlying genetic components for biological phenomena characteristic of these insect species.

Genomic analysis of detoxification genes in the mosquito Aedes aegypti

Annotation of the recently determined genome sequence of the major dengue vector, Aedes aegypti, reveals an abundance of detoxification genes. Here, we report the presence of 235 members of the cytochrome P450, glutathione transferase and carboxy/cholinesterase families in Ae. aegypti. This gene count represents an increase of 58% and 36% compared with the fruitfly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, respectively. The expansion is not uniform within the gene families. Secure orthologs can be found across the insect species for enzymes that have presumed or proven biosynthetic or housekeeping roles. In contrast, subsets of these gene families that are associated with general xenobiotic detoxification, in particular the CYP6, CYP9 and alpha esterase families, have expanded in Ae. aegypti. In order to identify detoxification genes associated with resistance to insecticides we constructed an array containing unique oligonucleotide probes for these genes and compared their expression level in insecticide resistant and susceptible strains. Several candidate genes were identified with the majority belonging to two gene families, the CYP9 P450s and the Epsilon GSTs. This 'Ae. aegypti Detox Chip' will facilitate the implementation of insecticide resistance management strategies for arboviral control programmes.

How functional genomics and genetics complements insect endocrinology

Insects are the most abundant animal group on Earth and have been the subject of genetic and physiological studies since the beginning of the 19th century. The public interest in understanding their biology increased as many insects have proven to exert a severe impact on human welfare and the environment. To trigger insect physiological and endocrinological research, the genome of several economical and ecological important insect species was recently sequenced. Following the availability of these genomic data many so called 'post-genomic' technologies have been developed to characterise gene function and to unravel signalling pathways underlying biological processes. For some species genomic research is further complemented with mutagenesis and reverse genetic studies. In the following, we present an overview of genomic and functional genetic methodologies that boosted endocrine research in insects.

A genome-wide inventory of neurohormone GPCRs in the red flour beetle Tribolium castaneum

Insect neurohormones (biogenic amines, neuropeptides, and protein hormones) and their G protein-coupled receptors (GPCRs) play a central role in the control of behavior, reproduction, development, feeding and many other physiological processes. The recent completion of several insect genome projects has enabled us to obtain a complete inventory of neurohormone GPCRs in these insects and, by a comparative genomics approach, to analyze the evolution of these proteins. The red flour beetle Tribolium castaneum is the latest addition to the list of insects with a sequenced genome and the first coleopteran (beetle) to be sequenced. Coleoptera is the largest insect order and about 30% of all animal species living on earth are coleopterans. Some coleopterans are severe agricultural pests, which is also true for T. castaneum, a global pest for stored grain and other dried commodities for human consumption. In addition, T. castaneum is a model for insect development. Here, we have investigated the presence of neurohormone GPCRs in Tribolium and compared them with those from the fruit fly Drosophila melanogaster (Diptera) and the honey bee Apis mellifera (Hymenoptera). We found 20 biogenic amine GPCRs in Tribolium (21 in Drosophila; 19 in the honey bee), 48 neuropeptide GPCRs (45 in Drosophila; 35 in the honey bee), and 4 protein hormone GPCRs (4 in Drosophila; 2 in the honey bee). Furthermore, we identified the likely ligands for 45 of these 72 Tribolium GPCRs. A highly interesting finding in Tribolium was the occurrence of a vasopressin GPCR and a vasopressin peptide. So far, the vasopressin/GPCR couple has not been detected in any other insect with a sequenced genome (D. melanogaster and six other Drosophila species, Anopheles gambiae, Aedes aegypti, Bombyx mori, and A. mellifera). Tribolium lives in very dry environments. Vasopressin in mammals is the major neurohormone steering water reabsorption in the kidneys. Its presence in Tribolium, therefore, might be related to the animal's need to effectively control water reabsorption. Other striking differences between Tribolium and the other two insects are the absence of the allatostatin-A, kinin, and corazonin neuropeptide/receptor couples and the duplications of other hormonal systems. Our survey of 340 million years of insect neurohormone GPCR evolution shows that neuropeptide/receptor couples can easily duplicate or disappear during insect evolution. It also shows that Drosophila is not a good representative of all insects, because several of the hormonal systems that we now find in Tribolium do not exist in Drosophila.

Construction and characterization of an expressed sequenced tag library for the mosquito vector Armigeres subalbatus

Background

The mosquito, Armigeres subalbatus, mounts a distinctively robust innate immune response when infected with the nematode Brugia malayi, a causative agent of lymphatic filariasis. In order to mine the transcriptome for new insight into the cascade of events that takes place in response to infection in this mosquito, 6 cDNA libraries were generated from tissues of adult female mosquitoes subjected to immune-response activation treatments that lead to well-characterized responses, and from aging, naïve mosquitoes. Expressed sequence tags (ESTs) from each library were produced, annotated, and subjected to comparative analyses.

Results

Six libraries were constructed and used to generate 44,940 expressed sequence tags, of which 38,079 passed quality filters to be included in the annotation project and subsequent analyses. All of these sequences were collapsed into clusters resulting in 8,020 unique sequence clusters or singletons. EST clusters were annotated and curated manually within ASAP (A Systematic Annotation Package for Community Analysis of Genomes) web portal according to BLAST results from comparisons to Genbank, and the Anopheles gambiae and Drosophila melanogaster genome projects.

Conclusion

The resulting dataset is the first of its kind for this mosquito vector and provides a basis for future studies of mosquito vectors regarding the cascade of events that occurs in response to infection, and thereby providing insight into vector competence and innate immunity.

Investigations of dengue-2 susceptibility and body size among Aedes aegypti populations

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary global vector for dengue virus (DENV), yet considerable genetic variation exists among populations in terms of its competence to vector DENV. Variability in adult body size has also been observed among various mosquito populations and several studies have reported a relationship between body size and arbovirus dissemination, although most of these relied on artificially derived variation in body size. Here we examine the relationship between body size and disseminated DENV infection among 10 Ae. aegypti populations reared under optimum laboratory conditions. Body size variability was inferred from wing length measurements and DENV competence was evaluated as the proportion of individuals with disseminated infections following exposure to the dengue-2 JAM1409 strain. There were significant differences in mean wing lengths among populations (anova, F(9,22)= 7.10, P < 0.0001), ranging from 2.16 mm (Bangkok population) to 2.79 mm (MOYO-S [susceptible] population). We also observed significant differences among some populations in mean DENV infection rates (Waller-Duncan K-ratio t-test), ranging from 19.54% (MOYO-R [refractory] population) to 56.60% (MOYO-S population). However, we did not observe evidence for significant interactions between body size and DENV dissemination. We suggest that either the two traits are genetically independent or that our ability to detect interactions between them was limited by their respective inheritances as quantitative traits.

Molecular cloning and characterization of the complete acetylcholinesterase gene (Ace1) from the mosquito Aedes aegypti with implications for comparative genome analysis

Insensitive acetylcholinesterase (AChE) has been shown to be responsible for resistance to organophosphates and carbamates in a number of arthropod species. Some arthropod genomes contain a single Ace gene, while others including mosquitoes contain two genes, but only one confers insecticide resistance. Here we report the isolation of the full-length cDNA and characterization of the complete genomic DNA sequence for the Ace1 gene in the yellow fever mosquito, Aedes aegypti. The Ace1 homolog in other mosquito species has been associated with insecticide resistance. The full-length cDNA consists of 2721bp and contains a 2109bp open reading frame that encodes a 702 amino acid protein. The amino acid sequence is highly conserved with that of other mosquitoes, including greater than 90% identity with Culex spp. and about 80% identity with Anopheles gambiae. The genomic DNA sequence includes 138,970bp and consists of eight exons with seven introns ranging from 59 to 114,350bp. Exons 2 and 8 show reduced amino acid conservation across mosquito species, while exons 3-7 are highly conserved. The Ace1 introns in Ae. aegypti reflect a high frequency of repetitive sequences that comprise about 45% of the total intron sequence. The Ace1 locus maps to the p-arm of chromosome 3, which corresponds to the orthologous genome regions in Culex spp. and An. gambiae.

Evolutionary dynamics of immune-related genes and pathways in disease-vector mosquitoes

Mosquitoes are vectors of parasitic and viral diseases of immense importance for public health. The acquisition of the genome sequence of the yellow fever and Dengue vector, Aedes aegypti (Aa), has enabled a comparative phylogenomic analysis of the insect immune repertoire: in Aa, the malaria vector Anopheles gambiae (Ag), and the fruit fly Drosophila melanogaster (Dm). Analysis of immune signaling pathways and response modules reveals both conservative and rapidly evolving features associated with different functional gene categories and particular aspects of immune reactions. These dynamics reflect in part continuous readjustment between accommodation and rejection of pathogens and suggest how innate immunity may have evolved.

nanos gene control DNA mediates developmentally regulated transposition in the yellow fever mosquito Aedes aegypti

Transposable elements (TEs) are proposed as a basis for developing drive systems to spread pathogen resistance genes through vector mosquito populations. The use of transcriptional and translational control DNA elements from genes expressed specifically in the insect germ line to mediate transposition offers possibilities for mitigating some of the concerns about transgene behavior in the target vector species and eliminating effects on nontarget organisms. Here, we describe the successful use of the promoter and untranslated regions from the nanos (nos) orthologous gene of the yellow fever mosquito, Aedes aegypti, to control sex- and tissue-specific expression of exogenously derived mariner MosI transposase-encoding DNA. Transgenic mosquitoes expressed transposase mRNA in abundance near or equal to the endogenous nos transcript and exclusively in the female germ cells. In addition, MosI mRNA was deposited in developing oocytes and localized and maintained at the posterior pole during early embryonic development. Importantly, four of five transgenic lines examined were capable of mobilizing a second MosI transgene into the mosquito genome, indicating that functional transposase was being produced. Thus, the nos control sequences show promise as part of a TE-based gene drive system.