An expression map for Anopheles gambiae

<p>Abstract</p> <p>Background</p> <p>Quantitative transcriptome data for the malaria-transmitting mosquito <it>Anopheles gambiae </it>covers a broad range of biological and experimental conditions, including development, blood feeding and infection. Web-based summaries of differential expression for individual genes with respect to these conditions are a useful tool for the biologist, but they lack the context that a visualisation of <it>all </it>genes with respect to <it>all </it>conditions would give. For most organisms, including <it>A. gambiae</it>, such a systems-level view of gene expression is not yet available.</p> <p>Results</p> <p>We have clustered microarray-based gene-averaged expression values, available from VectorBase, for 10194 genes over 93 experimental conditions using a self-organizing map. Map regions corresponding to known biological events, such as egg production, are revealed. Many individual gene clusters (nodes) on the map are highly enriched in biological and molecular functions, such as protein synthesis, protein degradation and DNA replication. Gene families, such as odorant binding proteins, can be classified into distinct functional groups based on their expression and evolutionary history. Immunity-related genes are non-randomly distributed in several distinct regions on the map, and are generally distant from genes with house-keeping roles. Each immunity-rich region appears to represent a distinct biological context for pathogen recognition and clearance (e.g. the humoral and gut epithelial responses). Several immunity gene families, such as peptidoglycan recognition proteins (PGRPs) and defensins, appear to be specialised for these distinct roles, while three genes with physically interacting protein products (LRIM1/APL1C/TEP1) are found in close proximity.</p> <p>Conclusions</p> <p>The map provides the first genome-scale, multi-experiment overview of gene expression in <it>A. gambiae </it>and should also be useful at the gene-level for investigating potential interactions. A web interface is available through the VectorBase website <url>http://www.vectorbase.org/</url>. It is regularly updated as new experimental data becomes available.</p

SNP Genotyping Defines Complex Gene-Flow Boundaries Among African Malaria Vector Mosquitoes

Mosquitoes in the Anopheles gambiae complex show rapid ecological and behavioral diversification, traits that promote malaria transmission and complicate vector control efforts. A high-density, genome-wide mosquito SNP-genotyping array allowed mapping of genomic differentiation between populations and species that exhibit varying levels of reproductive isolation. Regions near centromeres or within polymorphic inversions exhibited the greatest genetic divergence, but divergence was also observed elsewhere in the genomes. Signals of natural selection within populations were overrepresented among genomic regions that are differentiated between populations, implying that differentiation is often driven by population-specific selective events. Complex genomic differentiation among speciating vector mosquito populations implies that tools for genome-wide monitoring of population structure will prove useful for the advancement of malaria eradication

Proteomic analysis of the Plasmodium male gamete reveals the key role for glycolysis in flagellar motility.

BACKGROUND: Gametogenesis and fertilization play crucial roles in malaria transmission. While male gametes are thought to be amongst the simplest eukaryotic cells and are proven targets of transmission blocking immunity, little is known about their molecular organization. For example, the pathway of energy metabolism that power motility, a feature that facilitates gamete encounter and fertilization, is unknown. METHODS: Plasmodium berghei microgametes were purified and analysed by whole-cell proteomic analysis for the first time. Data are available via ProteomeXchange with identifier PXD001163. RESULTS: 615 proteins were recovered, they included all male gamete proteins described thus far. Amongst them were the 11 enzymes of the glycolytic pathway. The hexose transporter was localized to the gamete plasma membrane and it was shown that microgamete motility can be suppressed effectively by inhibitors of this transporter and of the glycolytic pathway. CONCLUSIONS: This study describes the first whole-cell proteomic analysis of the malaria male gamete. It identifies glycolysis as the likely exclusive source of energy for flagellar beat, and provides new insights in original features of Plasmodium flagellar organization

A major genetic locus controlling natural Plasmodium falciparum infection is shared by East and West African Anopheles gambiae

Background: Genetic linkage mapping identified a region of chromosome 2L in the Anopheles gambiae genome that exerts major control over natural infection by Plasmodium falciparum. This 2L Plasmodium-resistance interval was mapped in mosquitoes from a natural population in Mali, West Africa, and controls the numbers of P. falciparum oocysts that develop on the vector midgut. An important question is whether genetic variation with respect to Plasmodium-resistance exists across Africa, and if so whether the same or multiple geographically distinct resistance mechanisms are responsible for the trait. Methods: To identify P falciparum resistance loci in pedigrees generated and infected in Kenya, East Africa, 28 microsatellite loci were typed across the mosquito genome. Genetic linkage mapping was used to detect significant linkage between genotype and numbers of midgut oocysts surviving to 7–8 days post-infection. Results: A major malaria-control locus was identified on chromosome 2L in East African mosquitoes, in the same apparent position originally identified from the West African population. Presence of this resistance locus explains 75% of parasite free mosquitoes. The Kenyan resistance locus is named EA_Pfin1 (East Africa_ Plasmodium falciparum Infection Intensity). Conclusion: Detection of a malaria-control locus at the same chromosomal location in both East and West African mosquitoes indicates that, to the level of genetic resolution of the analysis, the same mechanism of Plasmodium-resistance, or a mechanism controlled by the same genomic region, is found across Africa, and thus probably operates in A. gambiae throughout its entire range

VectorBase: a data resource for invertebrate vector genomics

VectorBase (http://www.vectorbase.org) is an NIAID-funded Bioinformatic Resource Center focused on invertebrate vectors of human pathogens. VectorBase annotates and curates vector genomes providing a web accessible integrated resource for the research community. Currently, VectorBase contains genome information for three mosquito species: Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus, a body louse Pediculus humanus and a tick species Ixodes scapularis. Since our last report VectorBase has initiated a community annotation system, a microarray and gene expression repository and controlled vocabularies for anatomy and insecticide resistance. We have continued to develop both the software infrastructure and tools for interrogating the stored data

A chromosomal reference genome sequence for the malaria mosquito Anopheles gambiae, Giles, 1902, Ifakara strain

We present a genome assembly from an individual female Anopheles gambiae (the malaria mosquito; Arthropoda; Insecta; Diptera; Culicidae), Ifakara strain. The genome sequence is 264 megabases in span. Most of the assembly is scaffolded into three chromosomal pseudomolecules with the X sex chromosome assembled. The complete mitochondrial genome was also assembled and is 15.4 kilobases in length

Advancing vector biology research: a community survey for future directions, research applications and infrastructure requirements

Vector-borne pathogens impact public health, animal production, and animal welfare. Research on arthropod vectors such as mosquitoes, ticks, sandflies, and midges which transmit pathogens to humans and economically important animals is crucial for development of new control measures that target transmission by the vector. While insecticides are an important part of this arsenal, appearance of resistance mechanisms is increasingly common. Novel tools for genetic manipulation of vectors, use of Wolbachia endosymbiotic bacteria, and other biological control mechanisms to prevent pathogen transmission have led to promising new intervention strategies, adding to strong interest in vector biology and genetics as well as vector-pathogen interactions. Vector research is therefore at a crucial juncture, and strategic decisions on future research directions and research infrastructure investment should be informed by the research community. A survey initiated by the European Horizon 2020 INFRAVEC-2 consortium set out to canvass priorities in the vector biology research community and to determine key activities that are needed for researchers to efficiently study vectors, vector-pathogen interactions, as well as access the structures and services that allow such activities to be carried out. We summarize the most important findings of the survey which in particular reflect the priorities of researchers in European countries, and which will be of use to stakeholders that include researchers, government, and research organizations

Population biology of malaria within the mosquito: density-dependent processes and potential implications for transmission-blocking interventions

<p>Abstract</p> <p>Background</p> <p>The combined effects of multiple density-dependent, regulatory processes may have an important impact on the growth and stability of a population. In a malaria model system, it has been shown that the progression of <it>Plasmodium berghei </it>through <it>Anopheles stephensi </it>and the survival of the mosquito both depend non-linearly on parasite density. These processes regulating the development of the malaria parasite within the mosquito may influence the success of transmission-blocking interventions (TBIs) currently under development.</p> <p>Methods</p> <p>An individual-based stochastic mathematical model is used to investigate the combined impact of these multiple regulatory processes and examine how TBIs, which target different parasite life-stages within the mosquito, may influence overall parasite transmission.</p> <p>Results</p> <p>The best parasite molecular targets will vary between different epidemiological settings. Interventions that reduce ookinete density beneath a threshold level are likely to have auxiliary benefits, as transmission would be further reduced by density-dependent processes that restrict sporogonic development at low parasite densities. TBIs which reduce parasite density but fail to clear the parasite could cause a modest increase in transmission by increasing the number of infectious bites made by a mosquito during its lifetime whilst failing to sufficiently reduce its infectivity. Interventions with a higher variance in efficacy will therefore tend to cause a greater reduction in overall transmission than a TBI with a more uniform effectiveness. Care should be taken when interpreting these results as parasite intensity values in natural parasite-vector combinations of human malaria are likely to be significantly lower than those in this model system.</p> <p>Conclusions</p> <p>A greater understanding of the development of the malaria parasite within the mosquito is required to fully evaluate the impact of TBIs. If parasite-induced vector mortality influenced the population dynamics of <it>Plasmodium </it>species infecting humans in malaria endemic regions, it would be important to quantify the variability and duration of TBI efficacy to ensure that community benefits of control measures are not overestimated.</p

Anopheles Imd Pathway Factors and Effectors in Infection Intensity-Dependent Anti-Plasmodium Action

The Anopheles gambiae immune response against Plasmodium falciparum, an etiological agent of human malaria, has been identified as a source of potential anti-Plasmodium genes and mechanisms to be exploited in efforts to control the malaria transmission cycle. One such mechanism is the Imd pathway, a conserved immune signaling pathway that has potent anti-P. falciparum activity. Silencing the expression of caspar, a negative regulator of the Imd pathway, or over-expressing rel2, an Imd pathway-controlled NFkappaB transcription factor, confers a resistant phenotype on A. gambiae mosquitoes that involves an array of immune effector genes. However, unexplored features of this powerful mechanism that may be essential for the implementation of a malaria control strategy still remain. Using RNA interference to singly or dually silence caspar and other components of the Imd pathway, we have identified genes participating in the anti-Plasmodium signaling module regulated by Caspar, each of which represents a potential target to achieve over-activation of the pathway. We also determined that the Imd pathway is most potent against the parasite's ookinete stage, yet also has reasonable activity against early oocysts and lesser activity against late oocysts. We further demonstrated that caspar silencing alone is sufficient to induce a robust anti-P. falciparum response even in the relative absence of resident gut microbiota. Finally, we established the relevance of the Imd pathway components and regulated effectors TEP1, APL1, and LRIM1 in parasite infection intensity-dependent defense, thereby shedding light on the relevance of laboratory versus natural infection intensity models. Our results highlight the physiological considerations that are integral to a thoughtful implementation of Imd pathway manipulation in A. gambiae as part of an effort to limit the malaria transmission cycle, and they reveal a variety of previously unrecognized nuances in the Imd-directed immune response against P. falciparum

Targeting the X Chromosome during Spermatogenesis Induces Y Chromosome Transmission Ratio Distortion and Early Dominant Embryo Lethality in Anopheles gambiae

We have exploited the high selectivity of the homing endonuclease I-PpoI for the X-linked Anopheles gambiae 28S ribosomal genes to selectively target X chromosome carrying spermatozoa. Our data demonstrated that in heterozygous males, the expression of I-PpoI in the testes induced a strong bias toward Y chromosome–carrying spermatozoa. Notably, these male mosquitoes also induced complete early dominant embryo lethality in crosses with wild-type females. Morphological and molecular data indicated that all spermatozoa, irrespectively of the inheritance of the transgene, carried a substantial amount of I-PpoI protein that could attack the maternally inherited chromosome X of the embryo. Besides the obvious implications for implementing vector control measures, our data demonstrated the feasibility of generating synthetic sex distorters and revealed the intriguing possibility of manipulating maternally inherited genes using wild-type sperm cells carrying engineered endonucleases