Aedes aegypti ferritin.

Diseases transmitted by hematophagous (blood-feeding) insects are responsible for millions of human deaths worldwide. In hematophagous insects, the blood meal is important for regulating egg maturation. Although a high concentration of iron is toxic for most organisms, hematophagous insects seem unaffected by the iron load in a blood meal. One means by which hematophagous insects handle this iron load is, perhaps, by the expression of iron-binding proteins, specifically the iron storage protein ferritin. In vertebrates, ferritin is an oligomer composed of two types of subunits called heavy and light chains, and is part of the constitutive antioxidant response. Previously, we found that the insect midgut, a main site of iron load, is also a primary site of ferritin expression and that, in the yellow fever mosquito, Aedes aegypti, the expression of the ferritin heavy-chain homologue (HCH) is induced following blood feeding. We now show that the expression of the Aedes ferritin light-chain homologue (LCH) is also induced with blood-feeding, and that the genes of the LCH and HCH are tightly clustered. mRNA levels for both LCH- and HCH-genes increase with iron, H2O2 and hemin treatment, and the temporal expression of the genes is very similar. These results confirm that ferritin could serve as the cytotoxic protector in mosquitoes against the oxidative challenge of the bloodmeal. Finally, although the Aedes LCH has no iron responsive element (IRE) at its 5'-untranslated region (UTR), the 5'-UTR contains several introns that are alternatively spliced, and this alternative splicing event is different from any ferritin message seen to date.     

Comparison of the insecticide susceptibilities of laboratory strains of Aedes aegypti and Aedes albopictus

A susceptible strain of Aedes albopictus derived from the Gainesville strain (Florida, USA) was established in our laboratory. The larvicidal efficacies of the neurotoxic insecticides temephos, permethrin and the pure cis and trans-permethrin isomers and the microbial insecticide Bacillus thuringiensis israelensis (Bti) against Ae. albopictus were estimated and compared to a susceptible strain of Aedes aegypti. The larvicidal effect of insect growth regulator pyriproxyfen was also evaluated in both mosquito strains. The median lethal concentration/median emergency inhibition values for Ae. aegypti and Ae. albopictus, respectively, were: temephos, 3.058 and 6.632 ppb, permethrin, 3.143 and 4.933 ppb, cis-permethrin, 4.457 and 10.068 ppb, trans-permethrin, 1.510 and 3.883 ppb, Bti, 0.655 and 0.880 ppb and pyriproxyfen, 0.00774 and 0.01642 ppb. Ae. albopictus was more tolerant than Ae. aegypti to all six larvicides evaluated. The order of susceptibility for Ae. aegypti was pyriproxyfen > Bti > trans-permethrin > temephos > permethrin > cis-permethrin and for Ae. albopictus was pyriproxyfen > Bti > trans-permethrin > permethrin > temephos > cis-permethrin. Because both species can be found together in common urban, suburban and rural breeding sites, the results of this work provide baseline data on the susceptibility of Ae. albopictus to insecticides commonly used for controlling Ae. aegypti in the field.     

Trisomy in Aedes aegypti.

A trisomic (2n=6+1) pupa of the yellow fever mosquito Aedes aegypti has been found. The trisomy involved chromosome 3 which is intermediate in size between 1 and 2. The extra chromosome formed a univalent or a trivalent during meiosis.     

Aedes aegypti genomics

The mosquito, Aedes aegypti, is the primary, worldwide arthropod vector for the yellow fever and dengue viruses. As it is also one of the most tractable mosquito species for laboratory studies, it has been and remains one of the most intensively studied arthropod species. This has resulted in the development of detailed genetic and physical maps for Ae. aegypti and considerable insight into its genome organization. The research community is well-advanced in developing important molecular tools that will facilitate a whole genome sequencing effort. This includes generation of BAC clone end sequences, physical mapping of selected BAC clones and generation of EST sequences. Whole genome sequence information for Ae. aegypti will provide important insight into mosquito chromosome evolution and allow for the identification of genes and gene function. These functions may be common to all mosquitoes or perhaps unique to individual species, possibly specific to host-seeking and blood-feeding behaviors, as well as the innate immune response to pathogens encountered during blood-feeding. This information will be invaluable to the global effort to develop novel strategies for preventing arthropod-borne disease transmission.     

Identification and linkage relationships of three hexokinase genes in Aedes aegypti

Four regions of hexokinase activity are detected by starch gel electrophoresis of adult Aedes aegypti. Three of the regions, Hk-2, Hk-3, and Hk-4, are produced by three tightly linked loci, located on the third chromosome 7.25 map units from the locus fuzzy. The three loci show developmental differences as well as differences in substrate specificity.This work was supported by grants from the National Institutes of Health, AI 05118-02 and AI 12016.     

Isolation and identification of three RFamide-immunoreactive peptides from the mosquito Aedes aegypti

Three RFamide-immunoreactive peptides were isolated from headless Aedes aegypti mosquitoes. Their structures were identified by Edman degradation or a combination of amino acid composition analysis and mass spectrometry to be: Aedes head peptide 1 [23], [Pro4]-Aedes head peptide (i.e., pGlu-Arg-Pro-Pro-Ser-Leu-Lys-Thr- Arg-Phe-amide), and Leu-Lys-Thr-Arg-Phe-amide which have been named Aedes head peptides 3 and 4, respectively.     

The mosquito Aedes aegypti (L.): evidence for three new proteinases

The effect of inhibitors was studied on the proteolytic activity of crude extracts of the mosquito Aedes aegypti (L.), prepared 25 h after blood intake. This activity is only partially inhibited by the lima bean trypsin inhibitor (LBTI) or by EDTA. Experiments with mixed inhibitors are used to indicate that, apart from the well characterized trypsin-like enzymes, at least three other proteinases are present. These are an LBTI-resistant serine proteinase, a metal chelator-sensitive proteinase, and a proteinase which can only be inhibited by the ovomucoid inhibitor. These newly described proteinases are inactive against several model substrates developed for mammalian enzymes. They are partially separable by ion-exchange chromatography.     

Toxicity of Bacillus thuringiensis toward Aedes aegypti larvae.

Among six strains of Bacillus thuringiensis and five other species of Bacillus, only two strains of B. thuringiensis, strains HD-1 and BA-068, were toxic to Aedes aegypti larvae within 24 hr. The LC₅₀s were 5.6 × 10⁴ and 2.4 × 10⁵ spores/ml for strains HD-1 and BA-068, respectively. The toxic factor(s) was heat sensitive and γ ray resistant and preliminary evidences indicated that it was associated with the crystalline body of B. thuringiensis.     

Innate immune response of Aedes aegypti

Insects are able to protect themselves from invasion by pathogens by a rapid and potent arsenal of inducible immune peptides. This fast, extremely effective response is part of the innate immunity exhibited by all insects and many invertebrates, and shows striking similarities with the innate immune response of vertebrates. In Aedes aegypti invasion of the hemocoel by bacteria elicits the production of defensins, cecropins, a peptide active only against Gram-negative bacteria, and several other peptides that we are now characterizing. However, not all insects utilize the same peptides in the same concentrations, which may reflect the pathogens to which they may have been exposed through evolutionary time. These protective measures we see in mosquitoes are the current state of the evolution of a rapid immune response that has contributed to the success of insects in inhabiting essentially every niche on earth. The molecules involved in the response of Aedes aegypti to pathogens, and the potential role of these peptides against eukaryotic parasites ingested and transmitted by mosquitoes are discussed.     

The Aedes aegypti genome: complexity and organization.

We describe the use of DNA reassociation kinetics to determine the total genome size and complexity together with the individual complexity and copy number of the single copy, middle repetitive and highly repeated DNA fractions of cell line and larval DNA from the mosquito, Aedes aegypti. The genome of Ae. aegypti is both large and complex, being one third the size of the human genome, and exhibits a short period interspersed repeat pattern. The implications of patterns of sequence arrangement and genome complexities for experiments aimed at isolating specific classes of DNA sequences, such as mobile genetic elements, are discussed.     

Palp-antenna, a homeotic mutant in Aedes aegypti.

Palp-antenna is a homeotic mutant of Aedes aegypti that modifies the apex of the maxillary palps of both sexes into a variable number of antenna-like segments. The fine structure of the antenna, including sexual dimorphism, is apparent in the mutant palps. Palp-antenna is a sex-linked recessive. a linkage distance of 27.9 +/- 0.45 crossover units from sex is estimated from F2 and backcross data. Penetrance is complete; expressively is variable. The fitness of the mutant compares favorably with that of the wild type. The mapping of the ppa locus lengthens the known chromosome 1 linkage map of Aedes aegypti.     

Screening of Brazilian Bacillus sphaericus strains for high toxicity against Culex quinquefasciatus and Aedes aegypti

Abstract:  In this work, 246 Bacillus sphaericus strains were evaluated against Aedes aegypti and Culex quinquefasciatus larvae to select the most effective ones to be used as the basis of a national product. All strains were isolated from different regions of Brazil and they are stored in a Bacillus spp. collection at Embrapa Genetic Resources and Biotechnology. The selected strains were characterized by biochemical and molecular methods. Based on selective bioassays, 87 strains were identified as toxic to one or both target species. All of these strains contain genes that encode the 42, 51 kDa proteins that constitute the binary toxin and the 100 kDa Mtx1 toxin. All toxic strains presented a very high LC₅₀ against A. aegypti , so, a product based on any of these B. sphaericus strains would not be recommended for use in programmes to control A. aegypti . S201 had highest activity against C. quinquefasciatus , presenting the lowest LC₅₀ and LC₉₀ in bioassays.     

Aedes aegypti midgut remodeling during metamorphosis

The Aedes aegypti midgut is restructured during metamorphosis; its epithelium is renewed by replacing the digestive and endocrine cells through stem or regenerative cell differentiation. Shortly after pupation (white pupae) begins, the larval digestive cells are histolized and show signs of degeneration, such as autophagic vacuoles and disintegrating microvilli. Simultaneously, differentiating cells derived from larval stem cells form an electron-dense layer that is visible 24 h after pupation begins. Forty-eight hours after pupation onset, the differentiating cells yield an electron-lucent cytoplasm rich in microvilli and organelles. Dividing stem cells were observed in the fourth instar larvae and during the first 24 h of pupation, which suggests that stem cells proliferate at the end of the larval period and during pupation. This study discusses various aspects of the changes during midgut remodeling for pupating A. aegypti.     

Pathology of mosquito iridescent virus of Aedes taeniorhynchus in cell cultures of Aedes aegypti.

An electron microscopical study was conducted on the pathology of the mosquito iridescent virus (MIV) of Aedes taeniorhynchus in monolayer cultures of Aedes aegypti cells. The sequence of events in the pathology, from the initiation of attachment through maturation and release, is presented.MIV attaches to cells and is taken up by the process of viropexis (phagocytosis) within 15 min after inoculation. Intact virions are released into the cytoplasm at 30–60 min by disruption of the phagocytic vesicles. Discrete foci of replication (viroplasm) develop in the cytoplasm within 1 day after infection. Progeny virus is assembled in the viroplasm within 2 days after infection and later appears at the cell surface, where it acquires an envelope from the plasma membrane upon budding from the cell. Virus does not accumulate to form aggregates in the cytoplasm; instead, it buds from the cell after assembly.     

Midgut bacterial dynamics in Aedes aegypti

In vector mosquitoes, the presence of midgut bacteria may affect the ability to transmit pathogens. We have used a laboratory colony of Aedes aegypti as a model for bacterial interspecies competition and show that after a blood meal, the number of species (culturable on Luria-Bertani agar) that coexist in the midgut is low and that about 40% of the females do not harbor any cultivable bacteria. We isolated species belonging to the genera Bacillus, Elizabethkingia, Enterococcus, Klebsiella, Pantoea, Serratia, and Sphingomonas, and we also determined their growth rates, antibiotic resistance, and ex vivo inhibition of each other. To investigate the possible existence of coadaptation between midgut bacteria and their host, we fed Ae.?aegypti cohorts with gut bacteria from human, a frog, and two mosquito species and followed the bacterial population growth over time. The dynamics of the different species suggests coadaptation between host and bacteria, and interestingly, we found that Pantoea stewartii isolated from Ae.?aegypti survive better in Ae.?aegypti as compared to P.?stewartii isolated from the malaria mosquito Anopheles gambiae.