ABSTRACT. The composition and the seasonality of the natural populations of Drosophila species in relation to the climatic variables temperature and rainfall were analyzed from September 1998 through October 1999 by monthly collections, in two woodlands in the Northwest of the State of São Paulo, Brazil. The diversity dominance component curves were inclined, reflecting low diversity and high dominance of few species. Among the 25 species recorded, Drosophila sturtevanti Duda, 1927 was the most frequent and abundant. On the opposite to data in literature, D. paranaensis Barros, 1950 abundance and frequency were greater than those from D. mercatorum Patterson & Wheeler, 1942. A positive correlation between abundance and rainfall was observed for D. nebulosa Sturtevant, 1916. These data are indicative of changes in the populations structure due to new adaptive strategies arised in response to environmental modifications. Populations are entities in a state of change. Even when the community and the ecosystem appear not to change, the density, mortality, survival, age distribution, growth rate and other attributes of the component populations generally fluctuate, as species adjust constantly to the seasons, physical forces and to each other. Consequently, it is much more revealing to discover in what way and how quickly a given population is changing than what its size and composition may be at a certain moment (ODUM, 1988). KEYWORDS.In the natural world, it is important to distinguish between seasonal changes in the size of a population, largely controlled by seasonal adaptations linked to environmental factors, and annual fluctuations. Annual fluctuations may be considered in two categories: those controlled principally by annual differences in extrinsic factors such as temperature and rainfall, which are beyond the sphere of population interactions, and intrinsic factors, oscillations controlled principally by population dynamics, like biotic factors, such as the availability of food or energy. In many cases, year-on-year changes in abundance appear to be clearly correlated to variation in one or more of the principle extrinsic limiting factors, but some species maintain such a regular relative abundance, apparently irrespective of obvious environmental factors, that the term "cycles" appears to be appropriate. Species that have such a regular variation in population size are often described as "cyclical". Populations modify and compensate for the perturbations of physical factors, thus, the more organized and mature the community, or the more stable the physical environment, or both, the less will be the amplitude of the fluctuations in population density over time (KREBS, 1985).According to BRNCIC et al. (1985) the seasonality of each species in the natural world is the result of a long and continuous process of adaptation to environmental conditions in which the species usually lives.Flies of the Drosophila genus are appropriate for the study of population fluctuation, as they are insects highly sensitive to ...

The West Indian fruit fly, Anastrepha obliqua, is an important agricultural pest in the New World. The use of pesticide-free methods to control invasive species such as this reinforces the search for genes potentially useful in their genetic control. Therefore, the study of chemosensory proteins involved with a range of responses to the chemical environment will help not only on the understanding of the species biology but may also help the development of environmentally friendly pest control strategies. Here we analyzed the expression patterns of three OBP genes, Obp19d_2, Obp56a and Obp99c, across different phases of A. obliqua development by qPCR. In order to do so, we tested eight and identified three reference genes for data normalization, rpl17, rpl18 and ef1a, which displayed stability for the conditions here tested. All OBPs showed differential expression on adults and some differential expression among adult stages. Obp99c had an almost exclusive expression in males and Obp56a showed high expression in virgin females. Thereby, our results provide relevant data not only for other gene expression studies in this species, as well as for the search of candidate genes that may help in the development of new pest control strategies.

We studied two species of closely related South American fruit flies, Anastrepha fraterculus and Anastrepha obliqua which, despite being able to interbreed, still show some ecological and reproductive differences. Because part of these differences, such as host and mate preferences, may be related to olfactory perception, we focused our investigation on the differential expression of Odorant-binding protein (OBP) gene family, which participate in initial steps of the olfactory signal transduction cascade. We investigated patterns of expression of eight OBP genes by qPCR in male and female head tissues of both species. The expression patterns of these OBPs suggest that some OBP genes are more likely involved with the location of food resources, while others seem to be associated with mate and pheromone perception. Furthermore, the expression patterns obtained at different reproductive stages indicate that OBP expression levels changed significantly after mating in males and females of both species. All eight OBP genes analyzed here showed significant levels of differential expression between A. fraterculus and A. obliqua, suggesting that they may hold important roles in their olfactory perception differences, and consequently, may potentially be involved in their differentiation.

Several studies have demonstrated that genes differentially expressed between sexes (sex-biased genes) tend to evolve faster than unbiased genes, particularly in males. The reason for this accelerated evolution is not clear, but several explanations have involved adaptive and nonadaptive mechanisms. Furthermore, the differences of sex-biased expression patterns of closely related species are also little explored out of Drosophila. To address the evolutionary processes involved with sex-biased expression in species with incipient differentiation, we analyzed male and female transcriptomes of Anastrepha fraterculus and Anastrepha obliqua, a pair of species that have diverged recently, likely in the presence of gene flow. Using these data, we inferred differentiation indexes and evolutionary rates and tested for signals of selection in thousands of genes expressed in head and reproductive transcriptomes from both species. Our results indicate that sex-biased and reproductive-biased genes evolve faster than unbiased genes in both species, which is due to both adaptive pressure and relaxed constraints. Furthermore, among male-biased genes evolving under positive selection, we identified some related to sexual functions such as courtship behavior and fertility. These findings suggest that sex-biased genes may have played important roles in the establishment of reproductive isolation between these species, due to a combination of selection and drift, and unveil a plethora of genetic markers useful for more studies in these species and their differentiation.

ABSTRACT. Malaria is an endemic parasitosis and its causitive agent, Plasmodium, has a metabolism linked to iron supply. HFE is a gene with the polymorphisms C282Y and H63D, which are associated with a progressive iron accumulation in the organism leading to a disease called hereditary hemochromatosis. The aim of the present study was to determine the allelic and genotypic frequencies of the HFE gene polymorphisms in malaria patients and blood donors from the Brazilian Amazon region. We screened 400 blood donors and 400 malaria patients for the HFE C282Y and H63D polymorphisms from four states of the Brazilian Amazon region by polymerase chain reaction and restriction fragment length polymorphism analysis. We did not find any C282Y homozygous individuals, and the only five heterozygous individuals detected were from Pará State. The most frequent genotype in the North region of Brazil was the H63D heterozygote, in both study groups. Our Frequency of the HFE polymorphisms in Brazil results contribute to the concept that the Brazilian Amazon region should not be regarded as a single entity in South America. These polymorphisms did not influence the symptoms of malaria in the population studied, as neither severe signs nor high parasitemia were observed. Therefore, different hereditary hemochromatosis diagnostic and control measures must be developed and applied within its diverse locations. Investigations are currently being carried out in our laboratory in order to determine the importance of the coexistence of hereditary hemochromatosis in patients affected by parasitic diseases, such as malaria.

The nuclear receptor PPARγ is essential to maintain whole-body glucose homeostasis and insulin sensitivity, acting as a master regulator of adipogenesis, lipid, and glucose metabolism. Its activation through natural or synthetic ligands induces the recruitment of coactivators, leading to transcription of target genes such as cytokines and hormones. More recently, post translational modifications, such as PPARγ phosphorylation at Ser273 by CDK5 in adipose tissue, have been linked to insulin resistance trough the dysregulation of expression of a specific subset of genes. Here, we investigate how this phosphorylation may disturb the interaction between PPARγ and some coregulator proteins as a new mechanism that may leads to insulin resistance. Through cellular and in vitro assays, we show that PPARγ phosphorylation inhibition increased the activation of the receptor, therefore the increased recruitment of PGC1-α and TIF2 coactivators, whilst decreases the interaction with SMRT and NCoR corepressors. Moreover, our results show a shift in the coregulators interaction domains preferences, suggesting additional interaction interfaces formed between the phosphorylated PPARγ and some coregulator proteins. Also, we observed that the CDK5 presence disturb the PPARγ-coregulator’s synergy, decreasing interaction with PGC1-α, TIF2, and NCoR, but increasing coupling of SMRT. Finally, we conclude that the insulin resistance provoked by PPARγ phosphorylation is linked to a differential coregulators recruitment, which may promote dysregulation in gene expression.

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IntroduçãoCerca de 10% da população mundial é portadora assintomática de dois tipos importantes de anemia hereditá-ria: doença falciforme e talassemias. Ambas apresentam distribuição geográfica bastante diversificada na África, Ásia, Europa e América, apesar de originalmente estarem confinadas nas regiões tropicais e subtropicais. Desde a década de 50 tem sido discutido que as altas prevalências dessas duas anemias hereditárias, assim como a causada pela deficiência de glicose-6-fosfato desidrogenase, se deve à proteção seletiva de seus heterozigotos contra os efeitos letais das infecções causadas pelo Plasmodium falciparum. Uma similaridade entre a distribuição geográfica da α-talassemia e a incidência de malária em algumas áreas também tem sido demonstrada; entretanto, os mecanismos de proteção dos heterozigotos talassêmicos não são completamente compreendidos.2 Apesar de décadas de estudos epidemiológicos e especulações, o modo de seleção que favorece o gene da hemoglobina S continua pouco conhecido. Lisa et al (1994) 3 propuseram que a fertilidade diferencial seria uma explicação para a manutenção do polimorfismo de hemoglobinopatias em algumas populações.