Linkage disequilibrium and coadaptation of chromosomal inversions in Drosophila mediopunctata

Orientador: Louis Bernard KlaczkoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: O polimorfismo de inversões cromossômicas é um dos tópicos mais bem estudados em genética de populações, mesmo assim, os mecanismos que governam sua origem e manutenção ainda escapam à nossa completa compreensão. O polimorfismo de inversões em Drosophila mediopunctata é um exemplo claro de um caráter sob seleção cujo significado adaptativo ainda não é bem compreendido. O cromossomo II da espécie é rico em inversões que se distribuem em duas regiões cromossômicas: distal e proximal. Inversões distais e proximais (quase) nunca se sobrepõem. Contudo, conjuntos de inversões não sobrepostas frequentemente apresentam desequilíbrio de ligação em populações naturais. Nessa dissertação, nós realizamos uma análise dos padrões de desequilíbrio de ligação entre as inversões do cromossomo II de Drosophila mediopunctata no sentido de contribuir para a compreensão das forças evolutivas que agem sobre esse sistema. Especificamente, nós utilizamos uma abordagem mista, envolvendo experimentos de laboratório, dados empíricos de animais coletados no campo e modelagens teóricas simples para estudar o desequilíbrio de ligação entre inversões ligadas e não sobrepostas em uma população natural da espécie. No primeiro capítulo, como introdução, nós apresentamos uma visão geral sobre os efeitos que as inversões cromossômicas possuem sobre as taxas de recombinação em Drosophila, as questões que motivaram esse trabalho e uma breve descrição do conteúdo dessa dissertação. No segundo capítulo, nós analisamos os padrões de desequilíbrio de ligação na população de D. mediopunctata que habita o Parque Nacional do Itatiaia (RJ) decorrido um lapso de tempo de 30 anos do primeiro estudo. Subsequentemente, nós mostramos que as associações não aleatórias entre inversões distais e proximais se mantiveram praticamente inalteradas ao longo desse período, corroborando a hipótese de que o desequilíbrio entre inversões é mantido por seleção natural. No capítulo três, nós utilizamos uma série de cruzamentos controlados para responder questões simples acerca da influência das inversões sobre componentes do valor adaptativo. Entre outros resultados, nossos dados reforçam a hipótese de supressão da recombinação em heterozigotos para inversões paracêntricas ligadas e não sobrepostas. Finalmente, nós interpretamos a falta de recombinação em heterozigotos para arranjos não-sobrepostos como uma evidência a favor da existência de interações epistáticas entre locos contidos em (e entre) diferentes regiões invertidasAbstract: The chromosomal inversion polymorphism is one of the best-studied topics in population genetics, yet the mechanisms that govern its origin and maintenance still escape our full understanding. The inversion polymorphism in Drosophila mediopunctata is a clear example of a character under selection whose adaptive meaning is still not well understood. The chromosome II of D. mediopunctata is rich in inversions that are distributed in two chromosomal regions: distal and proximal. Distal and proximal inversions (almost) never overlap. However, sets of non-overlapping inversions often show linkage disequilibrium in natural populations. In this dissertation, we perform an analysis of the linkage disequilibrium patterns of the second chromosome of D. mediopunctata in order to contribute to the understanding of the evolutionary forces acting on this system. Specifically, we use a mixed approach based on laboratory experiments, data derived from animals collected in the field and simple theoretical modeling to study the patterns of linkage disequilibrium between linked and non-overlapping inversions in a natural population of the species. In the first chapter, as an introduction, we present an overview of the effects that chromosomal inversions have on Drosophila recombination rates, the questions that motivated this work, and a brief description of the content of this dissertation. In the second chapter, we assess the patterns of linkage disequilibrium in a population of D. mediopunctata that inhabits the Parque Nacional do Itatiaia 30 years after the first study took place. Subsequently, we show that non-random associations between distal and proximal inversions have remained virtually unchanged over the period, corroborating a hypothesis that natural selection maintains the disequilibrium between inversions. In chapter three, we perform a series of controlled crosses to answer simple questions about the influence of inversions on adaptive value components. Among other results, our data reinforce the hypothesis of heterozygous recombination suppression for linked and non-overlapping paracentric inversions. Finally, we interpret the lack of recombination in heterozygotes for non-overlapping arrangements as evidence in favor of the existence of epistatic interactions between loci contained within (and between) different inverted regionsMestradoGenetica Animal e EvoluçãoMestra em Genética e Biologia MolecularCAPE

Differential attraction of drosophilids to banana baits inoculated with Saccharomyces cerevisiae and Hanseniaspora uvarum within a Neotropical forest remnant

Background. Yeasts are a necessary requisite in the diet of most Drosophila species that, in turn, may vector their dispersal in natural environments. Differential attractiveness experiments and the isolation of yeasts consumed by Drosophila may be informative for characterizing this association. Hanseniaspora uvarum is among the most common yeast species isolated from Drosophila crops, with high attractiveness to drosophilids. Saccharomyces cerevisiae has been widely used to collect flies, and it allows broad sampling of almost all local Drosophila species. Pronounced differences in the field concerning Drosophila attractivity to baits seeded with these yeast species have been previously reported. However, few explicit generalizations have been set. Since late fifties, no field experiments of Drosophila attractivity were carried out in the Neotropical region, which is facing shifts in abiotic and biotic factors. Our objective is to characterize preference behavior that mediates the interaction in the wild among Neotropical Drosophila species and yeasts associated with them. We want to set a broad generalization about drosophilids attracted to these yeasts. Here we present the results of a differential attractiveness experiment we carried out in a natural Atlantic Rainforest fragment to assess the preferences of Drosophila species groups to baits inoculated with H. uvarum and S. cerevisiae. Methods. Both yeast species were cultured in GYMP broth and separately poured in autoclaved mashed banana that was left fermenting. In the field, we collected drosophilids over five arrays of three different baits: non-inoculated autoclaved banana and banana inoculated with each yeast. In the laboratory the drosophilids were sorted to five sets according to their external morphology and/or genitalia: tripunctata; guarani; willistoni; exotic; and the remaining flies pooled in others. Results and Conclusions. Uninoculated banana baits attracted virtually no flies. We found significant departures from random distribution over the other two baits (1:1 proportion) for all sets, except the pooled others. Flies of the sets willistoni and exotic preferred H. uvarum over S. cerevisiae, while the remaining sets were more attracted to S. cerevisiae. Previously, various authors reported similar patterns in attraction experiments with S. cerevisiae and H. uvarum. It is also noteworthy that both yeast species have been isolated from natural substrates and crops of Drosophila species. Taken together, these results suggest that the preferences among Drosophila species groups may be reflecting deep and stable relations with yeast species in natural environments. They can be summarized as: forest dwelling species from subgenus Drosophila (such as tripunctata and guarani groups) are attracted to banana baits seeded with S. cerevisiae; while exotic (as D. melanogaster) and subgenus Sophophora species are preferentially attracted to baits seeded with H. uvarum

The potential role of thioredoxin 1 and CD30 systems as multiple pathway targets and biomarkers in tumor therapy

Our progress in understanding pathological disease mechanisms has led to the identification of biomarkers that have had a considerable impact on clinical practice. It is hoped that the move from generalized to stratified approaches, with the grouping of patients into clinical/therapeutic subgroups according to specific biomarkers, will lead to increasingly more effective clinical treatments in the near future. This success depends on the identification of biomarkers that reflect disease evolution and can be used to predict disease state and therapy response, or represent themselves a target for treatment. Biomarkers can be identified by studying relationships between serum, tissue, or tumor microenvironment parameters and clinical or therapeutic parameters at onset and during the progression of the disease, using systems biology. Given that multiple pathways, such as those responsible for redox and immune regulation, are deregulated or altered in tumors, the future of tumor therapy could lie in the simultaneous targeting of these pathways using extracellular and intracellular targets and biomarkers. With this aim in mind, we evaluated the role of thioredoxin 1, a key redox regulator, and CD30, a cell membrane receptor, in immune regulation. Our results lead us to suggest that the combined use of these biomarkers provides more detailed information concerning the multiple pathways affected in disease and hence the possibility of more effective treatment