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Transposable elements (TEs) are almost ubiquitous components of eukaryotic genomes that have long been considered solely deleterious or ’junk DNA’. They are split into two main forms, retro-transposons and DNA transposons, depending on the method of replication employed. Hosts have developed strategies for combating TEs including RNAi, methylation and copy number con-trol. TEs have also evolved ways of persisting in the genome in order to survive, such as target site specificity. Two additional ways which may be utilised by TEs, positive selection and horizontal transfer, were investigated here primarily using the budding yeasts in the Saccharomyces sensu lato complex. These species typically contain up to five families of retrotransposons, designatedTy1-5, and multiple subfamilies, all of varying transpositional activity. Discoveries of insertions evolving under positive selection and providing benefits to their hosts have been sporadic and serendipitous findings in a number of organisms. Full genome screenings for such insertions are rarely published, despite the impact TE insertions have upon their hosts. A population genomics approach was performed to address this issue in the genomes of Saccha-romyces cerevisiae and sister species S. paradoxus. Signatures of positive selection acting upon Ty insertions were identified using Tajima’s statistical D test. Neighbouring genes were also analysed to ascertain the true target of selection where hitchhiking linked the two. A subset of LTR-gene pairings were explored using qPCR in order to identify any effects on host gene expression the occupied loci may cause. Two genes displayed significantly increased levels of expression, which may be due to the presence of positive selection candidate LTRs, which in turn may contribute to improving host fitness. This thesis further documents the systematic screening for Ty-like elements of all available genomes of budding yeast and related species. Extensive phylogenetic analyses estimated evolutionary relationships and possible horizontal transfer events of elements between the species. Evidence for in excess of 75 horizontal transfer events was uncovered here, around half of which were successful in propagating in new genomes. The occurrence of horizontal transfer of TEs in the genomes of budding yeast is therefore far more common than previously documented. During screening of genomes, a further potential method of avoiding host defences was uncovered. The divergence of the highly active Ty4 family, which coincided with population isolation of multiple Saccharomyces species into subfamilies, was surprising given previous reports of this family being of particularly low activity. Such events are rarely recorded in eukaryotic genomes, and may also illustrate the compulsive spread of a new subfamily via horizontal transfer. The investigations reported here represent the first genomic screening of Ty insertions in Saccharomyces for signatures of positive selection, and an updated, comprehensive search for evidence of HT between species of budding yeast. Both may act as methods for TE families to persist in the genomes of their hosts, and represent far more than simply ’junk DNA’.

Submitted by Cristiane Chim (cristiane.chim@ucpel.edu.br) on 2017-02-09T12:26:04Z No. of bitstreams: 1 Marta de Oliveira Gazal.pdf: 1058953 bytes, checksum: a3559296bba6ad1afe42c3d2a3a018d3 (MD5) / Made available in DSpace on 2017-02-09T12:26:04Z (GMT). No. of bitstreams: 1 Marta de Oliveira Gazal.pdf: 1058953 bytes, checksum: a3559296bba6ad1afe42c3d2a3a018d3 (MD5) Previous issue date: 2014-02-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES# / #2075167498588264571# / #600 / Chronic stressful stimuli influence disease susceptibility to depression, cardiovascular, metabolic and neurodegenerative disorders. The present work investigated antidepressant and antioxidant properties of the aqueous extract from Cecropia pachystachya in a mouse model of chronic unpredictable stress (CUS). Our results indicated that acute administration of the aqueous extract (AE) from Cecropia pachystachya (200 and 400 mg/kg, p.o.) produced an antidepressant-like effect in the forced swimming test (FST). In addition, chronic treatment with Cecropia pachystachya extract (200 mg/kg, p.o., for 14 days) prevented the depressantlike effect but not the anxiogenic effect induced by CUS. In addition to the behavioural modifications, the 14 days of CUS increased lipid peroxidation in the hippocampus (HP) and prefrontal cortex (PFC) and decreased total thiol content in the HP. Cecropia pachystachya AE administration during CUS protocol was able to prevent the oxidative damage induced by stress. However, no changes were observed in the activity of the antioxidant enzymes superoxide dismutase and catalase in the above cited brain areas after the stress protocol and treatment. Our results suggest that Cecropia pachystachya prevented both depressive behavior and oxidative damage induced by CUS, supporting its neuroprotective potential against behavioral and biochemical dysfunctions induced by chronic stress. / Estímulos estressantes crônicos influenciam a susceptibilidade à depressão, doenças cardiovasculares, Metabólicas e neurodegenerativas. O presente trabalho investigou antidepressivos e Propriedades antioxidantes do extrato aquoso de Cecropia pachystachya em um modelo de rato De estresse crônico imprevisível (CUS). Nossos resultados indicaram que a administração aguda O extrato aquoso (AE) de Cecropia pachystachya (200 e 400 mg / kg, p.o.) produziu Efeito antidepressivo no teste de natação forçada (FST). Além disso, o tratamento crônico Com extrato de Cecropia pachystachya (200 mg / kg, p.o., durante 14 dias) evitou a Mas não o efeito ansiogênico induzido pelo CUS. Além do comportamento Modificações, os 14 dias de CUS aumentaram a peroxidação lipídica no hipocampo (HP) e Córtex pré-frontal (PFC) e menor teor de tiol total na HP. Cecropia pachystachya A administração de AE ​​durante o protocolo CUS foi capaz de prevenir o dano oxidativo induzido por estresse. No entanto, não foram observadas alterações na actividade das enzimas antioxidantes Superóxido dismutase e catalase nas áreas do cérebro acima citadas após o protocolo de estresse e tratamento. Nossos resultados sugerem que Cecropia pachystachya impediu tanto o comportamento depressivo E danos oxidativos induzidos pelo CUS, apoiando seu potencial neuroprotetor contra Comportamentais e bioquímicas induzidas pelo estresse crônico.

Einwirkung elektrostatischer Aufladungen auf den Negativaufbau im Rollenoffsetdruck.

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The structural organisation of species-rich plant-pollinator networks is important to understanding their ecology and evolution and is essential for making informed conservation and restoration decisions. This thesis reports on a study located at different altitudes in nine tributary valleys of the Sacred Valley, Vilcanota Highlands, Peru. The assemblages of flower visitors were described and the plant-flower visitor matrices were analysed and compared to those found from other montane systems. Additionally, the thesis also addressed how the European honeybee (Apis mellifera) fits into these communities. Previous studies have predicted that abundance, diversity, and importance of hymenopterans as pollinators decrease with increasing altitude, where they are replaced by Lepidoptera and Diptera. Contrary to other temperate montane areas, Hymenoptera were more diverse at higher elevations. Diptera was the most abundant functional group overall but did not significantly increase in abundance with altitude as predicted. Species richness of visited plants reached a maximum at the highest altitudes. Using ordination analysis, hummingbirds, honeybees, flies and beetles were identified as major functional groups of flower visitors with significantly different visitation profiles. Nestedness analysis revealed that the plant-flower visitor networks had a similar structure to other published networks, consisting of core groups of generalist plants and animals which interacted with one another and with specialised flower visitors and plants, respectively. The core species varied in identity between valleys, but were usually the species in greatest abundance, implying that the networks were abundance structured. In addition, 85% of the interactions were observed only in single valleys. This context specificity may have implications for the conservation of plant-pollinator interactions in the Sacred Valley. Comparisons of the pollinator efficiencies of honeybees, hummingbirds, native bees and moths to Duranta mandonii (Verbenaceae) demonstrated significant variation among flower visitors in rates of visitation, pollen removal ability and contribution to fruit set. This variation was not correlated: hummingbirds were by far the most frequent visitors but removed virtually no pollen and did not contribute to fruit set. Despite the taxonomic diversity of flower visitors, the main pollinators were large native bumblebees and honeybees. Results highlighted the importance of measuring efficiency components when documenting plant-pollinator interactions, and also demonstrated that visitation rates may give little insight into the relative importance of flower visitors. Overall, the study showed that Apis was the most generalist flower visitor and a dominant core species within networks. However, although Apis visited a relatively large proportion of the flora compared to native taxa, they only intensively utilised a small proportion of available plant species. No evidence was found from the surveys to suggest that honeybees used interference competition and displaced other species. It was suggested that because specialised rare species are frequently dependent on a core of generalist taxa honeybees may play an important role for the possibilities of rare species to persist. However, perhaps the greatest threat to biodiversity and the persistence of plant-flower visitor communities in the Sacred Valley is from the destruction and fragmentation of habitats and from facilitative interactions between native and alien plants, mediated through visitation from honeybees

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