Orientador: Jose Roberto Trigo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-12T18:54:20Z (GMT). No. of bitstreams: 1 Stanton_MarianaAlves_M.pdf: 682844 bytes, checksum: 36b7ed46fcdc82eacc95256aae48e173 (MD5) Previous issue date: 2008 / Resumo: A produção de defesas contra a herbivoria é essencial para o sucesso reprodutivo das plantas, no entanto pode ser custosa. Esses custos resultam da redução de investimento em outras partes do metabolismo, como o crescimento e a reprodução. Nesse estudo, usamos Asclepias curassavica (Apocynaceae: Asclepiadoideae) como modelo para avaliar como uma planta divide seus recursos entre crescimento, reprodução e defesas. A. curassavica é uma planta anual que possui cardenolidas como defesas. Para verificar como esta responde a herbivoria, simulamos a mesma através de dano artificial (DA) e medimos crescimento (biomassa de folhas e raízes) e reprodução (número de flores, frutos e sementes e biomassa de sementes) em um experimento em longo prazo. Em um experimento em curto prazo, medimos a produção de defesas (concentração de cardenolidas), para avaliar se estas podem estar interferindo no crescimento e reprodução desta espécie. Correlacionamos também, em uma população natural, a concentração de cardenolidas com a percentagem de herbivoria foliar. O hormônio jasmonato de metila (JM) é usado para induzir compostos do metabolismo secundário em plantas, sem o custo adicional da remoção de tecido fotossinteticamente ativo causada por dano artificial ou natural. Usamos esse composto em ambos os desenhos experimentais acima ao invés de remoção da área foliar para avaliar se havia indução de cardenolidas e seu efeito sobre o crescimento e reprodução de A. curassavica. Nossos resultados demonstraram uma redução significativa do número total de frutos, sementes e da massa final de raízes em plantas com tratamento de DA em longo prazo. O crescimento do tratamento DA não diferiu do controle, sugerindo crescimento compensatório das folhas à custa do investimento em raízes e em reprodução. Os custos reprodutivos e de crescimento de raízes detectados no experimento de longo prazo podem resultar da diminuição da capacidade fotossintética em plantas danificadas e investimento simultâneo em crescimento compensatório das folhas. No experimento de curto prazo, não houve alteração da razão de indução de cardenolidas sugerindo que o dano artificial não induz defesas nessa espécie. A ausência de correlação entre cardenolidas e porcentagem de dano natural em plantas coletadas em campo pode sugerir dois cenários excludentes: 1. a indução de cardenolidas não seria importante para a defesa de A. curassavica, ou 2. a ausência de correlação, associada a baixa percentagem de herbivoria implicaria em uma defesa constitutiva eficaz contra herbívoros. O tratamento com JM a longo prazo também mostrou uma tendência à redução do crescimento de raízes e redução significativa da biomassa e porcentagem de germinação de sementes. Nas plantas tratadas com JM a curto prazo, houve um aumento significativo de cardenolidas tardio (384 h após tratamento) sugerindo que estas podem contribuir para a redução de aptidão observada no experimento de longo prazo e que existem custos da produção das mesmas. Dano artificial leva à diminuição da aptidão, através de desvio de investimento em raízes para o crescimento compensatório das folhas. No caso do jasmonato, não houve perda de massa fotossinteticamente ativa (folhas) e a redução do crescimento de raízes pode ser resultado de um efeito direto do tratamento de JM ou indireto causado pela indução de outras partes do metabolismo (p.ex. metabolismo secundário) causada por esse fitohormônio. Experimentos futuros devem comparar os presentes resultados com dano real por um dos herbívoros especialistas para avaliar a eficácia do dano artificial em induzir cardenolidas e o papel dessa indução sobre outras partes do metabolismo da mesma / Abstract: Although the investment in defensive traits against herbivory is essential to the reproductive success of plants, it may be costly. These costs result from reduced investment in other metabolic functions such as growth and reproduction. In the present study, we used the milkweed Asclepias curassavica (Apocynaceae: Asclepiadoideae) as a model to study how a plant divides its resources between growth, reproduction and defense. A. curassavica is an annual weed that uses cardenolides as defenses against herbivory. To evaluate how Asclepias curassavica responds to herbivores, we simulated herbivory by artificial damage (AD) and measured growth (leaf and root biomass) and reproduction (number of flowers, fruit and seeds and seed biomass) in a long term experiment. We also measured defensive traits (cardenolide concentration) in a short term experiment to verify whether there is an investment in defense that may interfere with growth and reproduction. We also correlated cardenolide concentration in a natural population with percent leaf damage. As the plant hormone, methyl jasmonate (MJ) is commonly used to induce secondary metabolism in plants without the additional costs of tissue removal, we used this compound in the same experimental designs instead of AD. Our results from the long term AD treatment showed a significant decrease in final root biomass and in total fruit set and seed number. Plants from the AD treatment did not differ from controls in leaf growth, suggesting that there was a compensatory growth in the former at the expense of root growth. The reproductive and growth costs detected in this experiment may result from reduced photosynthetic capacity in damaged plants and concomitant compensatory leaf growth. In the short term, we found no induction of cardenolides compared to controls, suggesting that artificial damage does not induce defenses. The lack of correlation between cardenolides and percentage leaf damage in plants collected from a natural population suggest two self-excluding scenarios: 1. the induction of cardenolides is not important for the defense of A. curassavica, or 2. the lack of correlation, coupled with low herbivore damage, suggests that this plant has an efficient constitutive defense against herbivores. The long term MJ treatment showed a trend in reduced root biomass and significantly reduced seed biomass and percentage germination. In the short term MJ treatment we found a significant increase in cardenolide concentration (after 384 h) suggesting that the production of these defenses is costly and this may have contributed to observed costs in the long term experiment. Apparently, the artificial damage treatment leads to reduced fitness through reduced root growth which is a consequence of compensatory leaf growth. In the methyl jasmonate treatment, there was no removal of photosythetically active tissue (leaves) and the reduced root growth may be a direct effect of this phytohormone or an indirect effect caused by the induction of other metabolic pathways (such as secondary metabolism) caused by this hormone. Future experiments should compare the present results with natural damage by specialist herbivores to evaluate the efficiency of artificial damage in inducing cardenolides and the role of the induction of these substances on other metabolic functions / Mestrado / Mestre em Ecologia

L’objectif de cette thèse a été de développer des outils d’exploration des modifications perceptuelles lors de l’écoute de sons complexes dans la schizophrénie et de confronter les résultats de ces outils à des données neurophysiologiques. Le premier résultat de notre thèse est d’avoir confirmé dans la modalité auditive des modifications de l’organisation perceptuelle lors de l’écoute de sons complexes. En effet, nous avons montré, chez les patients souffrant de schizophrénie comparativement aux témoins, d’une part une difficulté de catégorisation des sons environnementaux de type son d’impact, et d’autre part, une modification de la perception de la familiarité et de la bizarrerie pour des sons environnementaux et abstraits, indiquant une modification d’organisation des données de l’audition dans une forme univoque et consensuelle.Le deuxième résultat de notre thèse est d’avoir confirmé, par une méthode d’induction perceptuelle consistant à présenter des stimuli plus ou moins envahissants, la présence d’un sentiment d’envahissement perceptuel plus important chez les patients souffrants de schizophrénie comparativement aux témoins. Cet envahissement perceptuel était corrélé significativement avec une mesure neurophysiologique du filtrage sensoriel par potentiels évoqués dans le paradigme des doubles clics audio (diminution d’amplitude de la composante P50 au deuxième stimulus comparativement au premier stimulus). Nous avons également traduit et validé en langue française un auto-questionnaire appelé Sensory Gating Inventory (SGI) permettant de compléter l’évaluation psychophysiologique des modifications perceptuelles reliées aux anomalies du filtrage sensoriel. / The aim of this PhD was to develop tools for analyzing perceptual modifications induced by complex sounds in schizophrenia and to relate these changes to neurophysiological data. The first result of our work enabled to confirm that complex sounds modify the auditory perceptual organization. Indeed, we first showed a deficit of categorization of environmental sounds (impact sounds) in patients with schizophrenia compared with controls, and secondly a difference in the perception of familiarity and strangeness for environmental and abstract sounds, indicating a modification of data organization of hearing in a unique and consensual form.The second result of our work revealed, by a perceptual induction method, the presence of a larger perceptual sense of inundation in patients suffering from schizophrenia compared with controls when submitted to more or less invasive stimuli. This perceptual inundation was significantly correlated with a neurophysiological measurement of sensory gating with evoked responses in the paradigm of double audio clicks (decrease in amplitude of the P50 component after the second stimulus as compared to the first stimulus). We have also translated a self-administered questionnaire called “Sensory Gating Inventory” (SGI) to French and validated it in order to complete the psychophysiological assessment of perceptual changes related to abnormal sensory gating.

Les sirtuines sont une famille conservée de déacétylases NAD+-dépendantes qui sont impliquées dans divers processus. Les humains possèdent 7 sirtuines (SIRT1-7) qui jouent un rôle dans plusieurs voies cellulaires, tandis que la levure Saccharomyces cerevisiae possède 5 membres (Sir2, Hst1-4) qui influencent plusieurs voies comme le cycle cellulaire ou le vieillissement. Une absence d’activité des sirtuines mène toutefois à des défauts de croissance, une thermosensibilité et l’apparition de dommages spontanés à l’ADN par des mécanismes mal élucidés. Pour mieux caractériser ce phénomène, ce mémoire met en lumière certains résultats venant d’un crible chimiogénétique réalisé par traitement au nicotinamide (NAM), un pan-inhibiteur des sirtuines. Nos résultats indiquent que le NAM entraîne chez la levure Saccharomyces cerevisiae une forte activation des voies de réponses aux dommages à l’ADN, et que les défauts de croissance sont principalement dus à l’hyperacétylation de la lysine 56 de l’histone H3 (H3K56), une modification post-traductionnelle qui est renversée par les sirtuines Hst3 et Hst4. Lors d’hyperacétylation de H3K56, la protéine Slx4 et le complexe PP4 sont requis pour la croissance de la levure en modulant les niveaux d’activation de la kinase Rad53 lors de la RDA. Également, certains résultats préliminaires inclus dans ce mémoire mettent en évidence un rôle de l’activité des sirtuines dans la régulation de la recombinaison homologue, l’une des voies de réparation de l’ADN. Ensemble, nos résultats suggèrent que la déacétylation des histones par les sirtuines permet de moduler la réponse aux dommages à l’ADN en présence de stress réplicatif. / Sirtuins are a conserved family of NAD+-dependent deacetylases that are involved in various processes. Humans have seven sirtuins (SIRT1-7) and play a role in several cellular pathways, while the budding yeast Saccharomyces cerevisiae has 5 members (Sir2, Hst1-4) and influence several pathways, such as the cell cycle or aging. Lack of sirtuin activity however leads to growth defects, thermosensitivity and spontaneous DNA damage by poorly understood mechanisms. To further characterize this phenomenon, this thesis highlights results obtained from a chemogenetic screen realized by treatment with nicotinamide (NAM), a pan-inhibitor of all sirtuins. Our results indicate that NAM causes strong activation of DNA damage-induced signaling in budding yeast Saccharomyces cerevisiae, and that growth defects are mainly due to histone H3 lysine 56 (H3K56) hyperacetylation, a post-translational modification reversed by sirtuins Hst3 and Hst4. During H3K56 hyperacetylation, the Slx4 protein and PP4 complex are both required for yeast growth by modulating the activation levels of Rad53 kinase during the DDR. Also, preliminary results included in this thesis highlight that proper regulation of homologous recombination, one of DNA repair pathways, is essential for growth in the presence of NAM-induced sirtuin inhibition. Together, our results suggest that chromosome-wide histone deacetylation by sirtuins can modulate DNA damage response in presence of replicative stress.