No description available.

No description available.

No description available.

Cell signaling pathways are frequently used in multiple tissue and stage-specific contexts during multicellular development. The integration of these signaling pathways by transcriptional enhancers controls the tissue specific gene expression necessary for proper development. Enhancers are segments of DNA that interpret developmental signals to produce patterns of gene expression. A set of operational rules defines how different enhancers targeted by the same signals interpret and act on these signals. Using the Drosophila model system, my thesis work focuses on determining the operational rules used by developmental enhancers that integrate the Notch signaling pathway with other pathways. During development, the Notch signaling pathway in used to pattern cell territories involved in cell fate determination, and plays a role in differentiation. I first used a computational approach to identify a set of candidate Notch-target enhancers. From this set I carefully studied one specific enhancer from the nab gene that integrates the Notch and Bone Morphogenetic Protein (BMP) signaling pathways in the developing wing. This nab enhancer is a part of a cluster of enhancers that work together to drive the global nab expression pattern during development. Each of these enhancers drives the expected expression patterns as well as atypical expression patterns, which are silenced by adjacent enhancers. These results suggest that Notch targeted enhancers are involved in both tissue specific gene activation and gene silencing.

Polycomb-group (Pc-G) proteins regulate homeotic gene silencing associated with the repressive covalent histone modification, trimethylation of histone H3 lysine 27 (H3K27me3). Pc-G mediated silencing is believed to remodel chromatin, rendering target genes inaccessible to transcription factors. Pc-G mediated silencing might result in irreversible changes in chromatin structure, however, there has been little analysis addressing whether Pc-G mediated silencing is reversible. In this work we focused on CURLY LEAF (CLF), the first Pc-G homologue discovered in Arabidopsis. CLF mediated repression of the floral homeotic gene AGAMOUS (AG) was challenged during early and late leaf development. AG was activated by the late leaf promoter, revealing that Pc-G mediated silencing can be overcome in old leaves in the presence of CLF. AG was also activated in young leaf primordia, yet did not persist in older leaves, revealing that transient activation of a Pc-G target is not epigenetically stable. To address the mechanism of Pc-G action within an endogenous environment, the histone dynamics at the APETALA1 (AP1) locus were characterized by Chromatin Immunoprecipitation. Unexpectedly, we found that the activation of AP1 in leaves did not require the removal of H3K27me3, questioning whether H3K27me3 is sufficient to silence. The roles of CLF in leaf and flower development are masked due to partial redundancy with SWINGER (SWN). clf- swn- mutants form a callus-like mass on sterile-tissue culture with no distinguishable plant organs. The role of CLF in regulating flowering time in natural populations of A. thaliana was investigated by complementing clf- mutants with CLF alleles from two accessions. We found that natural variation in CLF did not affect flowering time. To dissect the roles of CLF and SWN in late leaf and flower development, two approaches were developed for targeted expression. Firstly, CLF was introduced into the LhG4/ pOp transactivation system to provide CLF during early plant development. For mosaic analysis, CLF was introduced into the CRE lox recombination system in order to create clf- sectors surrounded by CLF+ SWN+ and CLF+ swn- cells.

Made available in DSpace on 2015-04-11T13:38:43Z (GMT). No. of bitstreams: 1 Dissertacao Lidianne Lunguinho.pdf: 986527 bytes, checksum: 1ca17f21ab0579c64d64579574eb4365 (MD5) Previous issue date: 2007-02-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The guarana, Paulinia cupana var. sorbilis, is a native plant and grown in the Amazon region. His greatest production was concentrated in the State Amazonas, Bahia, but currently the largest producer and Acre, Para, Mato Grosso, Rondônia are major producers. (Calderazo et. Al., 1986). The expansion of its culture is attributed to great use in industry soft drinks and pharmacopeia. Belonging to the family Sapindaceae, is a plant lowland tropical, shrubs, woody vines adapted to the climate hot and humid, produces the fruit known as guarana. Geographically There are two varieties defined, and sorbilis typica: being the first is the most widely cultivated, accounting for nearly all domestic production, the the second found in limited quantities in the river basins of the Upper Orinoco and Rio Negro. The objectives of this dissertation were to verify the occurrence of patterns different flowering among clones of guarana, maintained with and without fertilization; probe the existence of orthologs (homologous sequences) of genes Arabidopsis involved in flowering in plants and guarana, analyze the spatial and temporal expression of orthologous genes LEAFY, AGAMOUS and apetala in vegetative tissues and reproductive guarana. Took place during the flowering period of 2004 (August to October) were counted in ten inflorescences of four plants of each clone in three segments of its rachis and number of flowers functionally male and functionally female. Statistical analysis was done by tabulating the weekly number of female flowers and male to facilitate the analysis of correlation with the length of inflorescences. The results suggest that the occurrence of phase predominantly in female inflorescences is a feature less that the number of plastic phases predominantly male. To amplify by RT-PCR total RNA from different tissues and DNA of guarana primers were synthesized for apetala, LEAFY, AGAMOUS and primers for the actin gene transcripts were used as control of RNA concentration. Transcription experiments RT and amplification were carried out at temperatures of annealing primers 45 to 50 ° C, generating very faint specific bands and / or mainly nonspecific. . The results achieved not by state shows that the guarana genes LEAFY, AGAMOUS and apetala 1 highly similar sequences that served as the template for the synthesis of primers. / O guaranazeiro, Paulínia cupana var. sorbilis, é uma planta nativa e cultivada na região Amazônica. Sua maior produção concentrou-se no Estado do Amazonas, mas atualmente a Bahia e o maior produtor e o Acre, Para, Mato Grosso, Rondönia são grandes produtores. (Calderazo et. al., 1986). A expansão de sua cultura é atribuída, à grande utilidade na indústria de refrigerantes e farmacopéia. Pertencente a família Sapindaceae, é uma planta tropical de baixa altitude, arbustiva, lenhosa, trepadeira adaptada ao clima quente e úmido, produz o fruto conhecido como guaraná. Geograficamente existem duas variedades definidas, a Sorbilis e a Typica: sendo que a primeira é a mais cultivada, responsável por quase toda a produção nacional, a segunda encontrada em quantidades restritas nas bacias fluviais do Alto Orenoco e Alto Rio Negro. Os objetivos dessa dissertação foram verificar a ocorrência de padrões diferentes de florescimento entre clones de guaranazeiro, mantidos com e sem adubação; sondar a existência de ortologos (seqüências homologas) de genes de Arabidopsis implicados no florescimento em plantas de guaranazeiro e, analisar o padrão espacial e temporal de expressão dos ortologos dos genes LEAFY, APETALA e AGAMOUS em tecidos vegetativos e reprodutivos de guaranazeiro. Realizou-se durante o período de florescimento do ano de 2004 (agosto a outubro) foi realizada a contagem em dez inflorescências de quatro plantas de cada clone em três segmentos do seu raquis do número de flores funcionalmente masculinas e funcionalmente femininas. A análise estatística foi realizada mediante a tabulação semanal do número de flores femininas e masculinas para facilitar a análise de correlação com o comprimento das inflorescências. Os resultados permitiram sugerir que a ocorrência de fases predominantemente femininas nas inflorescências é uma característica menos plástica que o número de fases predominantemente masculinas. Para amplificar por RT-PCR o RNA total de diferentes tecidos e o DNA de guaranazeiro foram sintetizados primers para APETALA, LEAFY, AGAMOUS e primers para os transcritos do gene da ACTINA foram utilizados como controle de concentração do RNA. Os experimentos de transcrição reversa e amplificação foram realizados em temperaturas de anelamento dos primers de 45 a 50 °C, gerando bandas especificas muito tênues e/ou, principalmente, inespecificas. .Os resultados alcançados não pertiram afirmar que o guaranazeiro apresenta genes LEAFY, APETALA 1 e AGAMOUS altamente similares as seqüências que serviram de modelo para a síntese dos primers.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

No description available.

<p>In multicellular organisms all cells in one individual have an identical genotype, and yet their bodies consist of many and very different tissues and thus many different cell types. Somehow there must be a difference in how genes are interpreted. So, there must be signals that tell the genes when and where to be active and inactive, respectively. In some instances a specific an expression pattern (active or inactive) is epigenetic; it is established and maintained throughout multiple rounds of cell divisions. In the developing <i>Drosophila</i> embryo, the proper expression pattern of e.g. the homeotic genes <i>Abd-B</i> and <i>Ubx</i> is to be kept active in the posterior part and silenced in the anterior. Properly silenced homeotic genes are crucial for the correct segmentation pattern of the fly and the Polycomb group (Pc-G) proteins are vital for maintaining this type of stable repression.</p><p>As part of this thesis, <i>Suppressor of zeste 12 (Su(z)12)</i> is characterized as a <i>Drosophila</i> Pc-G gene. Mutations in the gene cause widespread misexpression of several homeotic genes in embryos and larvae. Results show that the silencing of the homeotic genes <i>Abd-B</i> and <i>Ubx</i>, probably is mediated via physical binding of SU(Z)12 to Polycomb Response Elements in the BX-C. <i>Su(z)12</i> mutations are strong suppressors of position-effect-variegation and the SU(Z)12 protein binds weakly to the heterochromatic centromeric region. These results indicate that SU(Z)12 has a function in heterochromatin-mediated repression, which is an unusual feature for a Pc-G protein. The structure of the <i>Su(z)12</i> gene was determined and the deduced protein contains a C2-H2 zinc finger domain, several nuclear localization signals, and a region, the VEFS box, with high homology to mammalian and plant homologues. <i>Su(z)12 </i>was originally isolated in a screen for modifiers of the zeste-white interaction and I present results that suggests that this effect is mediated through an interaction between <i>Su(z)12 </i>and <i>zeste</i>. I also show that <i>Su(z)12</i> interact genetically with other Pc-G mutants and that the SU(Z)12 protein binds more than 100 euchromatic bands on polytene chromosomes. I also present results showing that SU(Z)12 is a subunit of two different E(Z)/ESC embryonic silencing complexes, one 1MDa and one 600 kDa complex, where the larger complex also contains PCL and RPD3. </p><p>In conclusion, results presented in this thesis show that the recently identified Pc-G gene, <i>Su(z)12</i>, is of vital importance for correct maintenance of silencing of the developmentally important homeotic genes.</p>