Determinantes macroeconômicos do investimento externo em ações: uma análise da economia brasileira para o período 1995-2005

TCC (graduação) - Universidade Federal de Santa Catarina. Centro Sócio-Econômico. Economia.Entre o final dos anos oitenta e início dos anos noventa, várias economias iniciaram reformas para liberalizar e desregulamentar seus mercados de capitais. De acordo com a Moderna Teoria de Alocação de Portfólio, à medida que se incluem ativos na carteira (com coeficiente de correlação menor que 1), elimina-se o risco diversificável, devendo apenas o investidor preocupar-se com o risco não-diversificável. Esse, reflete a contribuição do ativo ao risco da carteira e sua mensuração é extremamente importante, pois permite que o investidor escolha ativos que menos contribuam para o risco da carteira, ou seja, que tenham melhor relação risco-retorno. Assim, no contexto de inserção da economia brasileira no mercado mundializado, identificar quais as variáveis que atraem o investidor externo ao mercado de ações brasileiro possui relevante significância. Para tanto, verificase neste trabalho a influência de determinadas variáveis macroeconômicas em relação ao fluxo de investimento externo em ações no Brasil para o período compreendido entre janeiro de 1995 até dezembro de 2005. Os resultados evidenciaram que as variáveis riscoBrasil, agregados monetários M2 e M4, Ibovespa, dívida líquida do setor público em percentual do PIB, valor das empresas listadas no Ibovespa, inflação externa, índice de produção industrial externo e comportamento do mercado acionário externo influenciam na decisão do investimento estrangeiro em ações no Brasil. Além disso, o comportamento passado do fluxo externo (líquido ou de entrada) direcionado ao mercado bursátil brasileiro influencia no crescimento/redução do fluxo presente

Role of homeodomain leucine zipper (HD-Zip) iv transcription factors in plant development and plant protection from deleterious environmental factors

Homeobox genes comprise an important group of genes that are responsible for regulation of developmental processes. These genes determine cell differentiation and cell fate in all eukaryotic organisms, starting from the early stages of embryo development. Homeodomain leucine zipper (HD-Zip) transcription factors are unique to the plant kingdom. Members of the HD-Zip IV subfamily have a complex domain topology and can bind several cis-elements with overlapping sequences. Many of the reported HD-Zip IV genes were shown to be specifically or preferentially expressed in plant epidermal or sub-epidermal cells. HD-Zip IV TFs were found to be associated with differentiation and maintenance of outer cell layers, and regulation of lipid biosynthesis and transport. Insights about the role of these proteins in plant cuticle formation, and hence their possible involvement in plant protection from pathogens and abiotic stresses has just started to emerge. These roles make HD-Zip IV proteins an attractive tool for genetic engineering of crop plants. To this end, there is a need for in-depth studies to further clarify the function of each HD-Zip IV subfamily member in commercially important plant species.William Chew, Maria Hrmova and Sergiy Lopat

Molecular Characterization of Mitochondria Interactions with other Organelels

The topic of this PhD thesis was to study organelles in plant cells, analysing in particular the mitochondrial morphology. Recent papers have, in fact, reported that regulation of mitochondrial morphology is important not only for maintaining mitochondrial number during cell division, and mitochondrial distribution within each cell (Westermann, 2010; Logan, 2003), but also for executing many biological functions. In animals, a shift in mitochondrial morphology towards the organelle fragmentation is an early event during apoptosis (Suen et al., 2008). In plants, a link between mitochondrial morphology and senescence-associated cell death (i.e. a genetically controlled programme of self destruction) has been reported in Medicago truncatula cultured cells (Zottini et al., 2006). The understanding of molecular mechanisms, used by plants to regulate senescence, might allow biotechnological applications through genetic manipulations of key elements affecting senescence and provide interesting applicative outputs, especially in agronomically relevant species. In light of these findings, I focused on the study of mitochondrial morphology during senescence in grapevine (Vitis spp.) plants, one of the most important crops in Mediterranean area that has also the potentiality of becoming a model organism for fruit trees due to the knowledge of its genome sequence (Jaillon et al., 2007; Velasco et al., 2007). Suspension cell cultures of Vitis spp. were chosen as an initial model system to study mitochondrial morphology during senescence/PCD, because they are an accessible and not complex experimental system, sharing some of fundamental regulatory mechanisms with PCD processes in plant. Then, in order to study changes in mitochondrial morphology during different stages of leaf development and senescence, transgenic grapevine plants, expressing GFP (green fluorescent protein) fluorescent marker targeted to mitochondria, were generated. In the grapevine leaves the senescence/PCD process was characterized by analyzing the chlorophyll degradation and the expression of several VvSAGs genes (i.e. Vitis homologues of Arabidopsis senescence associated genes). Analyses performed in grapevine senescent leaves showed mitochondria prefunding altered in their morphology. Then, we moved to investigate to the molecular aspects of these morphological changes. Indeed, it is known that in eukaryotic cells, the number, size and distribution of mitochondria are regulated by continuous cycles of mitochondrial fusions and fission events (Logan, 2003) but so far in plants, no genes involved in mitochondrial fusion machinery have been identified, while several genes involved in mitochondrial fission have been recently described in Arabidopsis thaliana, a plant model organism. Hence, I moved to Arabidopsis plant and I focused on the study of the subcellular localization, expression and interaction of two proteins (ELM1 and BIGYIN), known to be involved in mitochondrial fission. ELM1 and BIGYIN subcellular localization was carefully analyzed, by using several organelle fluorescent markers and adopting different methods of transient expression in leaf cells, combined with confocal microscope analyses. Yet, I investigated whether in vivo interactions between ELM1 and BIGYIN occurred in plant cells. Then, I analyzed ELM1 and BIGYIN expression pattern in plant to verify if their presence in the same tissues was indeed detected. The analysis was carried out through histochemical GUS assay in transgenic plants, stable expressing the ELM1 and BIGYIN promoter region fused to the -glucuronidase (GUS) reporter. In order to define the physiological role of BIGYIN, a detailed subcellular localization of BIGYIN was performed in the whole plant, stably expressing BIGYIN under control of its own promoter, in order to mimic physiological conditions. These analyses allowed us to establish an association between BIGYIN and chloroplasts/plastids and, in particular, to identify protrusions, marked by YFP::BIGYIN, extruding from chloroplast, mitochondria and peroxisomes. Such kind of tubular protrusions has already been observed and termed matrixules, peroxules stromules respectively, and it has been proposed to play a role in physical inter-organellar interactions, by increasing the transfer efficiency of metabolites/molecules among organelles (Scott et al., 2007). The presence of BIGYIN on these protrusions is indeed an unexpected finding that led us to investigate more in detail this peculiar BIGYIN localization. I focused in detail on the dynamics and behaviour of these YFP::BIGYIN marked tubules, and investigated, in different tissues and different developmental stages, whether a protein trafficking through these organelles indeed occurred. The understanding of physical inter-organellar interactions is connected with the importance of elucidating relationships and cross-talks among organelles, key events to understand the mechanisms of interactions between plant and its environment that can be of particular importance for the coordination of the senescent program.In questa tesi di dottorato, è stata condotta un’analisi degli organelli in cellule vegetali, studiando, in particolare, i mitocondri e la loro morfologia in diverse condizioni fisiologiche. La regolazione della morfologia mitocondriale è importante sotto molteplici aspetti, infatti controlla il numero dei mitocondri durante la divisione cellulare e la loro distribuzione all’interno di ogni cellula (Wastermann, 2010; Logan, 2003), controlla infine alcune funzioni biologiche. Nelle cellule animali, per esempio, la frammentazione dei mitocondri è un evento precoce che caratterizza il processo di apoptosi (Suen et al., 2008). Un’associazione tra morfologia mitocondriale e senescenza/morte cellulare programmata (PCD) è stata riportata anche in colture cellulare vegetali (Zottini et al., 2006). La comprensione dei meccanismi molecolari, utilizzati dalla pianta per regolare il processo di senescenza/PCD, può essere importante da un punto di vista biotecnologico, in quanto potrebbe permettere una modulazione dei parametri di crescita e di sviluppo della pianta attraverso miglioramenti genetici e manipolazioni di fattori ambientali che regolano il processo di senescenza. I risvolti applicativi di tale approcio sono molto interessanti, soprattutto per le specie di rilevanza agronomica. Alla luce di tali premesse, la morfologia mitocondriale è stata dettagliatamente analizzata durante il processo di senescenza/PCD in vite (Vitis spp). La vite rapprensenta una delle più importanti piante coltivate della zona del Mediterraneo, ed a seguito del sequenziamento del suo genoma (Jaillon et al., 2007; Velasco et al., 2007), è ritenuta un organismo modello negli studi sugli alberi da frutto. Inizialmente l’analisi della morfologia mitocondriale durante il processo di senescenza/morte cellulare programmata è stata condotta in colture cellulari di Vitis spp.. In seguito, lo studio è stato continuato in pianta, in particolare è stata portata avanti un’analisi dettagliata della morfologia mitocondriale durante i differenti stadi di sviluppo e di senescenza della foglia. A tal fine, sono state prodotte ed analizzate piante transgeniche, esprimenti un marcatore fluorescente mitocondriale. Le analisi condotte hanno dimostrato che in foglie senescenti i mitocondri presentano delle morfologie caratteristiche. Questi risultati ci hanno indirizzato ad uno studio degli aspetti molecolari coinvolti nella regolazione della morfologia mitocondriale. In numerose cellule eucariotiche, la morfologia mitocondriale è regolata dal continuo alternarsi di eventi di fusione e fissione mitocondriale (Logan, 2003). Nelle piante, i componenti molecolari coinvolti nel meccanismo di fusione mitocondriale non sono stati ancora individuati, mentre i componenti proteici implicati nella fissione sono stati recentemente descritti in Arabidopsis. A tuttoggi non è stato ancora compreso nè il preciso ruolo svolto da tali proteine, nè le loro precise interazioni fisiche, responsabili del processo di fissione mitocondriale. Durante il mio dottorato, ho quindi analizzato, nel sistema modello Arabidopsis thaliana, la localizzazione subcellulare, l’espressione e l’interazione di due proteine (ELM1 ed BIGYIN), coinvolte nel processo di divisione mitocondriale. La localizzazione subcellulare di ELM1 e BIGYIN è stata determinata in cellule vegetali, utilizzando differenti metodi di espressione transiente combinati con analisi di microscopia confocale. Sono state poi eseguite analisi per verificare l’interazione di queste due proteine in vivo in cellule vegetali. Successivamente è stata condotta in pianta un’analisi del pattern di espressione di BIGYIN ed ELM1, in modo tale da verificarne l’espressione di queste due proteine negli stessi tessuti, prerequisito fondamentale per una loro eventuale interazione. A tal fine, sono state prodotte ed analizzate mediante saggio istochimico-colorimetrico piante transgeniche di Arabidopsis thaliana stabilmente esprimenti il promotore di tali geni fuso al gene che codifica per l’enzima -glucuronidasi (GUS). Per definire il ruolo fisiologico di BIGYIN, una dettagliata localizzazione subcellulare di questa proteina è stata eseguita in piante di Arabidopsis, stabilmente esprimenti il costrutto YFP::BIGYIN sotto il controllo del proprio promotore. Queste analisi hanno messa in evidenza un’associazione tra BIGYIN e cloroplasti/plastidi ed ha portato ad individuare particolari protrusioni, marcate con la proteina di fusione YFP::BIGYIN, che si estondono dai cloroplasti, mitocondri e perossisomi. Protrusioni simili erano già state riportate in letteratura e prendono il nome di ‘stromuli’, ‘matrixuli’, ‘peroxuli’ a seconda che si estendano rispettivamente da cloroplasti, mitocondri o perossisomi. Recentemente, è stato ipotizzato che tali le protrusioni abbiano un ruolo nelle interazioni fisiche tra i differenti organelli, aumentando i contatti fisici tra gli organuli e migliorando l’efficienza di scambio di metaboliti/molecule (Scott et al., 2007). Tuttavia nessun dato è stato riportato a conferma di tale ipotesi. L’inattesa presenza di BIGYIN su tali protrusioni, ci ha permesso di studiare in dettaglio la loro dinamicità e di analizzare la presenza di interazioni fisiche tra gli organelli. La comprensione delle interazioni fisiche tra gli organelli si colloca nel campo di indagine delle relazioni tra tali compartimenti subcellulari che viene ora considerato un campo fondamentale per la conoscenza dei meccanismi di base della biologia cellulare vegetale

Agroinfiltration of grapevine leaves for fast transient assays of gene expression and for long-term production of stable transformed cells

Agrobacterium-mediated transient assays for the analysis of gene function are used as alternatives to genetic complementation and stable plant transformation. Although such assays are routinely performed in several plant species, they have not yet been successfully applied to grapevines. We explored genetic background diversity of grapevine cultivars and performed agroinfiltration into in vitro cultured plants. By combining different genotypes and physiological conditions, we developed a protocol for efficient transient transformations of selected grapevine cultivars. Among the four cultivars analyzed, Sugraone and Aleatico exhibited high levels of transient transformation. Transient expression occurred in the majority of cells within the infiltrated tissue several days after agroinfiltration and, in a few cases, it later spread to a larger portion of the leaf. Three laboratory strains of Agrobacterium tumefaciens with different virulence levels were used for agroinfiltration assays on grapevine plants. This method promises to be a powerful tool to perform subcellular localization analyses. Grapevine leaf tissues were transformed with fluorescent markers targeted to cytoplasm (free GFP and mRFP1), endoplasmatic reticulum (GFP::HDEL), chloroplast (GAPA1::YFP) and mitochondria (beta::GFP). Confocal microscope analyses demonstrated that these subcellular compartments could be easily visualized in grapevine leaf cells. In addition, from leaves of the Sugraone cultivar agroinfiltrated with endoplasmic reticulum-targeted GFP-construct, stable transformed cells were obtained that show the opportunity to convert a transiently transformed leaf tissue into a stably transformed cell line

The Arabidopsis Athb-10 (GLABRA2) is an HD-Zip protein required for regulation of root hair development.

Homeodomain-leucine zipper (HD-Zip) proteins are putative transcription factors identified only in plants. Related Arabidopsis homeobox genes, isolated by virtue of sequence conservation within the helix-3 region of the homeodomain, fall into four families based on sequence similarity. This paper reports the characterization of Athb-10, a 747 amino acid protein belonging to the fourth HD-ZIP family. The studies indicate that, although less conserved, the leucine zipper of Athb-10 can functionally replace that of Athb-2 in an in vitro DNA-binding assay. Gene mapping experiments and sequence comparison analysis revealed that Athb-10 corresponds to GLABRA2, a homeodomain protein involved in trichome development. The mRNA expression analysis revealed that Athb-10/GLABRA2 is expressed not only in trichome-bearing organs, but also in the root. The analysis of wild-type and mutant plants showed that the Athb-10/GLABRA2 gene expression in the aerial part of the plant and in the root is affected by mutations at the TTG locus. Morphological analysis of the g/2-1 mutant revealed that the gene is necessary not only for local outgrowth of the trichome, but also for the regulation of root hair development in a subset of epidermal cells. Interestingly, the development of root hair cells in a position normally occupied by non-hair cells is dependent upon the ethylene regime in which the gl2-1 plants are grown. Sequence analysis of the gl2-1 allele revealed that the mutant gene encodes a truncated protein that might still retain a partial activity responsible for the formation of aborted trichomes and for the ethylene-dependent regulation of root hair formation