Navegando por Autor "Casal, Margarida"

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Biochemical and molecular characterization of Saccharomyces cerevisiae strains obtained from sugar-cane juice fermentations and their impact in cachaça production.
(2008) Oliveira, Valdinéia Aparecida de; Vicente, Maristela de Araújo; Fietto, Luciano Gomes; Castro, Ieso de Miranda; Coutrim, Maurício Xavier; Schüller, Dorit; Alves, Henrique; Casal, Margarida; Santos, Juliana de Oliveira; Araújo, Leandro Dias; Silva, Paulo Henrique Alves da; Brandão, Rogélio Lopes
Saccharomyces cerevisiae strains from different regions of Minas Gerais, Brazil, were isolated and characterized aiming at the selection of starter yeasts to be used in the production of cachac¸a, the Brazilian sugar cane spirit. The methodology established took into account the screening for biochemical traits desirable in a yeast cachac¸a producer, such as no H2S production, high tolerance to ethanol and high temperatures, high fermentative capacity, and the abilities to flocculate and to produce mycocins. Furthermore, the yeasts were exposed to drugs such as 5,5 ,5 -trifluor-D,L-leucine and cerulenin to isolate those that potentially overproduce higher alcohols and esters. The utilization of a random amplified polymorphic DNA-PCR method with primers based on intron splicing sites flanking regions of the COX1 gene, as well as microsatellite analysis, was not sufficient to achieve good differentiation among selected strains. In contrast, karyotype analysis allowed a clear distinction among all strains. Two selected strains were experimentally evaluated as cachac¸a producers. The results suggest that the selection of strains as fermentation starters requires the combined use of biochemical and molecular criteria to ensure the isolation and identification of strains with potential characteristics to produce cachac¸a with a higher quality standard.
Deficiency of Pkc1 activity affects glycerol metabolism in Saccharomices cerevisiae.
(2005) Gomes, Katia das Neves; Freitas, Suzy Magaly Alves Cabral de; Pais, Thiago Martins; Fietto, Juliana Lopes Rangel; Totola, Antonio Helvecio; Arantes, Rosa Maria Esteves; Martins, António; Lucas, Cândida Manuel Ribeiro Simões; Schuller, Dorit; Casal, Margarida; Castro, Ieso de Miranda; Fietto, Luciano Gomes; Rogelio, Lopes Brandão
Protein kinase C is apparently involved in the control of many cellular systems: the cell wall integrity pathway, the synthesis of ribosomes, the appropriated reallocation of transcription factors under specific stress conditions and also the regulation of N-glycosylation activity. All these observations suggest the existence of additional targets not yet identified. In the context of the control of carbon metabolism, previous data had demonstrated that Pkc1p might play a central role in the control of cellular growth and metabolism in yeast. In particular, it has been suggested that it might be involved in the derepression of genes under glucose-repression by driving an appropriated subcellular localization of transcriptional factors, such as Mig1p. In this work, we show that a pkc1D mutant is unable to grow on glycerol because it cannot perform the derepression of the GUT1 gene that encodes glycerol kinase. Additionally, active transport is also partially affected. Using this phenotype, we were able to isolate a new pkc1D revertant. We also isolated two transformants identified as the nuclear exportin Msn5 and the histone deacetylase Hos2 extragenic suppressors of this mutation. Based on these results, we postulate that Pkc1p may be involved in the control of the cellular localization and/or regulation of the activity of nuclear proteins implicated in gene expression.
Relationship between Protein kinase C and derepression of different enzymes.
(2002) Salgado, Ana Paula Carneiro; Schuller, Dorit; Casal, Margarida; Leão, Cecília; Leiper, F. C.; Carling, D.; Gomes, Luciano; Trópia, Maria José Magalhães; Castro, Ieso de Miranda; Brandão, Rogélio Lopes
The PKC1 gene in the yeast Saccharomyces cerevisiae encodes for protein kinase C which is known to control a MAP kinase cascade consisting of di¡erent kinases: Bck1, Mkk1 and Mkk2, and Mpk1. This cascade a¡ects the cell wall integrity but the phenotype of pkc1v mutants suggests additional targets that have not yet been identi¢ed [Heinisch et al., Mol. Microbiol. 32 (1999) 671^680]. The pkc1v mutant, as opposed to other mutants in the MAP kinase cascade, displays defects in the control of carbon metabolism. One of them occurs in the derepression of SUC2 gene after exhaustion of glucose from the medium, suggesting an involvement of Pkc1p in the derepression process that is not shared by the downstream MAP kinase cascade. In this work, we demonstrate that Pkc1p is required for the increase of the activity of enzymatic systems during the derepression process. We observed that Pkc1p is involved in the derepression of invertase and alcohol dehydrogenase activities. On the other hand, it seems not to be necessary for the derepression of the enzymes of the GAL system. Our results suggest that Pkc1p is acting through the main glucose repression pathway, since introduction of an additional mutation in the PKC1 gene in yeast strains already presenting mutations in the HXKII or MIG1 genes does not interfere with the typical derepressed phenotype observed in these single mutants. Moreover, our data indicate that Pkc1p participates in this process through the control of the cellular localization of the Mig1 transcriptional factor.