|
|
Long term sublethal stress in colonies of Saccharomyces cerevisiae deleted in WHI3
Krampotová, Ester ; Schierová, Michaela (advisor) ; Dušková, Michala (referee)
This diploma thesis is devoted to the topic of the development of natural non-pathogenic yeast colonies in non-laboratory diploid strain of Saccharomyces cerevisae with deletion WHI3, during long-term mild stress. The absence of Whi3 causes significantly higher senzitivity to medium composition relative to the parental strain, thus whi3Δ /whi3Δ colonies are a good model for study of the virulence induction due to environmental stress in pathogenic yeasts. Deletion of WHI3 in the BR-F strain results in a significant suppression of the ability to form structured colonies caused mainly by the reduced level of Flo11. The absence of Whi3 also has a negative effect on the expression of other genes involved in the stress response. The aim of the work is to determine whether changes in the expression of genes encoding stress proteins induced by sublethal doses of the inhibitor are dependent on Whi3, Yap6 and Mpt5 proteins. To induce stress in yeast, we used NaCl or CdSO4. The YAP6 and MPT5 genes encode regulatory proteins involved in the stress response, which expression is under control of Whi3. In whi3Δ /whi3Δ , the level of Hsp26, Tsa1, Pab1, and Gre2 was lower than in the parental strain. The Yap6 protein affects the response to the presence of Cd2+ in the medium, although according to SGD, only its...
|
|
|
Role of Ccr4 deadenylase in cell cycle regulation in yeast colonies
Daumová, Lenka ; Čáp, Michal (advisor) ; Převorovský, Martin (referee)
Regulation of cellular processes is of key importance for survival of cells. Many regulations are mediated by the CCR4-Not complex, a highly conserved protein complex, which is present in eucaryotic cells, from yeast to mammals. In this work I study mostly the role of the Ccr4 subunit on yeast survival in the aging colony of Saccharomyces cerevisiae, mainly during cell cycle progression. Ccr4 si a deadenylase, and its main function is cleavage of poly(A) tail of mRNA molecules, and by doing so, shortening the mRNA life-time. It is very important during strictly regulated cellular processes, because it is essential that gene expression of specific genes happens only at specific time. Saccharomyces cerevisiae BY 4742 is a haploid yeast strain, which can easily be used for making deletion mutants in specific genes. In this diploma thesis I focus on studying a deletion mutant of CCR4, along with deletion of other genes, which influence yeast cell cycle. By comparing the phenotype of these mutants with wild type, it is possible to identify changes in phenotype, caused by these deletions, and their influence on yeast cell survival. Key words: cell processes regulation, CCR4-Not complex, Ccr4 subunit, cell cycle, yeast, Saccharomyces cerevisiae, gene deletion
|
|
|
Studies of S. cerevisiae BR-S strain with deletion of SIR2 gene
Novotná, Pavla ; Kuthan, Martin (advisor) ; Pichová, Iva (referee)
Yeasts are unicellular eukaryotic microorganisms, capable of forming of organised multicellular communities, the colonies. Many yeast strains possess a characteristic colony morphology under defined living conditions. Another feature typical for many feral and pathogenic yeast strains is the ability to switch their morphotype. This phenomenon, called the phenotypic switching, contributes to a rapid adaptation to the changing harmful environment and is often connected with changes of the stress resistance or with the changes of virulence of pathogenic yeasts. Phenotypic switching can be observed even in non-pathogenic yeast Saccharomyces cerevisiae. The strain BR-F, isolated from nature, switches under laboratory conditions from fluffy to smooth morphology of the strain BR-S. This phenotypic switch is accompanied by broad changes in the phenotype. Transcriptome analyses of the strains BR-F and BR-S have shown, among others, changes in expression of the subtelomeric genes that are under control of the histone acetylases and deacetylases. My work was aimed to the histone deacetylase Sir2p, which could influence the phenotypic switching in Saccharomyces cerevisiae. The sir2 deletion mutant of the strain BR-S, prepared in our laboratory, was used for my studies. The results show, that the strain BR-S...
|
|
|
Study of the function of selected genes in the colonies of wild yeast strains
Tarabová, Eva ; Kuthan, Martin (advisor) ; Heidingsfeld, Olga (referee)
Saccharomyces cerevisiae strains isolated from the wild are able to exhibit multicellular social behaviour and to form complex structured colonies resembling in many properties highly resistant biofilms of pathogenic yeasts. The capability of phenotypic variability, i.e. high frequency transition between two or more different phenotypes, is another feature typical for the wild yeast strains. Such phenotypic changes are in case of pathogenic yeast often connected with changes in virulence and resistance to stress and antifungal treatment. Long-term cultivation of the wild yeast strains under laboratory conditions leads to their domestication, i.e. transition to smooth colonies and loss of some features typical for structured colonies. This process is, similarly to phenotypic switching, accompanied by significant changes in gene expression and global change of colony lifestyle. Mechanisms underlying yeast phenotypic transitions are ascribed to epigenetic regulation of gene expression via transcriptional silencing conferred by histone deacetylases. This work deals with the study of such mechanisms using knock-outs of selected genes with putative function in formation of structured colonies in wild and domesticated strains. The achieved results show, that NAD+-dependent histone deacetylase Sir2p influences...
|
|
|
Differentiation of yeast colonies and development of new approaches to monitor oxygen and nutrient availability
Vopálenská, Irena ; Janderová, Blanka (advisor) ; Demnerová, Kateřina (referee) ; Pichová, Iva (referee)
Yeast Saccharomyces cerevisiae as an unicellular organism is one of the best-studied experimental organisms. It is an important model organism for the study of intracellular processes of eukaryotic cells. Yeasts are also social organisms with cell-to-cell communication able to form organized multicellular structures (colonies and biofilms). Yeast and other microorganisms in nature prefer to form colonies on solid substrates rather than to grow as "planktonic" single cells (Palková, 2004; Wimpenny, 2009). The yeast S. cerevisiae typically forms colonies, biofilms were described only rarely. Yeast colonies exhibit an organized morphological pattern characteristic of each particular yeast strain (Kocková-Kratochvílová, 1982). This work is focusing on morphology and differentiation of the S. cerevisiae colonies of common laboratory strains forming less structured colonies, and strains of the Σ1278b genetic background forming highly structured "fluffy" colonies. It shows that polarized budding pattern and especially cell ability to form aggregates enable development of structured morphology. During development of "fluffy" colonies two differently regulated events of dimorphic switch from yeast form to filamentous growth occur. One of these events is dependent on the surface glycoprotein, Flo11p flocculin. This...
|
guest ::
