| Identification and investigation of osmostress-induced genes in Dictyostelium discoideum | |
Abstract/OtherAbstract
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D. discoideum is frequently subjected to environmental changes in its natural habitat, the forest soil. In order to survive, the organism had to develop effective mechanisms to sense and respond to such changes. When cells are faced with a hypertonic environment a complex response is triggered. It starts with signal sensing and transduction and leads to changes in cell shape, the cytoskeleton, transport processes, metabolism and gene expression. Certain aspects of the Dictyostelium osmotic stress response have been elucidated, however, no comprehensive picture was available up to now. To better understand the D. discoideum response to hyperosmotic conditions, we applied different methods. We first confirmed that actin is tyrosine phosphorylated, the F-actin cytoskeleton is redistributed, the cell volume is decreased considerably and cell viability is slightly diminished upon sorbitol treatment. Next, gene expression profiling using DNA microarrays was performed. Treatment of Dictyostelium cells with 200 mM sorbitol for 1 hour led to dramatic transcriptional changes, of which some were validated by real time PCR or Northern Blot. The transcriptional profile of cells treated during a 2-hour time course revealed a time-dependent induction or repression of 809 genes, more than 15% of the genes on the array, which peaked 45 to 60 minutes after the hyperosmotic shock. The differentially regulated genes were applied to cluster analysis and functional annotation using gene ontology (GO) terms. Two main responses appear to be the down-regulation of the metabolic machinery and the up-regulation of the stress response system, among them STATc (signal transducer and activator of transcription). Manual annotation revealed that many genes of the major metabolic pathways, including carbohydrate, amino acid and nucleotide metabolism were differentially regulated and could be responsible for the generation of osmolytes. We hypothesize that Dictyostelium uses a mixture of osmolytes to counteract the hyperosmotic stress. Interestingly we also found a number of differentially regulated genes that are involved in development. This is consistent with the notion that the cellular processes that protect amoebae from a hypertonic environment have been adapted for regulatory developmental process. Gene expression profiling with the STATc mutant and appropriate controls showed that STATc is a key regulator of the transcriptional response to hyperosmotic shock. Approximately 20% of the differentially regulated genes that were common between two or three experiments were dependent on the presence of STATc. Our results suggest that at least two signalling pathways are activated in Dictyostelium cells subjected to hypertonicity. STATc is responsible for the transcriptional changes of one of them. |
Authors
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Na, Jianbo |
Contributors
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Publication Detail
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Publisher : Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät. Biochemie I Type : Text.Thesis.Doctoral Format : application/pdf |
Date Detail
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2007 |
Subject
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osmotischer Stress, differential Genexpression, Gene Ontology, Signaltransduktion, Dictyostelium discoideum, osmotic stress, differential gene expression, gene ontology, signal transduction, Dictyostelium discoideum, Life sciences |
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Copyright Information
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Copyright der Metadaten: Universität zu Köln |
Other Details
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Languages : eng |
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