Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcription profiling of S. cerevisiae S. cerevisiae strain CEN.PK113.7D and the isogenic sfp1 null mutant were grown in chemostat cultures under ethanol(aerobic)- and glucose(anaerobic)- limitation to determine SFP1 dependent transcription

ABSTRACT: In Saccharomyces cerevisiae growth, size control and cell cycle progression are strictly coordinated and regulated according to the nutritional conditions. In particular, ribosome biogenesis appears a key event in this regulatory network. SFP1 encodes a zinc-finger protein promoting the transcription of a large cluster of genes involved in ribosome biogenesis. It has been suggested that Sfp1 is a cell size modulator acting at Start. To better study the regulatory role of Sfp1 and its putative involvement in cell size and cycle control, we analysed the behaviour of an sfp1 null mutant strain and of an isogenic reference strain growing in chemostat cultures. This approach allowed us to analyze both strains at the same specific growth rate, thus eliminating the secondary effects due to the slow growing phenotype that the sfp1 null mutant shows in shake flask. We studied glucose(anaerobic)- and ethanol(aerobic)-limited cultures, as paradigms of two different metabolic states. Major alterations of the transcriptional profile were observed during growth on glucose, while no significant differences were observed when comparing ethanol growing cultures. In particular, in the former growth condition, Sfp1 appears involved in the control of ribosome biogenesis but not of ribosomal protein gene expression. Experiment Overall Design: The reference S. cerevisiae strain CEN.PK113.7D and the isogenic sfp1 null mutant were grown in chemostat cultures under ethanol(aerobic)- and glucose(anaerobic)- limitation. The dilution rate was set at 0.10 h-1 and 0.05 h-1 for ethanol- and glucose-limited cultures, respectively. A genome-wide transcriptional analysis was performed for the reference and the sfp1 null mutant strains for each growth condition. All data presented in this work were derived from three independent chemostat cultures (12 samples in total were analysed).

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Chiara Cipollina

PROVIDER: E-GEOD-5238 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Revisiting the role of yeast Sfp1 in ribosome biogenesis and cell size control: a chemostat study.

Cipollina Chiara C van den Brink Joost J Daran-Lapujade Pascale P Pronk Jack T JT Vai Marina M de Winde Johannes H JH

Microbiology (Reading, England) 20080101 Pt 1

Saccharomyces cerevisiae SFP1 promotes transcription of a large cluster of genes involved in ribosome biogenesis. During growth in shake flasks, a mutant deleted for SFP1 shows a small size phenotype and a reduced growth rate. We characterized the behaviour of an sfp1Delta mutant compared to an isogenic reference strain growing in chemostat cultures at the same specific growth rate. By studying glucose (anaerobic)- and ethanol (aerobic)-limited cultures we focused specifically on nutrient-depend ...[more]

PMID: 18174152

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Project description:The Saccharomyces cerevisiae SFP1 is required for proper regulation of ribosome biogenesis and cell size in response to nutrients. A mutant deleted for SFP1 shows specific traits among which a slow growth phenotype, which is particularly evident during growth on glucose. To assess the effects of nutrients on the activity of Sfp1 independent by growth rate related feedback we grew an sfp1Î mutant and its isogenic reference strain in chemostat cultures, at the same specific growth rate, under glucose/ethanol-limitation. Our data show that Sfp1 is involved in the modulation of cell size and RiBi gene expression and that these two functions are differently influenced by nutrients. The continuous cultures were then pulsed with a glucose excess generating a situation of batch growth similar to shake flask cultures. The dynamic analysis of the metabolic and transcriptional response following the glucose addition suggested that Sfp1 plays a role at the crossroads of ribosome biogenesis and central carbon metabolism regulation. Finally, we show that the down-regulation of RP genes, which was observed in an sfp1Î strain during shake flask growth, cannot be directly ascribed to the absence of Sfp1 but is most probably a secondary effect due to the low growth potential of the mutant strain. Experiment Overall Design: After ten volume changes, few seconds after the samples for the steady state analysis were collected, the anaerobic glucose pulse experiments were started by sparging the medium reservoir and the fermenter with pure nitrogen gas (airflow of 0.5 L min-1, Hoek-Loos, Schiedam, <5 ppm O2). NorpreneTM tubing and butyl septa were used to minimize oxygen diffusion into the anaerobic culture. Two minutes after nitrogen sparging and just before the addition of glucose, the medium and the effluent pumps were switched off. At this time point (which we will refer to as time T=0) the 200 mM glucose pulse was injected aseptically through a rubber septum. Experiment Overall Design: Sampling from chemostats, total RNA extraction, probe preparation and hybridization to Affymetrix GenechipÂ® microarrays were performed as previously described (1). Samples were collected at steady state and then at 5, 10, 30, 60 and 120 minutes after the pulse. The results relative to steady state samples were derived from three independent cultures, those relative to the time course analysis were derived from two independent cultures. Experiment Overall Design: 1) Cipollina C., van den Brink J., Daran-Lapujade P., Pronk J.T., Vai M. and de Winde J.H. (2007) Revisiting the role of yeast Sfp1 in ribosome biogenesis and cell size control: A chemostat study. Microbiology. In press.

Project description:This SuperSeries is composed of the following subset Series: GSE3205: Homeostatic Adjustment and Metabolic Remodeling in Glucose-limited Yeast Cultures Time Course 1 GSE3206: Homeostatic Adjustment and Metabolic Remodeling in Glucose-limited Yeast Cultures Time Course 2 Abstract: We studied the physiological response to glucose limitation in batch and steady-state (chemostat) cultures of Saccharomyces cerevisiae by following global patterns of gene expression. Glucose-limited batch cultures of yeast go through two sequential exponential growth phases, beginning with a largely fermentative phase, followed by an essentially completely aerobic use of residual glucose and evolved ethanol. Judging from the patterns of gene expression, the state of the cells growing at steady state in glucose-limited chemostats corresponds most closely with the state of cells in batch cultures just before they undergo this "diauxic shift." Essentially the same pattern was found between chemostats having a fivefold difference in steady-state growth rate (the lower rate approximating that of the second phase respiratory growth rate in batch cultures). Although in both cases the cells in the chemostat consumed most of the glucose, in neither case did they seem to be metabolizing it primarily through respiration. Although there was some indication of a modest oxidative stress response, the chemostat cultures did not exhibit the massive environmental stress response associated with starvation that also is observed, at least in part, during the diauxic shift in batch cultures. We conclude that despite the theoretical possibility of a switch to fully aerobic metabolism of glucose in the chemostat under conditions of glucose scarcity, homeostatic mechanisms are able to carry out metabolic adjustment as if fermentation of the glucose is the preferred option until the glucose is entirely depleted. These results suggest that some aspect of actual starvation, possibly a component of the stress response, may be required for triggering the metabolic remodeling associated with the diauxic shift. Refer to individual Series

Project description:Cells must adjust their gene expression in order to compete in a constantly changing environment. Two alternative strategies could in principle ensure optimal coordination of gene expression with physiological requirement. First, the internal physiological state itself could feedback to regulated gene expression. Second, the expected physiological state could be inferred from the external environment, using evolutionary-tuned signaling pathways. Coordination of ribosomal biogenesis with the requirement for protein synthesis appears to be particularly important, since cells devote a large fraction of their biosynthetic capacity for ribosomal biogenesis. To define the relative importance of internal vs. external sensing to the regulation of ribosomal biogenesis gene expression, we subjected S. cerevisiae cells to conditions which decoupled the actual vs. environmentally-expected growth rate. Gene expression followed the environmental signal according to the expected, but not the actual, growth rate. Simultaneous monitoring of gene expression and growth rate in chemostat-grown cultures further confirmed that ribosome biogenesis genes responded rapidly to changes in the environments but were oblivious to longer-term changes in growth rate. Our results suggest that the capacity to anticipate and prepare for environmental changes presented a major selection force during yeast evolution. Keywords: Saccharomyces_Cerevisiae, Stress response, ADH1 deletion, time courses, chemostat Experiment 1: ADH1 deletion cells, which grow faster on glycerol rather then glucose medium, were grown in both glucose and glycerol medium. The cells expression on glycerol is compared to their expression glucose (5 microarrays). Experiment 2: Time course of ADH1 deletion cells upon growth on glycerol and on glucose (7 microarrays). Experiment 3: Response of steady state grown cells to environmental perturbations. Cells were grown in glucose or histidine limited chemostats and reached steady state. The cells were then subjected to perturbations such as DTT, heat shock, NaCl, Clotrimazole, H2O2, and addition of limiting factors (histidine and glucose, respectively). Overall we have examined 10 timecourses with 83 microarrays.

Project description:In contrast to batch cultivation, chemostat cultivation allows the identification of carbon source responses without interference by carbon-catabolite repression, accumulation of toxic products, and differences in specific growth rate. This study focuses on the yeast Saccharomyces cerevisiae, grown in aerobic, carbon-limited chemostat cultures. Genome-wide transcript levels and in vivo fluxes were compared for growth on two sugars, glucose and maltose, and for two C2-compounds, ethanol and acetate. In contrast to previous reports on batch cultures, few genes (180 genes) responded to changes of the carbon source by a changed transcript level. Very few transcript levels were changed when glucose as the growth-limiting nutrient was compared with maltose (33 transcripts), or when acetate was compared with ethanol (16 transcripts). Although metabolic flux analysis using a stoichiometric model revealed major changes in the central carbon metabolism, only 117 genes exhibited a significantly different transcript level when sugars and C2-compounds were provided as the growthlimiting nutrient. Despite the extensive knowledge on carbon source regulation in yeast, many of the carbon source-responsive genes encoded proteins with unknown or incompletely characterized biological functions. In silico promoter analysis of carbon source-responsive genes confirmed the involvement of several known transcriptional regulators and suggested the involvement of additional regulators. Transcripts involved in the glyoxylate cycle and gluconeogenesis showed a good correlation with in vivo fluxes. This correlation was, however, not observed for other important pathways, including the pentose-phosphate pathway, tricarboxylic acid cycle, and, in particular, glycolysis. These results indicate that in vivo fluxes in the central carbon metabolism of S. cerevisiae grown in steadystate, carbon-limited chemostat cultures are controlled to a large extent via post-transcriptional mechanisms. Experiment Overall Design: Cultivation of microorganisms in chemostats offers numerous advantages for studying the structure and regulation of metabolic networks (11). In chemostat cultures, individual culture parameters can be changed, while keeping other relevant physical and chemical culture parameters (composition of synthetic medium, pH, temperature, aeration, etc.) constant. An especially important parameter in this respect is the specific growth rate, which, in a chemostat, is equal to the dilution rate, which can be accurately controlled. This allows the experimenter to investigate the effects of environmental changes or genetic interventions at a fixed specific growth rate, even if these changes result in different specific growth rates in batch cultures. In a chemostat, growth can be limited by a single, selected nutrient. The very low residual concentrations of this growth-limiting nutrient in chemostat cultures alleviate effects of catabolite repression and inactivation. Furthermore, these low residual substrate concentrations prevent substrate toxicity, which, for example, occurs when S. cerevisiae is grown on ethanol or acetate as the carbon source in batch cultures . Experiment Overall Design: The central goal of the present study is to assess to what extent carbon source-dependent regulation of fluxes through central carbon metabolism in S. cerevisiae is regulated at the level of transcription. To this end, we compare the transcriptome of carbon-limited, aerobic chemostat cultures grown on four different carbon sources: glucose, maltose, ethanol, and acetate. Data from the transcriptome analysis are compared with flux distribution profiles calculated with a stoichiometric metabolic network model. Questions that will be addressed are as follows: (i) does glucose-limited aerobic cultivation lead to a complete alleviation of glucose-catabolite repression; (ii) how (in)complete is our understanding of the genes involved in the transcriptional response of S. cerevisiae to four of the most common carbon sources for this yeast; and (iii) to what extent do transcriptome analyses with microarrays provide a reliable indication of flux distribution in metabolic networks?

Project description:Prolonged cultivation of Saccharomyces cerevisiae in aerobic, glucose-limited chemostat cultures (dilution rate, 0Â·10 hâ1) resulted in a progressive decrease of the residual glucose concentration (from 20 to 8 mg lâ1 after 200 generations). This increase in the affinity for glucose was accompanied by a fivefold decrease of fermentative capacity, and changes in cellular morphology. These phenotypic changes were retained when single-cell isolates from prolonged cultures were used to inoculate fresh chemostat cultures, indicating that genetic changes were involved. Kinetic analysis of glucose transport in an âevolvedâ strain revealed a decreased Km, while Vmax was slightly increased relative to the parental strain. Apparently, fermentative capacity in the evolved strain was not controlled by glucose uptake. Instead, enzyme assays in cell extracts of the evolved strain revealed strongly decreased capacities of enzymes in the lower part of glycolysis. This decrease was corroborated by genome-wide transcriptome analysis using DNA microarrays. In aerobic batch cultures on 20 g glucose lâ1, the specific growth rate of the evolved strain was lower than that of the parental strain (0Â·28 and 0Â·37 hâ1, respectively). Instead of the characteristic instantaneous production of ethanol that is observed when aerobic, glucose-limited cultures of wild-type S. cerevisiae are exposed to excess glucose, the evolved strain exhibited a delay of 90 min before aerobic ethanol formation set in. This study demonstrates that the effects of selection in glucose-limited chemostat cultures extend beyond glucose-transport kinetics. Although extensive physiological analysis offered insight into the underlying cellular processes, the evolutionary âdriving forceâ for several of the observed changes remains to be elucidated Experiment Overall Design: A crucial feature of bakers' yeast is its capacity to produce CO2, referred to as fermentative capacity (van Hoek et al., 1998). After prolonged glucose-limited cultivation of S. cerevisiae, in addition to an increased affinity for glucose, we observed a dramatic decrease in fermentative capacity. Consequently, the aim of the present study was to perform an integral analysis of the long-term adaptation of S. cerevisiae during prolonged glucose-limited, aerobic cultivation in chemostat cultures, with special emphasis on the regulation of glucose transport and glycolytic capacity. To this end, we applied an integrated approach that combined transcriptome analysis, measurement of fermentative capacity and activities of glucose transport and glycolytic enzymes, and characterization of cellular morphology.

Dataset Information

Transcription profiling of S. cerevisiae S. cerevisiae strain CEN.PK113.7D and the isogenic sfp1 null mutant were grown in chemostat cultures under ethanol(aerobic)- and glucose(anaerobic)- limitation to determine SFP1 dependent transcription

Publications

Revisiting the role of yeast Sfp1 in ribosome biogenesis and cell size control: a chemostat study.

Similar Datasets

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