Transcription profiling by array of fission yeast during adaptation to respiratory medium
ABSTRACT: Fission yeast in high glucose media preferentially uses fermentation for energy production, even under aerobic conditions, an analogous metabolic programme, aerobic glycolysis, is a hallmark of cancer and enables the proliferation of tumor cells. Fission yeast, unlike budding yeast, requires mitochondrial genomes and oxidative phosphorylation for survival, mitochondrial inheritance, genome organisation and RNA processing are strikingly different between the two yeasts, and S. pombe mitochondria resemble more the human mitochondria. However, mitochondrial biology and respiratory control is poorly understood in fission yeast. In this study, we used microarrays to profile gene expression before and at six time points after the shift from fermentative to respiratory medium. Cells were grown in yeast extract based media with 3% glucose to early exponential phase (time point 0), then the carbon source was changed to 3% glycerol, 0.1% glucose. Transcript levels were monitored by microarrays at several time points after the switch (0.2, 0.5, 1, 2; 04 and 24 hours). Sample from each time point is hybrydized with sample of all pooled time points. Experiment was repeated twice with the dye swap.
Project description:Retrograde response was widely studied in budding yeast but the main transcription factors that transmit it (RTG1,2 and 3) are not conserved in other organisms, thus it is interesting to study how communication between mitochondria and nucleus evolved in distantly related fission yeast, and which are the common aspects of this conserved pathway between yeast and higher organisms.To analyse any retrograde response in fission yeast, we inhibited the electron transport chain activity by antimycin A and studied cellular gene expression changes by microarrays. Cells treated with antimycin A in fermentative medium (YE with 3% glucose), showed the same growth rate as untreated cells, but they reached a lower biomass in stationary phase. Antimycin A treated cells consumed glucose at a faster rate and produced more ethanol, indicating that the energy metabolism was shifted even more towards fermentation. We analyzed the transcriptomes of antimycin A-treated cells to untreated control cells during early exponential growth phase (OD 0.5).
Project description:When the yeast Saccharomyces cerevisiae is subjected to increasing glycolytic fluxes under aerobic conditions, there is a threshold value of the glucose uptake rate at which the metabolism shifts from being purely respiratory to mixed respiratory and fermentative. This shift is characterized by ethanol production, a phenomenon known as the Crabtree effect due to its analogy with lactate overflow in cancer cells. It is well known that at high glycolytic fluxes there is glucose repression of respiratory pathways resulting in a decrease in the respiratory capacity. Despite many years of detailed studies on this subject, it is not known whether the onset of the Crabtree effect (or overflow metabolism) is due to a limited respiratory capacity or caused by glucose-mediated repression of respiration. We addressed this issue by increasing respiration in S. cerevisiae by introducing a heterologous alternative oxidase, and observed reduced aerobic ethanol formation. In contrast, increasing non-respiratory NADH oxidation by overexpression of a water-forming NADH oxidase reduced aerobic glycerol formation. The metabolic response to elevated alternative oxidase occurred predominantly in the mitochondria, while NADH oxidase affected genes that catalyze cytosolic reactions. Moreover, NADH oxidase restored the deficiency of cytosolic NADH dehydrogenases in S. cerevisiae. These results indicate that NADH oxidase localizes in the cytosol, while alternative oxidase is directed to the mitochondria. The onset of aerobic ethanol formation is demonstrated to be a consequence of an imbalance in mitochondrial redox balancing. In addition to answering fundamental physiological questions, our findings are relevant for all biomass derived applications of S. cerevisiae. Experiment Overall Design: Heterologous gene expression in chemostats using Affymetrix Yeast Genome 2.0 arrays. Total RNA extraction and sample preparation, hybridization was done according to the manufacturer's protocol.
Project description:Objective: To study if diabetic and insulin-resistant states lead to mitochondrial dysfunction in the liver, or alternatively, if there is adaption of mitochondrial function to these states in the long-term range. Results: High-fat diet (HFD) caused insulin resistance and severe hepatic lipid accumulation, but respiratory chain parameters were unchanged. Livers from insulin-resistant IR/IRS-1+/- mice had normal lipid contents and normal respiratory chain parameters, however showed mitochondrial uncoupling. Livers from severely hyperglycemic and hypoinsulimic, streptozotocin (STZ)-treated mice had massively depleted lipid levels, but respiratory chain abundance was unchanged. However, their mitochondria showed increased abundance and activity of the respiratory chain, which was better coupled compared to controls. Conclusions: Insulin resistance, either induced by obesity or by genetic manipulation, does not cause mitochondrial dysfunction in the liver of mice. However, severe insulin deficiency and high blood glucose levels in mice cause an enhanced performance of the respiratory chain, probably in order to maintain the high energy requirement of the unsuppressed gluconeogenesis. We performed gene expression microarray analysis on liver tissue derived from mice treated with STZ or standard diet (control).
Project description:This experiment describes the transcriptional response to oleic acid as a sole carbon source of yeast strains differing in their respiratory competence: the BY4741 wild type strain is considered as normal, sco1 knock out mutant is respiratory deficient and sco2 knock out mutant has a better respiratory competence then the wild type strain. The three strains underwent metabolic shift from 2% glucose as a carbon source to oleic acid at both standard (0.1%) and high (5%) concentration. The transcriptional profiling comprises two time points after metabolic shift: 2 hours and 5 hours. mRNA levels were compared with reference growth condition: exponential phase in 2% glucose. The purpose of this experiment is to gain deeper insight in the relationship between fatty acid metabolism and respiratory metabolism.
Project description:Responses of Escherichia coli MG1655 as they grow anaerobically in M9 + glucose vs Aerobic growth OD 0.4 Keywords: time course Overall design: Escherichia coli cells sampled at several points (OD 0.08, 0.15, 0.34, 0.73, 1.02, 1,27) in anaerobic growth in M9 + glucose vs Aerobic growth on M9 + glucose,OD 0.4
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:Target of Rapamycin Complex 1 (TORC1) signaling promotes growth and ageing. Inhibition of TORC1 leads to a down-regulation of factors that stimulate protein translation, which in turn contributes to longevity. TORC1-dependent post-transcriptional regulation of protein translation has been well studied, while analogous transcriptional regulation is less understood. Here we screened fission yeast deletion mutants for resistance to Torin1, which inhibits TORC1 and cell growth. Cells lacking the GATA transcription factor Gaf1 (gaf1Δ) grew normally even in high doses of Torin1. The gaf1Δ mutation shortened the chronological lifespan of non-dividing cells and diminished the longevity triggered by Torin1 treatment. Expression profiling and genome-wide binding experiments showed that, upon TORC1 inhibition, Gaf1 directly up-regulated genes for small-molecule metabolic pathways and indirectly repressed genes for protein translation. Surprisingly, Gaf1 bound to, and down-regulated the tRNA genes, so also functions as a transcription factor for genes transcribed by RNA polymerase III. Thus, Gaf1 controls the transcription of both coding and tRNA genes to inhibit translation and growth downstream of TORC1.
Project description:Physiological effects of carbon dioxide and impact on genome-wide transcript profiles were analysed in chemostat cultures of Saccharomyces cerevisiae. In anaerobic, glucose-limited chemostat cultures grown at atmospheric pressure, cultivation under CO2-saturated conditions had only a marginal (<10%) impact on the biomass yield. Conversely, a 25% decrease of the biomass yield was found in aerobic, glucose-limited chemostat cultures aerated with a mixture of 79% CO2 and 21% O2. This observation indicated that respiratory metabolism is more sensitive to CO2 than fermentative metabolism. Consistent with the more pronounced physiological effects of CO2 in respiratory cultures, the number of CO2-responsive transcripts was higher in aerobic cultures than in anaerobic cultures. Many genes involved in mitochondrial functions showed a transcriptional response to elevated CO2 concentrations. This is consistent with an uncoupling effect of CO2 and/or intracellular bicarbonate on the mitochondrial inner membrane. Other transcripts that showed a significant transcriptional response to elevated CO2 included NCE103 (probably encoding carbonic anhydrase), PCK1 (encoding PEP carboxykinase) and members of the IMD gene family (encoding isozymes of inosine monophosphate dehydrogenase Keywords: Dose reponse Overall design: Knowledge on the genome-wide transcriptional response of S. cerevisiae to high CO2 concentrations may provide a deeper insight into the molecular mechanisms of CO2 stress. Such insight is essential to develop metabolic-engineering strategies for improving CO2 tolerance. Furthermore, identification of ‘signature transcripts’ that uniquely respond to CO2 stress may be applicable for diagnosing the CO2 status of industrial fermentations. It has recently been demonstrated that the combination of chemostat cultivation with DNA-microarray-based transcriptome analysis offers a powerful and reproducible approach to identify the transcriptional responses of yeasts to environmental parameters For this reason, in the present study we used chemostat cultures of S. cerevisiae to quantify the effect of CO2 on respiring and fermenting cells, and to determine the genome-wide transcriptional responses of this yeast to high CO2 concentrations.
Project description:Responses of Escherichia coli MG1655 as they grow anaerobically in M9 + glucose + fumarate (as electron acceptor) vs Aerobic growth OD 0.4 Keywords: time course Overall design: Escherichia coli cells sampled at several points (OD 0.15, 0.30, 0.63, 0.85, 1.07, 1.29) in anaerobic growth in M9 + glucose vs Aerobic growth OD 0.4
Project description:In examining NO signaling in the fission yeast Schizosaccharomyces pombe, we found that the putative NO dioxygenase SPAC869.02c (named Yhb1) and the S-nitrosoglutathione reductase Fmd2 cooperatively reduced intracellular NO levels as NO-detoxification enzymes. Although both protein levels were increased with exogenous NO, their expression patterns were different during growth phases. While expression of Yhb1 in the log phase was abrogated by treatment with an NO synthase inhibitor, induction of Fmd2 in the stationary phase was correlated with elevated mitochondrial respiratory chain (MRC) activity and reactive oxygen species (ROS) generation. Moreover, NO was localized in the mitochondria specifically in the stationary phase, suggesting that there are at least two distinctive types of NO signaling in S. pombe cells. For mitochondrial NO signaling, pretreatment with an NO donor effectively rescued the cell viability by repressing generation of ROS under oxidative stress. DNA microarray analysis revealed that exogenous NO contributes to tolerance to hydrogen peroxide (H2O2) stress by (i) inhibition of Fe3+ to Fe2+conversion, (ii) upregulation of the H2O2-detoxifying enzymes, and (iii) downregulation of the MRC genes. Therefore, NO is suggested to play a pivotal role in the negative feedback system to regulate ROS levels under oxidative stress in S. pombe cells. Overall design: We examined the effects of DETA NONOate treatment on gene expression of log-phase Scizosaccharomyces pombe cells by using Affymetrix Yeast Genome 2.0 Array. Total RNA samples were extracred from untreated cells (DetaNONOate 0) and cells treated with 0.5 mM DETA NONOate for 2 h (DetaNONOate 0.5) and were subjected for this DNA microarray analysis.