Project description:In response to limited nitrogen and abundant carbon sources, diploid Saccharomyces cerevisiae strains undergo a filamentous transition in cell growth as part of pseudohyphal differentiation. Use of the disaccharide maltose as the principal carbon source, in contrast to the preferred nutrient monosaccharide glucose, has been shown to induce a hyper-filamentous growth phenotype in a strain deficient for GPA2 which codes for a Galpha protein component that interacts with the glucose-sensing receptor Gpr1p to regulate filamentous growth. In this report, we compare the global transcript and proteomic profiles of wild-type and Gpa2p deficient diploid yeast strains grown on both rich and nitrogen starved maltose media. We find that deletion of GPA2 results in significantly different transcript and protein profiles when switching from rich to nitrogen starvation media. The results are discussed with a focus on the genes associated with carbon utilization, or regulation thereof, and a model for the contribution of carbon sensing/metabolism-based signal transduction to pseudohyphal differentiation is proposed. Keywords: Saccharomyces cerevisiae, nitrogen starvation, maltose, pseudohyphal differentiation, yeast, expression profiling
Project description:Metabolite concentrations can regulate gene expression, which can in turn regulate metabolic activity. The extent to which functionally related transcripts and metabolites show similar patterns of concentration changes, however, remains unestablished. We have therefore measured and analyzed the metabolomic (previously published in Brauer et al., PMID 17159141) and transcriptional responses (presented here) of Saccharomyces cerevisiae to carbon and nitrogen starvation.
Project description:DNA microarray analysis was used to profile gene expression in a commercial isolate of Saccharomyces cerevisiae grown in a synthetic grape juice medium under conditions mimicking a natural environment for yeast: High-sugar and variable nitrogen conditions. The high nitrogen condition displayed elevated levels of expression of genes involved in biosynthesis of macromolecular precursors across the time course as compared to low-nitrogen. In contrast, expression of genes involved in translation and oxidative carbon metabolism were increased in the low-nitrogen condition, suggesting that respiration is more nitrogen-conserving than fermentation. Several genes under glucose repression control were induced in low-nitrogen in spite of very high (17%) external glucose concentrations, but there was no general relief of glucose repression. Expression of many stress response genes was elevated in stationary phase. Some of these genes were expressed regardless of the nitrogen concentration while others were found at higher levels only under high nitrogen conditions. A few genes, FSP2, RGS2, AQY1, YFL030W, were expressed more strongly with nitrogen limitation as compared to other conditions. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set
Project description:In Saccharomyces cerevisiae, glycogen and trehalose are important reserve carbohydrates that accumulate under nutrient limitation in batch cultures. An inherent draw-back of batch studies is that specific growth rate and substrate and product concentrations are variable over time and between cultures. The aim of this present study was to identify the nutritional requirements associated with high accumulation of reserve carbohydrates at a fixed specific growth rate (0.10 h-1) in anaerobic chemostat cultures that were limited by one of five different nutrients (carbon, nitrogen, sulfur, phosphorus or zinc). Reserve carbohydrates accumulation is not a general response to nutrient limitation. Over the conditions tested, accumulation occurs essentially under nitrogen (and to a lesser extent carbon) limited conditions. This was confirmed by the transcriptional profile of the genes involved in trehalose biosynthesis. We show that the transcriptional induction of both glycogen and trehalose biosynthesis genes was to a large extent driven by the regulator Msn2/4. However, the main regulatory control of glycogen biosynthesis was post-translational. Under nitrogen limitation, the ratio of glycogen synthase over glycogen phosphorylase increased up to eight-fold, thus enabling an increased flux towards glycogen biosynthesis. Experiment Overall Design: We studied this in anaerobic chemostat cultures at a dilution rate of 0.10 h-1 where growth was limited by five different nutrients (carbon, nitrogen, sulfur, phosphorus or zinc limitations). In addition, we studied the expression of these pathways at transcriptional and post-transcriptional levels and assessed the role of Msn2/4 in mediating transcriptional induction of glycogen and trehalose genes in the absence of stress.
Project description:Reprogramming a non-methylotrophic industrial host, such as Saccharomyces cerevisiae, to a synthetic methylotroph reprents a huge challenge due to the complex regulation in yeast. Through TMC strategy together with ALE strategy, we completed a strict synthetic methylotrophic yeast that could use methanol as the sole carbon source. However, how cells respond to methanol and remodel cellular metabolic network on methanol were not clear. Therefore, genome-scale transcriptional analysis was performed to unravel the cellular reprograming mechanisms underlying the improved growth phenotype.
Project description:Microorganisms are exposed to large variations in nutrient availability in nature. To cope with these variations and sustain growth, they maximize the utility of the available nutrients and adapt to nutritional deficiencies. We studied the transcriptional and metabolic dynamics in Saccharomyces cerevisiae in response to a gradual transition from glucose-limited growth to ammonia-limited growth under aerobic or anaerobic conditions. Through exposing yeast to a gradual increase in glucose availability, we discovered new aspects of regulation that ensured a balanced metabolism of glucose and ammonia to sustain growth. This required tight coordination of metabolism with different cellular processes. The coordinated expression of the genes involved in key cellular processes implicated the role of signaling pathways mediated by Tor1, Pka1 and Hog1. This is in contrast to the rapid increase in glucose availability, when Snf1 appeared to be the key regulator. The results presented here provide clear insight into key cellular processes that are affected by nutrient limitation and have direct implications in further studies on genome-scale regulation of metabolism. Gene expression was measured in Saccharomyces cerevisiae as it was exposed to gradualy increasing amounts of glucose under aerobic or anaerobic conditions. Eight samples were collected in each case and gene expression measured.