Engineering Yeast Transcription Machinery for Improved Ethanol Tolerance and Production
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ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae Schizosaccharomyces pombe
PROVIDER: GSE5185 | GEO | 2006/11/30
SECONDARY ACCESSION(S): PRJNA96489
REPOSITORIES: GEO
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Project description:Global transcription machinery engineering (gTME) is an approach for reprogramming gene transcription to elicit cellular phenotypes important for technological applications. Here we show the application of gTME to Saccharomyces cerevisiae for improved glucose/ethanol tolerance, a key trait for many biofuels programs. Mutagenesis of the transcription factor Spt15p and selection led to dominant mutations that conferred increased tolerance and more efficient glucose conversion to ethanol. The desired phenotype results from the combined effect of three separate mutations in the SPT15 gene [serine substituted for phenylalanine (Phe177Ser) and, similarly, Tyr195His, and Lys218Arg]. Thus, gTME can provide a route to complex phenotypes that are not readily accessible by traditional methods. Experiment Overall Design: We measured transcription levels for two strains (wild type control and mutant spt15) under normal (0% ethanol, 20 g/L glucose) and stress (5% ethanol, 60 g/L glucose) in biological triplicate.
2008-06-13 | E-GEOD-5185 | biostudies-arrayexpress
Project description:The molecular mechanisms of ethanol toxicity and tolerance in bacteria, while important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and revealed multiple mechanisms of tolerance, but it remains difficult to separate direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, then characterized the mechanisms of toxicity and resistance associated with select mutations. Evolved alleles of metJ, rho, and rpsQ were sufficient to recapitulate much of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. We found that ethanol induces mistranslation errors during protein synthesis, and that the evolved rpsQ allele protects cells by rendering the ribosome hyper-accurate. Ribosome profiling and RNAseq analyses of the ethanol-tolerant strain versus the wild type established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ protect central dogma processes in the presence of ethanol.
2014-06-18 | GSE56407 | GEO
Project description:The molecular mechanisms of ethanol toxicity and tolerance in bacteria, while important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and revealed multiple mechanisms of tolerance, but it remains difficult to separate direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, then characterized the mechanisms of toxicity and resistance associated with select mutations. Evolved alleles of metJ, rho, and rpsQ were sufficient to recapitulate much of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. We found that ethanol induces mistranslation errors during protein synthesis, and that the evolved rpsQ allele protects cells by rendering the ribosome hyper-accurate. Ribosome profiling and RNAseq analyses of the ethanol-tolerant strain versus the wild type established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ protect central dogma processes in the presence of ethanol.
2014-06-18 | GSE56372 | GEO
Project description:Background: Growth in the global population and industrial activities has increased world energy consumption. Bioethanol is considered as an alternative renewable energy source. Among various ethanol-producing microbes, Zymomonas mobilis ZM4 has received special attention due to its higher ethanol yield and tolerance. Advances in genetic engineering are particularly important for developing microorganisms with improved ethanol production. However, the variety of factors involved in the response to high concentrations of ethanol makes it difficult to devise genetic engineering strategies to generate alcohol tolerant strains. For a better understanding of the ethanol tolerance phenomenon, we obtained and characterized two Z. mobilis ZM4 mutants (ER79ap and ER79ag) with increased ethanol tolerance. Results: Mutants were obtained using a strain adaptive evolution method in mini-fermentors and sequential transfers to higher ethanol concentrations. Mutations were identified by Illumina genomic sequencing. Strain ER79ap possesses three point mutations in the following genes: SpoT/RelA, which synthesizes and degrades the alarmone ppGpp; clpB, encoding a disgregase; and clpP, a component of the Clp protease. In contrast, strain ER79ag has four mutations in the subsequent genes: spoT/relA; rimO; clpP; and in a gene encoding a hypothetical protein with a CBS domain. Transcript profiles of ZM4 and ER79ap were obtained with microarray analysis and identified 126 genes in ZM4 and 148 genes in ER79ap that were differentially expressed in response to ethanol. Conclusions: Both mutants carry mutations in clpP and relA/spoT genes, suggesting that these genes are responsible of their enhanced ethanol tolerance. Transcript profile analysis of the ZM4 and ER79ap showed that they share a set of forty genes that are differentially expressed under ethanol stress and this set may correspond to those that are crucial for the ethanol response. The expression profiles indicate that ethanol induces a major reprograming of transcription that involves changes in the cell membrane, protein synthesis, and in some metabolic pathways, especially those involved in the amino acid metabolism. Our data suggest that clpP and in particular the relA/spoT gene can be targets for bioengineering ethanol tolerance.
2016-11-19 | GSE90043 | GEO
Project description:The molecular mechanisms of ethanol toxicity and tolerance in bacteria, while important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and revealed multiple mechanisms of tolerance, but it remains difficult to separate direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, then characterized the mechanisms of toxicity and resistance associated with select mutations. Evolved alleles of metJ, rho, and rpsQ were sufficient to recapitulate much of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. We found that ethanol induces mistranslation errors during protein synthesis, and that the evolved rpsQ allele protects cells by rendering the ribosome hyper-accurate. Ribosome profiling and RNAseq analyses of the ethanol-tolerant strain versus the wild type established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ protect central dogma processes in the presence of ethanol. RNA-seq comparison of wild-type and mutant strains to assess readthrough of Rho-dependent transcriptional terminators
2014-06-18 | E-GEOD-56407 | biostudies-arrayexpress
Project description:The molecular mechanisms of ethanol toxicity and tolerance in bacteria, while important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and revealed multiple mechanisms of tolerance, but it remains difficult to separate direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, then characterized the mechanisms of toxicity and resistance associated with select mutations. Evolved alleles of metJ, rho, and rpsQ were sufficient to recapitulate much of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. We found that ethanol induces mistranslation errors during protein synthesis, and that the evolved rpsQ allele protects cells by rendering the ribosome hyper-accurate. Ribosome profiling and RNAseq analyses of the ethanol-tolerant strain versus the wild type established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ protect central dogma processes in the presence of ethanol. Examination of wild-type and mutant strains at three different time points (one pre-ethanol-stress, two post-ethanol-stress)
2014-06-18 | E-GEOD-56372 | biostudies-arrayexpress
Project description:To improve ethanol production directly from CO2 in photosynthetic cyanobacterial systems, one key issue that needs to be addressed is the low ethanol tolerance of cyanobacterial cells. Our previous proteomic and transcriptomic analyses found that several regulatory proteins were up regulated by exogenous ethanol in Synechocystis sp. PCC 6803. In this study, through tolerance analysis of the gene disruption mutants of the up-regulated regulatory genes, we uncovered that one transcriptional regulator, Sll0794, was related directly to ethanol tolerance in Synechocystis. Using a quantitative iTRAQ-LC-MS/MS proteomics approach coupled with quantitative real-time reverse transcription-PCR (RT-qPCR), we further determined the possible regulatory network of Sll0794. The proteomic analysis showed that in the ∆sll0794 mutant grown under ethanol stress a total of 54 and 87 unique proteins were down- and up-regulated, respectively. In addition, electrophoretic mobility shift assays (EMSAs) demonstrated that the Sll0794 transcriptional regulator was able to bind directly to the upstream regions of sll1514, slr1512 and slr1838, which encode a 16.6 kDa small heat shock protein, a putative sodium-dependent bicarbonate transporter and a carbon dioxide concentrating mechanism protein CcmK, respectively. The study provided a proteomic description of the putative ethanol-tolerance network regulated by the sll0794 gene, and revealed new insights on the ethanol-tolerance regulatory mechanism in Synechocystis. As the first regulatory protein discovered related to ethanol tolerance, the gene may serve as a valuable target for transcription machinery engineering to further improve ethanol tolerance in Synechocystis.
2014-09-26 | PXD001266 | Pride
Project description:High glucose concentrations were desirable for ethanol fermentation of Zymomonas mobilis, but it can lead to decrease in ethanol production and productivity. Sorbitol as a compatible solute can be absorbed or synthesized to counteract the detrimental osmotic stress caused from external high glucose concentrations by Z. mobilis. Currently, molecular mechanisms of tolerance to high glucose concentrations and sorbitol promoting ethanol fermentation are still unclear for Z. mobilis. To better understand mechanisms with which high concentrations of glucose and sorbitol affect physiology and metabolism of Z. mobilis ATCC31821 (ZM4), the global transcriptional responses of ZM4 to the challenge of high glucose concentration and sorbitol were profiled using whole genome microarray analysis. Swings J, Deley J. Bacterial Rev. 1977, 41(1): 1-46. Loos H, Kramer R, Sahm H and Sprenger GA. J Bacteriol. 1994, 176(24):7688–7693.
2014-10-14 | GSE49620 | GEO
Project description:Combination of butanol-hyperproducing and hypertolerant phenotypes is essential for developing microbial strains suitable for industrial production of bio-butanol, i.e. one of most promising liquid biofuels. Clostridium cellulovorans is among the microbial strains with the highest potential for direct production of n-butanol from lignocellulosic wastes, a process that would significantly reduce the cost of bio-butanol. However, butanol exhibits higher toxicity compared to ethanol and C. cellulovorans tolerance to this solvent is low. In the present investigation, comparative proteomics was used to study the response of C. cellulovorans to butanol challenge and understand the tolerance mechanisms activated in this condition. The most important response concerned modulation of protein biosynthesis, folding and degradation. Coherent with previous studies on other bacteria, several heat shock proteins (involved in protein quality control) were upregulated. Globally, our data indicates that protein biosynthesis is reduced, likely not to overload heat shock proteins. Several additional metabolic adaptations were triggered by butanol exposure such as the upregulation of V- and F-type ATPases (involved in ATP synthesis/generation of proton motive force), enzymes involved in amino acid biosynthesis, proteins involved in cell envelope re-arrangement and a redistribution of carbon flux through fermentative pathways. These analyses eventually suggested several potential gene targets for metabolic engineering strategies aimed at improving butanol tolerance in C. cellulovorans.
2021-08-13 | PXD024183 | Pride
Project description:Industrial production of penicillin G by Penicillium chrysogenum requires medium supplementation with the side chain precursor phenylacetate. However, P.chrysogenum grown in presence of phenylalanine as sole nitrogen source formed detectable extracellular amounts of phenylacetate and penicillin G. To get more insights in the metabolism implicated, chemostat-cultivation in presence of 13C9-phenylalanine were carried out. Quantification and modeling of the labeled metabolite pools indicated that phenylalanine was i) incorporated in nascent protein, ii) transaminated to phenylpyruvate and further converted by oxidation or by decarboxylation and iii) oxidized into tyrosine and subsequently assimilated in the homogentisate pathway. Comparative transcriptome analysis of phenylalanine and (NH4)2SO4 grown P.chrysogenum cultures enabled to identify two putative 2-oxo acid decarboxylases Pc13g9300 and Pc18g01490. Both cDNAs were cloned and expressed in the decarboxylase-free Saccharomyces cerevisiae CEN.PK711-7C (pdc1delta, 5delta, 6delta, aro10delta, thi3delta) strain that has lost the ability to grow on glucose as sole carbon source or on phenylalanine as sole nitrogen source. Only Pc13g09300 was able to restore growth on glucose and on phenylalanine, demonstrating that this gene encodes a dual substrate pyruvate, phenylpyruvate decarboxylase. This newly identified thiamine-dependent 2-oxo acid decarboxylase provides clues to explain the formation of phenylacetate via an Ehrlich-like pathway in P.chrysogenum. Penicillium chrysogenum DS17690 was grown in aerobic glucose limited chemostat at 25oC, pH 6.5 and a dilution rate of 0.03h-1 with either amonia or phenylalanine
2011-11-05 | E-GEOD-32097 | biostudies-arrayexpress