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Induction of DAN/TIR yeast cell wall mannoprotein genes in response to high hydrostatic pressure and low temperature

ABSTRACT: Global transcriptional profiles of Saccharomyces cerevisiae were studied following changes in growth conditions to high hydrostatic pressure and low temperature. These profiles were quantitatively very similar, encompassing 561 co-upregulated genes and 161 co-downregulated genes. In particular, expression of the DAN/TIR cell wall mannoprotein genes, which are generally expressed under hypoxia, were markedly upregulated by high pressure and low temperature, suggesting the overlapping regulatory networks of transcription. In support of the role of the mannoproteins in cell wall integrity, cells acquired resistance against treatment with SDS, Zymolyase and lethal level of high pressure when preincubated under high pressure and low temperature. Keywords: stress response

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE9136 | GEO | 2007/10/05

SECONDARY ACCESSION(S): PRJNA102677

REPOSITORIES: GEO

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Project description:Wine produced at low temperature is often considered to improve sensory qualities. However, there are certain drawbacks to low temperature fermentations: e.g. low growth rate, long lag phase, and sluggish or stuck fermentations. Selection and development of new Saccharomyces cerevisiae strains well adapted at low temperature is interesting for future biotechnological applications. This study aimed to select and develop wine yeast strains that well adapt to ferment at low temperature through evolutionary engineering, and to decipher the process underlying the obtained phenotypes. To this end, we used a pool of 27 commercial yeast strains and set up batch serial dilution experiments to mimic wine fermentation conditions at 12 ºC. Evolutionary engineering was accomplished by using the natural yeast mutation rate and mutagenesis procedures. One strain (P5) outcompeted the others under both experimental conditions and was able to impose after 200 generations. The evolved strains showed improved growth and low-temperature fermentation performance compared to the ancestral strain. This improvement was acquired only under inositol limitation. The transcriptomic comparison between the evolved and parental strains showed the greatest up-regulation in four mannoprotein coding genes, which belong to the DAN/TIR family (DAN1, TIR1, TIR4 and TIR3). Genome sequencing of the evolved strain revealed the presence of a SNP in the GAA1 gene and the construction of a site-directed mutant (GAA1Thr108) in a derivative haploid of the ancestral strain resulted in improved fermentation performance. GAA1 encodes a GPI transamidase complex subunit that adds GPI, which is required for inositol synthesis, to newly synthesized proteins, including mannoproteins. Thus we demonstrate the importance of inositol and mannoproteins in yeast adaptation at low temperature and the central role of the GAA1 gene by linking both metabolisms. The first aim of this study was to assess the most competitive strains that grow under wine fermentation conditions at low temperature. To this end, we performed a growth competition assay with 27 commercial wine strains inoculated at equal population size in synthetic grape must. In spite of the economical and industrial importance of these strains, their phenotypic variation in the main enological traits, particularly those related to optimum growth temperature, and their ability to adapt to low temperature fermentation have been poorly investigated. The second goal was to obtain an improved strain to grow and ferment at low temperature by evolutionary engineering. For this purpose, we maintained growth competition in synthetic grape must during 200 generations to select for the mutations that produce phenotypes with improved growth in this medium. One of these evolved cultures was previously treated with ethyl methanesulfonate (EMS) to increase the mutation rate. Finally, we aimed to decipher the molecular basis underlying this improvement by analyzing the genomic and transcriptional differences between the parental strain and the strain evolved at low temperature.

Project description:Low temperature is the most wide-spread “hostile” environmental factor on earth while at the same time the most common condition for marine organisms. However, the unique adaptive mechanisms that enable the survival of marine microorganisms under low temperature are unclear. Since low temperature is always accompanied by high pressure and other adverse conditions in marine environment, here we studied the metabolic adaptation of a marine strain to prolonged low temperature under high pressure. The strain studied is a psychrotolerant Microbacterium sediminis isolated from deep sea sediment. By using 1H nuclear magnetic resonance (NMR)-based metabolomics approach, we detected the spectral data of polar extracts of the strain M. sediminis, and applied multivariate statistical analysis methods together with univariate analysis to analyze metabolic profiles associated to different conditions. The metabolic profiles of the M. sediminis strain cultivated under high pressure at low temperature were distinctly different from those cultivated under high pressure at normal temperature. We identified the differential metabolites which were responsible for distinguishing the metabolic profiles and compared their relative intensities between groups. We also compared the different adaptive responses of the strain at different growth stages to the prolonged low temperature under high pressure. We proposed that the low-temperature adapting process of the M. sediminis strain involves, 1) the regulation of osmotic pressure using amino acids as possible alternative osmolytes, and, 2) the strengthen of glycolysis and the maintenance of TCA cycle via amino acids anaplerotic reaction. We put forward that the main difference of adaptation to low temperature for the strain at different growth stages was related to energy metabolism. Our findings improved the understanding of the low-temperature adaptive mechanisms for marine microorganisms under high pressure on the metabolic level.

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Induction of DAN/TIR yeast cell wall mannoprotein genes in response to high hydrostatic pressure and low temperature

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