Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Strain abundance assay of barcoded DAmP loss of function S. cerevisiae strains exposed to various compounds

ABSTRACT: The ability to perform complex bioassays in parallel enables experiments otherwise impossible due to throughput and cost constraints. By way of example, highly parallel chemical-genetic screens using pooled collections of thousands of defined Saccharomyces cerevisiae gene deletion strains are feasible because each strain is barcoded with unique DNA sequences. It is, however, time consuming and expensive to individually barcode individual strains. To provide a simple and general method of barcoding yeast collections, we built a set of donor strains, called Barcoders, with unique barcodes that can be systematically transferred to any S. cerevisiae collection. We applied this technology by generating a collection of barcoded DAmP (Decreased Abundance by mRNA Perturbation) loss-of-function strains comprising 87.1% of all essential yeast genes. This test collection validates both the Barcoders and the DAmP collection as useful tools for genome-wide chemical genetic assays.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Zhun Yan

PROVIDER: E-MEXP-1671 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Phenotypic plasticity, the ability of one genotype to express different phenotypes in response to changing environmental conditions, is one of the most common phenomena characterising the living world and is not only relevant for the ecology but also for the evolution of species. Daphnia, the waterflea, is a textbook example for predator induced phenotypic plastic defences including changes in life-history, behaviour and morphology. However, the analysis of molecular mechanisms underlying these inducible defences is still in its early stages. We exposed Daphnia magna to chemical cues of the predator Triops cancriformis to identify key processes underlying plastic defensive trait formation. D. magna is known to develop an array of morphological changes in the presence of T. cancriformis including changes of carapace morphology and cuticle hardening. To get a more comprehensive idea of this phenomenon, we studied four different genotypes originating from habitats with different predation history, reaching from predator-free to temporary habitats containing T. cancriformis. We analysed the morphologies as well as proteomes of predator-exposed and control animals. Three genotypes showed morphological changes when the predator was present. Using a high-throughput proteomics approach, we found 294 proteins which were significantly altered in their abundance after predator exposure in a general or genotype dependant manner. Proteins connected to genotype dependant responses were related to the cuticle, protein synthesis and calcium binding whereas the yolk protein vitellogenin increased in abundance in all genotypes, indicating their involvement in a more general response. Furthermore, genotype dependant responses at the proteome level correlated well with local adaptation to Triops predation. Altogether, our study provides new insights concerning genotype dependant and general molecular processes involved in predator-induced phenotypic plasticity in D. magna.

Project description:This work was designed to identify yeast cellular functions specifically affected by the stress factors predominating during the first stages of wine fermentation and genes required for optimal growth under these conditions. The main experimental method used was quantitative fitness analysis by means of competition experiments of whole genome barcoded yeast knock-out collections in continuous culture. This methodology allowed the identification of haploinsufficient genes and homozygous deletions resulting in growth impairment in synthetic must. However, genes identified as haploproficient or homozygous deletions resulting in fitness advantage were of little predictive power concerning optimal growth in this medium. The relevance of these functions for enological performance of yeast was assessed in batch cultures with single strains. Previous studies addressing yeast adaptation to winemaking conditions by quantitative fitness analysis, were not specifically focused on the proliferative stages, and their results were greatly dependent on the effects of gene deletions on yeast survival during stationary phase. Since biomass production has a great influence on the whole fermentation kinetics, focusing on the proliferative stages of the fermentation process has practical implications. In some instances our results highlight the importance of genes not previously linked to winemaking. In other cases our results are complementary to those reported in previous studies concerning, for example, the relevance of some genes involved in vacuolar, peroxisomal, or ribosomal functions. Transport processes and glucose signaling seem to be negatively affected by the stress factors encountered by yeast in synthetic must. Vacuolar activity is important for continued growth during the transition to stationary phase. Finally, reduced biogenesis of peroxisomes also seems to be advantageous. However, in contrast to what was described for later stages, reduced protein synthesis is not advantageous for the first stages of the fermentation, when most cell proliferation takes place. Competition experiments of the genome-wide collections of mutants were performed in triplicate using conditions that mimicked Phases I or II of a batch fermentation (equivalent to around 14 and 22 hours after inoculation of a batch fermentation, respectively), as well as on YPD (complete medium) for reference purposes. To this end, different feed formulations were used. One mL of either the homozygote or heterozygote pool stored at -80 ºC was added to 50 mL of YPD broth supplemented with 200 µg/mL G418 and incubated overnight at 28 °C and 150 rpm to serve as inoculum for the competition experiments. Samples were taken before the onset of the continuous culture as t=0 (preculture) references. Variations in pool composition were always estimated against the cognate preculture (most often a single preculture served as inoculum for several competitions). After 10 or 20 generations in continuous culture, samples of cells were used for the genomic DNA extraction. lification of the barcodes (uptags and downtags), hybridization, and scanning were performed according to the protocol described elsewhere [Pierce SE, Davis RW, Nislow C, Giaever G (2007) Genome-wide analysis of barcoded Saccharomyces cerevisiae gene-deletion mutants in pooled cultures. Nat Protocols 2: 2958-2974]. Slight modifications concerning the hybridization of Tag4 microarrays by using reagents and protocols from the GeneChip Hybridization, Wash and Stain Kit (Affymetrix) were made.

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Strain abundance assay of barcoded DAmP loss of function S. cerevisiae strains exposed to various compounds

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