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Natural Variation in the Fitness Consequences of Gene Amplification in Wild Saccharomyces cerevisiae Isolates [Bar-seq]

ABSTRACT: Genetic variation that underlies phenotypic differences provides the material on which evolutionary selection acts. Gene duplication/amplification is one type of genetic variation that can allow an organism to rapidly respond to environmental changes by increasing gene dosage. While the potential benefits afforded by gene amplification during evolution are well known, there is also a significant fitness cost to increasing gene dosage including resource shortages and burdening cellular systems. Although the evolutionary importance of gene duplication has long been appreciated, little is known about natural variation in the tolerance of duplication of specific genes. To investigate this question, we expressed the same high-copy gene overexpression (OE) library in a laboratory strain and 14 different wild S. cerevisiae isolates, together representing 4 lineages and several admixed strains, to explore the natural variation in tolerance to gene OE. Our results distinguish universal effects common to many studied strains versus strain-specific effects including broad-scale and gene-specific differences in the consequences of OE. These results raise important implications for the accessibility of evolutionary trajectories afforded by gene OE, depending on genetic background.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE171586 | GEO | 2021/04/07

REPOSITORIES: GEO

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Project description:Gene copy-number variation, which provides the raw material for the evolution of novel genes, is surprisingly widespread in natural populations. Experimental evolution studies have demonstrated an extremely high spontaneous rate of origin of gene duplications. When organisms are suboptimally adapted to their environment, gene duplication may compensate for reduced fitness by amplifying promiscuous activity of a gene, or increasing dosage of a suboptimal gene. The overarching goal of this study is to inverstigate whether CNVs constitute a common mechanism of adaptive genetic change during compensatory evolution and to further characterize the role of natural selection in dictating their evolutionary spread at a population-genomic level. Outcrossing populations of C. elegans with low fitness were evolved for >200 generations and the frequencies of CNVs in these populations were analyzed by oligonucleotide array comparative genome hybridization, quantitative PCR, and single-worm PCR. Multiple duplications and deletions were detected in intermediate to high frequencies and several lines of evidence suggest that the changes in frequency were adaptive. 1) Many copy-number changes reached high frequency, were near fixation, or were fixed in a short time. 2) Many independent duplications and deletions in high frequency harbor overlapping regions which likely include genes that are under selection for either higher or lower rates of expression. 3) The size spectrum of deuplications and deletions in the adaptive recovery populations is significantly larger than that of spontaneous copy-number variants in mutation accumulation experiments. This is expected if larger CNVs are more likely to encompass genes that are being selected for altered gene dosage. Out results validate the great potential borne by gene copy-number changes for compensatory evolution and adaptation. Experimental genome evolution of copy-number variants in 25 experimental lines compared to 5 ancestral control lines.

Dataset Information

Natural Variation in the Fitness Consequences of Gene Amplification in Wild Saccharomyces cerevisiae Isolates [Bar-seq]

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