1. Computational and Systems Biology
  2. Evolutionary Biology
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Further support for aneuploidy tolerance in wild yeast and effects of dosage compensation on gene copy-number evolution

  1. Audrey P Gasch  Is a corresponding author
  2. James Hose
  3. Michael A Newton
  4. Maria Sardi
  5. Mun Yong
  6. Zhishi Wang
  1. University of Wisconsin-Madison, United States
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Cite this article as: eLife 2016;5:e14409 doi: 10.7554/eLife.14409

Abstract

In Hose et al., we performed a genome-sequencing survey and reported that aneuploidy was frequently observed in wild strains of S. cerevisiae. We also profiled transcriptome abundance in naturally aneuploid isolates and found that 10-30% of amplified genes, depending on the strain and affected chromosome, show lower-than-expected expression compared to gene copy number. We argued that this gene group is enriched for genes subject to one or more modes of dosage compensation, where mRNA abundance is decreased in response to higher dosage of that gene. A recent manuscript by Torres et al. refutes our prior work. Here we provide a response to Torres et al., along with additional analysis and controls to support our original conclusions. We maintain that aneuploidy is well tolerated in the wild strains of S. cerevisiae that we studied and that the group of genes enriched for those subject to dosage compensation show unique evolutionary signatures.

Article and author information

Author details

  1. Audrey P Gasch

    Laboratory of Genetics, University of Wisconsin-Madison, Madison, United States
    For correspondence
    agasch@wisc.edu
    Competing interests
    The authors declare that no competing interests exist.
  2. James Hose

    Laboratory of Genetics, University of Wisconsin-Madison, Madison, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Michael A Newton

    Genome Center of Wisconsin, University of Wisconsin-Madison, Madison, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Maria Sardi

    Laboratory of Genetics, University of Wisconsin-Madison, Madison, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Mun Yong

    Laboratory of Genetics, University of Wisconsin-Madison, Madison, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Zhishi Wang

    Department of Statistics, University of Wisconsin-Madison, Madison, United States
    Competing interests
    The authors declare that no competing interests exist.

Reviewing Editor

  1. Duncan T Odom, University of Cambridge, United Kingdom

Publication history

  1. Received: January 14, 2016
  2. Accepted: February 26, 2016
  3. Accepted Manuscript published: March 7, 2016 (version 1)
  4. Version of Record published: March 9, 2016 (version 2)

Copyright

© 2016, Gasch et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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Further reading

    1. Chromosomes and Gene Expression
    2. Genetics and Genomics
    James Hose et al.
    Research Article Updated

    Aneuploidy is linked to myriad diseases but also facilitates organismal evolution. It remains unclear how cells overcome the deleterious effects of aneuploidy until new phenotypes evolve. Although laboratory strains are extremely sensitive to aneuploidy, we show here that aneuploidy is common in wild yeast isolates, which show lower-than-expected expression at many amplified genes. We generated diploid strain panels in which cells carried two, three, or four copies of the affected chromosomes, to show that gene-dosage compensation functions at 10–30% of amplified genes. Genes subject to dosage compensation are under higher expression constraint in wild populations—but they show elevated rates of gene amplification, suggesting that copy-number variation is buffered at these genes. We find that aneuploidy provides a clear ecological advantage to oak strain YPS1009, by amplifying a causal gene that escapes dosage compensation. Our work presents a model in which dosage compensation buffers gene amplification through aneuploidy to provide a natural, but likely transient, route to rapid phenotypic evolution.

    1. Computational and Systems Biology
    2. Evolutionary Biology
    Mato Lagator et al.
    Research Article

    Predicting function from sequence is a central problem of biology. Currently, this is possible only locally in a narrow mutational neighborhood around a wildtype sequence rather than globally from any sequence. Using random mutant libraries, we developed a biophysical model that accounts for multiple features of σ70 binding bacterial promoters to predict constitutive gene expression levels from any sequence. We experimentally and theoretically estimated that 10–20% of random sequences lead to expression and ~80% of non-expressing sequences are one mutation away from a functional promoter. The potential for generating expression from random sequences is so pervasive that selection acts against σ70-RNA polymerase binding sites even within inter-genic, promoter-containing regions. This pervasiveness of σ70-binding sites implies that emergence of promoters is not the limiting step in gene regulatory evolution. Ultimately, the inclusion of novel features of promoter function into a mechanistic model enabled not only more accurate predictions of gene expression levels, but also identified that promoters evolve more rapidly than previously thought.