Abstract
Haldane's sieve posits that the majority of beneficial mutations that contribute to adaptation should be dominant, as these are the mutations most likely to establish and spread when rare. It has been argued, however, that if the dominance of mutations in their current and previous environments are correlated, Haldaneâ €™ s sieve could be eliminated. We constructed heterozygous lines of Saccharomyces cerevisiae containing single adaptive mutations obtained during exposure to the fungicide nystatin. Here we show that no clear dominance relationship exists across environments: mutations exhibited a range of dominance levels in a rich medium, yet were exclusively recessive under nystatin stress. Surprisingly, heterozygous replicates exhibited variable-onset rapid growth when exposed to nystatin. Targeted Sanger sequencing demonstrated that loss-of-heterozygosity (LOH) accounted for these growth patterns. Our experiments demonstrate that recessive beneficial mutations can avoid Haldaneâ €™ s sieve in clonal organisms through rapid LOH and thus contribute to rapid evolutionary adaptation.
Original language | English (US) |
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Article number | 3819 |
Journal | Nature communications |
Volume | 5 |
DOIs | |
State | Published - May 7 2014 |
Bibliographical note
Funding Information:A.C.G. and S.P.O. conceived the project. A.C.G. conducted all growth experiments and assays while A.K. conducted Illumina and Sanger sequencing and analysed Sanger sequencing results. A.C.G. and S.P.O. conducted all other analyses and drafted the paper. All authors read and approved the final manuscript. Illumina sequencing was performed at the NextGen Sequencing facility at UBC’s Biodiversity Research Centre, established with funding from the Canada Foundation for Innovation.
Funding Information:
We would like to thank D. Lo, W. Li, T. Hinder and J. Ono for laboratory assistance, and M. Whitlock, V. Measday, T. Schulte and the Delta Tea discussion group at UBC for valuable discussion. This study was funded by the National Science and Engineering Research Council of Canada (ACG and SPO), a Killam Trusts Predoctoral Fellowship (ACG) and a Faculty of Science graduate fellowship from the University of British Columbia (ACG).