title: Ecological and Genetic Barriers Differentiate Natural Populations of Saccharomyces cerevisiae.
abstract: How populations that inhabit the same geographical area become genetically differentiated is not clear. To investigate this, we characterized phenotypic and genetic differences between two populations of Saccharomyces cerevisiae that in some cases inhabit the same environment but show relatively little gene flow. We profiled stress sensitivity in a group of vineyard isolates and a group of oak-soil strains and found several niche-related phenotypes that distinguish the populations. We performed bulk-segregant mapping on two of the distinguishing traits: The vineyard-specific ability to grow in grape juice and oak-specific tolerance to the cell wall damaging drug Congo red. To implicate causal genes, we also performed a chemical genomic screen in the lab-strain deletion collection and identified many important genes that fell under quantitative trait loci peaks. One gene important for growth in grape juice and identified by both the mapping and the screen was SSU1, a sulfite-nitrite pump implicated in wine fermentations. The beneficial allele is generated by a known translocation that we reasoned may also serve as a genetic barrier. We found that the translocation is prevalent in vineyard strains, but absent in oak strains, and presents a postzygotic barrier to spore viability. Furthermore, the translocation was associated with a fitness cost to the rapid growth rate seen in oak-soil strains. Our results reveal the translocation as a dual-function locus that enforces ecological differentiation while producing a genetic barrier to gene flow in these sympatric populations.
authors.affiliation: Laboratory of Genetics, University of Wisconsin-Madison.
authors.forename: Katie J
authors.initials: KJ
authors.lastname: Clowers
authors.affiliation: Laboratory of Genetics, University of Wisconsin-Madison.
authors.forename: Justin
authors.initials: J
authors.lastname: Heilberger
authors.affiliation: Great Lakes Bioenergy Research Center, Madison, WI.
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Piotrowski
authors.affiliation: Laboratory of Genetics, University of Wisconsin-Madison.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Will
authors.affiliation: Laboratory of Genetics, University of Wisconsin-Madison Great Lakes Bioenergy Research Center, Madison, WI agasch@wisc.edu.
authors.forename: Audrey P
authors.initials: AP
authors.lastname: Gasch
mesh_terms: D000222:Adaptation, Physiological; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism; D017753:Ecosystem; D005285:Fermentation; D005800:Genes, Fungal; D058685:Genetic Pleiotropy; D008126:Lod Score; D010641:Phenotype; D040641:Quantitative Trait Loci; D029963:Quercus / Q000382:microbiology; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D027843:Vitis / Q000382:microbiology
chemical_list: D027321:Anion Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; C108311:Ssu1 protein, S cerevisiae
keywords: ecological divergence; environmental stress; genetic incompatibilities; quantitative trait mapping; reproductive isolation; speciation