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Data from: Loss-of-heterozygosity facilitates a fitness valley crossing in experimentally evolved multicellular yeast


Baselga-Cervera, Beatriz; Gettle, Noah; Travisano, Michael (2022), Data from: Loss-of-heterozygosity facilitates a fitness valley crossing in experimentally evolved multicellular yeast, Dryad, Dataset,


These data sets are generated to investigate a simple evolutionary landscape that arises from underdominance at a single locus where the fitness valley consists of only one less-fit genotype. We make use of an experimental system previous evolved in the laboratory, the Saccharomyces cerevisiae snowflake system. This system was experimentally selected resulting in a significant evolutionary shift, the transition from uni-to-multicellularity in asexual diploid populations. We carried out the phenotypic and fitness characterization of the strains. Additionally, we observed a rapid loss of heterozygosity (LOH) events in the heterozygote strains. Experimental evolution starting with the heterozygote strains suggests that LOH is common both under selection and without selection.  LOH event drive adaptation that may enable rapid evolution in diploid yeast. 


Phenotypic characterization of the ancestral wildtype and constructed heterozygous and homozygous recessive strains was conducted in a Coulter Counter Multisizer 4 and FlowCam® 3.0. Replicate populations of different isolated strains were analyzed to obtain the population distributions. Fitness assays were carried out by measuring absorbance with Tecan ® infinite 200pro microplate reader, by Colony formation Units (CFUs) of single strains, and by means of competition assays by replica plating. Cells were also counted under an optic microscope in a Neubauer chamber. Populations during the evolution experiment were monitored by Colony formation Units and imaged with the FlowCam® at the end of the experiment, after 10 cycles of selection. 

Data collected by:

-Beckman Coulter Counter Multisizer 4.

-Flow cytometer (FlowCam® 3.0 Fluid Imaging Technologies).

-Tecan ® infinite 200pro microplate reader growth curves data.

-Agar plating Colony formation Units (CFUs).

-Fitness assays were calculated with replica platting.

Usage Notes

Phenotyping data : 



Fitness assays: 



Experimental Evolution data:




Fundación Alfonso Martín Escudero, Award: becas 2048