Biology subjects

Smukowski Heil, C.

Publications and source records attributed to Smukowski Heil, C..

3 recordsLinked to original sources

bioRxiv2018

Fitness benefits of loss of heterozygosity in Saccharomyces hybrids

With two genomes in the same organism, interspecific hybrids have unique opportunities and costs. In both plants and yeasts, wild, pathogenic, and domesticated hybrids may eliminate portions of one parental genome, a phenomenon known as loss of heterozygosity (LOH). Laboratory evolution of hybrid yeast recapitulates these results, with LOH occurring in just a few hundred generations of propagation. In this study, we systematically looked for alleles that are beneficial when lost in order to determine how prevalent this mode of adaptation may be, and to determine candidate loci that might underlie the benefits of larger-scale chromosome rearrangements. These aims were accomplished by mating Saccharomyces uvarum with the S. cerevisiae deletion collection to create hybrids, such that each nonessential S. cerevisiae allele is deleted. Competitive fitness assays of these pooled, barcoded, hemizygous strains, and accompanying controls, revealed a large number of loci for which LOH is beneficial. We found that the fitness effects of hemizygosity are dependent on the species context, the selective environment, and the species origin of the deleted allele. Further, we found that hybrids have a larger distribution of fitness consequences vs. matched S. cerevisiae hemizygous diploids. Our results suggest that LOH can be a successful strategy for adaptation of hybrids to new environments, and we identify candidate loci that drive the chromosomal rearrangements observed in evolution of yeast hybrids.

genetics↗

bioRxiv2018

Temperature preference biases parental genome retention during hybrid evolution

Interspecific hybridization can introduce genetic variation that aids in adaptation to new or changing environments. Here we investigate how the environment, and more specifically temperature, interacts with hybrid genomes to alter parental genome representation over time. We evolved Saccharomyces cerevisiae x Saccharomyces uvarum hybrids in nutrient-limited continuous culture at 15{degrees}C for 200 generations. In comparison to previous evolution experiments at 30{degrees}C, we identified a number of temperature specific responses, including the loss of the S. cerevisiae allele in favor of the cryotolerant S. uvarum allele for several portions of the hybrid genome. In particular, we discovered a genotype by environment interaction in the form of a reciprocal loss of heterozygosity event on chromosome XIII. Which species haplotype is lost or maintained is dependent on the parental species temperature preference and the temperature at which the hybrid was evolved. We show that a large contribution to this directionality is due to temperature sensitivity at a single locus, the high affinity phosphate transporter PHO84. This work helps shape our understanding of what forces impact genome evolution after hybridization, and how environmental conditions may favor or disfavor hybrids over time.

evolutionary biology↗

bioRxiv2017

Identification of a novel interspecific hybrid yeast from a metagenomic open fermentation sample using Hi-C

Interspecific hybridization is a common mechanism enabling genetic diversification and adaptation; however, the detection of hybrid species has been quite difficult. The identification of microbial hybrids is made even more complicated, as most environmental microbes are resistant to culturing and must be studied in their native mixed communities. We have previously adapted the chromosome conformation capture method Hi-C to the assembly of genomes from mixed populations. Here, we show the methods application in assembling genomes directly from an uncultured, mixed population from a spontaneously inoculated beer sample. Our assembly method has enabled us to de-convolute 4 bacterial and 4 yeast genomes from this sample, including a putative yeast hybrid. Downstream isolation and analysis of this hybrid confirmed its genome to consist of Pichia membranifaciens and that of another related, but undescribed yeast. Our work shows that Hi-C-based metagenomic methods can overcome the limitation of traditional sequencing methods in studying complex mixtures of genomes.

genomics↗