Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Genomic structure of and genome-wide recombination in the Saccharomyces cerevisiae S288C progenitor isolate EM93

ABSTRACT: The diploid isolate EM93 is the main ancestor to the widely used Saccharomyces cerevisiae haploid laboratory strain, S288C. In this study, we first hybridise DNA from eight EM93 segregants from two tetrads to Affymetrix genechip S. cerevisiae Tiling 1.0R Arrays to generate a high-resolution overview of the genetic differences between EM93 and S288C. We show that EM93 is heterozygous for many polymorphisms, including large sequence polymorphisms, such as deletions and a Saccharomyces paradoxus introgression. We also find that many of the large sequence polymorphisms are associated with Ty-elements and sub-telomeric regions. We next utilize the hybridization profiles of the 3.2 million Tiling Array probes to identify 2,965 genetic markers, which we then used to design an EM93 genotyping array. By genotyping 120 EM93 tetrads, we deduced the structures of all EM93 chromosomes and found that the average EM93 meiosis produces 144 detectable recombination events, consisting of 87 crossover and 57 non-crossover events; we also identified 203 recombination hot-spots and provide evidence for crossover interference. We find that the effect of heterozygous large sequence polymorphisms on recombination is chromosome position-dependent, with sub-telomeric large sequence polymorphisms having no discernable effect on recombination but non-sub-telomeric large sequence polymorphisms reducing recombination. Finally, we find that recombination hotspots show limited conservation, with some but not all strain-specific hotspots being due to heterozygous non-sub-telomeric large sequence polymorphisms.

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Ludo Muller

PROVIDER: E-MEXP-3246 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The data set submitted here contains the raw SNP genotyping data obtained from the analysis of 24 biparental segregating maize (Zea mays L.) populations and their respective parents. The processed and filtered data were used to construct genetic linkage maps which we used in our study of variation of recombination rate in maize. In sexually reproducing organisms, meiotic crossovers ensure the proper segregation of chromosomes and contribute to genetic diversity by shuffling allelic combinations. Such genetic reassortment is exploited in breeding to combine favorable alleles, and in genetic research to identify genetic factors underlying traits of interest via linkage or association-based approaches. Crossover numbers and distributions along chromosomes vary between species, but little is known about their intraspecies variation. In our study, we report on the variation of recombination rates between 22 European maize inbred lines that belong to the Dent and Flint gene pools. We genotyped 23 doubled-haploid populations derived from crosses between these lines with a 50k-SNP array and constructed high-density genetic maps, showing good correspondence with the maize B73 genome sequence assembly. By aligning each genetic map to the B73 sequence, we obtained the recombination rates along chromosomes specific to each population. We identified significant differences in recombination rates at the genome-wide, chromosome, and intrachromosomal levels between populations, as well as significant variation for genome-wide recombination rates among maize lines. Crossover interference analysis using a two-pathway modeling framework revealed a negative association between recombination rate and interference strength. To our knowledge, the present work provides the most comprehensive study on intraspecific variation of recombination rates and crossover interference strength in eukaryotes. Differences found in recombination rates will allow for selection of high or low recombining lines in crossing programs. Our methodology should pave the way for precise identification of genes controlling recombination rates in maize and other organisms.

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Genomic structure of and genome-wide recombination in the Saccharomyces cerevisiae S288C progenitor isolate EM93

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