The evolution of recombination rates
General Genetics and Functional Genome Biology
Evolution, Anthropology
Final Report Abstract
Recombination, the exchange of genetic material between paired chromosomes during meiosis, generates new allele combinations and influences both short-term outcomes and longterm evolution. Variation in recombination rates exists between organisms and across genomic regions within species. However, the mechanisms driving this variation and its evolution remain poorly understood. This project used the model organism Schizosaccharomyces pombe to study recombination rate variation through experimental evolution, natural isolate analysis, and investigations into the effects of structural variation. To examine how recombination rates evolve, we conducted experimental evolution by selecting for increased or decreased recombination over 35 sexual generations using fluorescent markers and fluorescence-activated cell sorting (FACS). Results demonstrated that recombination rates could evolve under selection, with greater increases when selection targeted global recombination across two intervals than when focused on a single hotspot. Recombination rate reduction was also observed under strong selection against it, highlighting the plasticity of recombination as an evolvable trait. In exploring natural variation, we measured recombination rates at three genomic intervals in 57 natural isolates of S. pombe using a tetrad-based fluorescent imaging method enhanced by a convolutional neural network for image processing. Significant variation was observed between strains and chromosomes, but recombination rates did not correlate with genetic similarity, suggesting regulation is not global. A genome-wide association study (GWAS) did not identify loci linked to this variation, hinting at potential unknown mechanisms or environmental influences. In a complementary study, artificial chromosomal inversions were introduced to dissect the structural and genetic effects on recombination suppression. Inversions significantly reduced gamete viability and suppressed recombination near breakpoints in isogenic strains. However, in divergent strains, the genetic content within inverted regions had a greater impact than the structural features, challenging assumptions about inversions and recombination suppression. These findings provide insights into processes such as sex chromosome evolution and species divergence. Beyond generating novel insights, the project developed valuable tools, including new molecular techniques and a neural network for tetrad analysis, that will benefit future research. Collectively, these findings enhance our understanding of recombination as a dynamic and evolvable trait, with implications for genetic diversity, adaptation, and evolutionary biology. Future work will focus on uncovering the genetic mechanisms dri
Publications
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Inversions and integrations using CRISPR/Cas9 and a module-based plasmid construction kit for fission yeast. openRxiv.
Berenguer, Millanes Cristina & Nieuwenhuis, Bart P.S.
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Supplementary data for Berenguer Millanes et al. 2025.
Berenguer, Millanes Cristina & Nieuwenhuis, Bart P.S.
