Biology subjects

Paree, T.

Publications and source records attributed to Paree, T..

4 recordsLinked to original sources

bioRxiv2026

Self-fertilization reverses the direction of selection on recombination

The evolution of recombination is thought to be influenced by many factors, including the mating system. Here, we provide an experimental test of how self-fertilization (selfing) affects the evolution of a recombination modifier. We used experimental populations of Caenorhabditis elegans segregating for the recombination modifier rec-1, a mutant that redistributes crossovers from the genetically diverse chromosome arms toward the less diverse central regions. By evolving populations under varying selfing rates, we show that increasing selfing reverses selection acting on the rec-1 mutant, from positive to negative. Simulations show that this reversal can be explained by an expansion of the genomic region over which the modifier remains associated with the genetic combinations it creates. These results demonstrate that selfing can fundamentally alter the evolutionary fate of recombination modifiers and reveal a mechanism not predicted by previous theoretical models of recombination evolution under different mating systems, which assumed uniform recombination landscapes.

evolutionary biology↗

bioRxiv2026

Caenorhabditis becei recombinant inbred lines (beRILs) reveal the scope of heritable variation within a gonochoristic nematode population.

Caenorhabditis nematodes are a powerful model clade for evolutionary genetics. Isogenic lines and panels of recombinant inbred lines (RILs) are among the most essential tools for genetic studies in these species. While most Caenorhabditis species are gonochoristic, large RIL panels have only been developed for self-fertilizing species. This gap biases our understanding and limits our ability to address questions related to the genetic architecture of traits in outbred populations, which have radically higher genetic diversity, heterozygosity, and effective recombination than selfers. Having previously identified Caenorhabditis becei as a tractable gonochoristic species due to its moderate inbreeding depression, we generated two panels of advanced-intercross RILs derived from three individual outbred C. becei worms collected from a single locality on Barro Colorado Island, Panama. One panel derives from a pair of worms sampled from a single rotting fig; the other derives from a cross between worms from two different figs. The panels share one founder in common, yielding two half-sib RIL panels. We sequenced and haplotyped the lines, identifying millions of variants and thousands of recombination breakpoints. Using simulations, we demonstrate the suitability of these lines for quantitative genetics studies and QTL mapping. In our single-fig panel, we observe abundant heritable variation in population growth rate, individual body size, and sexual dimorphism for body size. We detected four QTLs associated with population growth rate and show that estimated allelic effects are good predictors of selection that occurred during panel derivation.

genetics↗

bioRxiv2024

Selection can favor a recombination landscape that limits polygenic adaptation

Meiotic crossover positions are uneven along eukaryotic chromosomes, giving rise to heterogeneous recombination rate landscapes. Genetic modifiers of local and genome-wide crossover positions have been described, but the selective pressures acting on them and their potential effect on adaptation in already-recombining populations remain unclear. We performed experimental evolution using a mutant that modifies the position of crossovers along chromosomes in the nematode Caenorhabditis elegans, without any detectable direct fitness effect. Our results show that when the recombination landscape is fixed, adaptation is facilitated by the modifier allele that, on average, increases recombination rates in genomic regions containing heritable fitness variation. However, in polymorphic populations containing both the wild-type and mutant modifier alleles, the allele that facilitates adaptation tends to decrease in frequency. This is likely because the allele that reduces recombination between selected loci at the genome-wide scale increases recombination in its chromosomal vicinity, and may thus benefit from local associations it establishes with beneficial genotype combinations. These results demonstrate that indirect selection acting on a recombination modifier mainly depends on its local effect, which may be decoupled from its consequences on genome-wide polygenic adaptation.

evolutionary biology↗

bioRxiv2023

rec-1 loss of function is insufficient to homogenize crossover distribution in Caenorhabditis elegans

Meiotic control of crossover (CO) position is critical for proper homologous chromosome segregation and organismal fertility, recombination of parental genotypes, and the generation of novel genetic combinations. We here characterize the recombination rate landscape of a loss of function genetic modifier of CO position in Caernorhabditis elegans. By averaging CO position across hermaphrodite and male meioses and by genotyping 203 single-nucleotide variants covering about 95% of the genome, we find that the characteristic chromosomal arm-center recombination rate domain structure is lost in a loss of function rec-1 mutant. The rec-1 loss of function mutant smooths the recombination rate landscape but is insufficient to eliminate the non-uniform position of CO. We further find that the rec-1 mutant is of little consequence for organismal fertility and embryo hatchability and thus for rates of autosomal non-disjunction. However, it specifically increases X chromosome non-disjunction rates and males appearance. Our findings question the maintenance of genetic diversity among C. elegans natural populations, and they further suggest that manipulating genetic modifiers of CO position will help map quantitative trait loci in low-recombining genomic regions.

genetics↗