Inter-strain variation in intra-chromosomal rates of recombination in Caenorhabditis elegans

Abstract

Meiotic recombination, the exchange of genetic material between homologous chromosomes, is a critical cellular process and a fundamental evolutionary parameter. Importantly, its rate varies dramatically across scales, from whole-genomes to kilobases. Although, the role of PRDM9 in intra-chromosomal variation in crossovers is well studied, our broader understanding of cellular and evolutionary dynamics driving intra-chromosomal patterns of recombination rate remains limited, in part due to the complexity of the landscape and the intrinsic difficulty of measuring this phenotype. Research on recombination rate variation in Caenorhabditis elegans is relatively sparse, but prior work suggests that this species provides a tractable system for studying intra-chromosomal recombination without many common confounding factors. Here, we measure variation in intra-chromosomal patterns of recombination rates in two genetically distinct populations (N2 and CB4856) of C. elegans. We find statistically significant, domain-specific differences in recombination rate between the two strains. Specifically, on chromosome IV, recombination is higher in the gene-rich central domain in N2, but higher in the gene-poor distal domain in CB4856. We detect no evidence of sex differences in recombination rate (heterochiasmy). Together, our findings demonstrate divergence in intra-chromosomal patterns of recombination between two widely utilized strains in a model system with an otherwise highly conserved recombination landscape.