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

Meiotic recombination results in the exchange of genetic material between homologous chromosomes. One consequence of meiotic recombination is the production of novel combination of alleles. Recombination rate varies dramatically within and between species, populations, sexes and individuals. Although, the role of PRDM9 in intra-chromosomal variation in crossovers is extensively studied, variation in recombination rate and the cellular and evolutionary dynamics that influence recombination is not well understood due to the complexity of the recombination landscape, intrinsic variation in recombination, and the limited experimental approaches. Though, there has only been limited research regarding the variation in recombination rates in Caenorhabditis elegans, observations from previous studies bring out the potential of C. elegans to be a convenient system for studying intra-chromosomal variation in recombination rate that avoid many of the common pitfalls. Therefore, we investigated the variation in intra-chromosomal patterns of recombination rates in two distinct populations of C. elegans in one of the two high recombination regions of chromosome IV. We used phenotypic fluorescent markers which are inserted in chromosome IV to estimate the recombination rate of the two most genetically distinct strains, N2 and CB4856. We identified statistically significant differences in recombination rate between the two strains, with a 3% higher frequency of recombinant offspring in CB4856 in this focal region. Additionally, we did not find any evidence of sex differences in recombination rate (heterochiasmy). Moreover, we looked at the plasticity of recombination rate in response to stressful conditions in the two C. elegans strains. Here we observed a significant decrease in the recombination rate in both strains when exposed to stressful conditions. These results open the door to using C. elegans to study evolution and genetics of variation in recombination rate.