Abstract

The majority of plants and animals are sexual, meaning they reproduce via meiosis. This is a variant cell division that halves the chromosome number, producing haploid sex cells (gametes). Gamete fusion allows genetic mixing within populations and potentially accelerates the response to selection. During meiosis our chromosomes also pair-up and undergo reciprocal crossover, that further increases genetic variability between progeny. It has long been appreciated that crossovers are non-randomly distributed. For example, they show crossover interference, which causes them to be more widely spaced than expected by chance. To understand recombination we have mapped crossovers along plant chromosomes at fine-scale. We have found that the major crossover hotspots are located at disease resistance genes, which encode pathogen immune receptors. We speculate that this may reflect a mechanism to improve co-evolutionary dynamics with pathogens, via boosting of genetic variability at the immunity genes between generations. The provides circumstantial support for the ‘Red Queen’ theory for the advantage of sex.