Interference Among Meiotic Crossovers Varies Between and Within Chromosomes in Arabidopsis thaliana

In most species, crossovers (COs) are essential for the proper segregation of homologous chromosomes at the first meiotic division. Their number and location are tightly regulated. We have undertaken a detailed, genome-wide, comparison of the interference between COs at the inter and intra-chromosomal levels in Arabidopsis thaliana. CO interference is the non-random occurrence of CO positions along chromosomes leading to a lowered probability of the occurrence of nearby COs. The work of Giraut et al. (PLoS Genetics 2011) localized precisely 13535 COs in male and female meiosis, based on two reciprocal backcross populations composed of 1500 plants each. Here we studied CO interference based on two-pathway modeling in which one pathway produces interfering COs (via the Gamma model), and the second pathway is non-interfering. This choice follows from recent evidence for two separate pathways of CO formation. We have used these models and statistical tests to infer local interference strengths and proportions of non-interfering COs. We found significant differences between male and female meiosis. We have further observed variation in interference between chromosomes as well as across different regions along each chromosome. Finally our analysis also reveals heterogeneities in the proportion of non-interfering pathway along all chromosomes.