The neddylation pathway regulates the localization of meiotic CO, the pairing of homologous chromosomes and the level of DNA methylation in Arabidopsis thaliana

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Christophorou, Nicolas | Hurel, Aurélie | Idir, Yassir | Tagliaro-Jahns, Marina | Vezon, Daniel | Chambon, Aurélie | Grelon, Mathilde | Bouché, Nicolas | Mézard, Christine

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International audience. Meiotic crossovers (COs) are important for reshuffling genetic information between homologous chromosomes and, are essential for their correct segregation. In all species studied, CO distribution along chromosomes is not homogeneous. The origin of such heterogeneity is still poorly understood but several lines of evidence point towards chromatin structure and chromosome dynamics issues (Mézard et al., 2015). We previously showed that meiotic COs are mis-localized in absence of AXR1, an enzyme involved in the neddylation/rubylation pathway of protein modification in Arabidopsis thaliana. Here, we report that, in axr1-/-, COs are massively redistributed towards subtelomeric ends of the chromosomes where they frequently form clusters, whereas large central regions of the chromosomes were depleted for recombination. We observed that axr1-/- meiocytes exhibit a strong perturbation in chromosome pairing. Furthermore, axr1-/- somatic cells displayed hypermethylation at all types of Transposable Elements (TEs), mainly in the CHG contexts. Consequently, levels of DNA methylation increase along the axr1-/- chromosomes, following the gradient in TE density that expand from the centromere towards the telomeres. We further showed that DNA is also hypermethylated in male meiocytes. COs of axr1-/- therefore preferentially occur in chrosomome regions that are hypomethylated compared to the genome average suggesting that reinforcing the silencing of TEs likely extents the area where COs are normally suppressed.

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