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Meiotic recombination dynamics in plants with repeat-based holocentromeres shed light on the primary drivers of crossover patterning
André Marques, Marco Castellani, Meng Zhang, Gokilavani Thangavel, Yennifer Mata Sucre, Thomas Lux, José Campoy, Magdalena Marek, Bruno Hüttel, Hequan Sun, Klaus Mayer, Korbinian Schneeberger
meiosis, recombination, centromeres, crossover, R. breviuscula
Centromeres strongly affect (epi)genomic architecture and meiotic recombination dynamics influencing the overall distribution and frequency of crossovers. Here, we studied how recombination is regulated and distributed in the holocentric plant Rhynchospora breviuscula, a species lacking localised centromeres. Combining immunocytochemistry, chromatin analysis and high-throughput single-pollen sequencing, we discovered that crossover frequency is distally-biased, in sharp contrast with the diffused distribution of hundreds of centromeric units and (epi)genomic features. Remarkably, we found that crossovers were abolished inside centromeric units but not in their proximity indicating the absence of a canonical centromere effect. We further show that telomere-led synapsis of homologs is the feature that best explains the observed recombination landscape. Our results hint at the primary influence of mechanistic features of meiotic pairing and synapsis rather than (epi)genomic features and centromere organisation in determining the distally biased crossover distribution in R. breviuscula. While centromeres and (epi)genetic properties only affect crossover positioning locally.