W799What Makes DNA Recombination Hot
Time: 5:00 PM
Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel.
During meiosis, the reciprocal exchange of homologous chromosomal segments is not uniform along chromosomes and differs between the male and female meiocytes. This differences maybe caused by genetics and/or epigenetics factors. We identified crossover events at high resolution using whole genome sequencing of Arabidopsis thaliana. From a detailed genetic and epigenetic analysis we found new recombination hotspots and we identified three DNA motifs that were enriched in crossover regions and were less abundant in centromeric regions. One of these motifs, a CCN repeat, previously unknown in plants resembles the human crossover motif that binds PRDM9, a histone3-lysine4 (H3K4) trimethyl transferase. The motifs at crossover sites contain a specific epigenetic architecture showing a direct association with open chromatin structure. This includes cytosine hypomethylation and a H3K4me3 peak around the CCN repeat. This landscape flanking the motifs was similar in both male and female and the higher rate of male recombination was conserved in the ddm1 mutant. Therefore, cytosine methylation does not account for the higher rate of recombination in the male. Finally, trying to understand the bottlenecks of DNA recombination we have induced DNA double-strand breaks in hot and cold regions of the genome. Results will be discussed.