RT Journal Article
SR Electronic
T1 Nucleosomes and DNA methylation shape meiotic DSB frequency in Arabidopsis transposons and gene regulatory regions
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 160911
DO 10.1101/160911
A1 Kyuha Choi
A1 Xiaohui Zhao
A1 Christophe Lambing
A1 Charles J. Underwood
A1 Thomas J. Hardcastle
A1 Heïdi Serra
A1 Andrew J. Tock
A1 Piotr A. Ziolkowski
A1 Nataliya E. Yelina
A1 Robert A. Martienssen
A1 Ian R. Henderson
YR 2017
UL http://biorxiv.org/content/early/2017/07/08/160911.abstract
AB Meiotic recombination initiates via DNA double strand breaks (DSBs) generated by SPO11 topoisomerase-like complexes. Recombination frequency varies extensively along eukaryotic chromosomes, with hotspots controlled by chromatin and DNA sequence. To map meiotic DSBs throughout a plant genome, we purified and sequenced Arabidopsis SPO11-1-oligonucleotides. DSB hotspots occurred in gene promoters, terminators and introns, driven by AT-sequence richness, which excludes nucleosomes and allows SPO11-1 access. A strong positive relationship was observed between SPO11-1 DSBs and final crossover levels. Euchromatic marks promote recombination in fungi and mammals, and consistently we observe H3K4me3 enrichment in proximity to DSB hotspots at gene 5’-ends. Repetitive transposons are thought to be recombination-silenced during meiosis, in order to prevent non-allelic interactions and genome instability. Unexpectedly, we found strong DSB hotspots in nucleosome-depleted Helitron/Pogo/Tc1/Mariner DNA transposons, whereas retrotransposons were coldspots. Hotspot transposons are enriched within gene regulatory regions and in proximity to immunity genes, suggesting a role as recombination-enhancers. As transposon mobility in plant genomes is restricted by DNA methylation, we used the met1 DNA methyltransferase mutant to investigate the role of heterochromatin on the DSB landscape. Epigenetic activation of transposon meiotic DSBs occurred in met1 mutants, coincident with reduced nucleosome occupancy, gain of transcription and H3K4me3. Increased met1 SPO11-1 DSBs occurred most strongly within centromeres and Gypsy and CACTA/EnSpm coldspot transposons. Together, our work reveals complex interactions between chromatin and meiotic DSBs within genes and transposons, with significance for the diversity and evolution of plant genomes.