[대학원 생명과학과 세미나 안내]
연사 : 최규하 교수(POSTECH 생명과학과)
연제 : Meiotic recombination in plants
일시 : 2017년 5월 19일 (금) 오후 4시
장소 : 하나과학관 A동 109호
초청교수 : 김옥매 교수
Abstract
Meiotic recombination profoundly influences genome diversity, and its frequency varies along chromosomes. Recombination hotspots occur in gene-dense euchromatin and coldspots within centromeres. Transposons are thought to be meiotic recombination-silenced, in order to prevent genome instability. To investigate recombination initiation landscape, we mapped meiotic DNA double strand breaks (DSBs) genome-wide by sequencing Arabidopsis SPO11-1-oligonucleotides. Recombination hotspots occur in gene promoters, terminators and introns, driven by AT-sequence richness, which excludes nucleosomes, thereby allowing SPO11-1 access to form DSBs. Unexpectedly, we observed strong DSB hotspots in nucleosome-depleted Helitron/Pogo/Tc1/Mariner DNA transposons, whereas retrotransposon are DSB coldspots. Transposons are transcriptionally silenced by DNA methylation. We found coordinated epigenetic reactivation of transposon recombination, with gain of transcription, chromatin accessibility and histone H3K4 trimethylation in met1 DNA methylation mutants. Interestingly, nucleosome-depleted transposons locate within gene regulatory regions, and are enriched in proximity to immunity genes. This reveals a novel mechanism by which specific DNA transposons act as meiotic recombination enhancers, via nucleosome-exclusion and SPO11-1 recruitment.