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Genomic features shaping the landscape of meiotic double-strand break hotspots in maize [MNase-Seq]

ABSTRACT: We report the application of next generation sequencing techonology to study nucleosomal occupancy in flowers containing zygotene meiocytes. The results show DSB enrichment in nucleosome depleted regions associated with RAD51

ORGANISM(S): Zea mays

PROVIDER: GSE84368 | GEO | 2016/07/13

SECONDARY ACCESSION(S): PRJNA328990

REPOSITORIES: GEO

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Genomic features shaping the landscape of meiotic double-strand break hotspots in maize [ChIP-Seq]

Project description:To generate the double-strand break (DSB) hotspot map in maize, we used a chromatin immunoprecipitation (ChIP) approach, in which chromatin from flowers containing zygotene meiocytes was enriched in fragments associated with RAD51.

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Genomic features shaping the landscape of meiotic double-strand-break hotspots in maize.

Project description:Meiotic recombination is the most important source of genetic variation in higher eukaryotes. It is initiated by formation of double-strand breaks (DSBs) in chromosomal DNA in early meiotic prophase. The DSBs are subsequently repaired, resulting in crossovers (COs) and noncrossovers (NCOs). Recombination events are not distributed evenly along chromosomes but cluster at recombination hotspots. How specific sites become hotspots is poorly understood. Studies in yeast and mammals linked initiation of meiotic recombination to active chromatin features present upstream from genes, such as absence of nucleosomes and presence of trimethylation of lysine 4 in histone H3 (H3K4me3). Core recombination components are conserved among eukaryotes, but it is unclear whether this conservation results in universal characteristics of recombination landscapes shared by a wide range of species. To address this question, we mapped meiotic DSBs in maize, a higher eukaryote with a large genome that is rich in repetitive DNA. We found DSBs in maize to be frequent in all chromosome regions, including sites lacking COs, such as centromeres and pericentromeric regions. Furthermore, most DSBs are formed in repetitive DNA, predominantly Gypsy retrotransposons, and only one-quarter of DSB hotspots are near genes. Genic and nongenic hotspots differ in several characteristics, and only genic DSBs contribute to crossover formation. Maize hotspots overlap regions of low nucleosome occupancy but show only limited association with H3K4me3 sites. Overall, maize DSB hotspots exhibit distribution patterns and characteristics not reported previously in other species. Understanding recombination patterns in maize will shed light on mechanisms affecting dynamics of the plant genome.

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Genomic features shaping the landscape of meiotic double-strand break hotspots in maize

Project description:This SuperSeries is composed of the SubSeries listed below.

2016-07-14 | GSE84369 | GEO

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Project description:This SuperSeries is composed of the SubSeries listed below.

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Project description:During Schizosaccharomyces pombe meiotic prophase, homologous chromosomes are co-aligned by linear elements (LinEs) analogous to the axial elements of the synaptonemal complex (SC) in other organisms. LinE proteins also promote the formation of meiotic DNA double-strand breaks (DSBs), the precursors of cross-overs. Rec10 is required for essentially all DSBs and recombination, and three others (Rec25, Rec27, and Mug20) are protein determinants of DSB hotspots - they bind DSB hotspots with high specificity and are required for DSB formation there. These four LinE proteins co-localize in the nucleus in an interdependent way, suggesting they form a complex. We used random mutagenesis to uncover recombination-deficient missense mutants with novel properties. Some missense mutations changed essential residues conserved among Schizosaccharomyces species. DSB formation, gene conversion, and crossing-over were coordinately reduced in the mutants tested. Based on our mutant analysis, we revised the rec27 open reading frame: the new start codon is in the previously annotated first intron. Genetic and fluorescence-microscopy assays indicated that the Rec10 N- and C-terminal regions have complex interactions with Rec25. These mutants are a valuable resource to elucidate further how LinE proteins and the related SCs of other species regulate meiotic DSB formation to form crossovers crucial for meiosis.

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