Abstract
Meiotic recombination drives eukaryotic sexual reproduction and the generation of genome diversity. Tetrad analysis, which examines the four chromatids resulting from a single meiosis, is an ideal method to study the mechanisms of homologous recombination. Here we develop a method to isolate the four microspores from a single tetrad in maize for the purpose of whole-genome sequencing. A high-resolution recombination map reveals that crossovers are unevenly distributed across the genome and are more likely to occur in the genic than intergenic regions, especially common in the 5′- and 3′-end regions of annotated genes. The direct detection of genomic exchanges suggests that conversions likely occur in most crossover tracts. Negative crossover interference and weak chromatid interference are observed at the population level. Overall, our findings further our understanding of meiotic recombination with implications for both basic and applied research.
Highlights
Meiotic recombination drives eukaryotic sexual reproduction and the generation of genome diversity
During prophase I of meiosis, chromosome double-strand breaks are initiated and repaired by homologous recombination between chromatids and result either in genomic exchanges or non-exchanges with synthesis-dependent strand annealing. Both CO and NCO may give rise to gene conversions (GCs), the non-reciprocal genomic exchange between homologous non-sister chromatids, which results in the generation of new alleles
There would be both 2:2 and 3:1 segregation of alleles among the four gamete cells of a single meiosis
Summary
Meiotic recombination drives eukaryotic sexual reproduction and the generation of genome diversity. During prophase I of meiosis, chromosome double-strand breaks are initiated and repaired by homologous recombination between chromatids and result either in genomic exchanges (crossover, CO) or non-exchanges with synthesis-dependent strand annealing (noncrossover, NCO). We describe a simple method to isolate and sequence the whole genome of each of the four microspores from a tetrad to facilitate the study of recombination at the single-cell level in plants. Complex chromatid interference was first observed in maize, which implies that the genetic background may affect genomic selection and evolution These findings provide beneficial information for better understanding of meiotic recombination enhancing plant breeding
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