The hexaploid bread wheat genome comprises over 16 gigabases of sequence across 21 chromosomes. Meiotic crossovers are highly polarized along the chromosomes, with elevation in the gene-dense distal regions and suppression in the Gypsy retrotransposon-dense centromere-proximal regions. We profiled the genomic landscapes of the meiotic recombinase DMC1 and the chromosome axis protein ASY1 in wheat and investigated their relationships with crossovers, chromatin state, and genetic diversity. DMC1 and ASY1 chromatin immunoprecipitation followed by sequencing (ChIP-seq) revealed strong co-enrichment in the distal, crossover-active regions of the wheat chromosomes. Distal ChIP-seq enrichment is consistent with spatiotemporally biased cytological immunolocalization of DMC1 and ASY1 close to the telomeres during meiotic prophase I. DMC1 and ASY1 ChIP-seq peaks show significant overlap with genes and transposable elements in the Mariner and Mutator superfamilies. However, DMC1 and ASY1 ChIP-seq peaks were detected along the length of each chromosome, including in low-crossover regions. At the fine scale, crossover elevation at DMC1 and ASY1 peaks and genes correlates with enrichment of the Polycomb histone modification H3K27me3. This indicates a role for facultative heterochromatin, coincident with high DMC1 and ASY1, in promoting crossovers in wheat and is reflected in distalized H3K27me3 enrichment observed via ChIP-seq and immunocytology. Genes with elevated crossover rates and high DMC1 and ASY1 ChIP-seq signals are overrepresented for defense-response and immunity annotations, have higher sequence polymorphism, and exhibit signatures of selection. Our findings are consistent with meiotic recombination promoting genetic diversity, shaping host–pathogen co-evolution, and accelerating adaptation by increasing the efficiency of selection.

中文翻译：

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小麦基因组的交叉活性区域由 DMC1、染色体轴、H3K27me3 和适应特征来区分

六倍体面包小麦基因组包含跨越 21 条染色体的超过 16 GB 的序列。减数分裂交叉沿染色体高度极化，基因密集远端区域升高，吉普赛人抑制逆转录转座子密集着丝粒近端区域。我们分析了小麦中减数分裂重组酶 DMC1 和染色体轴蛋白 ASY1 的基因组图谱，并研究了它们与交叉、染色质状态和遗传多样性的关系。DMC1 和 ASY1 染色质免疫沉淀随后测序 (ChIP-seq) 揭示了小麦染色体远端交叉活性区域的强共富集。远端 ChIP-seq 富集与减数分裂前期 I 期间靠近端粒的 DMC1 和 ASY1 的时空偏向细胞学免疫定位一致。DMC1 和 ASY1 ChIP-seq 峰显示与Mariner和Mutator中的基因和转座因子显着重叠超家族。然而，沿每条染色体的长度检测到 DMC1 和 ASY1 ChIP-seq 峰，包括在低交叉区域。在精细尺度上，DMC1 和 ASY1 峰和基因的交叉升高与多梳组蛋白修饰 H3K27me3 的富集相关。这表明兼性异染色质（与高 DMC1 和 ASY1 一致）在促进小麦交叉中的作用，并反映在通过 ChIP-seq 和免疫细胞学观察到的远端 H3K27me3 富集中。具有升高的交叉率和高 DMC1 和 ASY1 ChIP-seq 信号的基因在防御反应和免疫注释中被过度代表，具有更高的序列多态性，并表现出选择的特征。我们的研究结果与减数分裂重组促进遗传多样性、塑造宿主-病原体共同进化、