Centromere satellite repeats have undergone rapid changes in polyploid wheat subgenomes

Centromeres mediate the pairing of homologous chromosomes during meiosis; this pairing is particularly challenging for polyploid plants such as hexaploid wheat (Triticum aestivum), as their meiotic machinery must differentiate homologs from similar homoeologs. However, the sequence compositions (especially functional centromeric satellites) and evolutionary history of wheat centromeres are largely unknown. Here, we mapped T. aestivum centromeres by chromatin immunoprecipitation sequencing using antibodies to the centromeric-specific histone CENH3; this identified two types of functional centromeric satellites that are abundant in two of the three subgenomes. These centromeric satellites had unit sizes over 500 bp and contained specific sites with highly phased binding to CENH3 nucleosomes. Phylogenetic analysis revealed that the satellites have diverged in the three T. aestivum subgenomes, and the more homogeneous satellite arrays are associated with CENH3. Satellite signals decreased a...着丝粒（centromere）介导减数分裂过程中同源染色体的配对；对于六倍体普通小麦（Triticum aestivum）这类多倍体植物而言，该配对过程尤为艰巨，因其减数分裂机制需区分同源染色体与相似的同祖染色体（homoeolog）。然而，目前学界对小麦着丝粒的序列组成（尤其是功能性着丝粒卫星序列）及其演化历史仍知之甚少。本研究通过针对着丝粒特异性组蛋白CENH3的抗体开展染色质免疫沉淀测序（chromatin immunoprecipitation sequencing），对普通小麦的着丝粒进行了定位，最终在三个亚基因组中的两个亚基因组内鉴定出两类丰度较高的功能性着丝粒卫星序列。这类着丝粒卫星序列的单元长度均超过500 bp，且包含与CENH3核小体呈高度有序相位结合的特定位点。系统发育分析显示，这两类卫星序列在普通小麦的三个亚基因组中已发生分化，且序列更为均一的卫星阵列与CENH3存在关联。卫星信号逐渐减弱……