Comparing DNA replication programs reveals large timing shifts at centromeres of endocycling cells in maize roots.

摘要: Plant cells undergo two types of cell cycles-the mitotic cycle in which DNA replication is coupled to mitosis, and the endocycle occurs absence division. To investigate programs these cycles, we pulse labeled intact root tips maize (Zea mays) with 5-ethynyl-2'-deoxyuridine (EdU) used flow sorting nuclei examine timing (RT) during transition from a an endocycle. Comparison sequence-based RT profiles showed that most regions genome replicate at same time S phase endocycling cells, despite need twice as much fact typically associated differentiation. However, collectively corresponding 2% displayed significant changes between cycles. The majority are small median size 135 kb, shift later endocycle, enriched for genes expressed tip. We found larger shifted centromeres seven ten chromosomes. These covered previously defined functional centromere, ranged 1 2 Mb reference genome. They mainly mid but primarily late In contrast, immediately adjacent pericentromere sequences replicating both Analysis CENH3 enrichment levels 8C vs 2C suggested there only partial replacement nucleosomes after complete. possible reduction consistent hypothesis inactivated when their function no longer needed.