How eukaryotic cells assess and maintain sizes specific for their species and cell type remains unclear. We show that in the Arabidopsis shoot stem cell niche, cell size variability caused by asymmetric divisions is corrected by adjusting the growth period before DNA synthesis. KIP-related protein 4 (KRP4) inhibits progression to DNA synthesis and associates with mitotic chromosomes. The F BOX-LIKE 17 (FBL17) protein removes excess KRP4. Consequently, daughter cells are born with comparable amounts of KRP4. Inhibitor dilution models predicted that KRP4 inherited through chromatin would robustly regulate size, whereas inheritance of excess free KRP4 would disrupt size homeostasis, as confirmed by mutant analyses. We propose that a cell cycle regulator, stabilized by association with mitotic chromosomes, reads DNA content as a cell size–independent scale.

真核细胞如何评估和维持特定于其物种和细胞类型的大小仍不清楚。我们表明，在拟南芥中通过在 DNA 合成前调整生长期来纠正由不对称分裂引起的细胞大小变异。KIP 相关蛋白 4 (KRP4) 抑制 DNA 合成的进展并与有丝分裂染色体相关联。F BOX-LIKE 17 (FBL17) 蛋白可去除多余的 KRP4。因此，子细胞出生时具有相当数量的 KRP4。抑制剂稀释模型预测，通过染色质遗传的 KRP4 会强有力地调节大小，而过量游离 KRP4 的遗传会破坏大小的稳态，正如突变分析所证实的那样。我们建议通过与有丝分裂染色体结合而稳定的细胞周期调节器将 DNA 含量读取为与细胞大小无关的尺度。