Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Republic of Singapore.
Science. 2014 Jan 31;343(6170):1248559. doi: 10.1126/science.1248559.
Plant floral stem cells divide a limited number of times before they stop and terminally differentiate, but the mechanisms that control this timing remain unclear. The precise temporal induction of the Arabidopsis zinc finger repressor KNUCKLES (KNU) is essential for the coordinated growth and differentiation of floral stem cells. We identify an epigenetic mechanism in which the floral homeotic protein AGAMOUS (AG) induces KNU at ~2 days of delay. AG binding sites colocalize with a Polycomb response element in the KNU upstream region. AG binding to the KNU promoter causes the eviction of the Polycomb group proteins from the locus, leading to cell division-dependent induction. These analyses demonstrate that floral stem cells measure developmental timing by a division-dependent epigenetic timer triggered by Polycomb eviction.
植物花茎干细胞在停止和终末分化之前分裂有限次数，但控制这种时间的机制仍不清楚。拟南芥锌指抑制剂 KNUCKLES（KNU）的精确时间诱导对于花茎干细胞的协调生长和分化是必不可少的。我们确定了一种表观遗传机制，其中花同源蛋白 AGAMOUS（AG）在大约 2 天的延迟后诱导 KNU。AG 结合位点与 KNU 上游区域的 Polycomb 反应元件共定位。AG 与 KNU 启动子的结合导致 Polycomb 组蛋白从该基因座中被驱逐，从而导致细胞分裂依赖性诱导。这些分析表明，花茎干细胞通过由 Polycomb 驱逐触发的、依赖于分裂的表观遗传计时器来测量发育时间。
