背景回顾：Quantitative variation in expression of the Arabidopsis floral repressor FLC influences whether plants overwinter before flowering, or have a rapid cycling habit enabling multiple generations a year. 

提出问题：Genetic analysis has identified activators and repressors of FLC expression but how they interact to set expression level is poorly understood. 

主要发现：Here, we show that antagonistic functions of the FLC activator FRIGIDA (FRI) and the repressor FCA, at a specific stage of embryo development, determine FLC expression and flowering. 

结果：FRI antagonizes an FCA-induced proximal polyadenylation to increase FLC expression and delay flowering. Sector analysis shows that FRI activity during the early heart stage of embryo development maximally delays flowering. 

结论：Opposing functions of cotranscriptional regulators during an early embryonic developmental window thus set FLC expression levels and determine flowering time.

拟南芥开花抑制因子FLC基因表达的数量变异会影响植物在开花前进入越冬，或是有一个快速的循环习性，使得一年内循环多个世代。遗传分析已经鉴定了FLC基因表达的激活子和抑制子，但是这些调控子如何互作以设定FLC基因的表达量还不清楚。本文中，作者发现FLC基因的激活子FRIGIDA和抑制子FCA在胚胎发育某个特定时期的拮抗作用，决定了FLC基因的表达量和植株的开花。FRI会拮抗FAC诱导的近轴多聚腺苷化，增强FLC的表达，从而延迟开花。扇区分析显示FRI在胚胎发育过程的早期心形胚时期具有活性能够最大化延迟开花。在早期胚胎发育时间窗期，共转录调节因子的相反功能设定了FLC的表达水平，并决定植株的开花时间。