Coordination of shoot apical meristem shape and identity by APETALA2 during floral transition in Arabidopsis

Plants flower in response to environmental signals. These signals change the shape and developmental identity of the shoot apical meristem (SAM), causing it to form flowers and inflorescences. We show that the increases in SAM width and height during floral transition correlate with changes in size of the central zone (CZ), defined by CLAVATA3 expression, and involve a transient increase in the height of the organizing center (OC), defined by WUSCHEL expression. The APETALA2 (AP2) transcription factor is required for the rapid increases in SAM height and width, by maintaining the width of the OC and increasing the height and width of the CZ. AP2 expression is repressed in the SAM at the end of floral transition, and extending the duration of its expression increases SAM width. Transcriptional repression by SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) represents one of the mechanisms reducing AP2 expression during floral transition. Moreover, AP2 represses SOC1 transcription, and we find that reciprocal repression of SOC1 and AP2 contributes to synchronizing precise changes in meristem shape with floral transition.

植物对环境信号作出开花反应。这些信号改变顶端分生组织（SAM）的形态和发育特性，使其形成花朵和花序。本研究表明，SAM宽度与高度在开花转化过程中的增加与中心区（CZ）尺寸的变化相关，中心区由CLAVATA3表达定义，并涉及组织中心（OC）高度的一过性增加，OC由WUSCHEL表达定义。APETALA2（AP2）转录因子对于SAM高度和宽度的快速增加是必需的，通过维持OC的宽度并增加CZ的高度和宽度来实现。在开花转化结束时，AP2在SAM中的表达被抑制，延长其表达持续时间可增加SAM宽度。由抑制CONSTANS1过度表达（SOC1）的抑制子（SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1，SOC1）介导的转录抑制是减少开花转化期间AP2表达的一种机制。此外，AP2抑制SOC1的转录，我们发现SOC1和AP2的相互抑制有助于同步分生组织形态的精确变化与开花转化。