背景回顾：Stem cells play important roles in animal and plant biology, as they sustain morphogenesis and tissue replenishment following aging or injury. In plants, stem cells are embedded in multicellular structures called meristems. The formation of new meristems is essential for the plastic expansion of the highly branched shoot and root systems. In particular, axillary meristems that produce lateral shoots arise from the division of boundary domain cells at the leaf base. The CUP-SHAPED COTYLEDON (CUC) genes are major determinants of the boundary domain and are required for axillary meristem initiation. 

提出问题：However, how axillary meristems get structured and how stem cells become established de novo remain elusive. 

主要发现：Here, we show that two NGATHA-LIKE (NGAL) transcription factors, DEVELOPMENT-RELATED PcG TARGET IN THE APEX4 (DPA4)/NGAL3 and SUPPRESSOR OF DA1-1 7 (SOD7)/NGAL2, redundantly repress CUC expression in initiating axillary meristems of Arabidopsis thaliana. 

结果：Ectopic boundary fate leads to abnormal growth and organisation of the axillary meristem and prevents de novo stem cell establishment. Floral meristems of the dpa4 sod7 double mutant show a similar delay in de novo stem cell establishment. 

结论：Altogether, while boundary fate is required for the initiation of axillary meristems, our work reveals how it is later repressed to allow proper meristem establishment and de novo stem cell niche formation. 

 摘 要 

干细胞在动物和植物生物学中均扮演者重要作用，其能够在年龄老化或者遭受损伤后维持形态发生和组织重建。在植物中，干细胞嵌在多细胞结构，即分生组织的内部。新分生组织的形成对于高度分枝的地上或地下系统的可塑性扩张是至关重要的。其中，产生侧芽的腋分生组织起源于叶基部边界结构域细胞的分裂。CUC基因是主要的边界结构域决定因子，对于腋生分生组织的起始是必须的。但是，腋生分生组织如何结构化，以及干细胞如何从头建立还不清楚。本文中，作者发现两个NGAL转录因子DPA4/NGAL3和SOD7/NGAL2在拟南芥腋生分生组织起始过程中，冗余地抑制CUC基因的表达。异位的边界命运会导致腋生分生组织的异常生长和组织化，防止从头干细胞建立。dpa4 sod7双突变体的花分生组织表现出从头干细胞建立的延迟。综上，在边界命运作用于腋生分生组织起始的研究基础上，本文的工作揭示了其后来是如何被抑制的，从而使得分生组织得以正常建立、干细胞微环境得以从头形成。