The mechanisms that allow cells in the plant meristem to coordinate tissue-wide maturation gradients with specialized cell networks are critical for indeterminate growth. Here, we reconstructed the protophloem developmental trajectory of 19 cells from cell birth to terminal differentiation at single cell resolution in the Arabidopsis root. We found that cellular specification is mediated near the stem cell niche by PHLOEM EARLY DOF (PEAR) transcription factors. However, the PEAR dependent differentiation program is repressed by a broad gradient of PLETHORA (PLT) transcription factors, which directly inhibit PEARs' own direct target ALTERED PHLOEM DEVELOPMENT (APL). The dissipation of PLT gradient around 7 cells from the stem cell activates APL expression, and a subsequent transitional network that results in a "seesaw" pattern of mutual inhibition over developmental time. Together, we provide a mechanistic understanding of how morphogen-like maturation gradients interface with cell-type specific transcriptional regulators to stage cellular differentiation.

中文翻译：

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韧皮部轨迹的分析将组织成熟与细胞特化联系起来。

允许植物分生组织中的细胞与专门的细胞网络协调组织范围内的成熟梯度的机制对于不确定的生长至关重要。在这里，我们在拟南芥根中以单细胞分辨率重建了19个细胞从细胞诞生到终末分化的原上皮发育轨迹。我们发现细胞规格是由PHLOEM EARLY DOF（PEAR）转录因子介导的干细胞环境附近。但是，PEARHORA（PLT）转录因子的广泛梯度抑制了PEAR依赖的分化程序，这直接抑制了PEARs自身的直接靶标ALTERED PHLOEM DEVELOPMENT（APL）。干细胞周围7个细胞周围PLT梯度的耗散激活了APL表达，随后的过渡网络导致了在发育时间内相互抑制的“跷跷板”模式。在一起，我们提供了一个机制的理解，如吗啡样成熟梯度与细胞类型的特定转录调节因子介导阶段的细胞分化。