Protodermal Stem Cells in the Brachypodium Leaf

原胚层干细胞是发育中的草叶片基部表皮L1层中的分生组织细胞。这些干细胞有能力产生所有的表皮细胞类型的草叶子像密封和稳定路面细胞，气体交换气孔复合体，叶片滚动泡状细胞和功能神秘，但可能是植食性威慑刺毛细胞和硅细胞。许多这些表皮细胞类型不存在于真双子叶植物模型系统如拟南芥（例如泡状细胞，刺毛细胞）或显示草特异性特征（例如气孔）。叶表皮作为保护“内部”叶片生理免受“外部”非生物和生物胁迫的最终屏障，对植物生存至关重要。然而，关于原胚层干细胞如何终止其多能性状态并致力于不同的发育轨迹以形成草叶表皮的多种细胞类型，人们知之甚少。在这里，我建议使用模型草Brachypodium distachyon-野生草，可用作模型系统的Pooid草，如小麦和大麦-来破译如何以及在哪里原胚层干细胞失去多能性和分支到不同的发展轨迹。为此，我们将使用单细胞转录组学，发育遗传学和显微镜。我们将利用我的实验室广泛收集的短柄草资源和我们立即获得的突变短柄草集合，这是完全重新测序与所有突变精确映射到基因组位置（NaN人口）。总之，该项目将产生一个前所未有的解决方案的原胚层干细胞轨迹在短柄草，测试的作用，关键转录因子家族调节表皮谱系轨迹承诺和空间映射的地方正好谱系承诺发生在分生区的草叶子。

Protodermal stem cells are meristematic cells in the epidermal L1 layer at the base of the developing grass leaf. These stem cells have the capacity to produce all epidermal cell types of a grass leaf like the sealing and stabilizing pavement cells, gas-exchanging stomatal complexes, leaf-rolling bulliform cells and the functionally enigmatic but probably herbivore-deterring prickle hair cells and silica cells. Many of these epidermal cell types do not exist in eudicot model systems like Arabidopsis (e.g. bulliform cells, prickle hair cells) or show grass-specific features (e.g. stomata). As the ultimate barrier shielding the “inner” leaf physiology from “outer” abiotic and biotic stressors, the leaf epidermis is absolutely essential to plant survival. Yet, little is known regarding how protodermal stem cells terminate their pluripotent state and commit to distinct developmental trajectories to make the manifold cell types of the grass leaf epidermis. Here, I propose to use the model grass Brachypodium distachyon—a wild grass that can be used as a model system for Pooid grasses like wheat and barley—to decipher how and where protodermal stem cells lose pluripotency and branch into distinct developmental trajectories. To this end, we will use single-cell transcriptomics, developmental genetics and microscopy. We will leverage my lab’s extensive collection of Brachypodium resources and our immediate access to a mutant Brachypodium collection, which is fully resequenced with all mutations exactly mapped to genomic locations (NaN population). Together, this project will produce an unprecedented resolution of protodermal stem cell trajectories in Brachypodium, test the role of key transcription factor families regulating epidermal lineage trajectory commitment and spatially map where exactly lineage commitment occurs in the meristematic zone of the grass leaf.