背景回顾：The leaf epidermis is the outermost cell layer forming the interface between plants and the atmosphere that must both provide a robust barrier against (a)biotic stressors and facilitate carbon dioxide uptake and leaf transpiration. To achieve these opposing requirements, the plant epidermis developed a wide range of specialized cell types such as stomata and hair cells. 

提出问题：Although factors forming these individual cell types are known, it is poorly understood how their number and size are coordinated. 

主要发现：Here, we identified a role for BdPRX76/BdPOX, a class III peroxidase, in regulating hair cell and stomatal size in the model grass Brachypodium distachyon. 

结果1-突变体表型：In bdpox mutants, prickle hair cells were smaller and stomata were longer. Because stomatal density remained unchanged, the negative correlation between stomatal size and density was disrupted in bdpox and resulted in higher stomatal conductance and lower intrinsic water-use efficiency. 

结果2-自主和非自主性作用：BdPOX was exclusively expressed in hair cells, suggesting that BdPOX cell-autonomously promotes hair cell size and indirectly restricts stomatal length. 

结果3-作用方式：Cell-wall autofluorescence and lignin stainings indicated a role for BdPOX in the lignification or crosslinking of related phenolic compounds at the hair cell base. Ectopic expression of BdPOX in the stomatal lineage increased phenolic autofluorescence in guard cell (GC) walls and restricted stomatal elongation in bdpox. 

结论：Together, we highlight a developmental interplay between hair cells and stomata that optimizes epidermal functionality. We propose that cell-type-specific changes disrupt this interplay and lead to compensatory developmental defects in other epidermal cell types.

叶表皮是植物最外层的细胞层，是植物和空气之间的交界面，因此必须为植物提供一个坚固的屏障来抵御（非）生物胁迫，并促进二氧化碳的吸收和叶的蒸腾作用。为了实现这些相互矛盾的需求，植物的表皮发育出了一系列特化的细胞类型，比如气孔和毛细胞。尽管形成这些单个细胞类型的因素是已知的，但是我们对其细胞数量和大小之间的协调还所知不多。本文中，作者在短柄草中鉴定到了一个class III过氧化物酶BdPRX76/BdPOX，其作用于短柄草叶表皮上毛细胞和气孔的大小。在bdpox突变体中，刺毛细胞变得更小，而气孔会变得更长。由于气孔密度保持不变，bdpox突变体中气孔大小和密度之间的负相关不复存在，这导致了bdpox突变体的气孔导度更高，从而降低了其对自身水分的利用效率。BdPOX仅在毛细胞中表达，表明BdPOX通过细胞自主性的方式促进了毛细胞的大小，并间接限制了气孔的长度。细胞壁自发荧光和木质素染色实验表明，BdPOX在毛细胞基部参与了相关酚类化合物的木质素化或交联。在bdpox突变体的气孔谱系细胞中异位表达BdPOX基因会增强保卫细胞壁中的酚类自发荧光，并限制气孔的伸长。综上，本文的研究结果揭示了植物毛细胞和气孔之间的发育互作，共同作用于表皮功能的优化。作者认为，细胞类型特异性改变会破坏这种相互作用，并导致其他表皮细胞类型的补偿性发育缺陷。