Cell differentiation is a key event in organ development; it involves auxin gradient formation, cell signaling, and transcriptional regulation. Yet, how these processes are orchestrated during leaf morphogenesis is poorly understood. Here, we demonstrate an essential role for the receptor-like kinase OsCR4 in leaf development. oscr4 loss-of-function mutants displayed short shoots and roots, with tiny, crinkly, or even dead leaves. The delayed outgrowth of the first three leaves and seminal root in oscr4 was due to defects in plumule and radicle formation during embryogenesis. The deformed epidermal, mesophyll, and vascular tissues observed in oscr4 leaves arose at the postembryo stage; the corresponding expression pattern of proOsCR4:GUS in embryos and young leaves suggests that OsCR4 functions in these tissues. Signals from the auxin reporter DR5rev:VENUS were found to be altered in oscr4 embryos and disorganized in oscr4 leaves, in which indole-3-acetic acid accumulation was further revealed by immunofluorescence. OsWOX3A, which is auxin responsive and related to leaf development, was activated extensively and ectopically in oscr4 leaves, partially accounting for the observed lack of cell differentiation. Our data suggest that OsCR4 plays a fundamental role in leaf morphogenesis and embryogenesis by fixing the distribution of auxin.

细胞分化是器官发育中的关键事件。它涉及生长素梯度形成，细胞信号传导和转录调控。然而，人们对如何在叶片形态发生过程中协调这些过程的了解却很少。在这里，我们证明了受体样激酶OsCR4在叶片发育中的重要作用。oscr4功能丧失的突变体显示出短的芽和根，具细小，皱折甚至枯死的叶子。oscr4的前三片叶子和精根的延迟生长是由于胚发生过程中小管和胚根形成缺陷所致。oscr4叶片中观察到的变形的表皮，叶肉和维管组织出现在胚后阶段。proOsCR4：GUS的相应表达模式在胚胎和幼叶中的表达提示OsCR4在这些组织中起作用。发现生长素记者DR5rev：VENUS的信号在oscr4胚胎中发生了变化，并在oscr4叶片中变得混乱，其中通过免疫荧光进一步揭示了吲哚-3-乙酸的积累。OsWOX3A是生长素反应性的并且与叶片发育有关，在oscr4叶片中被广泛和异位激活，部分解释了观察到的细胞分化缺乏。我们的数据表明，OsCR4通过固定生长素的分布在叶片形态发生和胚发生中起着基本作用。