Compound leaves show more complex patterns than simple leaves, and this is mainly because of a specific morphogenetic process (leaflet initiation and arrangement) that occurs during their development. How the relevant morphogenetic activity is established and modulated to form a proper pattern of leaflets is a central question. Here we show that the trifoliate leaf pattern of the model leguminous plant Medicago truncatula is controlled by the BEL1-like homeodomain protein PINNATE-LIKE PENTAFOLIATA1 (PINNA1). We identify PINNA1 as a determinacy factor during leaf morphogenesis that directly represses transcription of the LEAFY (LFY) orthologue SINGLE LEAFLET1 (SGL1), which encodes an indeterminacy factor key to the morphogenetic activity maintenance. PINNA1 functions alone in the terminal leaflet region and synergizes with another determinacy factor, the C2H2 zinc finger protein PALMATE-LIKE PENTAFOLIATA1 (PALM1), in the lateral leaflet regions to define the spatiotemporal expression of SGL1, leading to an elaborate control of morphogenetic activity. This study reveals a framework for trifoliate leaf-pattern formation and sheds light on mechanisms generating diverse leaf forms.

中文翻译：

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蒺藜苜蓿复合叶模式下的分子框架。


复合叶比简单叶表现出更复杂的图案，这主要是由于其发育过程中发生的特定形态发生过程（小叶起始和排列）。如何建立和调节相关的形态发生活动以形成正确的小叶模式是一个中心问题。在这里，我们发现模型豆科植物蒺藜苜蓿的三叶叶图案是由 BEL1 样同源域蛋白 PINNATE-LIKE PENTAFOLIATA1 (PINNA1) 控制。我们将 PINNA1 确定为叶形态发生过程中的决定性因子，它直接抑制 LEAFY (LFY) 直系同源物 SINGLE LEAFLET1 (SGL1) 的转录，SGL1 编码对形态发生活性维持至关重要的不确定性因子。 PINNA1 在末端小叶区域单独发挥作用，并在侧小叶区域与另一个决定性因子 C2H2 锌指蛋白 PALMATE-LIKE PENTAFOLIATA1 (PALM1) 协同作用，定义 SGL1 的时空表达，从而对形态发生活性进行精细控制。这项研究揭示了三叶叶图案形成的框架，并揭示了产生不同叶子形状的机制。