Kim Minsung, McCormick Sheila, Timmermans Marja, Sinha Neelima
Section of Plant Biology, University of California at Davis, 1 Shields Avenue, Davis, California 95616, USA.
Nature. 2003 Jul 24;424(6947):438-43. doi: 10.1038/nature01820.
Diverse leaf forms in nature can be categorized as simple or compound. Simple leaves, such as those of petunia, have a single unit of blade, whereas compound leaves, such as those of tomato, have several units of blades called leaflets. Compound leaves can be pinnate, with leaflets arranged in succession on a rachis, or palmate, with leaflets clustered together at the leaf tip. The mechanisms that generate these various leaf forms are largely unknown. The upper (adaxial) surface is usually different from the bottom (abaxial) surface in both simple and compound leaves. In species with simple leaves, the specification of adaxial and abaxial cells is important for formation of the leaf blade, and the MYB transcription factor gene PHANTASTICA (PHAN) is involved in maintaining the leaf adaxial (upper) domain. Here we show that downregulation of PHAN is sufficient to reduce the adaxial domain of leaf primordia and to change pinnate compound leaves into palmate compound leaves. Furthermore, this mechanism seems to be shared among compound leaves that arose independently.
自然界中多样的叶片形态可分为单叶或复叶。单叶，如矮牵牛的叶子，有单个叶片单元，而复叶，如番茄的叶子，有几个称为小叶的叶片单元。复叶可以是羽状的，小叶沿叶轴依次排列，也可以是掌状的，小叶在叶尖聚集在一起。产生这些不同叶片形态的机制在很大程度上尚不清楚。在单叶和复叶中，上（近轴）表面通常与下（远轴）表面不同。在具有单叶的物种中，近轴和远轴细胞的特化对于叶片的形成很重要，并且MYB转录因子基因PHANTASTICA（PHAN）参与维持叶片近轴（上）区域。在这里，我们表明PHAN的下调足以减少叶原基的近轴区域，并将羽状复叶转变为掌状复叶。此外，这种机制似乎在独立出现的复叶中是共有的。
