Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Plant Physiol. 2011 Nov;157(3):1151-62. doi: 10.1104/pp.111.185066. Epub 2011 Aug 31.
Leaves are the most important, fundamental units of organogenesis in plants. Although the basic form of a leaf is clearly divided into the leaf blade and leaf petiole, no study has yet revealed how these are differentiated from a leaf primordium. We analyzed the spatiotemporal pattern of mitotic activity in leaf primordia of Arabidopsis (Arabidopsis thaliana) in detail using molecular markers in combination with clonal analysis. We found that the proliferative zone is established after a short interval following the occurrence of a rod-shaped early leaf primordium; it is separated spatially from the shoot apical meristem and seen at the junction region between the leaf blade and leaf petiole and produces both leaf-blade and leaf-petiole cells. This proliferative region in leaf primordia is marked by activity of the ANGUSTIFOLIA3 (AN3) promoter as a whole and seems to be differentiated into several spatial compartments: activities of the CYCLIN D4;2 promoter and SPATULA enhancer mark parts of it specifically. Detailed analyses of the an3 and blade-on-petiole mutations further support the idea that organogenesis of the leaf blade and leaf petiole is critically dependent on the correct spatial regulation of the proliferative region of leaf primordia. Thus, the proliferative zone of leaf primordia is spatially differentiated and supplies both the leaf-blade and leaf-petiole cells.
叶片是植物器官发生的最重要、最基本的单位。虽然叶片的基本形态明显分为叶片和叶柄，但目前还没有研究揭示这些结构是如何从叶原基分化而来的。我们利用分子标记物结合克隆分析，详细分析了拟南芥（Arabidopsis thaliana）叶片原基中细胞有丝分裂活性的时空模式。我们发现，在棒状早期叶原基发生后很短的时间间隔内，就建立了增殖区；它与茎尖分生组织在空间上分离，并在叶片和叶柄的交界处观察到，产生叶片和叶柄细胞。整个叶片原基的增殖区以 ANGUSTIFOLIA3（AN3）启动子的活性为标志，似乎分化为几个空间区室：CYCLIN D4;2 启动子和 SPATULA 增强子的活性特异性地标记其中的一部分。对 an3 和 blade-on-petiole 突变体的详细分析进一步支持了这样的观点，即叶片和叶柄的器官发生严重依赖于叶片原基增殖区的正确空间调控。因此，叶片原基的增殖区在空间上是分化的，并为叶片和叶柄细胞提供物质。
