Royal Botanic Garden Edinburgh, Edinburgh, UK.
Curr Top Dev Biol. 2010;91:141-68. doi: 10.1016/S0070-2153(10)91005-3.
Most leaves are dorsiventrally flattened and develop clearly defined upper and lower surfaces. Light capturing is the specialization of the adaxial or upper surface and the abaxial or lower surface is specialized for gas exchange (Fig. 5.1). This division into adaxial and abaxial domains is also key for the outgrowth of the leaf blade or lamina, which occurs along the boundary between the upper and lower sides. How this polarity is set up is not clear but genetic analysis in a range of species suggests that several highly conserved interlocking pathways are involved. Positional information from the meristem is reinforced by signaling through the epidermal layer as the meristem grows away from the leaf primordium. Opposing ta-siRNA and miRNA gradients help refine distinct adaxial and abaxial sides, and mutual inhibition between the genes expressed on each side stabilizes the boundary. In this review we consider how recent work in a range of species is clarifying our understanding of these processes.
大多数叶子是背腹扁平的，并发育出明显的上表面和下表面。光捕获是上表面（近轴面）的特化，而下表面（远轴面）则特化用于气体交换（图 5.1）。这种分为近轴面和远轴面的划分对于叶片或叶板的生长也很关键，叶片或叶板的生长是沿着上下两面之间的边界进行的。目前尚不清楚这种极性是如何建立的，但对一系列物种的遗传分析表明，涉及几个高度保守的连锁途径。随着分生组织远离叶原基生长，分生组织的位置信息通过表皮层的信号传递得到加强。来自 ta-siRNA 和 miRNA 梯度的拮抗作用有助于细化明显的近轴面和远轴面，而在每一侧表达的基因之间的相互抑制作用则稳定了边界。在这篇综述中，我们将讨论最近在一系列物种中开展的工作如何澄清我们对这些过程的理解。
