植物叶缘形态的发育调控机理

生物多样性研究的关键问题之一是表型多样性的形成和演化机制, 因为表型多样性与物种多样性密切相关, 同时又承载着遗传和环境的变异信息。植物的叶具有丰富的形态多样性, 而叶形多样性很大程度上体现在叶边缘形态的变异。叶边缘的形态可从全缘、锯齿状到具有不同程度(深浅)和不同式样(羽状或掌状、回数等)的裂片(在发育研究中复叶的小叶也描述为裂片)。关于叶缘齿/裂的发育调控机制, 在拟南芥(Arabidopsis thaliana)、碎米荠(Cardamine hirsuta)、番茄(Solanum lycopersicum)等模式植物中已有较深入的探讨。研究发现, 很多转录因子、小分子RNA及植物激素对叶齿/裂或小叶的形成具有调控作用, 其中生长素输出途径中的转录因子NAM/CUC、miR164以及高浓度生长素的反馈调控可能起到核心作用, 而且该调控模块在真双子叶植物中较为保守; TCP类、SPL类转录因子和其他一些miRNA也在生长素输出途径中发挥作用; 关于KNOX家族转录因子的作用, 虽然多数研究是围绕复叶的形态建成, 但也有数据显示其在叶裂发育中发挥作用。此外, 对拟南芥和碎米荠等十字花科植物的研究还发现, 调控基因RCO通过抑制小叶/裂片之间的细胞增殖而对小叶/叶裂的发育发挥作用。本文综述上述多角度的研究进展, 并尝试概括叶边缘形态的发育调控网络, 为关于叶缘形态多样性形成机制的研究提供可参考的切入点。     

Adaxial–abaxial polarity: The developmental basis of leaf shape diversity

Leaves of flowering plants are diverse in shape. Part of this morphological diversity can be attributed to differences in spatiotemporal regulation of polarity in the upper (adaxial) and lower (abaxial) sides of developing leaves. In a leaf primordium, antagonistic interactions between polarity determinants specify the adaxial and abaxial domains in a mutually exclusive manner. The patterning of those domains is critical for leaf morphogenesis. In this review, we first summarize the gene networks regulating adaxial–abaxial polarity in conventional bifacial leaves and then discuss how patterning is modified in different leaf type categories. genesis 52:1–18, 2014. © 2013 The Authors. Genesis Published byWiley Periodicals, Inc.     

Nanos and Pumilio are essential for dendrite morphogenesis in Drosophila peripheral neurons

Much attention has focused on dendritic translational regulation of neuronal signaling and plasticity. For example, long-term memory in adult Drosophila requires Pumilio (Pum), an RNA binding protein that interacts with the RNA binding protein Nanos (Nos) to form a localized translation repression complex essential for anterior-posterior body patterning in early embryogenesis. Whether dendrite morphogenesis requires similar translational regulation is unknown. Here we report that nos and pum control the elaboration of high-order dendritic branches of class III and IV, but not class I and II, dendritic arborization (da) neurons. Analogous to their function in body patterning, nos and pum require each other to control dendrite morphogenesis, a process likely to involve translational regulation of nos itself. The control of dendrite morphogenesis by Nos/Pum, however, does not require hunchback, which is essential for body patterning. Interestingly, Nos protein is localized to RNA granules in the dendrites of da neurons, raising the possibility that the Nos/Pum translation repression complex operates in dendrites. This work serves as an entry point for future studies of dendritic translational control of dendrite morphogenesis.