Sawchuk Megan G, Head Philip, Donner Tyler J, Scarpella Enrico
Department of Biological Sciences, University of Alberta, CW-405 Biological Sciences Building, Edmonton AB, T6G 2E9 Canada.
New Phytol. 2007;176(3):560-571. doi: 10.1111/j.1469-8137.2007.02193.x.
The principles underlying the formation of leaf veins have long intrigued developmental biologists. In leaves, networks of vascular precursor procambial cells emerge from seemingly homogeneous subepidermal tissue through the selection of anatomically inconspicuous preprocambial cells. Understanding dynamics of procambium formation has been hampered by the difficulty of observing the process in vivo. Here we present a live-imaging technique that allows visual access to complex events occurring in developing leaves. We combined this method with stage-specific fluorescent markers in Arabidopsis (Arabidopsis thaliana) to visualize preprocambial strand formation and procambium differentiation during the undisturbed course of development and upon defined perturbations of vein ontogeny. Under all experimental conditions, we observed extension, termination and fusion of preprocambial strands and simultaneous initiation of procambium differentiation along entire individual veins. Our findings strongly suggest that progressiveness of preprocambial strand formation and simultaneity of procambium differentiation represent inherent properties of the mechanism underlying vein formation.
叶脉形成的基本原理长期以来一直吸引着发育生物学家。在叶片中，维管前体细胞的网络从看似均匀的表皮下组织中通过选择解剖学上不显眼的前形成层细胞而出现。由于难以在体内观察这一过程，对形成层形成动态的理解受到了阻碍。在这里，我们提出了一种实时成像技术，该技术能够直观地观察发育中的叶片中发生的复杂事件。我们将这种方法与拟南芥中特定阶段的荧光标记相结合，以可视化在未受干扰的发育过程中以及在叶脉个体发育受到特定扰动时前形成层束的形成和形成层的分化。在所有实验条件下，我们观察到前形成层束的延伸、终止和融合，以及沿着整个叶脉同时启动形成层的分化。我们的研究结果有力地表明，前形成层束形成的渐进性和形成层分化的同时性代表了叶脉形成机制的固有特性。
