Dawe R K, Freeling M
Department of Plant Biology, University of California, Berkeley 94720.
Development. 1992 Dec;116(4):1077-85. doi: 10.1242/dev.116.4.1077.
The near absence of cell movement in plants makes clonal analysis a particularly informative method for reconstructing the early events of organ formation. We traced the patterns of cell division during maize anther development by inducing sector boundaries that preceded the earliest events of anther initiation. In doing this, we were able to estimate the smallest number of cells that are fated to form an anther, characteristic cell division patterns that occur during anther morphogenesis, and the relationship between the pre-existing symmetry of the initial cells and the final symmetry of the mature anther. Four general conclusions are made: (1) anthers are initiated from small groups of 12 or fewer cells in each of two floral meristematic layers; (2) the early growth of the anther is more like a shoot than a glume or leaf; (3) cell ancestry does not dictate basic structure and (4) the orientation of initial cells predicts the orientation of the four pollen-containing microsporangia, which define the axes of symmetry on the mature anther. The final point is discussed with other data, and an explanation involving a 'structural template' is invoked. The idea is that the orientation of initial cells within the floral meristem establishes an architectural pattern into which anther cells are recruited without regard to their cellular lineages. The structural template hypothesis may prove to be generally applicable to problems of pattern formation in plants.
植物中细胞移动几乎不存在，这使得克隆分析成为重建器官形成早期事件的一种特别有用的方法。我们通过诱导在花药起始最早事件之前的扇形边界，追踪了玉米花药发育过程中的细胞分裂模式。通过这样做，我们能够估计注定形成花药的最少细胞数量、花药形态发生过程中出现的特征性细胞分裂模式，以及初始细胞预先存在的对称性与成熟花药最终对称性之间的关系。得出了四个一般性结论：（1）花药在两个花分生组织层中的每一层由12个或更少的小细胞群起始；（2）花药的早期生长更像茎尖而不是颖片或叶子；（3）细胞谱系并不决定基本结构；（4）初始细胞的取向预测了四个含花粉小孢子囊的取向，这定义了成熟花药上的对称轴。最后一点结合其他数据进行了讨论，并援引了一个涉及“结构模板”的解释。其观点是，花分生组织内初始细胞的取向建立了一种架构模式，花药细胞被招募到这种模式中，而不考虑它们的细胞谱系。结构模板假说可能被证明普遍适用于植物中的模式形成问题。
