Clonal analysis of cell lineage patterns in plant development

Somatic sectors induced by ionizing radiation provide a great deal of information about cell lineage pattems in both plants and animals. Somatic sectors arise when the dominant allele of a mutation with a visible, cell-autonomous phenotype is lost as a result of a deletion or somatic recombination. In addition to marking the fate of cells in a primordium at different stages of development and in different tissues, this technique also provides information about the distribution, orientation, rate, and duration of cell division. The technology and underlying assumptions of this method, termed clonal analysis, are described in this paper. IN ORDER TO DEFINE the cellular processes that control morphogenesis it is important to have detailed information about the number of cells and their fate in a primordium and an accurate picture of the pattern of cell division, cell expansion, and cellular differentiation in the primordium at different stages in its development. This.descriptive information is crucial for subsequent experimental analyses of the morphogenetic process and provides important clues about the factors that govern morphogenesis. Unfortunately, this information is not easily obtained. Although a wide variety of methods can be used to observe cell behavior in animal systems in vivo, in plants many of these approaches are either impossible or difficult to exploit. Thus, much of what we know about the cellular dynamics of plant morphogenesis has come from histological analyses of specimens killed and fixed at different stages of development. Although this approach has proven extremely useful, it has some serious drawbacks, such as the tedium involved in conducting quantitative studies on sectioned ma

电离辐射诱导的体细胞区段为植物和动物的细胞谱系模式提供了大量信息。当具有可见的细胞自主表型的突变的显性等位基因由于缺失或体细胞重组而丢失时，就会产生体细胞区段。除了标记原基中处于不同发育阶段和不同组织的细胞的命运外，该技术还提供了有关细胞分裂的分布、方向、速率和持续时间的信息。本文描述了这种称为克隆分析的方法的技术和基本假设。为了确定控制形态发生的细胞过程，重要的是要有关于原基中细胞数量及其命运的详细信息，以及原基在其发育的不同阶段的细胞分裂、细胞扩展和细胞分化模式的准确图像。这种描述性信息对于形态发生过程的后续实验分析至关重要，并为控制形态发生的因素提供了重要线索。不幸的是，这种信息不容易获得。虽然有各种各样的方法可用于在动物体内系统中观察细胞行为，但在植物中，许多这些方法要么不可能要么难以利用。因此，我们对植物形态发生的细胞动力学的了解大多来自对在不同发育阶段杀死和固定的标本的组织学分析。虽然这种方法已被证明非常有用，但它有一些严重的缺点，比如对切片材料进行定量研究的繁琐。