GENETIC ANALYSIS OF CELL DIVISION PATTERN IN MAIZE

胞质分裂的空间控制是发展的一个重要方面。 在多细胞生物体中。分区平面定位不仅 对染色体和细胞器的适当分离至关重要 子代细胞，但也可以影响胚胎的发育命运 子代细胞。胞质分裂的空间控制是特殊的。 在植物发育中的重要意义，在植物发育中，细胞嵌入刚性的 细胞外基质，细胞壁：细胞的相对位置 在植物组织内，细胞分裂平面在出生时是固定的。 尽管划分平面的确定和胞质分裂的过程 在某些方面，动物和植物是不同的，在这两种情况下，它们都 涉及细胞骨架介导的相互作用 核/微管组织中心和位于该位置的细胞皮质 分裂细胞内适当的细胞分裂装置。这个 这些相互作用背后的分子机制尚不清楚。 在动物和植物中都存在，目前正在通过 生物化学和遗传学方法。本建议书中所述的项目 代表了一种遗传学的方法来理解 高等植物玉米的胞质分裂。因为缺乏亲人 植物组织中的细胞运动，细胞分裂改变的突变体 模式可以通过在 成熟玉米叶片的规则细胞模式。这项提案集中了 关于胞质分裂空间调控所需基因的分析 以这种方式被识别的，纠缠(Tan)。更具体地说， 该突变体的表型表明Tan基因是 拉长的细胞在平行于细胞长轴的平面上分裂。 L的具体目的是让人们更好地理解 这一基因通过研究棕色突变缺陷的细胞学基础。 这将通过比较变异体和变异体 野生型叶片涉及：1)细胞骨架重排 细胞分裂，2)可以观察到的细胞分裂的方面 视频显微镜下的活组织，以及3)各种组织的分裂 在整个植物中涉及不同形状的细胞。晒黑的皮肤 突变是由插入转座元件引起的；片段 与转座子插入位点相邻的Tan基因已经 都被克隆了。具体目标2是完成Tan基因的克隆， 对预测的ITS产物氨基酸序列进行同源性分析 其他蛋白质，并检查组织和亚细胞定位 这种蛋白质试图在分子水平上理解它的参与 在细胞质分裂的空间方面。具体目标3是使用基因 嵌合体分析以确定Tan基因是否具有细胞功能 自主性，并探索细胞-细胞相互作用在 植物组织中细胞分裂模式的控制。最后(具体目标 4)，进一步筛选改变细胞模式的隐性突变 将完成对玉米叶片的研究，以确定 植物细胞分裂的空间控制。从这些方面获得的见解 研究将有助于我们理解调控机制 真核生物中正常生长所必需的细胞分裂 发育，而这种缺失与肿瘤疾病有关 在人类和动物身上。

The spatial control of cytokinesis is an important aspect of development in multicellular organisms. Division plane positioning is not only critical for the proper segregation of chromosomes and organelles to daughter cells, but can also influence the developmental fates of the daughter cells. The spatial control of cytokinesis is of particular significance in plant development, where cells are embedded in a rigid extracellular matrix, the cell wall: the relative positions of cells within plant tissues are fixed at birth by planes of cell division. Although the processes of division plane determination and cytokinesis are in some respects different in animals and plants, in both cases they involve cytoskeleton-mediated interactions between the nucleus/microtubule organizing centers and the cell cortex that position the cytokinetic apparatus appropriately within the dividing cell. The molecular mechanisms underlying these interactions are poorly understood in both animals and plants, and are currently being studied by means of biochemical and genetic methods. The project described in this proposal represents a genetic approach to understanding the spatial control of cytokinesis in a higher plant, Zea mays. Because of the lack of relative cell movement in plant tissues, mutants with alterations in cell division pattern can be recognized by means of the resulting alterations in the regular cell pattern of the mature maize leaf. The proposal concentrates on the analysis of a gene required for the spatial control of cytokinesis that was identified in this way, Tangled (Tan). More specifically, the phenotype of this mutant indicates that the Tan gene is required for elongated cells to divide in a plane parallel to the cell's long axis. Specific Aim l is to develop a better understanding of the function of this gene by investigating the cellular basis of the tan mutant defect. This will be accomplished by means of comparisons between mutant and wild-type leaves with respect to: 1) cytoskeletal rearrangements m dividing cells, 2) aspects of cell division that can be observed in living tissues by video microscopy, and 3) divisions in various tissues throughout the plant involving cells of different shapes. The tan mutation was caused by the insertion of a transposable element; fragments of the Tan gene adjacent to the transposon insertion site have already been cloned. Specific Aim 2 is to complete the cloning of the Tan gene, analyze the predicted amino acid sequence of its product for homology to other proteins, and examine the tissue and subcellular localization of this protein to try to understand at a molecular level its involvement in spatial aspects of cytokinesis. Specific Aim 3 is to use genetic mosaic analysis to determine whether the Tan gene functions cell autonomously, and to explore the role of cell-cell interactions in the control of cell division pattern in plant tissues. Finally (Specific Aim 4), further screening for recessive mutations altering the cell pattern of the maize leaf will be done to identify other genes required for the spatial control of cell division in plants. Insights gained from these studies will contribute to our understanding of mechanisms regulating cell division in eukaryotic organisms that are essential for normal development, and the loss of which is associated with neoplastic diseases in humans and animals.