GENETIC ANALYSIS OF CELL DIVISION PATTERN IN MAIZE

胞质分裂的空间控制是发育的重要方面 在多细胞生物中。司平面定位不仅是 对于染色体和细胞器的正确分离至关重要， 子细胞，但也可以影响发育的命运， 子细胞胞质分裂的空间控制是特别的 在植物发育中的重要性，其中细胞嵌入刚性的 细胞外基质，细胞壁：细胞的相对位置 在植物组织中，细胞分裂的平面在出生时就固定下来了。 虽然分裂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， 涉及细胞因子介导的 细胞核/微管组织中心和细胞皮层， 分裂细胞内的细胞动力学装置。的 这些相互作用的分子机制尚不清楚 在动物和植物中，目前正在通过 生物化学和遗传学方法。本建议书所述的项目 代表了一种遗传学的方法来理解空间控制， 高等植物玉米的胞质分裂。由于缺乏相对 植物组织中的细胞运动，细胞分裂改变的突变体 模式可以通过在所产生的变化的方式来识别。 成熟玉米叶片的规则细胞图案。提案集中 对胞质分裂空间控制所需基因的分析 这是以这种方式确定的，纠结（棕褐色）。更具体而言是 该突变体的表型表明Tan基因是 在平行于细胞长轴的平面内分裂。 具体目标1是更好地了解 通过研究tan突变缺陷的细胞基础来研究该基因。 这将通过比较突变体和 野生型叶：1）细胞骨架重排 分裂细胞，2）细胞分裂的方面，可以观察到， 通过视频显微镜观察活组织，以及3）在各种组织中的分裂 包括不同形状的细胞。谭 转座因子插入引起的突变;片段 邻近转座子插入位点的Tan基因的序列已经 被克隆了具体目标2是完成Tan基因的克隆， 分析其产物的预测氨基酸序列与 其他蛋白质，并检查组织和亚细胞定位的 试图在分子水平上了解这种蛋白质 在胞质分裂的空间方面。具体目标3是利用遗传 嵌合体分析，以确定Tan基因是否在细胞中起作用 自主，并探讨细胞间相互作用的作用， 植物组织中细胞分裂模式的控制。具体目标（Specific Aim） 4）进一步筛选改变细胞模式的隐性突变 将完成玉米叶片的基因组测序，以确定其他基因所需的基因， 植物细胞分裂的空间控制。从中获得的见解 这些研究将有助于我们理解 真核生物中的细胞分裂， 发展，其损失与肿瘤性疾病有关 在人类和动物中。

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.