Molecular Genetics of Arabidopsis Titan Mutants

Meinke 9723090，PI研究的长期目标是通过分离和鉴定拟南芥的胚胎缺陷(Emb)突变体来鉴定大量在植物胚胎发生过程中具有重要功能的基因。该研究所的实验室在促进利用这种模式生物进行植物发育遗传学研究方面发挥了积极作用。在这项建议中，描述了一类新的emb突变体，称为提坦突变体，它们表现出戏剧性的表型，应该有助于分析种子发育过程中的细胞周期控制。这些突变体的共同特征是胚乳细胞核变得巨大且高度多倍体。PI在这里提出了描述性、遗传学和分子研究的组合，旨在识别泰坦基因，解释突变表型，并确定这些基因在调节细胞周期中扮演的角色。描述性研究将提供有关泰坦种子中核和细胞骨架组织的进一步细节。遗传学研究的重点将是完成基因定位、构建双突变体、分析标记基因的表达以及鉴定更多的泰坦突变体。TTN基因的分子克隆是该提案的主要重点。首先将重点放在ttn3上，因为它似乎被标记了。PI还建议通过基于地图的克隆来分离TTN1。双受精如何在胚胎和胚乳中建立不同的有丝分裂和胞质分裂模式是植物生殖生物学的中心问题。该项目的研究结果将为被子植物细胞周期调控和胚胎-胚乳相互作用提供有价值的见解。虽然对酵母和果蝇细胞周期调控的研究应该提供大量适用于植物的信息，但需要对拟南芥突变株进行分析，以建立贯穿植物发育的细胞周期调控的精确机制。

Meinke 9723090 The long-term goal of the PI's research is to identify large numbers of genes with essential functions during plant embryogenesis through the isolation and characterization of embryo-defective (emb) mutants of Arabidopsis. The PI's laboratory has played an active role in promoting the use of this model organism for research in plant developmental genetics. In this proposal a novel class of emb mutants, called titan mutants, is described which exhibit a dramatic phenotype that should facilitate the analysis of cell cycle control during seed development. The common feature among these mutants is that endosperm nuclei become gigantic and highly polyploid. The PI proposes here a combination of descriptive, genetic, and molecular studies designed to identify TITAN genes, explain the mutant phenotype, and determine what role these genes play in regulating cell cycles. Descriptive studies will provide further details on nuclear and cytoskeletal organization in titan seeds. Genetic studies will focus on completion of gene mapping, construction of double mutants, analysis of marker gene expression, and characterization of additional titan mutants. Molecular cloning of TTN genes is a major focus of the proposal. Emphasis will be placed first on ttn3 because it appears to be tagged. The PI also proposes to isolate TTN1 through map-based cloning. How double fertilization leads to the establishment of distinct patterns of mitosis and cytokinesis in the embryo and endosperm is a central question in plant reproductive biology. Results obtained from this project should provide valuable insights into cell cycle regulation and embryo-endosperm interactions in angiosperms. Although research on cell cycle regulation in yeast and Drosophila should provide a wealth of information applicable to plants, analysis of Arabidopsis mutants such as those described here will be needed to establish the precise mechanisms of cell cycle control employed throughout plant development.