RUI: Mechanisms of Early Embryogenesis in Arabidopsis: Characterization of the twn1 and emb88 Mutants

弗农96-04344在植物中，胚胎发生是发育的关键阶段，在这个阶段定义了许多细胞类型，建立了分生组织，并形成了基本的身体计划。尽管胚胎发育很重要，但它可能仍然是植物发育过程中最不为人所知的时期。研究胚胎发生的一个强有力的策略是分析在胚胎发育的各个方面受损的突变。许多这样的胚胎缺陷(Emb)突变体已经在模式植物拟南芥系统中被鉴定出来。这项研究将通过对两个有趣的拟南芥胚胎缺陷突变体emb88和tw1的鉴定来帮助我们理解植物的胚胎发生。Emb88是一类很少被研究的早期胚胎缺陷突变体，圆形胚胎(Rem)突变体。这些突变体表现出混乱的细胞结构和不完整的形态发生。最近对EMB88的分子分析表明，该基因编码一种新的植物蛋白，类似于参与细胞信号转导的动物蛋白。因此，EMB88可能有助于定义一条以前没有在植物中发现的重要细胞信号通路。Emb88的特征包括EMB88 CDNA的克隆和测序，EMB88基因表达的分析，突变和野生型等位基因的基因组结构比较，以及突变表型和野生型基因的互补。这种分子特征将阐明该基因在胚胎发育中的作用，并为未来对EMB88可能发挥作用的途径的生化和遗传学剖析铺平道路。第二个突变体TUN I表现出一种不同寻常的表型：通常在一粒种子内发育两个或更多的可存活胚胎。当胚柄的细胞失去它们的特性并经历胚性转化时，次生胚胎就产生了。胚柄是胚胎发生早期形成的一种特殊结构。因此，TnI基因似乎抑制了胚柄细胞中的一条默认的胚胎发生途径，该突变为研究植物早期胚胎细胞分化和全能性抑制之间的关系提供了一个很好的系统。关于TnI的拟议实验将解决TnI表型的生理基础，并更好地确定该基因在胚胎发育中的作用。

Vernon 96-04344 In plants, embryogenesis is a crucial stage of development in which numerous cell types are defined, meristems are established, and the basic body plan is formed. Despite its importance, embryogenesis remains perhaps the least-understood period of plant development. One powerful strategy for investigating embryogenesis is the analysis of mutants impaired in various aspects of embryonic development. Many such embryo-defective (emb) mutants have been identified in the model plant system Arabidopsis thaliana. The proposed research will contribute to our understanding of plant embryogenesis via characterization of two intriguing Arabidopsis embryo-defective mutants, emb88 and twn 1. Emb88 is representative of a little-studied class of early embryo-defectives, the round embryo (rem) mutants. These mutants exhibit disorganized cell architecture and incomplete morphogenesis. Recent molecular analysis of EMB88 indicates that this gene encodes a novel plant protein similar to animal proteins involved in cell signal transduction. Thus, EMB88 may help define an essential cell signaling pathway not previously identified in plants. The proposed characterization of emb88 includes cloning and sequencing of the EMB88 CDNA, analysis of EMB88 gene expression, comparison of genomic structure of the mutant and wild-type alleles, and complementation of the mutant phenotype with the wild-type gene. This molecular characterization will elucidate the role of this gene in embryogenesis, and pave the way for future biochemical and genetic dissection of the pathway in which EMB88 may play a role. The second mutant, twn I, displays an unusual phenotype: two or more viable embryos often develop within a single seed. Secondary embryos arise when cells of the suspensor, a specialized structure that forms early in embryogenesis, lose their identity and undergo embryogenic transformation. Thus the twn I gene appears to suppress a default embryogenic pathway in suspensor cells, and this mutant offers an excellent system in which to investigate the relationship between cell differentiation and suppression of totipotency in the early plant embryo. The proposed experiments on twn I will address the physiological basis of the twn I phenotype and better define the role of this gene in embryo development.