MOLECULAR GENETIC ANALYSIS OF ROOT MORPHOGENESIS

拟议研究的长期目标是了解 利用辐射调节器官形成的发育过程 组织的拟南芥根作为一个模型。根径向组织 是由三种不同的发展战略形成的。主根利用 一种干细胞策略，胚根使用连续分裂策略 侧根是由分化的细胞增殖形成的 组织.这三种不同的策略导致根与近 相同的放射状组织。一种分子遗传学方法被用来 鉴定调控根放射状组织的基因。稻草人（SCR） 和SHORTROOT（SHR）基因调节一个关键的不对称分裂所需的 在这三个战略中，的序列 SCARECROW基因表明它可能是一个转录因子。稻草人 在不对称分裂之前在母细胞内表达， 只在分裂后的一个子细胞中。其表达 这种模式也表明在原基的早期阶段， 建立。潜在的上游监管机构和下游目标 稻草人已经被发现。稻草和短根在植物生长发育中的作用 根放射状组织的调节将被描述为一个范例 来理解植物的器官发生。与类似研究的比较 将解决共享的发展过程的起源。的 具体目标是： 1.确定SCR调节不对称性的分子机制 产生皮层和内皮层的分裂。抗体将用于 定位SCR和SCR活性的下游和上游调节器将 被识别。SCR在原基建立过程中的作用将是 通过表型分析和SCR表达分析表征 在胚根突变体中。 2.利用克隆的SCR基因作为分子工具， 关于放射状组织信息如何在 胚根、主根和侧根。组织特异性和诱导性 表达，扇区分析和激光烧蚀将用于确定 SCR活动的发展要求，以及放射式组织如何 信息在根发育期间传递。 3.确定短根在调节放射状组织中的作用， 内胚层规格短根基因将被分离，其 与SCARECROW介导的分裂途径的相互作用将是 表征了 4.在根辐射中分离和表征另外等位基因和突变体 organization.其他等位基因和新的突变体将使用 一种筛选放射状组织突变的光学清除方法。

The long-term goal of the proposed research is to understand the developmental processes that regulate organ formation using radial organization of the Arabidopsis root as a model. Root radial organization is formed by three different developmental strategies. Primary roots employ a stem cell strategy, embryonic roots use a sequential division strategy and lateral roots are formed by cell proliferation from differentiated tissue. These three diverse strategies result in roots with nearly identical radial organization. A molecular-genetic approach was used to identify genes that regulate root radial organization. The SCARECROW(SCR) and SHORTROOT(SHR) genes regulate a key asymmetric division required for radial organization during all three strategies. The sequence of the SCARECROW gene indicates that it may be a transcription factor. SCARECROW is expressed within the mother cell prior to the asymmetric division and in only one of the daughter cells after the division. Its expression pattern also suggests a role during the early stages of primordia establishment. Potential upstream regulators and downstream targets of SCARECROW have been identified. The role of SCARECROW and SHORT-ROOT in the regulation of root radial organization will be characterized as a paradigm for understanding organogenesis in plants. Comparison to similar studies in animals will address the origins of shared developmental processes. The specific objectives are to: 1. Determine the molecular mechanism by which SCR regulates the asymmetric division that generates cortex and endodermis. Antibodies will be used to localize SCR and downstream and upstream regulators of SCR activity will be identified. The role of SCR during primordia establishment will be characterized by phenotypic analysis and by analysis of expression of SCR in embryonic root mutants. 2. Use the cloned SCR gene as a molecular tool to test alternative hypotheses as to how radial organization information is transmitted in embryonic, primary and lateral roots. Tissue-specific and inducible expression, sector analysis, and laser ablation will be used to determine the developmental requirements for SCR activity and how radial organization information is transmitted during root development. 3. Determine the role of SHORT-ROOT in regulating radial organization and endodermal specification. The SHORT-ROOT gene will be isolated and its interaction with the SCARECROW-mediated division path way will be characterized. 4. isolate and characterize additional alleles and mutants in root radial organization. Additional alleles and new mutants will be identified using an optical clearing method to screen for radial organization mutations.