MOLECULAR GENETIC ANALYSIS OF ROOT MORPHOGENESIS

拟议研究的长期目标是了解 利用径向调节器官形成的发育过程 以拟南芥根部组织为模型。根径向组织 由三种不同的发展战略构成。初级根员工 一种干细胞策略，胚根使用顺序分裂策略 侧根是由分化的细胞增殖而成的 组织。这三种不同的策略导致了几乎 相同的径向组织。分子遗传学方法被用来 确定调控根径向组织的基因。稻草人(SCR) 和SHORTROOT(SHR)基因调节关键的不对称分裂 在所有这三个战略中都进行了放射式组织。按顺序排列的 稻草人基因提示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，并且 分裂后只有一个子代细胞。其表达方式 花纹也表明在原基的早期阶段 建制派。潜在的上游监管机构和下游目标 稻草人已经被确认。稻草人和短根在水稻生长发育中的作用 根径向组织的调节将被描述为一种范式 以了解植物的器官发生。与同类研究的比较 将探讨共同发育过程的起源。这个 具体目标是： 1.确定SCR调节不对称的分子机制 产生皮质和内胚层的部门。抗体将被用来 将SCR和SCR活动的下游和上游监管机构本地化将 被指认出来。SCR在原基建立过程中的作用将是 以表型分析和Scr表达分析为特征 在胚根突变体中。 2.利用克隆的SCR基因作为分子工具进行替代试验 关于放射状组织信息如何在 胚根、初生根和侧根。组织特异性和诱导性 将使用表达式、扇区分析和激光消融来确定 SCR活动的发展要求及如何辐射组织 信息是在根的发育过程中传递的。 3.确定短根在调节放射状组织和 内胚层规格。短根基因将被分离出来，其 与稻草人相互作用的方式将通过稻草人介导的分裂路径 特色化的。 4.分离和鉴定根径向附加等位基因和突变体 组织。更多的等位基因和新的突变体将通过 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.