A Molecular Genetic Analysis of Root Morphogenesis

描述（申请人摘要）：拟议研究的长期目标 是了解调节器官形成的发育过程。 目前的工作集中在拟南芥根的放射状组织作为一个 简单易操作系统。战略是确定和描述 基因在通过控制放射状图案形成中起关键作用， 细胞分裂和细胞特化。一种遗传学方法被用来识别 SCARECROW（SCR）和SHORT-ROOT（SHR）基因突变，导致 缺少一层细胞的根。SHR和SCR的克隆显示， 编码推定转录因子的GRAS家族的成员。SHR是 在导致SCR转录激活的途径中位于SCR上游。 遗传和分子证据表明，SHR的行为是非细胞自主的， 激活SCR并指定小区标识。自发性高血压大鼠的非细胞自主活动 这是一个信号中心位于内部细胞层的证据， 拟南芥的根提供模式信息给周围的细胞 层次。SHR和SCR基因将被用作分子工具，以解决如何 建立信令中心并发挥作用，其信号的性质， 以及哪些细胞有能力产生并响应信号。 关于SHR介导的信号的性质的替代假设将是 测试.第一个是SHR编码一种转录因子， 参与中柱信号转导途径的一个或多个基因 相邻细胞层（间接模型）。另一种假设是， SHR基因产物本身是一种信号分子， 中柱的邻近组织（直接模型）。的条件表达 SHR和SCR将用于测试自上而下的模型，该模型假设： 放射状图案在胚胎发生期间开始，并通过 不断向分生组织发出信号。遗传学和基因组学方法将是 用于识别控制放射性的信号通路的新成分 模式化具体目标是：1。识别SHR介导的 径向模式信号：测试直接和间接模型。2.表征 根和芽细胞对SHR介导的信号传导的能力和反应。3. 确定SHR介导的信号传导的时间要求： 自上而下的模型4.识别SHR-SCR径向图案的新组件 使用遗传和基因组方法的途径。

DESCRIPTION (Applicant's Abstract): The long-term goal of the proposed research is to understand the developmental processes that regulate organ formation. Current work focuses on the radial organization of the Arabidopsis root as a simple and tractable system. The strategy has been to identify and characterize genes that play key roles in regulating radial patterning through control of cell division and cell specification. A genetic approach was used to identify mutations in the SCARECROW (SCR) and SHORT-ROOT (SHR) genes which result in roots that lack one cell layer. Cloning of SHR and SCR revealed that they encode members of the GRAS family of putative transcription factors. SHR is upstream of SCR in a pathway which leads to transcriptional activation of SCR. Genetic and molecular evidence indicates that SHR acts non-cell autonomously to activate SCR and specify cell identity. The non-cell autonomous activity of SHR is evidence for a signaling center located in the internal cell layers of the Arabidopsis root which provides pattern information to the surrounding cell layers. The SHR and SCR genes will be used as molecular tools to address how the signaling center is established and functions, the nature of its signal(s), and which cells are competent to generate and respond to the signal(s). Alternative hypotheses as to the nature of the SHR-mediated signal will be tested. The first is that SHR encodes a transcription factor that activates a gene or genes which participate in a signal transduction pathway from the stele to the adjacent cell layers (indirect model). An alternative hypothesis is that the SHR gene product itself is a signal molecule and is able to translocate to the adjacent tissue from the stele (direct model). Conditional expression of SHR and SCR will be used to test the top-down model which postulates that radial patterning is initiated during embryogenesis and is propagated through continual signaling to the meristem. Genetic and genomic approaches will be used to identify new components of the signaling pathway controlling radial patterning. Specific aims are to: 1. Identify the nature of the SHR-mediated radial pattern signal: test direct and indirect models. 2. Characterize the competence and response of root and shoot cells to SHR-mediated signaling. 3. Determine the temporal requirements for SHR-mediated signaling: test the top-down model. 4. Identify new components of the SHR-SCR radial patterning pathway using genetic and genomic approaches.