A Molecular Genetic Analysis of Root Morphogenesis

描述(申请人摘要)：拟议研究的长期目标 就是了解调节器官形成的发育过程。 目前的工作主要集中在拟南芥根作为一种 简单易用的系统。战略一直是识别和描述 调控放射状图案形成的关键基因 细胞分裂和细胞规格。一种遗传方法被用于鉴定 稻草人(SCR)和短根(SHR)基因突变导致 缺少一层细胞层的根。SHR和SCR的克隆表明它们 编码GRAS家族成员，推测为转录因子。SHR是 位于SCR上游的一条途径，可导致SCR的转录激活。 遗传和分子证据表明，SHR非细胞自主地作用于 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 是位于细胞内部细胞层的信号中心的证据 为周围细胞提供图案信息的拟南芥根 层次感。SHR和SCR基因将被用作分子工具来解决如何 信令中心的建立和运行，其信号的性质(S)， 以及哪些细胞有能力产生和响应信号(S)。 关于SHR介导的信号的性质的替代假设将是 测试过。第一种是SHR编码一种转录因子，激活一种 参与中柱信号转导途径的一个或多个基因 到相邻的细胞层(间接模型)。另一种假设是 SHR基因产物本身是一种信号分子，能够转位到 中柱附近的组织(直接模型)。的条件表达式 SHR和SCR将用于测试自上而下的模型，该模型假设 放射状图案化是在胚胎发生期间启动的，并通过 不断地向分生组织发出信号。基因和基因组方法将是 用于识别控制RADIUS的信号通路的新组件 图案化。具体目标是：1.确定SHR介导的性质 径向模式信号：测试直接模式和间接模式。2.描述 根和地上部细胞对SHR介导的信号的能力和反应。3. 确定SHR介导的信号传递的时间需求：测试 自上而下的模型。4.确定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.