Molecular Genetic Analysis of Root Morphogenesis

描述（由申请人提供）：拟议研究的长期目标是了解调节器官形成的发育过程。这通常涉及干细胞的不对称分裂，其后代承担新的命运以指定细胞类型，进而沿着终末期分化的途径发展。在植物中，拟南芥的根已经成为器官发生的主要模式。根尖端特定干细胞的不对称分裂是由两个转录因子，SHORTROOT （SHR）和稻草人（SCR）之间精细协调的相互作用控制的。至少有两种交叉的途径似乎导致产生基质组织的干细胞的不对称分裂。最近的研究结果表明，其中一条途径直接依赖于SHR和SCR与编码细胞周期机制的基因启动子的结合。另一个途径涉及通过新发现的转录因子亚家族的转录级联，其中BLUEJAY （BLJ）似乎起着核心作用。在动物和植物中，器官发生的调控在很大程度上依赖于转录网络。本研究的目标是确定将SHR和SCR在不对称细胞分裂、细胞规范和随后的基质组织分化中的早期作用联系起来的转录网络。工作模型是，在干细胞子细胞不对称分裂后，SHR和SCR的直接靶点启动了转录级联，指定了两种基本组织谱系，即内皮层和皮层，并最终导致两种细胞类型的终末期分化。BLJ和其他SHR/SCR下游基因的直接靶点将被鉴定，然后它们的直接靶点将被表征。高分辨率的表达数据集将用于识别特定于地面组织谱系的共调控基因。从这些集群中，转录调控因子将被确定并在调节发育途径中测试其作用。定量建模方法将用于分析集群和确定监管单位之间的联系。具体目标是：1)识别和表征与SHR和SCR一起调节干细胞不对称分裂的因素；2)描述连接非对称细胞分裂和终末分化的网络；3)沿分化路径建立网络连通性模型。

DESCRIPTION (provided by applicant): The long-term goal of the proposed research is to understand the developmental processes that regulate organ formation. This frequently involves asymmetric divisions of stem cells whose progeny take on new fates to specify cell types, which in turn progress down a pathway toward end-stage differentiation. In plants, the Arabidopsis root has emerged as a leading model for organogenesis. Asymmetric division of specific stem cells at the tip of the root is controlled by a finely orchestrated interplay between two transcription factors, SHORTROOT (SHR) and SCARECROW (SCR). At least two intersecting pathways appear to lead to asymmetric division of the stem cells that generate the ground tissue. Recent results indicate that one pathway depends directly on SHR and SCR binding to the promoters of genes encoding the cell cycle machinery. The other pathway involves a transcriptional cascade through a newly identified transcription factor subfamily of which BLUEJAY (BLJ) appears to play a central role. In both animals and plants the regulation of organogenesis depends heavily on transcriptional networks. A goal of this proposal is to identify the transcriptional networks that link SHR and SCR's early role in asymmetric cell division with cell specification and subsequent differentiation of the ground tissue. The working model is that after asymmetric division of the stem cell daughter, direct targets of SHR and SCR set in motion a transcriptional cascade that specifies the two ground tissue lineages, endodermis and cortex and ultimately results in the end-stage differentiation of both cell types. Direct targets of BLJ and other SHR/SCR downstream genes will be identified and then their direct targets will be characterized. High-resolution expression datasets will be used to identify co-regulated genes specific to either of the ground tissue lineages. From these clusters, transcriptional regulators will be identified and their role in regulating the developmental pathway tested. Quantitative modeling approaches will be used to analyze the clusters and identify linkages between regulatory units. Specific aims are to: 1) Identify and characterize the factors that work with SHR and SCR to regulate stem cell asymmetric divisions; 2) Characterize the networks that link asymmetric cell division to end- stage differentiation; 3) Model network connectivity along the differentiation pathway. PUBLIC HEALTH RELEVANCE: Understanding the molecular mechanisms underlying asymmetric cell division and its links with cell specification and differentiation can lead to insights into developmentally related health concerns such as birth defects and cancer. Comparing and contrasting plant and animal development can provide important insights into both, leading to a better understanding of human disease as well as improvements in biotechnology and agriculture. )