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，其后代采取新的命运来指定细胞类型，这反过来又沿着通向终末期分化的途径前进。在植物中，拟南芥根已经成为器官发生的主要模型。根尖特定干细胞的不对称分裂由两种转录因子SHORTROOT（SHR）和SCARECROW（SCR）之间精心协调的相互作用控制。至少有两个交叉的途径似乎导致产生基础组织的干细胞的不对称分裂。最近的结果表明，一个途径直接依赖于SHR和SCR结合到编码细胞周期机制的基因的启动子。另一个途径涉及通过新鉴定的转录因子亚家族的转录级联反应，其中BLUEJAY（BLJ）似乎起着核心作用。在动物和植物中，器官发生的调节在很大程度上依赖于转录网络。这个建议的一个目标是确定的转录网络，链接SHR和SCR的早期作用，在不对称细胞分裂与细胞规格和随后的分化的地面组织。工作模型是，在干细胞子细胞的不对称分裂后，SHR和SCR的直接靶点启动了一个转录级联反应，该转录级联反应指定了两个基础组织谱系，内皮层和皮质，并最终导致两种细胞类型的终末期分化。将鉴定BLJ和其他SHR/SCR下游基因的直接靶标，然后表征其直接靶标。高分辨率的表达数据集将被用来识别特定于任一基本组织谱系的共调节基因。从这些集群中，转录调节因子将被确定和他们的作用，在调节发育途径的测试。定量建模方法将被用来分析集群，并确定监管单位之间的联系。具体目标是：1）鉴定和表征与SHR和SCR一起工作以调节干细胞不对称分裂的因子; 2）表征将不对称细胞分裂与终末期分化联系起来的网络; 3）沿着分化途径对网络连接性进行建模沿着。 公共卫生相关性：了解细胞不对称分裂的分子机制及其与细胞特化和分化的联系，可以深入了解与发育相关的健康问题，如出生缺陷和癌症。比较和对比植物和动物的发展可以为两者提供重要的见解，从而更好地了解人类疾病以及生物技术和农业的改进。)

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. )