A novel genetic network controlling meristem initiation and stem cell patterning

 描述（由申请人提供）：在植物和动物系统中，干细胞生物学的一个中心问题是干细胞群如何建立并长期维持。我们的研究旨在解决这个核心问题。根分生组织的形成是植物胚胎发生过程中最重要的事件之一。根分生组织来源于胚胎发生早期的单个细胞，称为垂体细胞，由远端和近端干细胞群包围的静止中心（QC）组成。我们的研究指出了激素信号和转录因子之间的相互作用产生并维持远端干细胞群的机制。了解这种动态信号的相互作用和干细胞命运的稳定建立之间的逻辑可能在农业和健康科学中具有广泛的应用。 我们以前证明，一氧化氮传输道（NTT）基因编码的转录因子，是所需的正常心皮和果实发育。目前的建议集中在我们最近的发现，在NTT的突变，当结合在两个最密切相关的基因，WIP 4和WIP 5的突变，废除根分生组织的形成。我们的研究表明，NTT，WIP 4和WIP 5（以下简称NWW基因）的作用是冗余的，是必要的，也是足够的，以指定胚胎发生过程中的远端干细胞的命运。重要的是，所有三个基因在胚胎发育早期在垂体细胞中表达，并且这种表达模式依赖于生长素信号通路。我们的研究直接反驳了广泛接受的模型，并提供了一个简单的假设来解释植物激素生长素如何模式干细胞身份。我们的研究表明，在胚胎发生过程中干细胞模式的关键步骤之一涉及NWW基因表达的精确时间和空间模式。 我们建议测试这一假设，以提供一个机制的理解干细胞规格。由于它们在分生组织形成中的关键作用，我们建议使用NWW基因作为一个平台，以确定在胚胎和根中指定和维持干细胞命运的关键因素 分生组织这些因子包括NWW基因表达的上游调节因子以及与NWW相互作用和/或在NWW下游起作用的因子。我们提出了一系列的分子和遗传学方法来识别和表征这些因素，以提供一个框架，为未来的努力，旨在了解干细胞的规格和维护。

 DESCRIPTION (provided by applicant): In both plant and animal systems, a central question of stem cell biology is how stem cell populations are established and then maintained long term. Our studies aim to address this central question. One of the most important events during plant embryogenesis involves formation of the root meristem. The root meristem is derived from a single cell, referred to as the hypophyseal cell, early in embryogenesis and consists of the quiescent center (QC) surrounded by distal and proximal stem cell populations. Our studies point to a mechanism whereby an interplay between hormone signaling and transcription factors creates and maintains the distal stem cell population. Understanding the logic between this interplay of dynamic signaling and stable establishment of stem cell fate is likely to have broad applications in both the agricultural and health sciences. We previously demonstrated that the NO TRANSMITTING TRACT (NTT) gene encodes a transcription factor that is required for normal carpel and fruit development. The current proposal focuses on our recent discovery that mutations in NTT, when combined with mutations in the two most closely related genes, WIP4 and WIP5, abolish root meristem formation. Our studies suggest that NTT, WIP4 and WIP5 (hereafter, the NWW genes) act redundantly and are both necessary and sufficient to specify distal stem cell fate during embryogenesis. Importantly, all three genes are expressed early in embryo development in the hypophyseal cell, and this expression pattern is dependent on the auxin-signaling pathway. Our studies directly refute widely accepted models and provide a simple hypothesis to explain how the plant hormone auxin patterns stem cell identity. Our studies suggest that one of the critical steps in stem cell patterning during embryogenesis involves the precise temporal and spatial pattern of NWW gene expression. We propose to test this hypothesis in order to provide a mechanistic understanding of stem cell specification. Because of their critical role in meristem patterning, we propose to use the NWW genes as a platform to identify the key factors that specify and maintain stem cell fate in embryonic and root meristems. These factors include the upstream regulators of NWW gene expression as well as the factors that interact with and/or function downstream of NWW. We propose a series of molecular and genetic approaches to identify and characterize these factors in order to provide a framework for future efforts aimed at understanding stem cell specification and maintenance.