Mechanisms governing floral stem cell maintenance and miRNA functions in Arabidop

描述（由申请人提供）：发育生物学的一个基本问题是多能干细胞如何维持以及它们如何分化成多细胞生物中的各种谱系。模式植物拟南芥的花朵发育提供了一个很好的系统来解决干细胞生物学的关键问题。我们的长期目标之一是揭示控制花干细胞维持和终止的机制。我们和其他人发现了一个由三个转录因子组成的还不完整的网络，该网络由基于 microRNA (miRNA) 的转录后机制叠加，控制花干细胞的维持。在拟议的研究中，我们将通过识别花干细胞调节的核心成分来扩展该网络。我们将1）鉴定两个关键转录因子的靶基因，2）将新鉴定的花干细胞调节因子ARF2、ARF3和ARF4以及调节这三个转录因子基因的小RNA整合到现有的花干细胞调节框架中，以及3）探讨Polycomb组蛋白在花干细胞终止中的作用。 miRNA 是序列特异性调节分子，影响包括发育在内的许多生物过程。反式作用 siRNA (ta-siRNA) 是一类植物特异性、类 miRNA 的小 RNA，具有重要的发育作用。另一个长期研究目标是剖析小RNA生物发生和作用模式的一般机制，并研究特定miRNA或ta-siRNA的生物发生或活性在发育过程中如何受到调节。尽管miRNA生物发生的主要框架已经建立，但miRNA如何抑制靶基因表达目前仍存在很大争议。该领域还处于了解特定小 RNA 的活性如何在发育环境中受到调节的早期阶段。剖析 miRNA 的作用模式并了解小 RNA 活性在发育过程中如何受到调节的关键是鉴定介导或调节小 RNA 活性的蛋白质。我们已经在小RNA介导的靶基因调控中鉴定了两种这样的蛋白质，AGO10和AMP1。拟议的研究旨在揭示这两种蛋白质的分子功能。 这项工作无疑将为干细胞调控和 miRNA 功能提供新的见解。了解植物中干细胞如何维持和终止将有助于得出控制干细胞生物学的基本原理，并有助于干细胞在再生医学中的最终应用。由于植物和动物之间 miRNA 生物发生和功能的机制高度保守，我们的工作对 miRNA 功能机制理解的进展将直接影响我们利用小 RNA 的力量对抗病原体和人类疾病的能力。 公共健康相关性：了解干细胞如何维持以及它们如何分化是未来利用干细胞力量进行再生医学的关键。这项研究将揭示控制干细胞时间调控的转录和转录后网络中的主要参与者。这项研究还将加深我们对 miRNA 作用模式的理解，miRNA 是影响生物学各个方面的调节分子，其错误调节与人类疾病有关。

DESCRIPTION (provided by applicant): A fundamental question in developmental biology is how pluripotent stem cells are maintained and how they differentiate into various lineages in multicellular organisms. Flower development in the model plant Arabidopsis thaliana offers a great system to address key questions in stem cell biology. One of our long-term goals is to uncover the mechanisms that govern the maintenance and termination of floral stem cells. We and others have uncovered an as yet incomplete network of three transcription factors superimposed by a microRNA (miRNA)-based posttranscriptional mechanism that governs the maintenance of floral stem cells. In the proposed research, we will expand this network by identifying core components at the heart of floral stem cell regulation. We will 1) identify target genes of the two key transcription factors, 2) incorporate the newly identified floral stem cell regulators, ARF2, ARF3 and ARF4, and the small RNA that regulates the three transcription factor genes into the existing framework of floral stem cell regulation, and 3) probe the role of the Polycomb group proteins in floral stem cell termination. miRNAs are sequence-specific regulatory molecules that impact numerous biological processes including development. The trans-acting siRNAs (ta-siRNAs) are a class of plant-specific, miRNA-like small RNAs with important developmental roles. Another long-term research goal is to dissect the general mechanisms underlying the biogenesis and mode of action of small RNAs and to study how the biogenesis or activities of specific miRNAs or ta-siRNAs are modulated in development. Whereas the major framework of miRNA biogenesis is established, how miRNAs inhibit target gene expression is highly controversial at present. The field is at its very early stages of understanding how the activities of specific small RNAs are regulated in developmental contexts. A key to dissecting the mode of action of miRNAs and understanding how small RNA activity is regulated in development is to identify proteins that mediate or modulate the activities of small RNAs. We have identified two such proteins, AGO10 and AMP1 in small RNA-mediated target gene regulation. The proposed research is aimed at uncovering the molecular functions of these two proteins. The proposed work will undoubtedly provide novel insights into stem cell regulation and miRNA function. Understanding how stem cells are maintained and terminated in plants will help derive basic principles that govern stem cell biology and contribute to the ultimate use of stem cells in regenerative medicine. Due to the highly conserved mechanisms underlying miRNA biogenesis and function between plants and animals, an advance in the mechanistic understanding of miRNA function from our work will directly impact our abilities to harness the power of small RNAs to fight pathogens and human diseases. PUBLIC HEALTH RELEVANCE: Understanding how stem cells are maintained and how they differentiate is key to harnessing the power of stem cells for regenerative medicine in the future. This research will reveal major players in the transcriptional and post-transcriptional networks that govern the temporal regulation of stem cells. This research will also advance our understanding of the mode of action of miRNAs, regulatory molecules that impact all aspects of biology and whose mis-regulation is associated with human diseases.