Analysis of Meristem Function and Floral Patterning in the Arabidopsis ULTRAPETALA Mutant

干细胞活动的控制对所有高等生物的正常发育至关重要，因为干细胞是构成人体的器官和组织的前体。植物为研究和操作干细胞提供了极好的模型系统，因为它们在生长的顶端（称为顶分生组织）的整个生命周期中都保持着干细胞池。茎尖分生组织在产生叶、茎、花等器官的同时，不断地维持着一个干细胞库。分生组织如何在干细胞生产和器官发生之间保持恒定的平衡尚不清楚，但弗莱彻博士和其他人利用模式植物拟南芥（Arabidopsis thaliana）进行的研究揭示了调节这种平衡的基因，从而影响茎尖分生组织的活性。本项目的目的是了解拟南芥ULTRAPETALA （ULT）位点如何控制茎和花分生组织的活性。我们已经分离出了从扩大的分生组织中产生额外的花和花器官的突变植物，并且在花的中心也改变了器官的身份。因此，ULT是茎尖分生组织功能和花形态的候选调节因子。我们的第一个目标是通过分析区域特异性分子标记的分布来确定潜在的嫩枝和花分生组织表型的缺陷。我们还将破译ULT与其他已知的茎和花发育调节因子之间的遗传关系，这些调节因子在许多不同的途径中起作用。我们的第三个目标是绘制和克隆ULT基因，并在发育过程中确定其mRNA表达模式，作为基因产物功能分析的前奏。这些实验将确定ULT调节分生组织大小和花模式的具体机制，并将ULT与已知影响这些过程的其他拟南芥基因联系起来。分析ULT提供了一个独特的机会来研究平衡终身干细胞生产和器官发生的机制，并确定单个分子如何在生长控制和模式形成中发挥作用，以协调发育过程中这两个关键过程。

0110667FletcherThe control of stem cell activity is critical for the proper development of all higher organisms, as stem cells are the precursors of the organs and tissues that comprise the body. Plants make excellent model systems in which to study and manipulate stem cells, because they maintain pools of such cells throughout their life cycle at growing tips called apical meristems. The shoot apical meristem continuously maintains a stem cell reservoir while simultaneously generating organs such as leaves, stems and flowers. How the meristem keeps a constant balance between stem cell production and organogenesis is poorly understood, but studies by Dr. Fletcher and others using the model plant Arabidopsis thaliana are uncovering genes that regulate this balance and thereby affect shoot apical meristem activity. The goal of this project is to understand how the Arabidopsis ULTRAPETALA (ULT) locus controls the activity of shoot and floral meristems. We have isolated ult mutant plants that generate extra flowers and floral organs from enlarged meristems, and also have altered organ identity in the center of the flower. ULT is therefore a candidate regulator of both shoot apical meristem function and floral patterning. Our first objective is to identify the defect(s) underlying the ult shoot and floral meristem phenotypes by analyzing the distribution of region-specific molecular markers. We will also decipher the genetic relationship between ULT and other known regulators of shoot and flower development, which act in a number of different pathways. Our third goal is to map and clone the ULT gene, and determine its mRNA expression pattern during development as a prelude to functional analysis of the gene product. These experiments will identify specific mechanisms through which ULT regulates meristem size and floral patterning, and place ULT in context with other Arabidopsis genes known to affect these processes. Analysis of ULT provides a unique opportunity to investigate the mechanisms that balance life-long stem cell production and organogenesis, and also to determine how a single molecule functions both in growth control and pattern formation to coordinate these two crucial processes during development.