Molecular Genetic Analysis of Shoot Apical Meristem Development in Arabidopsis Thaliana

拟南芥茎尖分生组织发育的分子遗传学分析

• 批准号: 9408731
• 负责人: M. Kathryn Barton
• 金额: $ 28.5万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-09-01 至 1997-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9408731&HistoricalAwards=false
• 关键词: Molecular; Genetic; Analysis; Shoot; Apical

Populations of stem cells exist in many organisms. Their most significant attribute is that they replenish themselves as well as give rise to many terminally differentiated cell types. In plants, the meristems or growing tips of roots or shoots are groups of stem cells. Shoot apical meristems in angiosperm plants are formed during embryogenesis and are comprised of a small number of undifferentiated, dividing cells. These cells will give rise to all of the above- ground portions of the plant. Thus, understanding the developmental biology of shoot apical meristems is absolutely fundamental to understanding plant growth and development. How is the shoot apical meristem initiated during embryogenesis? How are additional meristems initiated postembryonically in the axils of leaves? How is a group of undifferentiated, dividing cells maintained in the meristem? How are the positions of organs generated by the meristem determined? The long term goal of this study is to answer these questions in molecular detail. The small cruciferous plant Arabidopsis thaliana has been chosen as an experimental organism -- its short generation time and small genome size make it especially well suited for molecular genetic analysis. The focus of this project is the shoot meristemless (STM) locus. Seedlings homozygous for a loss- of-function mutation in this gene lack a shoot apical meristem but are otherwise normal. Careful morphological examination of homozygous stm-1 mutants has shown that the defect lies in their inability to initiate a shoot apical meristem during embryogenesis. Evidence that the STM gene corresponds to an Arabidopsis homolog of the maize Knotted gene is presented. This gene encodes a homeodomain containing protein and therefore probably acts as a transcriptional regulator. Although homeodomain proteins have been identified in plants previously, this is the first case in which a loss-of-function mutation has been identified in such a gene and hence its wild-type function deduced. To understand how STM promotes shoot apical meristem formation, experiments are proposed that are designed to shed light on how the STM gene is regulated and, in the long term, to identify genes that STM in turn regulates.

干细胞群体存在于许多生物体中。它们最重要的特征是自我补充，并产生许多终末分化的细胞类型。在植物中，根或芽的分生组织或生长尖端是一组干细胞。被子植物的顶端分生组织是在胚胎发生过程中形成的，由少量未分化的分裂细胞组成。这些细胞将形成植物的所有地上部分。因此，了解顶端分生组织的发育生物学对于了解植物的生长发育是绝对重要的。新梢顶端分生组织是如何在胚胎发生过程中启动的？额外的分生组织是如何在胚后在叶腋处启动的？分生组织中如何维持一组未分化的分裂细胞？分生组织产生的器官的位置是如何确定的？这项研究的长期目标是从分子上详细回答这些问题。小的十字花科植物拟南芥被选为实验生物--它的世代时间短，基因组大小小，特别适合于分子遗传分析。本项目的重点是无分生组织(STM)基因座。该基因功能缺失突变的纯合子幼苗没有顶端分生组织，但其他方面都是正常的。对纯合子STM-1突变体的仔细形态检查表明，缺陷在于它们在胚胎发生过程中不能启动顶端分生组织。有证据表明，STM基因对应于玉米打结基因的拟南芥同源基因。该基因编码含有同源结构域的蛋白质，因此可能起到转录调节的作用。虽然之前已经在植物中发现了同源结构域蛋白，但这是第一次在这样的基因中发现功能缺失突变，从而推断其野生型功能。为了了解STM如何促进茎顶端分生组织的形成，人们提出了一些实验，旨在阐明STM基因是如何调控的，并从长远来看，确定STM反过来调控的基因。