Molecular Specification and Development of the Carpel Margin Meristem

种子植物的生存，以及人类食物供应的安全，都需要胚珠的发育，这些胚珠受精后会发育成种子。在开花植物中，胚珠在雌蕊内发育，雌蕊是雌性的生殖结构。拟南芥的雌蕊由两个心皮组成，心皮沿其边缘或边缘融合形成管状结构。胚珠从称为心皮边缘分生组织（cmm）的特殊分生组织区域产生于雌蕊管的内表面。破坏CMM发育的基因突变导致种子形成减少。因此，CMMs的正常发育对拟南芥的雌性繁殖和许多作物的农业生产力至关重要。提出的研究的主要目的是产生对早期CMM发展的分子机制的理解。发育中的雌蕊内部的区域规范是指对结构的不同部分分配不同的位置身份。区域规范对CMM的发展至关重要。具体地说，必须正确指定正面（或内部）和边缘的同一性，以确保CMM的形成，从而确保胚珠的发育。实验数据表明，三个关键调控基因SEUSS、LEUNIG和AINTEGUMENTA在CMM的早期发育中起着至关重要的作用。Franks博士提出了一个二分模型，其中1)SEUSS， LEUNIG和AINTEGUMENTA基因是发育中的雌蕊中近轴同一性标记PHABULOSA表达所必需的，2)PHABULOSA表达对CMM的早期发育至关重要。他提出了多种分子遗传学实验来彻底验证这一模型：1)在上述一个或多个关键调控因子（SEUSS， LEUNIG和AINTEGUMENTA）的活性受损的突变植物中，特定的分子标记将被用于遵循区域规范的雌蕊发育过程；2)确定发育中的雌蕊中SEUSS和LEUNIG基因产物的表达模式；3)探讨PHABULOSA基因在CMM发育过程中近轴同源性规范的意义；4)和一个独特的基因修饰筛选将用于鉴定新的CMM发展调节因子。在许多作物植物中，CMM的发展对农业生产力至关重要。通过提高对CMM发育调控的分子理解，提出的研究可能使设计提高产量的农业品种的方法成为可能，从而满足日益增长的全球粮食需求。此外，通过将他的科研工作与研究生和本科生的教学和培训职责充分结合起来，他将提高他的研究项目的社会效益。材料和研究成果将通过在科学期刊上发表和通过网络工具广泛传播给感兴趣的科学家和各级教育工作者。此外，弗兰克斯博士将组织感兴趣的研究生在当地小学准备和展示演示，这将有助于鼓励从小对科学研究的兴趣。

Project SummaryThe survival of seed plants, and thus the security of humankind's food supply, requires the development of ovules that when fertilized will develop into seeds. In flowering plants the ovules develop within the gynoecium, the female reproductive structure. In Arabidopsis thaliana the gynoecium is made up of two carpels that are fused along their edges or margins to form a tube-like structure. Ovules arise on the inner surface of the gynoecial tube from specialized meristematic regions known as the Carpel Margin Meristems (CMMs). Genetic mutations that disrupt the development of the CMM result in a reduction of seed formation. Thus proper development of the CMMs is critical for female fertility in Arabidopsis and agricultural productivity in many crop plants. The main objective of the proposed research is to generate an understanding of the molecular mechanisms of early CMM development.Regional specification within the developing gynoecium refers to the assignment of different positional identities to different parts of the structure. Regional specification is critical for the development of the CMM. Specifically, adaxial (or inner) identity and margin identity must be properly specified to ensure CMM formation and thus ovule development. Experimental data indicates that three key regulatory genes, SEUSS, LEUNIG and AINTEGUMENTA, play a crucial role in the early development of the CMM. Dr Franks proposes a bipartite model in which 1) the SEUSS, LEUNIG and AINTEGUMENTA genes are required for the expression of the adaxial identity marker PHABULOSA within the developing gynoecium and 2) PHABULOSA expression is critical for the early development of the CMM. He proposes a variety of molecular genetic experiments to thoroughly test this model: 1) specific molecular markers will be used to follow regional specification during gynoecial development in mutant plants in which the activity of one or more of above-mentioned key regulators (SEUSS, LEUNIG and AINTEGUMENTA) is compromised; 2) the expression patterns of the SEUSS and LEUNIG gene products within the developing gynoecium will be determined; 3) the significance of adaxial identity specification during CMM development by the PHABULOSA gene will be investigated; 4) and a unique genetic modifier screen will be utilized to identify novel regulators of CMM development. In many crop plants the development of the CMM is critical for agricultural productivity. By generating an enhanced molecular understanding of the regulation and control of CMM development, the proposed research may enable methods to engineer agricultural varieties with enhanced yield and thus meet the growing global demand for food. Additionally, the PI will enhance the societal benefits of his research program by fully integrating his scientific research efforts with his graduate and undergraduate teaching and training responsibilities. Materials and research results will be widely dispersed through publication in scientific journals and through web-based vehicles to interested scientists and all levels of educators. Furthermore, Dr. Franks will organize interested graduate students to prepare and present demonstrations at local elementary schools that will help to encourage an interest in scientific studies from this early age.