Control of Embryo Development in Higher Plants

主要研究者：约翰J.原田2003年12月1日高等植物胚胎发育的控制第3页NSF 0344753摘要胚胎发生描述了植物生命周期的一个时期，在此期间，单细胞受精卵经历了一系列的分化事件，导致形成成熟的和代谢静止的胚胎。 高等植物的胚胎发生包括两个概念上不同的阶段。 最早的是形态发生阶段，在此期间，植物的基本身体计划形成。随后是成熟阶段，在此期间，胚胎积累蛋白质和脂质，诱导过程，使它们能够承受干燥，并成为代谢静止。 这项建议有两个主要目标。 一个目标是了解这两个胚胎阶段是如何协调的。 成熟阶段的进化使高等植物能够产生种子。 由于低等植物不经历成熟或产生种子，因此在高等植物中，成熟阶段很可能被插入形态发生的连续阶段。 第二个目标是定义允许细胞改变其命运并进入胚胎发育模式的发育过程。 可以诱导多种高等植物细胞类型经历胚胎发生。 虽然已知这些胚胎中的许多遵循类似的形态发生途径，但实际上对允许这些细胞启动胚胎程序的分子过程一无所知。 我们将使用拟南芥叶子叶2（LEC 2）解决这些问题。 LEC 2编码一种调节其他基因转录的蛋白质，是胚胎发生过程的中心调节因子，这些过程发生在形态发生和成熟阶段。 例如，我们已经表明，LEC 2基因的过表达激活营养和生殖器官的成熟过程，并诱导营养细胞的体细胞胚胎形成。 这个提议解决了LEC 2如何建立一个激活成熟程序并促进细胞能力进行体细胞胚胎发生的环境的总体问题。 一个直接的目标是确定基因直接调控的LEC 2转录因子。 激活和抑制的基因谱应提供深入了解直接由LEC 2控制的调节程序。 第二个目的是确定与LEC 2协同工作的其他胚胎调节因子，以发现控制胚胎发生的调节网络中的其他参与者。 总之，这些实验方法应该为控制胚胎发育提供新的见解。除了提供有关高等植物胚胎发生的新的基础知识，从这些研究中获得的信息可能与策略的设计有关，以操纵种子发育用于应用目的。 该项目的教育价值在于它将为本科生、研究生和高中生提供强大的培训机会。

PI: John J. Harada December 1, 2003Control of Embryo Development in Higher Plants Page 3NSF 0344753ABSTRACTEmbryogenesis describes the period of the plant life cycle during which a single-celledzygote undergoes a series of differentiation events, resulting in the formation of a mature and metabolically quiescent embryo. Embryogenesis in higher plants consists of two conceptually distinct phases. The earliest is the morphogenesis phase during which the basic body plan of the plant is formed. This is followed by the maturation phase during which the embryo accumulates proteins and lipids, induces processes that allow them to withstand desiccation, and becomes metabolically quiescent. There are two major goals of this proposal. One objective is to understand how these two embryonic phases are coordinated. The maturation phase evolved to permit higher plants to make seeds. Given that lower plants do not undergo maturation or make seeds, it is likely that, in higher plants, the maturation phase was inserted into a continuous phase of morphogenesis. The second objective is to define the developmental processes that allow cells to change their fate and enter into an embryonic mode of development. A diversity of higher plant cell types can be induced to undergo embryogenesis. Although it is known that many of these embryos follow similar morphogenetic pathways, virtually nothing is known of the molecular processes that allow these cells to initiate embryonic programs. We will address these problems using Arabidopsis LEAFY COTYLEDON2 (LEC2). LEC2 encodes a protein that regulates the transcription of other genes and is a central regulator of embryogenesis required for processes that occur during both the morphogenesis andmaturation phases. For example, we have shown that overexpression of the LEC2 gene activates maturation processes in vegetative and reproductive organs and induces somatic embryo formation from vegetative cells. This proposal addresses the overall question of how LEC2 establishes an environment that activates the maturation program and promotes cellular competence to undergo somatic embryogenesis. An immediate objective is to identify genes directly regulated by the LEC2 transcription factor. The spectrum of genes activated and repressed should provide insight into the regulatory programs directly controlled by LEC2. A second aim is to identify other embryonic regulators that work in concert with LEC2 to discover other participants in the regulatory network controlling embryogenesis. Together, these experimental approaches should provide new insights into the control of embryo development. In addition to providing new basic knowledge about higher plant embryogenesis, information derived from these studies may be relevant to the design of strategies to manipulate seed development for applied purposes. The educational value of the project is that it will provide strong training opportunities for undergraduate, graduate students, and high schoolstudents.