Integrated Studies on Cellular and Physiological Roles of Higher Plant Plasmodesmata

高等植物胞间连丝细胞和生理作用的综合研究

• 批准号: 9900539
• 负责人: William Lucas
• 金额: $ 76.21万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-08-01 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9900539&HistoricalAwards=false
• 关键词: Integrated; Studies; Cellular; Physiological; Roles

In plants, cell-to-cell contact is established by special intercellular organelles, termed plasmodesmata. These unique cytoplasmic bridges interconnect the protoplasm of the cells within an organ, such as a leaf, forming a symplasmic state, which potentiates the exchange of both metabolites and information molecules. In recent years, genetic, molecular, cellular and physiological studies provided direct evidence that plasmodesmata have the capacity to mediate the transport of macromolecules, such as proteins and nucleic acids (RNA and DNA). Importantly, it has been shown that nucleic acids move cell to cell in the form of nucleoprotein complexes. Based on these studies, the emerging concept is that plasmodesmata have evolved to (a) enhance the efficacy of biochemical processes occurring within specific organs, and (b) facilitate the coordination of both physiological and developmental events, via the selective trafficking of information molecules. To better understand the mechanisms by which plants exert control over these plasmodesmal functions, experiments are described that will allow identification and cloning of the component parts involved in the selective trafficking of macromolecules between plant cells. An integrated approach will be taken to achieve this goal, and will incorporate the use of biochemical, cellular, molecular and ultrastructural techniques. Methods developed for the identification of the components involved in protein trafficking between the cytoplasm and the nucleoplasm will be integrated into these experiments. The specific involvement of chaperones in the overall process of protein and nucleoprotein transport to and through plasmodesmata will also be explored. Attention will be focused on a class of cytoplasmic chaperones termed the heat shock proteins. These studies will be integrated with an analysis of the symplasmic pathway that exists within the vascular system of higher plants. This vascular system is comprised of the xylem, which conducts water and mineral nutrients from the root to the aerial regions of the plant, and the phloem, which translocates fixed carbon (sugars) and nitrogen (amino acids) to developing organs. Two cell types, the companion cells and the sieve elements, form the conducting tissue of the phloem. The plasmodesmata that interconnect these cell types fulfill an important function in the operation of this long-distance translocation system. Experiments will be conducted to identify, at the genetic level, ways by which the plant can control this pivotal symplasmic route, from the photosynthetic tissues of the leaf, all the way to the phloem conducting tissue. These studies will provide a framework for understanding how the plant employs the phloem long-distance translocation system to orchestrate processes at the whole-plant level.

在植物中，细胞与细胞之间的接触是由特殊的细胞间细胞器建立的，称为胞间连丝。这些独特的细胞质桥梁将器官(如叶子)内细胞的原生质相互连接，形成共质状态，加强代谢物和信息分子的交换。近年来，遗传、分子、细胞和生理研究提供了直接证据，证明胞间连丝具有调节蛋白质和核酸(RNA和DNA)等大分子运输的能力。重要的是，已有研究表明，核酸以核蛋白复合体的形式在细胞间移动。在这些研究的基础上，新出现的概念是，胞间连丝已经进化为：(A)通过选择性地传递信息分子，提高发生在特定器官内的生化过程的效率，以及(B)促进生理和发育事件的协调。为了更好地了解植物对这些胞间连丝功能的控制机制，描述了一些实验，这些实验将允许鉴定和克隆参与植物细胞间大分子选择性运输的组成部分。将采取综合方法来实现这一目标，并将结合使用生化、细胞、分子和超微结构技术。为鉴定与细胞质和核质之间的蛋白质运输有关的成分而开发的方法将纳入这些实验。还将探讨伴侣蛋白在蛋白质和核蛋白运输到胞间连丝和通过胞间连丝的整个过程中的具体参与。人们的注意力将集中在一类称为热休克蛋白的细胞质伴侣蛋白上。这些研究将与高等植物维管系统中存在的共质途径的分析相结合。这个维管系统由木质部和韧皮部组成，木质部负责将水分和矿物质营养从植物的根部输送到地上部分，韧皮部负责将固定的碳(糖)和氮(氨基酸)输送到发育中的器官。韧皮部的传导组织由伴胞和筛分子两种类型的细胞组成。连接这些细胞类型的胞间连丝在这个长距离转运系统的运行中发挥着重要的作用。将进行实验，在基因水平上确定植物控制这一关键的共质途径的方式，从叶片的光合作用组织，一直到韧皮部传导组织。这些研究将为理解植物如何利用韧皮部远程运输系统在整个植物水平上协调过程提供一个框架。