Integrated Studies on Cellular and Physiological Roles of Higher Plant Plasmodesmata

虽然人们早就知道，在植物中，胞间连丝（plasmodesmata， PD）在相邻细胞之间建立细胞质连续性，但直到最近才确定这些细胞器在细胞间信息大分子（蛋白质和RNA）的运输中发挥作用。这一作用的第一个直接证据来自对植物病毒感染的遗传、分子和细胞研究。在这些被感染的植物中，病毒编码的运动蛋白（MPs）通过PD在细胞间传递，并在此过程中介导感染性RNA/DNA的传播。鉴于这一发现，我们提出了一种假设，即植物同样利用PD大分子运输途径对发育和生理过程施加位置依赖的控制。这一假说的推论是，植物的功能是独特的超细胞生物，而不是多细胞生物。对这种超细胞模型的支持一直在积累；在这方面，一个开创性的发现是，许多植物转录因子现在已被证明以非细胞自主的方式，通过PD的运动发挥作用。目前正在出现的情况是，PD运输大分子的能力将真核核孔复合物进化的特性扩展到邻近细胞之间的连接，从而使植物能够发展出这种新的调节途径。在目前的工作中，实验旨在表征PD的分子组成和非细胞自主蛋白（NCAP）易位途径。对于这些研究，将采用一系列结合遗传、分子、细胞、生理和发育方法的实验技术。本资助期的主要目标是利用突变体筛选方法在拟南芥中确定NCAP转运/PD功能的潜在调节因子。这些研究将为植物非细胞自主转运途径的建立和调控提供必要的分子成分信息。这些信息对于植物综合生物学和发育领域的重要性可能是通过对整个植物信号传导背后的事件的更深入的理解而实现的。这些通过植物维管系统传递的远距离信号，目前被认为在植物对环境和生物胁迫的反应整合中起作用。所请求的资金将允许在这一综合植物生物学领域培训初级科学家。这些科学家对我们社会的重要性将是通过将知识应用于开发对植物过程的新控制，包括将资源分配给目标器官。这种应用很可能在农业和动物/人类营养/健康方面产生重大影响。

Although it has long been known that, in plants, plasmodesmata (PD) establish cytoplasmic continuity between neighboring cells, it has only recently been established that these intercellular organelles play a role in the cell-to-cell trafficking of information macromolecules (proteins and RNA). The first direct evidence for this role came from genetic, molecular and cellular studies of viral infection in plants. In these infected plants, viral encoded movement proteins (MPs) traffic cell to cell through PD and, in this process, they mediate the spread of infectious RNA/DNA. In view of this finding, the hypothesis was advanced that plants similarly utilize this PD macromolecular trafficking pathway to exert positional-dependent control over developmental and physiological processes. The corollary to this hypothesis was advanced that plants function as unique supracellular, rather than multicellular, organisms. Support for this supracellular model has been accumulating; in this regard, a seminal discovery was that a number of plant transcription factors have now been shown to function in a non-cell-autonomous manner, via movement through PD. The picture that is emerging is that this ability of PD to transport macromolecules extended the properties evolved by the eukaryotic nuclear pore complex to the junctions between neighboring cells, and thereby allowed plants to develop this novel regulatory pathway.In the present work, experiments are aimed at characterizing the molecular constituents of PD and the non-cell-autonomous protein (NCAP) translocation pathway. For these studies a range of experimental techniques will be employed that combine genetic, molecular, cellular, physiological and developmental approaches. The major goal over this funding period will be to identify potential regulators of NCAP trafficking/PD function using a mutant screening approach in Arabidopsis. These studies should provide much needed information on the molecular components that function in the establishment and regulation of the non-cell-autonomous translocation pathway of plants. The importance of this information to the areas of integrative plant biology and development will likely be through the development of a greater understanding of the events that underlie whole plant signaling. These long-distance signals, delivered via the plant vascular system, are presently thought to function in the integration of the plant's response to environmental and biotic stresses.The requested funds will permit the training of junior scientists in this area of integrative plant biology. The importance of these scientists to our society will be through the application of knowledge towards the development of novel controls over plant processes, including the allocation of resources to targeted organs. Such applications could well have major ramifications in terms of agriculture and animal/human nutrition/health.