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(PD)建立了相邻细胞之间的胞质连续性，但直到最近才证实，这些胞间细胞器在信息大分子(蛋白质和RNA)的细胞间运输中发挥作用。这一作用的第一个直接证据来自对植物中病毒感染的遗传、分子和细胞研究。在这些受感染的植物中，病毒编码的运动蛋白(MPS)通过PD从一个细胞运输到另一个细胞，在这个过程中，它们介导了传染性RNA/DNA的传播。鉴于这一发现，提出了一种假设，即植物类似地利用这种PD大分子运输途径来对发育和生理过程施加位置依赖的控制。这一假设的推论是，植物是独特的超细胞生物体，而不是多细胞生物体。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，一些植物转录因子现在被证明通过PD运动以非细胞自主的方式发挥作用。目前正在出现的情况是，PD运输大分子的能力将真核细胞核孔复合体所进化的特性扩展到相邻细胞之间的连接，从而使植物能够开发这一新的调控途径。在本工作中，实验旨在表征PD的分子组成和非细胞自主蛋白(NCAP)的易位途径。对于这些研究，将采用一系列实验技术，结合遗传、分子、细胞、生理和发育方法。在这一资助期内的主要目标将是利用拟南芥中的突变筛选方法来确定NCAP贩运/PD功能的潜在调节者。这些研究应该提供关于在植物非细胞自主易位途径的建立和调控中起作用的分子成分的迫切需要的信息。这些信息对综合植物生物学和发育领域的重要性可能是通过更好地了解整个植物信号转导所依据的事件而实现的。这些通过植物维管系统传递的远程信号目前被认为在植物对环境和生物胁迫的反应中起着整合作用。申请的资金将允许培训这一综合植物生物学领域的初级科学家。这些科学家对我们社会的重要性将是通过应用知识来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.