Molecular Investigation into the Role Played by Tobacco and Arabidopsis NCAPP1 Genes in Plasmodesmal Function

在进化过程中，生物系统发展了越来越复杂的控制系统，以调节细胞、发育和生理程序背后的复杂过程。复杂的动植物组织和器官的功能需要一个信号通路网络的发展。当今的信令系统可以分为两类。第一个涉及信号分子，这些分子在表达它们的细胞内起作用；也就是说，这些分子被认为是细胞自主行为。第二类涉及超出其产生部位的信号；即，这些信号分子以非细胞自主的方式发挥作用，可能涉及激素、化合物、蛋白质和RNA分子。这样的信号可以通过分泌转移到邻近的细胞，然后通过细胞外空间扩散；这一途径对所有生物来说都是常见的。或者，在植物界，这些信号可以通过被称为胞间连丝的特殊结构在细胞之间传递。胞间连丝的结构创造了细胞质通道，这些信号可以在不离开细胞的情况下通过这些通道移动。这里，重要的是要注意到胞间连丝的结构允许蛋白质和RNA分子的运动。生物体周围的信号通过植物维管系统传递。这里，胞间连丝的特殊性质又促进了蛋白质和RNA的运动。这些信号通路和信号分子的重要性在已发表的研究中得到了很好的支持；然而，很少有研究提供关于这些重要成分的性质的明确信息。此外，人们对非细胞自主信号传输的调控方式知之甚少。现在，通过开发用于鉴定胞间连丝蛋白的生化方法来调控非细胞自主功能信号分子的细胞间传输，这些开放问题的解决方案是可能的。使用这种方法鉴定的第一个基因是非细胞自主途径蛋白-1(NCAPP-1)。本提案描述了旨在进一步确定NCAPP-1基因家族特征的实验。这项工作将涉及三个目标：(A)确定NCAPP-1基因家族在细胞间信号通路中所起的作用；(B)分离和鉴定与NCAPP1相互作用的蛋白质；以及(C)使用非活性形式的NCAPP-1来测试蛋白质通过胞间连丝的运输是否在整个植物水平的生理和发育过程的整合中发挥作用。这些研究应该为这些蛋白质影响蛋白质向邻近细胞输送的方式提供重要的见解。这一知识将使科学家能够更全面地了解在细胞、组织和全植物水平上运行的信号网络。这种进展将直接影响到综合和发育植物生物学领域，为未来对全植物信号转导的研究建立一个实验基础。最后，这些研究应该为植物界从单细胞进化到复杂的超细胞生物体所采取的路径提供新的视角。更广泛的影响：该研究项目将用于培训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是双重的。首先，他们将担任训练有素的教师，能够在生物科学和生物技术领域教育社会。其次，同样重要的是，这些科学家可以将这些知识应用于开发对植物过程的新控制，包括各种植物器官之间营养物质的分享方式。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。

During the process of evolution, biological systems developed ever-increasingly sophisticated control systems to regulate the complex processes underlying cellular, developmental and physiological programs. The functioning of complex animal and plant tissues and organs required the development of a network of signaling pathways. Present day signaling systems can be divided into two categories. The first involves signaling molecules that act within the cell in which they are expressed; i.e., these molecules are said to be cell-autonomous in behavior. The second group involves signals that act beyond their sites of production; i.e., these signaling molecules act in a non-cell-autonomous manner and can involve hormones, chemical compounds, proteins and RNA molecules. Such signals can move to neighboring cells by secretion, followed by diffusion through the extra-cellular space; this pathway is common to all organisms. Alternatively, in the plant kingdom, these signals can move between cells through specialized structures termed plasmodesmata. The architecture of the plasmodesmata creates cytoplasmic channels through which these signals can move without exiting the cell. Here, it is important to note that the structure of plasmodesmata allows for the movement of proteins and RNA molecules. Signaling around the body of the organism occurs by passage through the plant vascular system. Here again, the movement of proteins and RNA is facilitated by the special properties of the plasmodesmata. The importance of these signaling pathways and signaling molecules is well-supported by published works; however, few studies have provided explicit information on the nature of the essential components. In addition, little is known about the manner in which trafficking of non-cell-autonomous signals is regulated.Solutions to these open questions are now possible through work that developed biochemical methods for the identification of plasmodesmata proteins that regulate the cell-to-cell trafficking of non-cell-autonomously functioning signaling molecules. The first gene identified using this approach was NON-CELL-AUTONOMOUS PATHWAY PROTEIN-1 (NCAPP-1). The present proposal describes experiments aimed at further characterizing the NCAPP-1 gene family. This work will involve three objectives: (a) establishing the role played by the NCAPP-1 gene family in the cell-to-cell signaling pathway; (b) isolating and characterizing proteins that interact with NCAPP1; and (c) employing an inactive form of NCAPP-1 to test whether transport of proteins through plasmodesmata plays a role in the integration of physiological and developmental processes at the whole-plant level. These studies should provide important insights into the way these proteins can influence protein delivery to neighboring cells. This knowledge would allow scientists to more fully understand the signaling networks operating at the cellular, tissue and whole-plant levels. Such progress would have direct bearing on the areas of integrative and developmental plant biology, by establishing an experimental basis for future studies on whole-plant signaling. Finally, these studies should provide new perspectives on the path taken by the plant kingdom during its evolution from single cells to complex, supracellular, organisms. Broader Impacts: This research project would be used to train junior scientists within the area of integrative plant biology. The importance of these scientists to our society would be two-fold. First they would serve as trained teachers who can educate society in the areas of the biological sciences and biotechnology. Secondly, and of equal importance, these scientists could apply this knowledge to the development of new controls over plant processes, including the way nutrients are shared between the various plant organs. Such applications could well have major ramifications in terms of agriculture and animal/human nutrition/health.