Mezitt L A, Lucas W J
Section of Plant Biology, University of California, Davis 95616, USA.
Plant Mol Biol. 1996 Oct;32(1-2):251-73. doi: 10.1007/BF00039385.
The complexity associated with post-translational processing, in terms of protein sorting and delivery is now well understood. Although such studies have been focused almost exclusively on the fate of proteins within the cell in which they are synthesized, recent studies indicate that it is time to broaden this focus to incorporate the concept of intercellular targeting of proteins. Direct evidence is now available that viral and endogenous proteins can be synthesized in a particular cell and subsequently transported into neighboring (or more distant) cells. Plasmodesmata, plasma membrane-lined cytoplasmic pores, are thought to establish the intercellular pathway responsible for this cell-to-cell trafficking of macromolecules (proteins and nucleic acids). These recent findings establish a new paradigm for understanding the manner in which higher plants exert control over developmental processes. We discuss the concept that programming of plant development involves supracellular control achieved by plasmodesmal trafficking of informational molecules, herein defined as supracellular control proteins (SCPs). This novel concept may explain why, in plants, cell fate is determined by position rather than cell lineage. Finally, the circulation of long-distance SCPs, within the phloem, may provide the mechanism by which the plant signals to the shoot apical meristem that it is time to switch to the reproductive phase of its development.
就蛋白质分选和运输而言，与翻译后加工相关的复杂性现已得到充分理解。尽管此类研究几乎完全集中在蛋白质在其合成细胞内的命运，但最近的研究表明，现在是时候拓宽这一关注点，纳入蛋白质细胞间靶向的概念了。现在有直接证据表明，病毒蛋白和内源性蛋白可以在特定细胞中合成，随后运输到相邻（或更远）的细胞中。胞间连丝是由质膜衬里的细胞质通道，被认为是建立负责大分子（蛋白质和核酸）这种细胞间运输的细胞间途径。这些最新发现为理解高等植物控制发育过程的方式建立了一个新的范例。我们讨论了这样一个概念，即植物发育的编程涉及通过信息分子的胞间连丝运输实现的超细胞控制，在此定义为超细胞控制蛋白（SCPs）。这个新颖的概念可能解释了为什么在植物中，细胞命运是由位置而不是细胞谱系决定的。最后，可以在韧皮部内长距离循环的SCPs，可能提供了一种机制，通过该机制植物向茎尖分生组织发出信号，表明是时候进入其发育的生殖阶段了。
