Schattat Martin H, Barton Kiah A, Mathur Jaideep
Martin-Luther-Universität Halle-Wittenberg Pflanzenphysiologie, Weinbergweg 10, 06120, Halle (Saale), Germany,
Protoplasma. 2015 Jan;252(1):359-71. doi: 10.1007/s00709-014-0666-4. Epub 2014 Jun 26.
Studies spread over nearly two and a half centuries have identified the primary plastid in autotrophic algae and plants as a pleomorphic, multifunctional organelle comprising of a double-membrane envelope enclosing an organization of internal membranes submerged in a watery stroma. All plastid units have been observed extending and retracting thin stroma-filled tubules named stromules sporadically. Observations on living plant cells often convey the impression that stromules connect two or more independent plastids with each other. When photo-bleaching techniques were used to suggest that macromolecules such as the green fluorescent protein could flow between already interconnected plastids, for many people this impression changed to conviction. However, it was noticed only recently that the concept of protein flow between plastids rests solely on the words "interconnected plastids" for which details have never been provided. We have critically reviewed botanical literature dating back to the 1880s for understanding this term and the phenomena that have become associated with it. We find that while meticulously detailed ontogenic studies spanning nearly 150 years have established the plastid as a singular unit organelle, there is no experimental support for the idea that interconnected plastids exist under normal conditions of growth and development. In this review, while we consider several possibilities that might allow a single elongated plastid to be misinterpreted as two or more interconnected plastids, our final conclusion is that the concept of direct protein flow between plastids is based on an unfounded assumption.
历经近两个半世纪的研究已确定，自养藻类和植物中的初级质体是一种多形态、多功能的细胞器，它由双层膜包膜构成，包膜内包裹着浸没在水性基质中的内膜结构。所有质体单位都偶尔会观察到伸出和缩回名为基质小管的充满基质的细管。对活植物细胞的观察常常给人这样的印象，即基质小管将两个或更多独立的质体相互连接起来。当使用光漂白技术表明诸如绿色荧光蛋白等大分子可以在已经相互连接的质体之间流动时，对许多人来说，这种印象就变成了确信。然而，直到最近才注意到，质体间蛋白质流动的概念仅仅基于“相互连接的质体”这一表述，而从未有人提供过相关细节。为了理解这个术语及其相关现象，我们严格审查了可追溯到19世纪80年代的植物学文献。我们发现，虽然近150年来细致入微的个体发育研究已将质体确立为单一的单位细胞器，但在正常生长和发育条件下存在相互连接的质体这一观点并无实验依据。在本综述中，虽然我们考虑了几种可能导致单个伸长的质体被误解为两个或更多相互连接的质体的情况，但我们的最终结论是，质体间直接蛋白质流动的概念是基于一个毫无根据的假设。
