Abstract Plasmodesmata (PD) are intercellular channels in plant tissues providing continuity of the cytoplasm, the plasma membrane (PM) and the endoplasmic reticulum (ER) of neighboring cells. These channels allow the active transport of macromolecules such as proteins or RNAs. Thus, PD are believed to play a critical role in the functional unity of plant tissues and the transport of signals required for plant development and responses to external stimuli. Recent findings indicate that the PD channel contains a specialized type of ER-PM membrane contact sites (MCSs), structural links formed between ER and PM with tethering proteins. As shown for animal cells, MCSs are essential for lipid and protein trafficking between ER and PM membranes as well as for stress responses or the maintenance of ER structural integrity. On the other hand, our knowledge of the PD-specific MCSs is still scarce, and experimentally supported models of organization of their structural elements are only starting to emerge. Here, we review the structural and functional properties of proteins that can take part in establishing MCSs in PD. We also discuss the significance of cytoskeleton, lipid membrane microdomains and cell wall components for the maintenance and remodeling of PD-specific MCS in response to various biotic and abiotic stresses.

中文翻译：

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Plasmodesmata 中的膜接触：结构组件及其功能

摘要 Plasmodesmata (PD) 是植物组织中的细胞间通道，为相邻细胞的细胞质、质膜 (PM) 和内质网 (ER) 提供连续性。这些通道允许大分子如蛋白质或 RNA 的主动运输。因此，PD 被认为在植物组织的功能统一和植物发育所需的信号传输和对外部刺激的反应中起关键作用。最近的研究结果表明，PD 通道包含一种特殊类型的 ER-PM 膜接触位点 (MCS)，即 ER 和 PM 之间通过束缚蛋白形成的结构联系。正如动物细胞所示，MCS 对于 ER 和 PM 膜之间的脂质和蛋白质运输以及应激反应或维持 ER 结构完整性至关重要。另一方面，我们对 PD 特定 MCS 的知识仍然很少，并且实验支持的结构元素组织模型才刚刚开始出现。在这里，我们回顾了可以参与在 PD 中建立 MCS 的蛋白质的结构和功能特性。我们还讨论了细胞骨架、脂质膜微区和细胞壁成分对于维持和重塑 PD 特异性 MCS 以响应各种生物和非生物胁迫的重要性。