[原生質絲] 原生質絲形成的調控。20191125 Plant Physiology

Putting the Squeeze on Plasmodesmata: A Role for Reticulons in Primary Plasmodesmata Formation

Kirsten Knox, Pengwei Wang, Verena Kriechbaumer, Jens Tilsner, Lorenzo Frigerio, Imogen Sparkes, Chris Hawes, and Karl Oparka

Abstract

Primary plasmodesmata (PD) arise at cytokinesis when the new cell plate forms. During this process, fine strands of endoplasmic reticulum (ER) are laid down between enlarging Golgi-derived vesicles to form nascent PD, each pore containing a desmotubule, a membranous rod derived from the cortical ER. Little is known about the forces that model the ER during cell plate formation. Here, we show that members of the reticulon (RTNLB) family of ER-tubulating proteins in Arabidopsis (Arabidopsis thaliana) may play a role in the formation of the desmotubule. RTNLB3 and RTNLB6, two RTNLBs present in the PD proteome, are recruited to the cell plate at late telophase, when primary PD are formed, and remain associated with primary PD in the mature cell wall. Both RTNLBs showed significant colocalization at PD with the viral movement protein of Tobacco mosaic virus, while superresolution imaging (three-dimensional structured illumination microscopy) of primary PD revealed the central desmotubule to be labeled by RTNLB6. Fluorescence recovery after photobleaching studies showed that these RTNLBs are mobile at the edge of the developing cell plate, where new wall materials are being delivered, but significantly less mobile at its center, where PD are forming. A truncated RTNLB3, unable to constrict the ER, was not recruited to the cell plate at cytokinesis. We discuss the potential roles of RTNLBs in desmotubule formation.

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擠壓原生質絲：Reticulons在初級原生質絲形成時扮演的一個角色

摘要

初級原生質絲，是在胞質分裂（細胞分裂最後期）的細胞板形成過程中出現的。在這個過程中，細小的內質網會被放置在由高基氏體衍生出的微小囊泡間，當囊泡增大後會形成未成熟的原生質絲，每個孔洞中都會含有一個連絲微管，一個由皮質內質網衍生出的帶有膜的微管。對於在細胞板形成的過程中，內質網會受到哪些力的影響，我們知道得非常少。在此，我們展示了阿拉伯芥reticulon（幫助內質網形成微管的蛋白質RTNLB） 家族中的成員們可能在形成連孔微管得過程中演了一個腳色。RTNLB3以及RTNLB6兩個在原生質絲蛋白質體中存在的兩個蛋白，在細胞分裂的末期、初級原生質絲形成時，被招集到細胞板，並且在細胞壁成熟時，一直與初級原生質絲有關連。這兩個RTNLB與菸草鑲嵌病毒的移動蛋白都會座落在原生質絲。利用超高解析度影像系統（3D結構解析顯微鏡）來觀察初級原生質絲發現，中央的連孔微管會被RTNLB6蛋白標記。在光漂白後的螢光復原實驗中顯示，RTNLB蛋白在發育中的細胞板周圍，新的細胞版合成物質運送抵達的位置，移動性較高。而在原生質絲形成的中央位置，明顯的比較不移動。而一個截短的、無法壓縮內質網的RTNLB3，不會再胞質分裂時，被著急到細胞板處。我們討論了RTNLB蛋白質在連孔微管形成時的可能角色。

原文出處： http://www.plantphysiol.org/content/168/4/1563