Synaptotagmin-Associated Endoplasmic Reticulum-Plasma Membrane Contact Sites Are Localized to Immobile ER Tubules
The plant endoplasmic reticulum (ER), which is morphologically divided into tubules and sheets, seems to flow continuously as a whole, but locally, mobile and immobile regions exist. In eukaryotes, the ER physically and functionally interacts with the plasma membrane (PM) at domains called ER-PM con...
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Published in | Plant physiology (Bethesda) Vol. 178; no. 2; pp. 641 - 653 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society of Plant Biologists
01.10.2018
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Subjects | |
Online Access | Get full text |
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Summary: | The plant endoplasmic reticulum (ER), which is morphologically divided into tubules and sheets, seems to flow continuously as a whole, but locally, mobile and immobile regions exist. In eukaryotes, the ER physically and functionally interacts with the plasma membrane (PM) at domains called ER-PM contact sites (EPCSs). Extended synaptotagmin family proteins are concentrated in the cortical ER to form one type of EPCS; however, it is unclear whether the localization of extended synaptotagmin corresponds to the EPCS and where in the cortical ER the EPCSs are formed. Here, we analyzed the spatiotemporal localization of SYNAPTOTAGMIN1 (SYT1), a synaptotagmin in Arabidopsis (Arabidopsis thaliana), to investigate the precise distribution of SYT1-associated EPCSs in the cortical ER. Three-dimensional imaging using superresolution confocal live imaging microscopy demonstrated that SYT1 was specifically localized to the ER-PM boundary. Time-lapse imaging revealed that SYT1 was distributed to immobile ER tubules, but not to mobile tubules. Moreover, SYT1 was frequently localized to the edges of ER sheets that were transformed into immobile ER tubules over time. A lower intracellular calcium ion concentration resulted in an increased EPCS area and disrupted the ER network. Finally, SYT1 deficiency caused a reduction of the immobile tubules and enlargement of the ER meshes. Taken together, our findings show that SYT1-associated EPCS are distributed to immobile tubules and play an important role in the formation of the tubular ER network. This provides important insight into the relationship between the function and dynamics/morphology of the cortical ER. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 www.plantphysiol.org/cgi/doi/10.1104/pp.18.00498 Senior authors. Current address: Department of Environmental and Life Sciences, School of Food and Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Tomoo Shimada (tshimada@gr.bot.kyoto-u.ac.jp). K.I. conceived the research plans and performed most of the experiments including data analysis; K.T. and T.S. supervised the experiments; H.U. generated a transgenic line; H.U., Y.I., A.N., and I.H.-N. provided technical assistance; K.I. wrote the article; all authors other than K.I. supervised and complemented the writing. |
ISSN: | 0032-0889 1532-2548 |
DOI: | 10.1104/pp.18.00498 |