title: Multiscale Structural Analysis of Plant ER-PM Contact Sites.
abstract: Membrane contact sites are recognized across eukaryotic systems as important nanostructures. Endoplasmic reticulum (ER)-plasma membrane (PM) contact sites (EPCS) are involved in excitation-contraction coupling, signaling, and plant responses to stress. In this report, we perform a multiscale structural analysis of Arabidopsis EPCS that combines live cell imaging, quantitative transmission electron microscopy (TEM) and electron tomography over a developmental gradient. To place EPCS in the context of the entire cortical ER, we examined green fluorescent protein (GFP)-HDEL in living cells over a developmental gradient, then Synaptotagmin1 (SYT1)-GFP was used as a specific marker of EPCS. In all tissues examined, young, rapidly elongating cells showed lamellar cortical ER and higher density of SYT1-GFP puncta, while in mature cells the cortical ER network was tubular, highly dynamic and had fewer SYT1-labeled puncta. The higher density of EPCS in young cells was verified by quantitative TEM of cryo-fixed tissues. For all cell types, the size of each EPCS had a consistent range in length along the PM from 50 to 300 nm, with microtubules and ribosomes excluded from the EPCS. The structural characterization of EPCS in different plant tissues, and the correlation of EPCS densities over developmental gradients illustrate how ER-PM communication evolves in response to cellular expansion.
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.|School of Biosciences, University of Melbourne, Australia.
authors.forename: Heather E
authors.initials: HE
authors.lastname: McFarlane
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.
authors.forename: Eun Kyoung
authors.initials: EK
authors.lastname: Lee
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.|Laboratory of Cell Biology, Wageningen University, PB Wageningen, The Netherlands.|Cryo-Electron Microscopy, Bijvoet Center for Biomolecular Research, Faculty of Science, Utrecht University, CH Utrecht, The Netherlands.
authors.forename: Laura S
authors.initials: LS
authors.lastname: van Bezouwen
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.
authors.forename: Bradford
authors.initials: B
authors.lastname: Ross
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.
authors.forename: Abel
authors.initials: A
authors.lastname: Rosado
authors.affiliation: Department of Botany, University of British Columbia, University Blvd., Vancouver, Canada.
authors.forename: A Lacey
authors.initials: AL
authors.lastname: Samuels
mesh_terms: D017360:Arabidopsis / Q000378:metabolism / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure*; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure*; D049452:Green Fluorescent Proteins / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D012270:Ribosomes / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D049452:Green Fluorescent Proteins
keywords: Arabidopsis; EPCS; Endoplasmic reticulum; Membrane contact site; Plant cell expansion; Plasma membrane