Architecture and permeability of post-cytokinesis plasmodesmata lacking cytoplasmic sleeves

Nat Plants. 2017 Jun 12;3:17082. doi: 10.1038/nplants.2017.82.

Abstract

Plasmodesmata are remarkable cellular machines responsible for the controlled exchange of proteins, small RNAs and signalling molecules between cells. They are lined by the plasma membrane (PM), contain a strand of tubular endoplasmic reticulum (ER), and the space between these two membranes is thought to control plasmodesmata permeability. Here, we have reconstructed plasmodesmata three-dimensional (3D) ultrastructure with an unprecedented level of 3D information using electron tomography. We show that within plasmodesmata, ER-PM contact sites undergo substantial remodelling events during cell differentiation. Instead of being open pores, post-cytokinesis plasmodesmata present such intimate ER-PM contact along the entire length of the pores that no intermembrane gap is visible. Later on, during cell expansion, the plasmodesmata pore widens and the two membranes separate, leaving a cytosolic sleeve spanned by tethers whose presence correlates with the appearance of the intermembrane gap. Surprisingly, the post-cytokinesis plasmodesmata allow diffusion of macromolecules despite the apparent lack of an open cytoplasmic sleeve, forcing the reassessment of the mechanisms that control plant cell-cell communication.

MeSH terms

  • Actins / metabolism
  • Cell Communication
  • Cell Membrane / metabolism
  • Cell Membrane / ultrastructure
  • Cytokinesis*
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum / ultrastructure
  • Permeability
  • Plant Cells / metabolism
  • Plant Cells / ultrastructure
  • Plant Roots / cytology
  • Plant Roots / metabolism
  • Plant Roots / ultrastructure
  • Plasmodesmata / metabolism*
  • Plasmodesmata / ultrastructure

Substances

  • Actins