MEMBRANE CONTACTS CONTROLLING PLANT INTERCELLULAR COMMUNICATION – STAYING-TIGHT

Cell biology, electron tomography, molecular dynamics

Major achievement into the project has been the identification of the molecular elements controlling ER-PM contact specifically at PD and their impact of cell-to-cell trafficking and plant development. In the last 18 months, we identified and demonstrated that MCTPs (Multiple C2 domains Transmembrane region Proteins) act as tethering elements within PD, by inserting in the ER through their transmembrane region and docking to the PM by electrostatic interaction with anionic lipids and more specifically PI4P. Mctp3.4 loss-of-mutant in Arabidopsis shows defective cell-to-cell trafficking and severe growth/patterning phenotype at the root and shoot levels

Future work will focus on understanding the molecular mechanisms of MCTP action and function of ER for cell to cell communication

1. Noack LC, Jaillais Y. Functions of Anionic Lipids in Plants. Annu Rev Plant Biol. 2020;71:71-102. doi:10.1146/annurev-arplant-081519-035910
2. Jaillais Y, Ott T. The Nanoscale Organization of the Plasma Membrane and Its Importance in Signaling: A Proteolipid Perspective. Plant Physiol. 2020;182(4):1682-1696. doi:10.1104/pp.19.01349
3. Colin LA, Jaillais Y. Phospholipids across scales: lipid patterns and plant development. Curr Opin Plant Biol. 2020;53:1-9. doi:10.1016/j.pbi.2019.08.007
4.• Brault ML+, Petit JD+, Immel F, Nicolas WJ, Glavier M, Brocard L, Gaston A, Fouché M, Hawkins TJ, Crowet J, Grison SM, Germain V, Rocher M, Kraner M, Alva V, Claverol S, Paterlini A, Helariutta Y, Deleu M, Lins L, Tilsner J*, Bayer EM* (2019) Multiple C2 domains and transmembrane region proteins (MCTP) tether membranes at plasmodesmata. EMBO Rep. e47182, p1–26

Plant life depends on cell-to-cell connectivity through plasmodesmata (PD) channels. PD are indispensable for plant development,
environmental adaptation and defence signalling. A striking feature of PD organisation, setting them apart from animal cell junctions,
is a strand of endoplasmic reticulum (ER) running through the pore, tethered extremely tight (~10nm) to the plasma membrane (PM)
by unidentified “spokes”. This classifies PD as a specialised type of membrane contact site (MCS), whose function remains a mystery.
Combining interdisciplinary approaches in membrane biophysics, molecular cell biology and electron tomography, we propose a
pioneer research program, which will for the first time address the mechanisms and function of ER-PM tethering at PD. We aim to
1)Identify/characterise PD membrane-tethering elements at atomic level 2)defines the role of anionic lipids in PD MCS regulation
3)Uncover the function of ER-PM apposition for plant intercellular communication