Diffusion and clustering of individual ROP6 molecules in a living Arabidposis root cells

Science. 2019 Apr 5;364(6435):57-62.
Developmental control of plant Rho GTPase nano-organization by the lipid phosphatidylserine
Platre MP 1, Bayle V 1, Armengot L 1, Bareille J 1, Marquès-Bueno MDM 1, Creff A 1, Maneta-Peyret L 2, Fiche JB 3, Nollmann M 3, Miège C 1, Moreau P 2,4, Martinière A 5, Jaillais Y 6.
1 Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342 Lyon, France.
2 UMR 5200 Membrane Biogenesis Laboratory, CNRS-University of Bordeaux, INRA Bordeaux Aquitaine, 33140 Villenave d’Ornon, France.
3 Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Univ Montpellier, 34090 Montpellier, France.
4 Bordeaux Imaging Center, UMS 3420 CNRS, US4 INSERM, University of Bordeaux, 33000 Bordeaux, France.
5 BPMP, CNRS, INRA, Montpellier SupAgro, Univ Montpellier, Montpellier, France.
6 Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342 Lyon, France. yvon.jaillais@ens-lyon.fr.

Rho guanosine triphosphatases (GTPases) are master regulators of cell signaling, but how they are regulated depending on the cellular context is unclear. We found that the phospholipid phosphatidylserine acts as a developmentally controlled lipid rheostat that tunes Rho GTPase signaling in Arabidopsis Live superresolution single-molecule imaging revealed that the protein Rho of Plants 6 (ROP6) is stabilized by phosphatidylserine into plasma membrane nanodomains, which are required for auxin signaling. Our experiments also revealed that the plasma membrane phosphatidylserine content varies during plant root development and that the level of phosphatidylserine modulates the quantity of ROP6 nanoclusters induced by auxin and hence downstream signaling, including regulation of endocytosis and gravitropism. Our work shows that variations in phosphatidylserine levels are a physiological process that may be leveraged to regulate small GTPase signaling during development.