Feedback between PI4P signaling and ER-PM contact sites orchestrates polarized root hair growth
Abstract
Eukaryotic cells are composed of different organelles that communicate with one another through direct contacts, which are necessary for a host of cellular reactions and for responding to different developmental and environmental changes. Plasma membrane (PM) forms extensive contacts with the endoplasmic reticulum (ER) at specific sites named ER-PM contact sites. These contacts play crucial functions in lipid homeostasis, Ca 2+ regulation and signaling in all eukaryotes. However, the mechanisms by which plant ER-PM contact site proteins tether to the PM, as well as the dynamics of these contact sites, remain poorly understood. Here, we investigate the importance of phosphoinositides in the establishment and dynamics of ER-PM contact site proteins in plants. We found that phosphatidylinositol-4-phosphate (PI4P), rather than phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ), is required for the association of ER-PM contact site proteins with the PM. Furthermore, we identified a PI4P phosphatase, SUPPRESSOR-OF-ACTIN7 (SAC7), that associates with the ER-PM contact site protein SYNAPTOTAGMIN1 (SYT1) and regulates its dynamic association with the PM. In particular, we found that in growing root hairs, a highly polarized cell type, SAC7 removes SYT1-containing contact sites at the growing tip. Consistently, optogenetic induction of ER–PM tethering reduced root hair elongation within minutes of blue light induction. Altogether, we propose a link between SAC7-mediated regulation of PI4P, dynamic ER-PM contact site establishment and polarized cell growth in plants.
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BibTeX
@misc{markovic2026feedback,
title = {{Feedback between PI4P signaling and ER-PM contact sites orchestrates polarized root hair growth}},
author = {Vedrana Marković and Vincent Bayle and Gwennogan Dubois and Frédérique Rozier and Vítor Amorim-Silva and Jorge Morello-López and Sacha Grenet and Selene García-Hernández and Miguel A Botella and Yvon Jaillais},
howpublished = {HAL},
year = {2026},
month = jun,
url = {https://hal.science/hal-05797861v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Feedback between PI4P signaling and ER-PM contact sites orchestrates polarized root hair growth
AU - Vedrana Marković
AU - Vincent Bayle
AU - Gwennogan Dubois
AU - Frédérique Rozier
AU - Vítor Amorim-Silva
AU - Jorge Morello-López
AU - Sacha Grenet
AU - Selene García-Hernández
AU - Miguel A Botella
AU - Yvon Jaillais
PY - 2026
DA - 2026/06/27
PB - HAL
UR - https://hal.science/hal-05797861v1
AB - Eukaryotic cells are composed of different organelles that communicate with one another through direct contacts, which are necessary for a host of cellular reactions and for responding to different developmental and environmental changes. Plasma membrane (PM) forms extensive contacts with the endoplasmic reticulum (ER) at specific sites named ER-PM contact sites. These contacts play crucial functions in lipid homeostasis, Ca 2+ regulation and signaling in all eukaryotes. However, the mechanisms by which plant ER-PM contact site proteins tether to the PM, as well as the dynamics of these contact sites, remain poorly understood. Here, we investigate the importance of phosphoinositides in the establishment and dynamics of ER-PM contact site proteins in plants. We found that phosphatidylinositol-4-phosphate (PI4P), rather than phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ), is required for the association of ER-PM contact site proteins with the PM. Furthermore, we identified a PI4P phosphatase, SUPPRESSOR-OF-ACTIN7 (SAC7), that associates with the ER-PM contact site protein SYNAPTOTAGMIN1 (SYT1) and regulates its dynamic association with the PM. In particular, we found that in growing root hairs, a highly polarized cell type, SAC7 removes SYT1-containing contact sites at the growing tip. Consistently, optogenetic induction of ER–PM tethering reduced root hair elongation within minutes of blue light induction. Altogether, we propose a link between SAC7-mediated regulation of PI4P, dynamic ER-PM contact site establishment and polarized cell growth in plants.
ER -