Phosphatidylinositol 4‐phosphate: a key determinant of plasma membrane identity and function in plants

Abstract

Summary Phosphatidylinositol 4‐phosphate (PI4P) is an anionic phospholipid which has been described as a master regulator of the Golgi apparatus in eukaryotic cells. However, recent evidence suggests that PI4P mainly accumulates at the plasma membrane in all plant cells analyzed so far. In addition, many functions that are typically attributed to phosphatidylinositol 4,5‐bisphosphate (PI(4,5)P2) in animal and yeast cells are also supported by PI4P in plants. For example, PI4P is the key anionic lipid that powers the strong electrostatic properties of the plasma membrane. Phosphatidylinositol 4‐phosphate is also required for the establishment of stable membrane contacts between the endoplasmic reticulum and the plasma membrane, for exocytosis and to support signaling pathways. Thus, we propose that PI4P has a prominent role in specifying the identity of the plasma membrane and in supporting some of its key functions and should be considered a hallmark lipid of this compartment.

The Arabidopsis SAC9 enzyme is enriched in a cortical population of early endosomes and restricts PI(4,5)P2 at the plasma membrane

“…Here, we can speculate that SAC9 may not be the only 5-phosphatase enzyme that can control PI(4,5)P 2 homeostasis during endocytosis. In addition, while PI(4,5)P 2 is the main phosphoinositide regulating the recruitment of endocytic regulators in animals, it is likely not the case in plants ( Marković and Jaillais, 2022 ). Indeed, PI4P, not PI(4,5)P 2 , is the major anionic lipids that powers the plasma membrane electrostatic field ( Simon et al, 2016 ), and is very likely key to recruit endocytic proteins in plants ( Yperman et al, 2021b ; Yperman et al, 2021a ).…”

“…However, biochemical measurements also showed that the sac9 mutant accumulates less PI4P than its wild-type counterpart. Given the importance of PI4P for plant cell function ( Marković and Jaillais, 2022 ; Noack et al, 2022 ; Noack et al, 2020b ; Simon et al, 2016 ), it is possible that PI4P rather than (or in combination with) PI(4,5)P 2 defects are involved in the sac9 phenotypes. Given that phosphoinositide metabolism is highly intricate, we recognize that it is difficult to fully untangle the specific involvement of each lipid in the observed phenotypes.…”

Plasma membrane association and resistosome formation of plant helper immune receptors

“…In plants, PI4P is the main driver of PM electrostatics (36, 37). Phosphatidic acid (PA) and phosphatidylserine and PI(4,5)P 2 also contribute to PM (inner leaflet) surface charges, but to a lesser extent.…”

“…These data demonstrate that effector activation of a TNL induces AtNRG1.1 resistosome formation at the PM and that AtNRG1.1 DV faithfully mimics the functionality of effector activated AtNRG1.1. In plants, PI4P is the main driver of PM electrostatics (36,37). Phosphatidic acid (PA) and phosphatidylserine and PI(4,5)P2 also contribute to PM (inner leaflet) surface charges, but to a lesser extent.…”

The Arabidopsis SAC9 Enzyme is enriched in a cortical population of early endosomes and restricts PI(4,5)P2 at the Plasma Membrane

“…However, biochemical measurements also showed that the sac9 mutant accumulates less PI4P than its wild-type counterpart. Given the importance of PI4P for plant cell function (Marković & Jaillais 2022; Noack et al;, 2022; Noack et al 2020; Simon et al 2016), it is possible that PI4P rather than (or in combination with) PI(4,5)P 2 defects are involved in the sac9 phenotypes. Given that phosphoinositide metabolism is highly intricate, we recognize that it is difficult to fully untangle the specific involvement of each lipid in the observed phenotypes.…”