A PtdIns(4)P-driven electrostatic field controls cell membrane identity and signalling in plants

Abstract

Many signaling proteins permanently or transiently localize to specific organelles for function. It is well established that certain lipids act as biochemical landmarks to specify compartment identity. However, they also influence membrane biophysical properties, which emerge as important features in specifying cellular territories. Such parameters include the membrane inner surface potential, which varies according to the lipid composition of each organelle. Here, we found that the plant plasma membrane (PM) and the cell plate of dividing cells have a unique electrostatic signature controlled by phosphatidylinositol-4-phosphate (PI4P). Our results further reveal that, contrarily to other eukaryotes, PI4P massively accumulates at the PM, establishing it as a critical hallmark of this membrane in plants. Membrane surface charges control the PM localization and function of the polar auxin transport regulator PINOID, as well as proteins from the BRI1 KINASE INHIBITOR1 (BKI1)/MEMBRANE ASSOCIATED KINASE REGULATORs (MAKRs) family, which are involved in brassinosteroid and receptor-like kinase signaling. We anticipate that this PI4P-driven physical membrane property will control the localization and function of many proteins involved in development, reproduction, immunity and nutrition.

Phospholipid composition and a polybasic motif determine D6 PROTEIN KINASE polar association with the plasma membrane and tropic responses

“…Conversely, the PI4-KINASE inhibitor PAO caused a strong plasma membrane dissociation of YFP:D6PK (Fig. 2B,C) (Hammond et al, 2012;Simon et al, 2016). As expected, PAO treatment specifically led to the internalization of the PdtIns4P sensor (FAPP1) but, interestingly, also blocked FM4-64 uptake as well as the accumulation of PIN2:GFP in BFA compartments, suggesting that PAO treatment might block endocytosis (Fig.…”

“…In turn, genetic evidence indicates that PtdIns(3,5)P 2 might be produced at the tonoplast and late endosomes (Heilmann and Heilmann, 2015;Hirano et al, 2015;Novakova et al, 2014;Simon et al, 2014Simon et al, , 2016Vermeer et al, 2006Vermeer et al, , 2009. The cellular distribution of PtdIns5P in plants is unknown and neither PtdIns (3,4)P 2 nor PtdIns(3,4,5)P 3 have as yet been detected in plants (Heilmann, 2009;Munnik and Nielsen, 2011).…”

“…Black arrows, biosynthetic steps analysed in this study; grey arrows, biosynthetic steps that could not be selectively manipulated (Simon et al, 2016;Heilmann, 2009;Meijer and Munnik, 2003;Potocký et al, 2014 (Fig. S1).…”

“…S1). Interestingly, the PI3-KINASE inhibitors LY294002 and Wortmannin (WM) led to a significant depletion of YFP:D6PK from the plasma membrane (Baggiolini et al, 1987;Simon et al, 2016;Vlahos et al, 1994). Our WM and LY294002 treatments efficiently altered the localization of the PdtIns3P sensor (P18Y) but not of the PdtIns4P (FAPP1) nor PdtIns(4,5)P 2 (P24Y) sensors.…”

“…Analysis of PtdIns(4,5)P 2 biosensors and respective PIP5Ks (PtdIns4P 5-KINASES) revealed that PtdIns(4,5)P 2 and PIP5Ks are polarly localized in many cell types and required for PIN polarity control (Ischebeck et al, 2013;Tejos et al, 2014). More recently, PtdIns4P was identified as a major PI, conferring negative charges to the plant plasma membrane (Simon et al, 2016).…”