Biology subjects

Bayle, V.

Publications and source records attributed to Bayle, V..

13 recordsLinked to original sources

bioRxiv2026

Feedback between PI4P signaling and ER-PM contact sites orchestrates polarized root hair growth

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, Ca2+ 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)P2), 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.

Plant Biology↗

bioRxiv2025

An embryo-derived peptide signal directs endosperm polarity in Arabidopsis

Angiosperm seed formation requires the coordinated development of the products of double fertilization, the embryo and the endosperm. The endosperm mediates efficient nutrient transfer from surrounding maternal tissues to the developing embryo. This function requires a polarized tissue organization, which manifests as early polar gene expression and polar cellularization dynamics. We show that the receptor kinase HAIKU2 acts in coordination with the transcription factor WRKY10/MINISEED3 to ensure robust endosperm polarity establishment through the activity of the homeodomain transcription factors WUSCHEL-RELATED HOMEOBOX 8 and 9. This process depends on egg cell fertilization and is mediated through the peptide PATHOGEN-INDUCED PEPTIDE-LIKE 7, which acts as a HAIKU2 ligand. Our results reveal how a molecular paracrine dialogue between the embryo and endosperm ensures optimal seed developmental coordination.

plant biology↗

bioRxiv2025

Sphingolipid-driven interleaflet coupling orchestrates Rho-GTPase recruitment to nanodomains for signal activation in plants

Biological membranes are both laterally heterogeneous and asymmetrical across leaflets, yet how this asymmetry contributes to signal transduction remains unclear. Here we show that sphingolipid-driven interleaflet coupling coordinates nanodomain organization and Rho-GTPase activation in plants. Using molecular dynamics simulations, super-resolution and single-molecule imaging, quantitative genetics, and biochemistry, we find that very long acyl chain (VLCFA)-containing sphingolipids in the outer leaflet interdigitate with phosphatidylserine (PS) in the inner leaflet, forming a vertical molecular bridge that organizes PS into nanodomains. This coupling promotes recruitment and activation of the Rho-GTPase ROP6 in response to auxin, whereas disruption of VLCFA synthesis or sphingolipid composition disperses PS and ROP6 nanodomains, impairing cytoskeletal reorganization and directional growth. Our findings reveal interleaflet coupling as a fundamental organizing principle linking membrane asymmetry to signaling, providing a conceptual framework for spatial and temporal control of signal transduction across eukaryotic membranes.

plant biology↗

bioRxiv2025

Actin Counters Geometry to Guide Plant Cell Division

In multicellular organisms, cell division shapes tissue architecture, cell identity, and function. In walled organisms like plants, division plane orientation irreversibly defines tissue topology and is tightly regulated. While divisions often follow the shortest path enclosing cell volume, certain cells deviate, dividing perpendicular to the growth axis. Tissue-scale mechanical stress has been proposed to guide such orientation, but how these cues are integrated remains unclear. Here, we re-examine the role of the actin cytoskeleton in orienting cell division in Arabidopsis root epidermis. Combining cell biology, genetics, pharmacological treatments, 3D segmentation, and modelling, we show that actin is a central molecular actor required to establish cell division orientation against the geometrical rules, highlighting its role in integrating spatial information.

plant biology↗

bioRxiv2023

Invasion of the stigma by the pollen tube or an oomycete pathogen: striking similarities and differences

The epidermis is the first barrier that protects organisms from surrounding stresses. Similar to the hyphae of filamentous pathogens that penetrate and invade the outer tissues of the host, the pollen germinates and grows a tube within epidermal cells of the stigma. Early responses of the epidermal layer are therefore decisive for the outcome of these two-cell interaction processes. Here, we aim at characterizing and comparing how the papillae of the stigma respond to intrusion attempts, either by hypha of the hemibiotrophic oomycete root pathogen, Phytophthora parasitica or by the pollen tube. We found that P. parasitica spores attach to the papillae and hyphae subsequently invade the entire pistil. Using transmission electron microscopy, we examined in detail the invasive growth characteristics of P. parasitica and found that the hypha passed through the stigmatic cell wall to grow in contact with the plasma membrane, contrary to the pollen tube that advanced engulfed within the two cell wall layers of the papilla. Further quantitative image analysis revealed that the pathogen and the pollen tube trigger reorganization of the endomembrane system (trans Golgi network, late endosome) and the actin cytoskeleton. Some of these remodeling processes are common to both invaders, while others appear to be more specific showing that the stigmatic cells trigger an appropriate response to the invading structure and somehow can recognize the invader that attempts to penetrate.

plant biology↗

bioRxiv2022

Driving forces behind remorin nanodomain formation in anionic lipid membranes

Remorins are a family of multigenic phosphoproteins of the plasma membrane, involved in biotic and abiotic plant interaction mechanisms, partnering in molecular signaling cascades. Signaling activity of remorins depends on their phosphorylation states and subsequent clustering into nano-sized membrane domains. The presence of a coiled-coil domain and a C-terminal domain is crucial to anchor remorins to negatively charged membrane domains, however the exact role of the N-terminal intrinsically disordered domain (IDD) on protein clustering and lipid interactions is largely unknown. Here we combine chemical biology and imaging approaches to study the partitioning of group 1 remorin into anionic model membranes mimicking the inner leaflet of the plant plasma membrane. Using reconstituted membranes containing a mix of saturated and unsaturated PhosphatidylCholine (PC), PhosphatidylInositol Phosphates (PIPs), and sterol, we investigate the clustering of remorins to the membrane and monitor the formation of nano-sized membrane domains. REM1.3 promoted membrane nanodomain organization on the exposed external leaflet of both spherical lipid vesicles and flat supported lipid bilayers. Our results reveal that REM1.3 drives a mechanism allowing lipid reorganization, leading to the formation of remorin-enriched nanodomains. Phosphorylation of the N-terminal IDD by the calcium protein kinase CPK3 influences this clustering and can lead to the formation of smaller and more disperse domains. Our work reveals the phosphate-dependent involvement of the N-terminal IDD in the remorin-membrane interaction process by driving structural rearrangements at lipid-water interfaces. Summary headingUsing reconstituted membranes, we demonstrated the clustering of the plant protein remorins StREM1.3 to the lipid bilayer external leaflet and monitor the formation of nanodomains of the protein.

plant biology↗

bioRxiv2021

The Arabidopsis SAC9 Enzyme defines a cortical population of early endosomes and restricts PI(4,5)P2 to the Plasma Membrane

Membrane lipids, and especially phosphoinositides, are differentially enriched within the eukaryotic endomembrane system. This generates a landmark code by modulating the properties of each membrane. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] specifically accumulates at the plasma membrane in yeast, animal and plant cells, where it regulates a wide range of cellular processes including endocytic trafficking. However, the functional consequences of mispatterning PI(4,5)P2 in plants are unknown. Here, we functionally characterized the putative phosphoinositide phosphatase SUPPRESSOR OF ACTIN9 (SAC9) in Arabidopsis thaliana (Arabidopsis). We found that SAC9 depletion led to the ectopic localization of PI(4,5)P2 on cortical intracellular compartments, which depends on PI4P and PI(4,5)P2 production at the plasma membrane. SAC9 localizes to a subpopulation of trans-Golgi Network/early endosomes that are enriched in a region close to the cell cortex and that are coated with clathrin. Furthermore, it interacts and colocalizes with Src Homology 3 Domain Protein 2 (SH3P2), a protein involved in endocytic trafficking. In the absence of SAC9, SH3P2 localization is altered and the clathrin-mediated endocytosis rate is reduced. Together, our results highlight the importance of restricting PI(4,5)P2 at the plasma membrane and illustrate that one of the consequence of PI(4,5)P2 misspatterning in plants is to impact the endocytic trafficking. One-sentence summarySAC9 prevents the accumulation of PI(4,5)P2 in intracellular compartments, thereby contributing to clathrin-mediated endocytosis at the plasma membrane and regulating the cortical localization of its protein partner SH3P2.

plant biology↗

bioRxiv2021

Endosperm turgor pressure both promotes and restricts seed growth and size

Organ size depends on complex biochemical and mechanical interactions between cells and tissues. Here, we investigate the control of seed size, a key agronomic trait, by mechanical interactions between two compartments: the endosperm and the testa. By combining experiments with computational modelling, we tested an incoherent mechanical feedforward loop hypothesis in which pressure-induced stresses play two antagonistic roles; directly driving seed growth, but indirectly inhibiting it through mechanosensitive stiffening of the seed coat. We show that our model can recapitulate wild type growth patterns and explain the small seed phenotype of the haiku2 mutant. Our work further reveals that the developmental regulation of endosperm pressure is needed to prevent a precocious reduction of seed growth rate induced by force-dependent seed coat stiffening.

plant biology↗

bioRxiv2020

A nanodomain anchored-scaffolding complex is required for PI4K? function and localization in plants

Phosphoinositides are low-abundant lipids that participate in the acquisition of membrane identity through their spatiotemporal enrichment in specific compartments. PI4P accumulates at the plant plasma membrane driving its high electrostatic potential, and thereby facilitating interactions with polybasic regions of proteins. PI4K1 has been suggested to produce PI4P at the plasma membrane, but how it is recruited to this compartment is unknown. Here, we pin-point the mechanism that tethers PI4K1 to the plasma membrane via a nanodomain-anchored scaffolding complex. We identified that PI4K1 is part of a complex composed of proteins from the NO-POLLEN-GERMINATION, EFR3-OF-PLANTS, and HYCCIN-CONTAINING families. Comprehensive knock-out and knock-down strategies revealed that subunits of the PI4K1 complex are essential for pollen, embryonic and post-embryonic development. We further found that the PI4K1 complex is immobilized in plasma membrane nanodomains. Using synthetic mis-targeting strategies, we demonstrate that a combination of lipid anchoring and scaffolding localizes PI4K1 to the plasma membrane, which is essential for its function. Together, this work opens new perspectives on the mechanisms and function of plasma membrane nanopatterning by lipid kinases.

plant biology↗

bioRxiv2020

A plasma membrane nanoplatform ensures signal specificity during osmotic signaling in plants

In the course of their growth and development plants have to constantly perceive and react to their environment. This is achieved in cells, by the coordination of complex combinatorial signaling networks. However, how signal integration and specificity are achieved in this context is unknown. With a focus on the hyperosmotic stimulus, we use live super-resolution light imaging methods to demonstrate that a Rho GTPase, Rho-of-Plant 6 (ROP6), forms stimuli-dependant nanodomains within the PM. These nanodomains are necessary and sufficient to transduce production of reactive oxygen species (ROS),that act as secondary messengers and trigger several plant adaptive responses to osmotic constraints. Furthermore, ROP6 activation triggers the nanoclustering of two NADPH oxidases that subsequently generates ROS. ROP6 nanoclustering is also needed for cell surface auxin signaling, but short-time auxin treatment does not induce ROS accumulation. We show that auxin-induced ROP6 nanodomains, unlike osmotically-driven ROP6 clusters, do not recruit the NADPH oxidase, RBOHD. Together, our results suggest that Rho GTPase nano-partitioning at the PM ensure signal specificity downstream of independent stimuli.

plant biology↗

bioRxiv2019

Dissection of the early pollen-stigma interactions by live-cell imaging

Early events occurring at the surface of the female organ are critical for plant reproduction, especially in species with a dry stigma. Following landing on the stigmatic papilla cells, the pollen hydrates and germinates a tube, which penetrates the cell wall and grows towards the ovules to convey the male gametes to the embryo sac. In self-incompatible (SI) species within the Brassicaceae, these processes are blocked when the stigma encounters an incompatible pollen. Here, based on the generation of SI-Arabidopsis lines and by setting up a live imaging system, we showed that control of pollen hydration has a central role in pollen selectivity. The faster pollen pumps water from the papilla during an initial period of 10 minutes, the faster it germinates. Furthermore, we found that the SI barriers act to block the proper hydration of incompatible pollen and when hydration is promoted by high humidity, an additional control prevents pollen tube penetration into the stigmatic wall. In papilla cells, actin bundles focalize at the contact site with the compatible pollen but not with the incompatible one, raising the possibility that stigmatic cells react to the mechanical pressure applied by the invading growing tube. HighlightA live imaging system coupled with self-incompatible Arabidopsis lines highlight the role of stigmatic cells in controlling pollen hydration and in reacting to pollen tube intrusion by remodeling actin cytoskeleton.

plant biology↗

bioRxiv2018

In vivo phosphatidylserine variations steer Rho GTPase signaling in a cell-context dependent manner

AbstractRho GTPases are master regulators of cell signaling, but how they are regulated depending on the cellular context is unclear. Here, we show that the phospholipid phosphatidylserine acts as a developmentally-controlled lipid rheostat that tunes Rho GTPase signaling in Arabidopsis. Live super-resolution single molecule imaging revealed that RHO-OF-PLANT6 (ROP6) is stabilized by phosphatidylserine into plasma membrane (PM) nanodomains, which is required for auxin signaling. Furthermore, we uncovered that the PM 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 reveals that variations in phosphatidylserine levels are a physiological process that may be leveraged to regulate small GTPase signaling during development.\n\nOne Sentence SummaryPhosphatidylserine acts as a developmentally-controlled lipid rheostat that regulates cellular auxin sensitivity and plant development.

plant biology↗

bioRxiv2018

A combinatorial lipid code shapes the electrostatic landscape of plant endomembranes

Membrane surface charge is critical for the transient, yet specific recruitment of proteins with polybasic regions to certain organelles. In all eukaryotes, the plasma membrane (PM) is the most electronegative compartment of the cell, which specifies its identity. As such, membrane electrostatics is a central parameter in signaling, intracellular trafficking and polarity. Here, we explore which are the lipids that control membrane electrostatics using plants as a model. We show that phosphatidic acidic (PA), phosphatidylserine (PS) and phosphatidylinositol-4-phosphate (PI4P) are separately required to generate the electrostatic signature of the plant PM. In addition, we reveal the existence of an electrostatic territory that is organized as a gradient along the endocytic pathway and is controlled by PS/PI4P combination. Altogether, we propose that combinatorial lipid composition of the cytosolic leaflet of cellular organelles not only defines the plant electrostatic territory but also distinguishes different compartments within this territory by specifying their varying surface charges.

plant biology↗