Biology subjects

Morello-Lopez, J.

Publications and source records attributed to Morello-Lopez, J..

4 recordsLinked to original sources

bioRxiv2026

Integration of SYT1 Interactomics and Dual-Localization Proteomics Links ER-PM Contacts to Lignin Deposition

Membrane contact sites (MCSs) are evolutionarily conserved intracellular nanodomains that physically bridge opposing lipid bilayers to facilitate non-vesicular communication and maintain cellular homeostasis. In plants, endoplasmic reticulum-plasma membrane (ER-PM) contact sites play fundamental roles in environmental adaptation, and are populated by specialized proteins which act as tethers such as Synaptotagmin 1 (SYT1). However, a comprehensive view of the molecular machinery governing processes at these junctions is still needed. In this work, we integrate affinity purification mass spectrometry, TurboID proximity labeling, and a dual-localization reanalysis of HyperLOPIT spatial proteomics to functionally map the protein interaction landscape of the ER-PM contact sites protein SYT1. Beyond recovering established ER-PM MCS functions, our analysis identified uncharacterized proteins as bona fide resident components of these junctions, and revealed that these nanodomains act as docking platforms that anchor the monolignol biosynthetic complex. By spatially organizing Membrane Steroid Binding Proteins and cytochrome P450 enzymes, our findings support a model where SYT1-mediated anchoring of this metabolon to ER-PM contact sites optimizes monolignol export required for stress-induced lignification. Ultimately, this proteomic framework expands the functional repertoire of ER-PM contact sites, opening new avenues to uncover hidden roles of MCSs across diverse eukaryotic systems.

molecular biology↗

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↗

bioRxiv2026

Molecular mechanisms of E-Syt-mediated stress resistance

Membrane contact sites (MCS) between the endoplasmic reticulum (ER) and the plasma membrane (PM) enable direct intermembrane exchange of signals and metabolites. The Extended Synaptotagmins (E-Syts) are an evolutionary conserved family of ER-PM tethers essential to maintain PM integrity under stress conditions. To investigate the underlying molecular mechanisms, we employed cellular reconstitution experiments in yeast and plants. We show that E-Syt-mediated stress tolerance relies on ER-PM MCS targeting, which requires the E-Syt N-terminal membrane anchor, a minimal set of two C2 domains and an SMP domain. C2 domains are sufficiently conserved that interspecies domains can sustain both PM localization and stress response. The role of the SMP domain in ER-PM localization is also conserved, but SMP function in stress resistance is species-specific. Furthermore, cryo-electron tomography uncovers a scaffolding role for the SMP domain in maintaining ER-PM distance, and in the formation of ER membrane peaks with extreme curvature that appear necessary for stress tolerance. Collectively, our findings reveal the individual and synergistic roles of all E-Syt modules in maintaining cellular homeostasis under stress.

cell biology↗

bioRxiv2022

Identification of plant exclusive lipid transfer SMP proteins at membrane contact sites in Arabidopsis and Tomato

Membrane contact sites (MCS) are regions where two membranes of different organelles are close but not fused; they coordinate non-vesicular communication between organelles and are involved in a wide variety of physiological functions, including membrane lipid homeostasis. Amongst proteins localized at MCS are those containing a lipid transport domain known as synaptotagmin-like mitochondrial-lipid binding protein (SMP), being the mammalian Extended Synaptotagmins, the yeast Tricalbins and the plant Synaptotagmin 1 (SYT1) the best SMP proteins characterized so far. They are all localized at endoplasmic reticulum-plasma membrane contact sites (ER-PM CS). We have carried out in-silico genome-wide identification of genes encoding SMP proteins in Arabidopsis and tomato. We have identified the plant exclusive NTMC2T5 proteins as ER-chloroplast CS components which make them extremely interesting as the route for lipid trafficking into and out of chloroplasts remains unknown. Additionally, NTMC2T5 over-expressions caused a significant clustering of chloroplast around nucleus. Moreover, SYT6, NTMC2T6 and TEX2 have been identified as ER-Trans-Golgi Network CS proteins. These proteins associated between them and with the exocytosis related proteins VAMP721 and VAMP727. Since the functional roles of many of these genes are unknown, this gene collection provides a useful resource for future studies. HIGHLIGHTPlant exclusive lipid transport proteins were identified at membrane contact sites. SYT6, TEX2 and NTMC2T6 proteins are localized at ER-TGN. NTMC2T5 proteins are localized at ER-Chloroplast and induced chloroplast-nucleus clustering.

plant biology↗