Endosomal membrane budding patterns in plants.

Multivesicular endosomes (MVEs) sequester membrane proteins destined for degradation within intralumenal vesicles (ILVs), a process mediated by the membrane-remodeling action of Endosomal Sorting Complex Required for Transport (ESCRT) proteins. In , endosomal membrane constriction and scission are uncoupled, resulting in the formation of extensive concatenated ILV networks and enhancing cargo sequestration efficiency. Here, we used a combination of electron tomography, computer simulations, and mathematical modeling to address the questions of when concatenated ILV networks evolved in plants and what drives their formation.

Deciphering sphingolipid biosynthesis dynamics in cell cultures: Quantitative analysis amid data variability.

Sphingolipids are pivotal for plant development and stress responses. Growing interest has been directed toward fully comprehending the regulatory mechanisms of the sphingolipid pathway. We explore its biosynthesis and homeostasis in cell cultures, shedding light on fundamental metabolic mechanisms.

Sphingolipid homeostasis: How do cells know when enough is enough? Implications for plant pathogen responses.

Sphingolipid homeostatic regulation is important for balancing plant life and death. Plant cells finely tune sphingolipid biosynthesis to ensure sufficient levels to support growth through their basal functions as major components of endomembranes and the plasma membrane. Conversely, accumulation of sphingolipid biosynthetic intermediates, long-chain bases (LCBs) and ceramides, is associated with programmed cell death.

Quantitative Dynamic Analysis of Sphingolipid Biosynthesis in .

Sphingolipids are pivotal for plant development and stress responses. Growing interest has been directed towards fully comprehending the regulatory mechanisms of the sphingolipid pathway. We explore its biosynthesis and homeostasis in cell cultures, shedding light on fundamental metabolic mechanisms.

The autophagy receptor NBR1 directs the clearance of photodamaged chloroplasts.

The ubiquitin-binding NBR1 autophagy receptor plays a prominent role in recognizing ubiquitylated protein aggregates for vacuolar degradation by macroautophagy. Here, we show that upon exposing plants to intense light, NBR1 associates with photodamaged chloroplasts independently of ATG7, a core component of the canonical autophagy machinery. NBR1 coats both the surface and interior of chloroplasts, which is then followed by direct engulfment of the organelles into the central vacuole via a microautophagy-type process.

Sphingolipid Long-Chain Base Signaling in Compatible and Non-Compatible Plant-Pathogen Interactions in Arabidopsis.

The chemical diversity of sphingolipids in plants allows the assignment of specific roles to special molecular species. These roles include NaCl receptors for glycosylinositolphosphoceramides or second messengers for long-chain bases (LCBs), free or in their acylated forms. Such signaling function has been associated with plant immunity, with an apparent connection to mitogen-activated protein kinase 6 (MPK6) and reactive oxygen species (ROS).

Plant endosomes as protein sorting hubs.

Endocytosis, secretion, and endosomal trafficking are key cellular processes that control the composition of the plasma membrane. Through the coordination of these trafficking pathways, cells can adjust the composition, localization, and turnover of proteins and lipids in response to developmental or environmental cues. Upon being incorporated into vesicles and internalized through endocytosis, plant plasma membrane proteins are delivered to the trans-Golgi network (TGN).

Proteolytic activities and profiles as useful traits to select barley cultivars for beer production.

Barley malting depends on hydrolytic enzymes that degrade storage macromolecules. Identifying barley cultivars with proteolytic activity that guarantees appropriate foaming, flavor, and aroma in the beer is of great importance. In this work, the proteolytic activity and profiles of brewing malt from Mexican barley cultivars were analyzed.

Mass Spectrometry-Based Profiling of Plant Sphingolipids from Typical and Aberrant Metabolism.

Mass spectrometry has increasingly been used as a tool to complement studies of sphingolipid metabolism and biological functions in plants and other eukaryotes. Mass spectrometry is now essential for comprehensive sphingolipid analytical profiling because of the huge diversity of sphingolipid classes and molecular species in eukaryotes, particularly in plants. This structural diversity arises from large differences in polar head group glycosylation as well as carbon-chain lengths of fatty acids and desaturation and hydroxylation patterns of fatty acids and long-chain bases that together comprise the ceramide hydrophobic backbone of glycosphingolipids.

Plasma and vacuolar membrane sphingolipidomes: composition and insights on the role of main molecular species.

Lipid structures affect membrane biophysical properties such as thickness, stability, permeability, curvature, fluidity, asymmetry, and interdigitation, contributing to membrane function. Sphingolipids are abundant in plant endomembranes and plasma membranes (PMs) and comprise four classes: ceramides, hydroxyceramides, glucosylceramides, and glycosylinositolphosphoceramides (GIPCs). They constitute an array of chemical structures whose distribution in plant membranes is unknown.

Dissecting the regulatory roles of ORM proteins in the sphingolipid pathway of plants.

Sphingolipids are a vital component of plant cellular endomembranes and carry out multiple functional and regulatory roles. Different sphingolipid species confer rigidity to the membrane structure, facilitate trafficking of secretory proteins, and initiate programmed cell death. Although the regulation of the sphingolipid pathway is yet to be uncovered, increasing evidence has pointed to orosomucoid proteins (ORMs) playing a major regulatory role and potentially interacting with a number of components in the pathway, including both enzymes and sphingolipids.

Organized Disassembly of Photosynthesis During Programmed Cell Death Mediated By Long Chain Bases.

In plants, pathogen triggered programmed cell death (PCD) is frequently mediated by polar lipid molecules referred as long chain bases (LCBs) or ceramides. PCD interceded by LCBs is a well-organized process where several cell organelles play important roles. In fact, light-dependent reactions in the chloroplast have been proposed as major players during PCD, however, the functional aspects of the chloroplast during PCD are largely unknown.

Unregulated Sphingolipid Biosynthesis in Gene-Edited Arabidopsis Mutants Results in Nonviable Seeds with Strongly Reduced Oil Content.

Orosomucoid-like proteins (ORMs) interact with serine palmitoyltransferase (SPT) to negatively regulate sphingolipid biosynthesis, a reversible process critical for balancing the intracellular sphingolipid levels needed for growth and programmed cell death. Here, we show that ORM1 and ORM2 are essential for life cycle completion in Arabidopsis (). Seeds from mutants, generated by crossing CRISPR/Cas9 knockout mutants for each gene, accumulated high levels of ceramide, indicative of unregulated sphingolipid biosynthesis.

A Plant Immune Receptor Degraded by Selective Autophagy.

Plants recycle non-activated immune receptors to maintain a functional immune system. The Arabidopsis immune receptor kinase FLAGELLIN-SENSING 2 (FLS2) recognizes bacterial flagellin. However, the molecular mechanisms by which non-activated FLS2 and other non-activated plant PRRs are recycled remain not well understood.

Transcriptional Regulation of Vitamin E Biosynthesis during Germination of Dwarf Fan Palm Seeds.

Vitamin E, a potent antioxidant either presents in the form of tocopherols and/or tocotrienols depending on the plant species, tissue and developmental stage, plays a major role in protecting lipids from oxidation in seeds. Unlike tocopherols, which have a more universal distribution, the occurrence of tocotrienols is limited primarily to monocot seeds. Dwarf fan palm (Chamaerops humilis var.

Plant lipid environment and membrane enzymes: the case of the plasma membrane H+-ATPase.

Several lipid classes constitute the universal matrix of the biological membranes. With their amphipathic nature, lipids not only build the continuous barrier that confers identity to every cell and organelle, but they are also active actors that modulate the activity of the proteins immersed in the lipid bilayer. The plasma membrane H(+)-ATPase, an enzyme from plant cells, is an excellent example of a transmembrane protein whose activity is influenced by the hydrophilic compartments at both sides of the membrane and by the hydrophobic domains of the lipid bilayer.

Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species.

It is essential to establish the composition of the plant plasma membrane in order to understand its organization and behavior under continually changing environments. Knowledge of the lipid phase, in particular the fatty acid (FA) complex repertoire, is important since FAs determine many of the physical-chemical membrane properties. FAs are constituents of the membrane glycerolipid and sphingolipid backbones and can also be linked to some sterols.

Arabidopsis mutants in sphingolipid synthesis as tools to understand the structure and function of membrane microdomains in plasmodesmata.

Plasmodesmata-intercellular channels that communicate adjacent cells-possess complex membranous structures. Recent evidences indicate that plasmodesmata contain membrane microdomains. In order to understand how these submembrane regions collaborate to plasmodesmata function, it is necessary to characterize their size, composition and dynamics.

Reactive oxygen species as transducers of sphinganine-mediated cell death pathway.

Long chain bases or sphingoid bases are building blocks of complex sphingolipids that display a signaling role in programmed cell death in plants. So far, the type of programmed cell death in which these signaling lipids have been demonstrated to participate is the cell death that occurs in plant immunity, known as the hypersensitive response. The few links that have been described in this pathway are: MPK6 activation, increased calcium concentrations, and reactive oxygen species (ROS) generation.

MPK6, sphinganine and the LCB2a gene from serine palmitoyltransferase are required in the signaling pathway that mediates cell death induced by long chain bases in Arabidopsis.

Long chain bases (LCBs) are sphingolipid intermediates acting as second messengers in programmed cell death (PCD) in plants. Most of the molecular and cellular features of this signaling function remain unknown. We induced PCD conditions in Arabidopsis thaliana seedlings and analyzed LCB accumulation kinetics, cell ultrastructure and phenotypes in serine palmitoyltransferase (spt), mitogen-activated protein kinase (mpk), mitogen-activated protein phosphatase (mkp1) and lcb-hydroxylase (sbh) mutants.