Electron microscopy Facility University of Lausanne

Great collaboration with Marie Barberon and Niko Geldner! Our article on Extracellular vesiculo-tubular structures associated with suberin deposition in plant cell walls is now published in NatureComms.

Extracellular vesiculo-tubular structures associated with suberin deposition in plant cell walls

Damien De Bellis,  Lothar Kalmbach,  Peter Marhavy,  Jean Daraspe,  Niko Geldner &  Marie Barberon

Nat Commun 13, 1489 (2022). https://doi.org/10.1038/s41467-022-29110-0

Suberin is a fundamental plant biopolymer, found in protective tissues, such as seed coats, exodermis and endodermis of roots. Suberin is deposited in most suberizing cells in the form of lamellae just outside of the plasma membrane, below the primary cell wall. How mono- meric suberin precursors, thought to be synthesized at the endoplasmic reticulum, are transported outside of the cell, for polymerization into suberin lamellae has remained obscure. Using electron-microscopy, we observed large numbers of extracellular vesiculo- tubular structures (EVs) to accumulate specifically in suberizing cells, in both chemically and cryo-fixed samples. EV presence correlates perfectly with root suberization and we could block suberin deposition and vesicle accumulation by affecting early, as well as late steps in the secretory pathway. Whereas many previous reports have described EVs in the context of biotic interactions, our results suggest a developmental role for extracellular vesicles in the formation of a major cell wall polymer.

L’EMF a eu la joie d’accueillir les artistes Hunter Longe et Matheline Marmy dans le cadre de la première exposition collective célébrant la réouverture de la Grange

Grâce à Hunter Longe et Jean Daraspe, l’EMF montre les supports matériels et visuels menant à une image de microscopie électronique.

Allez y faire un tour!

La Grange propose, déployée dans le foyer d’accueil et Le Café, une exposition collective lente et ouverte qui évolue – parfois en phase, parfois en décalage – avec la programmation du lieu. Dédié·e à sa propre allure s’inspire des domaines de la chronobiologie et de l’évolution minérale et prend forme à partir des rythmes superposés qui guident notre monde – solaire, lunaire, sidéral et circadien. Comme les saisons qui se superposent aux jours et aux marées, la présence des images, des sculptures et des installations se chevauchent les unes aux autres. Certaines œuvres se déplacent dans l’espace et certaines vont et viennent, tandis que d’autres changent et grandissent. La durée devient une forme, ponctuée par les performances et les spectacles qui se déroulent au-dessus, sur la scène du théâtre.

Cette première phase de l’exposition inaugurée le 25 février est fortement inspirée par la croissance des minéraux et leur relation intrinsèque avec le vivant, qui a été baptisée la bio-géo-coévolution. En parcourant des premières formes de vie, leurs traces et leurs effets sur leur environnement, ainsi que sur les voies de réaction ouvertes par la vie organique par lesquelles de nouveaux minéraux se forment, l’exposition estompe les distinctions entre le vivant et le non-vivant ainsi que celles entre les sciences et les arts, laissant entrevoir une créativité intrinsèque à la matière

Kian Hématy, Damien De Bellis, Xin Wang, Ari Pekka Mähönen, Niko Geldner. 

Analysis of exocyst function in endodermis reveals its widespread contribution and specificity of action. 

Plant Physiology, 2022;, kiac019, https://doi.org/10.1093/plphys/kiac019

Abstract
The exocyst is the main plasma membrane vesicle-tethering complex in eukaryotes and is composed of eight different subunits. Yet, in plant genomes, many subunits display multiple copies, thought to reflect evolution of complex subtypes with
divergent functions. In Arabidopsis thaliana root endodermal cells, the isoform EXO70A1 is required for positioning of
CASP1 at the Casparian Strip Domain, but not for its non-targeted secretion to the plasma membrane. Here, we show that
exo84b resembles exo70a1 mutants regarding CASP1 mistargeting and secretion of apoplastic proteins, but exo84b additionally affects secretion of other integral plasma membrane proteins. Moreover, conditional, cell-type-specific gene editing of
the single-copy core component SEC6 allows visualization of secretion defects in plant cells with a complete lack of exocyst
complex function. Our approach opens avenues for deciphering the complexity/diversity of exocyst functions in plant cells
and enables analysis of central trafficking components with lethal phenotypes.

First publication of the year!

Front. Plant Sci., 05 January 2022

Trafficking Processes and Secretion Pathways Underlying the Formation of Plant Cuticles

Glenn Philippe¹, Damien De Bellis^2,3, Jocelyn K. C. Rose¹ and Christiane Nawrath^2*

¹Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, United States

²Department of Plant Molecular Biology, University of Lausanne, Lausanne, Switzerland

³Electron Microscopy Facility, University of Lausanne, Lausanne, Switzerland

Cuticles are specialized cell wall structures that form at the surface of terrestrial plant organs. They are largely comprised lipidic compounds and are deposited in the apoplast, external to the polysaccharide-rich primary wall, creating a barrier to diffusion of water and solutes, as well as to environmental factors. The predominant cuticle component is cutin, a polyester that is assembled as a complex matrix, within and on the surface of which aliphatic and aromatic wax molecules accumulate, further modifying its properties. To reach the point of cuticle assembly the different acyl lipid-containing components are first exported from the cell across the plasma membrane and then traffic across the polysaccharide wall. The export of cutin precursors and waxes from the cell is known to involve plasma membrane-localized ATP-binding cassette (ABC) transporters; however, other secretion mechanisms may also contribute. Indeed, extracellular vesiculo-tubular structures have recently been reported in Arabidopsis thaliana (Arabidopsis) to be associated with the deposition of suberin, a polyester that is structurally closely related to cutin. Intriguingly, similar membranous structures have been observed in leaves and petals of Arabidopsis, although in lower numbers, but no close association with cutin formation has been identified. The possibility of multiple export mechanisms for cuticular components acting in parallel will be discussed, together with proposals for how cuticle precursors may traverse the polysaccharide cell wall before their assimilation into the cuticle macromolecular architecture.