Responsibles: Sébastien Mongrand, Research Diresctor CNRS et Véronique Germain, Professor associate at Bordeaux University

Sébastien Mongrand is DR2 at the CNRS. He defended his Ph.D. in 1998 at the LBM in chloroplastic lipid biosynthesis. After a three years post doc at the university of Rockefeller (New-York, USA) working on ABA signaling pathway, he was recruited CNRS in 2002. He is now co-leading the “Lipids, Membrane Compartmentalization, Trafficking and Morphogenesis in Plant and Yeast” with P. Moreau. He also works in the lipidomic platform as scientific co-leader.

ORCID 0000-0002-9198-015X

Véronique Germain is a lecturer at the University of Bordeaux since 1999. She obtained her PhD in 1997 on the response of plants to hypoxia and is qualified to direct research (HDR).  She completed a post-doctoral fellowship at the University of Edinburgh on the characterization of mutants involved in lipid mobilization during germination in Arabidopsis. She joined the LBM in 2010.

Members:

T. Robbe (AI), D. J. Ahmed (Post-Doc), MD. Jolivet (PhD)

Thematique:

Plant membranes are highly dynamic cellular compartments. They are made of three main families of lipids: glycerolipids, which often contain highly unsaturated fatty acids, sphingolipids and sterols. They also contain a large amount of proteins (ca 20-30% of protein in the plasma membrane). (Suda et al. 2011). The plasma membrane is continuous between plant cells across intercellular symplastic junctions called plasmodesmata (PD). Permanent re-organisation of membranes sustains the regulation of signalling and exchanges processes and occurs through the formation of specialised membrane domains of different scales (nano or macro domains) which display specific lipids and proteins content. Such sub-compartmentalisation of biological membranes has been described in cyanobacteria, animal and plants (Schaaf et al., 2009; Lopez and Kolter, 2010; Schmolzer et al, 2011; Cacas et al, 2012; Li et al, 2012.). The formation of membrane-domains is highly regulated and allows the clustering of specific activities within the membrane (endocytosis, polarisation, signalling, etc). The precise molecular organization of these domains defines physiological activities of membranes and their study is therefore essential for understanding how cells regulate specialised functions at the membrane level. We were pioneers in the characterization of membrane domains at the PM in plants (Mongrand et al, 2004, recent review: Cacas et al, 2012.), which formation is essentially due to sterols and sphingolipids (Roche et al., 2008; Morel et al., 2006; Lefebvre et al, 2007). We tackle all these questions on suitable model organisms. Our main objectives are to determine the role of these lipid classes, as well as specific proteins such as Remorin in the structure, fluidity, signal transduction, membrane homeostasis, and dynamics of various membrane functions.

GIPC, stérols et polyphosphoinositides

Glycosylinositolphosphorylceramides (GIPCs) are the most abundant sphingolipids in plants and fungi (Cacas et al., 2011 Buré et al., 2013, revised Buré et al., 2014). Nevertheless, 50 years after their discovery, GIPCs remain poorly characterized in term of structure and chemical diversity. In addition, their subcellular distributions, their exact structures and biological functions remain poorly understood in plants. To elucidate the structure of these lipids, we developed strategies based on mass spectrometry to analyse their long-chain bases (LCB), Fatty acids (FA) and polar heads (Cacas et al, 2012). We determined that the polar head may contain up to seven monosaccharide sugars (Cacas et al., 2011 Buré et al., 2013, review Buré et al., 2014). Furthermore, GIPCs, sterols and polyphosphoinositides (Furt et al., 2010) are enriched in membrane microdomains of the PM. We recently showed that GIPCs represent up to 60mol% of the lipids in membrane rafts together with free and conjugated sterols (Cacas et al. 2015). GIPCs are the receptor of necrototic toxin of plant pathogen (Lenarcic et al., 2017). 

StREMORIN1.3, a raft-located phosphoprotein, involved in virus propagation and plasmodesmata opening

We have established that StREMORIN1.3 (REM) is a plant raftophilic protein, predominantly associated with sterol- and sphingolipid-rich membrane rafts of approximately 70-nm membrane domains located at the PM and in plasmodesmata (PD) (Raffaele et al., 2009 a and 2009b). This was the first evidence of membrane rafts in plants (for review, Mongrand et al., 2011). We also identified a new C-terminal domain (RemCA) sufficient for anchoring REM to the PM (Perraki et al., 2013, Gronnier et al., 2017). From a manipulation of REM levels in transgenic tomato, we showed that REM is involved in the regulation of viral cell-to-cell movement of Potato virus X (PVX), movement being inversely correlated with REM accumulation (Raffaele et al., 2009). The novel C-terminal anchor is required for the restriction of Potato Virus X (PVX) movement (Perraki et al., 2013, Gronnier et al., 2017), and affects the ability of the virus to increase PD permeability. By contrast, over-expressed REM does not impair the silencing suppressor activity of the PVX viral protein TGBp1. A similar effect on PD permeability was observed with other movement proteins, suggesting that REM is a general regulator of PD size exclusion limit (Perraki et al., 2014). Finally, we showed that the phosphorylation of REM is necessary for its activation as PD regulator. We showed that the kinase responsible is raft-located. Its activity is stimulated by the presence of the virus. These results add to our knowledge on the mechanisms underlying the role of REM and rafts in virus infection and PD regulation.

L’ancrage de la REM à la membrane plasmique est nécessaire à la restriction du mouvement du PVX (Perraki et al., 2013), et inhibe la capacité du virus à augmenter la perméabilité des PD. En revanche, REM sur-exprimé ne porte pas atteinte à ‘activité « suppresseur de silencing » de la protéine virale TGBp1. Un effet similaire sur la perméabilité des PD a été observé avec d’autres protéines de mouvement viral, suggérant que REM est un régulateur général de la taille d’exclusion limite des PD (Perraki et al., 2014, Gronnier et al.,2017). Enfin, nous avons montré qe la phosphorylation de REM est nécessaire pour son activation comme régulateur des PD. Nous avons montré que la kinase responsable est situé dans les radeaux membranaires, dont l’activité est stimulé par la présence du virus. Ces résultats ajoutent à notre connaissance sur les mécanismes d’action de REM et des radeaux dans ‘infection par le virus et la régulation de la perméabilité des PD, un mécanisme clé dans la coordination intercellulaire des réponses aux stress et aux pathogènes, et du développement des plantes.

Key articles:

• Mamode Cassim A., Navon Y., Gao Y., Decossas M., Fouillen L, Grélard A., Nagano M., Lambert O., Bahammou D., Van Delft P, Maneta-Peyret L, Simon-Plas F., Heux L., Fragneto G, Mortimer JC., Deleu M., Lins L, & Mongrand S*. (2020) Purification, characterization and influence on membrane properties of the plant-specific sphingolipids GIPC. Submitted to JBC https://biorxiv.org/cgi/content/short/2020.10.01.313304v1*corresponding authors     
• Gouguet P, Gronnier J, Legrand J, Perraki A, Jolivet MD, Deroubaix AF, German-Retana S, Boudsocq M, Habenstein B, Mongrand S* & Germain V (2020) Connecting the dots: from nanodomains to physiological functions of REMORINs. Review in special issue « Dynamic Membranes » Plant physiology. doi: 10.1093/plphys/kiaa063 *corresponding authors
• Mamode Cassim A., Grison M., Ito Y., Simon-Plas F., Mongrand S*. & Boutté Y* (2020) Sphingolipids in plants: a tour guide into structures, membranes, cellular processes and responses to environmental or developmental signals. FEBS letters (invited review) Nov;594(22):3719-3738. doi: 10.1002/1873-3468.13987 *co-corresponding authors.
• Legrand A, Martinez D, Grélard A, Morvan E, Loquet A, Mongrand S, & Habenstein B (2019) Nanodomain clustering of the plant protein remorin by solid-state NMR. Frontiers Molecular Biosciences. Oct 15;6:107. doi: 10.3389/fmolb.2019.00107  
• Mamode-Cassim A & Mongrand S* (2019) Lipids light up in plant membranes. News & Views, Nature Plants. Sep;5(9):913-914. doi: 10.1038/s41477-019-0494-9. *corresponding authors  
• Gronnier J, Legrand A, Loquet A, Habenstein B, Germain V & Mongrand S*. (2019) Mechanisms governing organization and sub-compartmentalization of biological membranes. Review. Current Opinion in Plant Biology. Sep 20;52:114-123. doi: 10.1016/j.pbi.2019.08.003 *corresponding authors
• Mamode-Cassim A#, Gouguet P#, Gronnier J, Nelson L, Germain V, Boutté Y, Gerbeau-Pissot P, Simon-Plas F*, Mongrand S* (2018) Plant lipids: key players of plasma membrane organization, Progress in Lipid Resarch, Jan;73:1-27. doi: 10.1016/j.plipres.2018.11.002. (invited review). #co-first author, *co-corresponding authors  
• Gronnier J, Gerbeau-Pissot P, Germain V, Mongrand S*, Simon-Plas F* (2018) Divide and Rule: Plant Plasma Membrane Organization, Trends in Plant Science, Oct;23(10):899-917. doi: 10.1016/j.tplants.2018.07.007 (invited review), *co- corresponding autho.
• Perraki A#, Gronnier J#, Gouguet P, Boudsocq M, Deroubaix AF, Simon V, German-Retana S, Anthony Legrand, Birgit Habenstein, Zipfel C, Bayer EE, Mongrand S*, Germain V (2018) REM1.3’s phospho-status defines its plasma membrane nanodomain organization and activity in restricting PVX cell-to-cell movement. Plos Pathogens. Nov 12;14(11):e1007378. doi: 10.1371/journal.ppat.1007378. #co-first authors, *corresponding authors. 
• Martinez D, Legrand A, Gronnier J, Decossas M, Gouguet P, Lambert O, Berbona M, Verrona L, Grélard A, Germain V, Loquet A*, Mongrand S*, Habenstein B* (2018) Coiled-coil oligomerization controls localisation of the plasma membrane REMORINs. Journal of Structural Biology J Struct Biol. 2019 Apr 1;206(1):12-19. doi: 10.1016/j.jsb.2018.02.003. *co- corresponding authors

Collaborateurs :

C Buré, JM Schmitter CBMN, F Simon-Plas et P Gerbeau, INRA Dijon
German-Retana S., Douliez JP, BFP INRA Bordeaux
S Raffaele, INRA Toulouse
L. Lins, M. Deleu GEMBLOUX Belgique
Y. Jaillais ENS Lyon

Former members:

2002-2003 D. PALOMO (BTS)
2003-2004 L. Cerf (M2)
2004-2005 D. Lafarge (M2)
2005-2006 T. Stanislas (M1, M2)
2007-2008 R. Zallot (M)
2008-2009 A. Perraki (M2, PhD)
2009-2010 J. Naj and F. Wang (M2)
2011 M. Binaghi, (EMBO short fellowship)
2012 Z. Venel (L3)
2012-2016 J. Gronnier, (M2, PhD)
2013 JY. Taburet (BTS)
2013 C. Dariceau (L3)
2013 F. Puccio, (PhD)
2014 C. Bossard, (M2)

2015-2019 AF. Deroubaix (M2, PhD)

2015-2019 A. Mamode-Cassim (M2, PhD)