[Seminar] Re-investigation of plant plasma membrane lipids: role in sphingolipid- and sterol-enriched membrane rafts, and their involvement in plant defense through the phosphorylated protein REMORIN

Seminar

Title: Re-investigation of plant plasma membrane lipids: role in sphingolipid- and sterol-enriched membrane rafts, and their involvement in plant defense through the phosphorylated protein REMORIN

Speaker: Sebastien Mongrand

Affiliation: Laboratoire de Biogenèse Membranaire, Université Bordeaux, France

Abstract:

Sphingolipids and sterols in plant plasma membrane display striking differences by comparison with their animal's counterparts in term of chemistry and abundance. In this talk, I would like to reinvestigate the role for the major sphingolipid on earth, namely Glycosylinositol phosphoceramides, GIPC, in their roles in structuring membrane domains with sterols, in their asymmetrical distributions and structural diversity. Very broad methods were currently used to answer these questions from lipid purification, liposomes studies, environment-sensitive probes, MS-based lipidomics and solid-phase NMR.
Beside lipids, Remorin (REM) proteins are plant-specific oligomeric proteins that have been reported to localize to the plasma membrane raft microdomain enriched in sterols and sphingolipids, despite their overall hydrophilic nature. There is evidence that the REM protein phosphorylation is potentially implicated in the early signaling and defense. Benschop et al. (2007) detected the AtREM1.3 (group 1b of REM protein family) to be phosphorylated in response to treatment with the general elicitor flg22, while the Widjaja et al. (2008) suggested that the phosphorylation of AtREM1.2 is potentially implicated in early signaling upon infection with Pseudomonas syringae. The precise exact function of the group 1 REM protein phosphorylation remains unknown.
Beside, we showed that Potato virus X (PVX) movement is inversely related to potato StREM1.3 accumulation and that StREM1.3 can interact physically with the movement protein TRIPLE GENE BLOCK PROTEIN1 from PVX. In this talk, I will discuss the role of StREM1.3 and its phosphorylation in presence of virus. The physiological consequence of this phosphorylation, virus spreading, posttranlational gene silencing, plasmodesmata gating, size exclusion limit, kinase activation were studied. The role of raft microdomain during virus infection will be particularly discussed, together with the role and the structure of sphingolipids and sterols in plants, that allow lateral segregation of lipids and proteins in the plasma membrane.

1. Widjaja, I., et al. (2009). Combining subproteome enrichment and Rubisco depletion enables identification of low abundance proteins differentially regulated during plant defense. Proteomics 9: 138-147.
2. Benschop et al. 2007 Quantitative phosphoproteomics of early elicitor signaling in Arabidopsis Jul;6(7):1198-214.
    

Invited Speaker in ITQB PhD International Program - Plants For Life - Plant Metabolic Regulation Course (16-20 March)