Epiplasmins and Epiplasm in Paramecium: The Building of a Submembraneous Cytoskeleton

• Published in: Protist Vol. 164; no. 4; pp. 451 - 469
• Main Authors: Aubusson-Fleury, Anne, Bricheux, Geneviève, Damaj, Raghida, Lemullois, Michel, Coffe, Gérard, Donnadieu, Florence, Koll, France, Viguès, Bernard, Bouchard, Philippe
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.07.2013; Elsevier
• Subjects: Basal body docking; Cell Cycle; cell morphogenesis; ciliates; ciliogenesis; Cytoskeleton - genetics; Cytoskeleton - metabolism; Cytoskeleton - ultrastructure; Life Sciences; Microbiology and Parasitology; Microscopy, Electron; Paramecium - classification; Paramecium - cytology; Paramecium - growth & development; Paramecium - metabolism; Phylogeny; Protistology; Protozoan Proteins - genetics; Protozoan Proteins - metabolism; structural heredity; transition zone; ciliogenesis; Basal body docking; cell morphogenesis; ciliates; transition zone; structural heredity
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1016/j.protis.2013.04.003

In ciliates, basal bodies and associated appendages are bound to a submembrane cytoskeleton. In Paramecium, this cytoskeleton takes the form of a thin dense layer, the epiplasm, segmented into regular territories, the units where basal bodies are inserted. Epiplasmins, the main component of the epiplasm, constitute a large family of 51 proteins distributed in 5 phylogenetic groups, each characterized by a specific molecular design. By GFP-tagging, we analyzed their differential localisation and role in epiplasm building and demonstrated that: 1) The epiplasmins display a low turnover, in agreement with the maintenance of an epiplasm layer throughout the cell cycle; 2) Regionalisation of proteins from different groups allows us to define rim, core, ring and basal body epiplasmins in the interphase cell; 3) Their dynamics allows definition of early and late epiplasmins, detected early versus late in the duplication process of the units. Epiplasmins from each group exhibit a specific combination of properties. Core and rim epiplasmins are required to build a unit; ring and basal body epiplasmins seem more dispensable, suggesting that they are not required for basal body docking. We propose a model of epiplasm unit assembly highlighting its implication in structural heredity in agreement with the evolutionary history of epiplasmins.