title: The mitochondrial respiratory chain of the secondary green alga Euglena gracilis shares many additional subunits with parasitic Trypanosomatidae.
abstract: The mitochondrion is an essential organelle for the production of cellular ATP in most eukaryotic cells. It is extensively studied, including in parasitic organisms such as trypanosomes, as a potential therapeutic target. Recently, numerous additional subunits of the respiratory-chain complexes have been described in Trypanosoma brucei and Trypanosoma cruzi. Since these subunits had apparently no counterparts in other organisms, they were interpreted as potentially associated with the parasitic trypanosome lifestyle. Here we used two complementary approaches to characterise the subunit composition of respiratory complexes in Euglena gracilis, a non-parasitic secondary green alga related to trypanosomes. First, we developed a phylogenetic pipeline aimed at mining sequence databases for identifying homologues to known respiratory-complex subunits with high confidence. Second, we used MS/MS proteomics after two-dimensional separation of the respiratory complexes by Blue Native- and SDS-PAGE both to confirm in silico predictions and to identify further additional subunits. Altogether, we identified 41 subunits that are restricted to E. gracilis, T. brucei and T. cruzi, along with 48 classical subunits described in other eukaryotes (i.e. plants, mammals and fungi). This moreover demonstrates that at least half of the subunits recently reported in T. brucei and T. cruzi are actually not specific to Trypanosomatidae, but extend at least to other Euglenozoa, and that their origin and function are thus not specifically associated with the parasitic lifestyle. Furthermore, preliminary biochemical analyses suggest that some of these additional subunits underlie the peculiarities of the respiratory chain observed in Euglenozoa.
authors.affiliation: Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium; Eukaryotic Phylogenomics, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium.
authors.forename: Emilie
authors.initials: E
authors.lastname: Perez
authors.affiliation: Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium.
authors.forename: Marie
authors.initials: M
authors.lastname: Lapaille
authors.affiliation: Institut des Sciences de la Vie, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Hervé
authors.initials: H
authors.lastname: Degand
authors.affiliation: Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium.
authors.forename: Laura
authors.initials: L
authors.lastname: Cilibrasi
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Alexa
authors.initials: A
authors.lastname: Villavicencio-Queijeiro
authors.affiliation: Institut des Sciences de la Vie, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Morsomme
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
authors.forename: Diego
authors.initials: D
authors.lastname: González-Halphen
authors.affiliation: Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, Scotland DD1 5EH, United Kingdom.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Field
authors.affiliation: Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium; PhytoSYSTEMS, University of Liège, B-4000 Liège, Belgium.
authors.forename: Claire
authors.initials: C
authors.lastname: Remacle
authors.affiliation: Eukaryotic Phylogenomics, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium; PhytoSYSTEMS, University of Liège, B-4000 Liège, Belgium. Electronic address: denis.baurain@ulg.ac.be.
authors.forename: Denis
authors.initials: D
authors.lastname: Baurain
authors.affiliation: Genetics and Physiology of Microalgae, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium; PhytoSYSTEMS, University of Liège, B-4000 Liège, Belgium. Electronic address: Pierre.cardol@ulg.ac.be.
authors.forename: Pierre
authors.initials: P
authors.lastname: Cardol
mesh_terms: D019295:Computational Biology; D004579:Electron Transport; D015180:Electrophoresis, Gel, Two-Dimensional; D005056:Euglena gracilis / Q000201:enzymology* / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D053719:Tandem Mass Spectrometry; D014351:Trypanosomatina / Q000201:enzymology* / Q000235:genetics*
keywords: Euglenozoa; Large-scale phylogenetics; OXPHOS; Proteomics; Sequence database mining; Trypanosomatidae