TFK1, a basal body transition fibre protein that is essential for cytokinesis in Trypanosoma brucei

In Trypanosoma brucei, transition fibres (TFs) form a nine-bladed pattern-like structure connecting the base of the flagellum to the flagellar pocket membrane. Despite the characterization of two TF proteins, CEP164C and T. brucei (Tb)RP2, little is known about the organization of these fibres. Here, we report the identification and characterization of the first kinetoplastid-specific TF protein, named TFK1 (Tb927.6.1180). Bioinformatics and functional domain analysis identified three distinct domains in TFK1 – an N-terminal domain of an unpredicted function, a coiled-coil domain involved in TFK1–TFK1 interaction and a C-terminal intrinsically disordered region potentially involved in protein interaction. Cellular immunolocalization showed that TFK1 is a newly identified basal body maturation marker. Furthermore, using ultrastructure expansion and immuno-electron microscopies we localized CEP164C and TbRP2 at the TF, and TFK1 on the distal appendage matrix of the TF. Importantly, RNAi-mediated knockdown of TFK1 in bloodstream form cells induced misplacement of basal bodies, a defect in the furrow or fold generation, and eventually cell death. We hypothesize that TFK1 is a basal body positioning-specific actor and a key regulator of cytokinesis in the bloodstream form Trypanosoma brucei

La transmission comme outil stratégique de pérennisation de l’entreprise viticole - Le cas de la Bourgogne vitivinicole

International audienceBien que la transmission relève d’un choix, d’une stratégie individuelle, ce processus a également des impacts en termes de dynamique et stratégique collectives et en termes de pérennité du vignoble (prix du foncier, maintien du modèle économique « familial », etc..). Cette question est d’autant plus cruciale que le foncier viticole, en Bourgogne en particulier, est aujourd’hui difficilement accessible. Tout d’abord, du fait de son niveau de forte valorisation, et ensuite, du fait de la rareté des parcelles mises sur le marché.La pérennisation vise à garantir la survie du modèle économique choisi, pour autant cela n’empêche pas une certaine mutation de ce primo-modèle afin justement de garantir la transmission.Cette communication s’appuie sur un travail de recherche post-doctoral financé par la Région Bourgogne-Franche-Comté et le BIVB (Bureau Interprofessionnel des Vins de Bourgogne) sur les entreprises viticoles bourguignonnes. Cette recherche s’articule autour de deux axes : une compilation bibliographique et théorique sur la thématique de la transmission dans le secteur vitivinicole et une série d’enquêtes réalisées en Bourgogne auprès de différents acteurs de la filière.Après avoir interrogé de nombreux experts privés et publics concernés par ces aspects transmission en Bourgogne (études notariales, experts-comptables, avocats, cabinet de conseil stratégique, Safer,…) nous avons élaboré un questionnaire de manière à analyser les évolutions du modèle viticole bourguignon. Pour ce faire, nous avons mené une enquête qualitative auprès d’une vingtaine de viticulteurs sous la forme d’entretiens semi-directifs, et une enquête quantitative à l’aide d’une enquête en ligne. Les grandes parties des questionnaires s’intéressent au montage juridique des entreprises, à leur taille, et aux motivations des viticulteurs. Nous cherchons ainsi à analyser les effets combinés des évolutions à la hausse des prix de vente (de la production et du foncier) sur le modèle économique viticole bourguignon correspondant majoritairement à un modèle familial. Cette analyse est complétée par deux extractions de bases de données : celle de l’INSEE et celle de la SAFER.Nous proposons ainsi d’exposer dans le cadre de la présentation les résultats obtenus dans le cadre des enquêtes effectuées auprès des viticulteurs bourguignons en ce qui concerne les principales modalités de transmission mobilisées ainsi que l’impact de la réglementation juridique et fiscale sur le processus décisionnel lors de la cession des structures

The mitochondrial phosphatidylserine decarboxylase Psd1 is involved in nitrogen starvation-induced mitophagy in yeast

International audienceMitophagy, the selective degradation of mitochondria by autophagy, is a central process that is essential for the maintenance of cell homeostasis. It is implicated in the clearance of superfluous or damaged mitochondria and requires specific proteins and regulators to perform. In yeast, Atg32, an outer mitochondrial membrane protein, interacts with the ubiquitin-like Atg8 protein, promoting the recruitment of mitochondria to the phagophore and their sequestration within autophagosomes. Atg8 is anchored to the phagophore and autophagosome membranes thanks to a phosphatidylethanolamine tail. In Saccharomyces cerevisiae, several phosphatidylethanolamine synthesis pathways have been characterized, but their contribution to autophagy and mitophagy are unknown. Through different approaches, we show that Psd1, the mitochondrial phosphatidylserine decarboxylase, is involved in mitophagy induction only after nitrogen starvation, whereas Psd2, which is located in vacuole, Golgi and endosome membranes, is required preferentially for mitophagy induction in the stationary phase of growth but also to a lesser extent for nitrogen starvation-induced mitophagy. Our results suggest that the mitophagy defect observed in Δpsd1 yeast cells after nitrogen starvation may be due to a failure of Atg8 recruitment to mitochondria.This article has an associated First Person interview with the first author of the paper

TbFlabarin, a flagellar protein of Trypanosoma brucei, highlights differences between Leishmania and Trypanosoma flagellar-targeting signals

International audienceTbFlabarin is the Trypanosoma brucei orthologue of the Leishmania flagellar protein LdFlabarin but its sequence is 33% shorter than LdFlabarin, as it lacks a C-terminal domain that is indispensable for LdFlabarin to localize to the Leishmania flagellum. TbFlabarin is mainly expressed in the procyclic forms of the parasite and localized to the flagellum, but only when two palmitoylable cysteines at positions 3 and 4 are present. TbFlabarin is more strongly attached to the membrane fraction than its Leishmania counterpart, as it resists complete solubilization with as much as 0.5% NP-40. Expression ablation by RNA interference did not change parasite growth in culture, its morphology or apparent motility. Heterologous expression showed that neither TbFlabarin in L. amazonensis nor LdFlabarin in T. brucei localized to the flagellum, revealing non-cross-reacting targeting signals between the two species

LdFlabarin, a new BAR domain membrane protein of Leishmania flagellum.

International audienceDuring the Leishmania life cycle, the flagellum undergoes successive assembly and disassembly of hundreds of proteins. Understanding these processes necessitates the study of individual components. Here, we investigated LdFlabarin, an uncharacterized L. donovani flagellar protein. The gene is conserved within the Leishmania genus and orthologous genes only exist in the Trypanosoma genus. LdFlabarin associates with the flagellar plasma membrane, extending from the base to the tip of the flagellum as a helicoidal structure. Site-directed mutagenesis, deletions and chimera constructs showed that LdFlabarin flagellar addressing necessitates three determinants: an N-terminal potential acylation site and a central BAR domain for membrane targeting and the C-terminal domain for flagellar specificity. In vitro, the protein spontaneously associates with liposomes, triggering tubule formation, which suggests a structural/morphogenetic function. LdFlabarin is the first characterized Leishmania BAR domain protein, and the first flagellum-specific BAR domain protein

Identification of new components of the basal pole of Toxoplasma gondii provides novel insights into its molecular organization and functions

International audienceThe Toxoplasma gondii tachyzoite is a singled-cell obligate intracellular parasite responsible for the acute phase of toxoplasmosis. This polarized cell exhibits an apical complex, a hallmark of the phylum Apicomplexa, essential for motility, invasion, and egress from the host cell. Located on the opposite end of the cell is the basal complex, an elaborated cytoskeletal structure that also plays critical roles in the lytic cycle of the parasite, being involved in motility, cell division, constriction and cytokinesis, as well as intravacuolar cell-cell communication. Nevertheless, only a few proteins of this structure have been described and functionally assessed. In this study, we used spatial proteomics to identify new basal complex components (BCC), and in situ imaging, including ultrastructure expansion microscopy, to position them. We thus confirmed the localization of nine BCCs out of the 12 selected candidates and assigned them to different sub-compartments of the basal complex, including two new domains located above the basal ring and below the posterior cup. Their functional investigation revealed that none of these BCCs are essential for parasite growth in vitro . However, one BCC is critical for constricting of the basal complex, likely through direct interaction with the class VI myosin heavy chain J (MyoJ), and for gliding motility. Four other BCCs, including a phosphatase and a guanylate-binding protein, are involved in the formation and/or maintenance of the intravacuolar parasite connection, which is required for the rosette organization and synchronicity of cell division