Comparison of two Phaeodactylum tricornutum ecotypes under nitrogen starvation and resupply reveals distinct lipid accumulation strategies but a common degradation process

IntroductionPhaeodactylum tricornutum is a model species frequently used to study lipid metabolism in diatoms. When exposed to a nutrient limitation or starvation, diatoms are known to accumulate neutral lipids in cytoplasmic lipid droplets (LDs). Those lipids are produced partly de novo and partly from the recycle of plastid membrane lipids. Under a nitrogen resupply, the accumulated lipids are catabolized, a phenomenon about which only a few data are available. Various strains of P. tricornutum have been isolated around the world that may differ in lipid accumulation patterns.MethodsTo get further information on this topic, two genetically distant ecotypes of P. tricornutum (Pt1 and Pt4) have been cultivated under nitrogen deprivation during 11 days followed by a resupply period of 3 days. The importance of cytoplasmic LDs relative to the plastid was assessed by a combination of confocal laser scanning microscopy and cell volume estimation using bright field microscopy pictures.Results and discussionWe observed that in addition to a basal population of small LDs (0.005 μm3 to 0.7 μm3) present in both strains all along the experiment, Pt4 cells immediately produced two large LDs (up to 12 μm3 after 11 days) while Pt1 cells progressively produced a higher number of smaller LDs (up to 7 μm3 after 11 days). In this work we showed that, in addition to intracellular available space, lipid accumulation may be limited by the pre-starvation size of the plastid as a source of membrane lipids to be recycled. After resupplying nitrogen and for both ecotypes, a fragmentation of the largest LDs was observed as well as a possible migration of LDs to the vacuoles that would suggest an autophagic degradation. Altogether, our results deepen the understanding of LDs dynamics and open research avenues for a better knowledge of lipid degradation in diatoms

Production of HIV Particles Is Regulated by Altering Sub-Cellular Localization and Dynamics of Rev Induced by Double-Strand RNA Binding Protein

Human immunodeficiency virus (HIV)-1 encoded Rev is essential for export from the nucleus to the cytoplasm, of unspliced and singly spliced transcripts coding for structural and nonstructural viral proteins. This process is spatially and temporally coordinated resulting from the interactions between cellular and viral proteins. Here we examined the effects of the sub-cellular localization and dynamics of Rev on the efficiency of nucleocytoplasmic transport of HIV-1 Gag transcripts and virus particle production. Using confocal microscopy and fluorescence recovery after bleaching (FRAP), we report that NF90ctv, a cellular protein involved in Rev function, alters both the sub-cellular localization and dynamics of Rev in vivo, which drastically affects the accumulation of the viral protein p24. The CRM1–dependent nuclear export of Gag mRNA linked to the Rev Response Element (RRE) is dependent on specific domains of the NF90ctv protein. Taken together, our results demonstrate that the appropriate intracellular localization and dynamics of Rev could regulate Gag assembly and HIV-1 replication

Observer des plantes à différentes longueurs d’onde pour mieux étudier les maladies transmises par les sols

https://theconversation.com/observer-des-plantes-a-differentes-longueurs-donde-pour-mieux-etudier-les-maladies-transmises-par-les-sols-18657

Repenser l’agriculture dans l’enseignement supérieur : Le Campus Comestible d’UniLaSalle

International audienceLe projet Campus Comestible d’UniLaSalle vise à créer un espace d'apprentissage dédié à l'agriculture urbaine. Initialement motivé par le manque d'espaces agricoles sur le campus de Mont-Saint-Aignan, ce projet a été initié par des étudiants en quatrième année du cycle ingénieur d'UniLaSalle. L'objectif était de concevoir et mettre en place un jardin potager collectif, participatif et respectueux de l'environnement sur une superficie de 100 m2. Ce projet présente des avantages alimentaires, environnementaux (favorisant des services écosystémiques), sociaux (création de liens, lieu de détente) et éducatifs (expérimentations de substrats, associations de cultures, etc.).La conception du projet impliquait la subdivision de l'espace en quatre parties égales dédiées à différentes cultures. Les aménagements incluent des bacs de culture en lasagne, des abris d'insectes, des bacs d'expérimentation de substrats, des buttes permacoles et des zones de cultures sous abris pour les jeunes plants. Une zone est réservée aux grandes cultures, servant de démonstration des stades repères de la végétation de céréales telles que le blé, l'orge et le sarrasin. Le respect de l'environnement (recyclage des matériaux, compost) et de la biodiversité locale (notamment autour de la mare déjà présente) ont guidé la mise en œuvre du projet.Aujourd'hui, cet espace est devenu un lieu d'apprentissage des bases du métier d'agriculteur, mobilisant une communauté d'élèves-ingénieurs en agronomie et agro-industrie conscients des impacts de la production alimentaire sur l'environnement. Pour UniLaSalle, le projet Campus Comestible répond à un besoin réel en enrichissant la formation des jeunes sur les techniques alternatives de production alimentaire. La collaboration avec les cocottes urbaines, impliquées dès les phases de conception jusqu'à l'exécution technique, s'inscrit dans le cadre de l'économie de fonctionnalité.Au-delà de l'éducation, le projet devient un outil de communication pour UniLaSalle en sensibilisant les acteurs de l'écosystème territorial aux enjeux de l'agriculture urbaine, contribuant ainsi à une meilleure prise en charge de ces projets à l'échelle du territoire

Daclatasvir Prevents Hepatitis C Virus Infectivity by Blocking Transfer of Viral Genome to Assembly Sites.

International audienceDaclatasvir is a direct-acting antiviral agent and potent inhibitor of NS5A, which is involved in replication of the hepatitis C virus (HCV) genome, presumably via membranous web shaping, and assembly of new virions, likely via transfer of the HCV RNA genome to viral particle assembly sites. Daclatasvir inhibits the formation of new membranous web structures and, ultimately, of replication complex vesicles, but also inhibits an early assembly step. We investigated the relationship between daclatasvir-induced clustering of HCV proteins, intracellular localization of viral RNAs and inhibition of viral particle assembly.HCVcc particles were produced from Huh7.5 hepatocarcinoma cells in presence of daclatasvir for short time periods. Infectivity as well as production of physical particles were quantified and producer cells were subjected to subcellular fractionation. Intracellular colocalization between core, E2, NS5A, NS4B proteins, and viral RNAs was quantitatively analyzed by confocal microscopy and by structured illumination microscopy.Short exposure of HCV-infected cells to daclatasvir reduced viral assembly and induced clustering of structural proteins with non-structural HCV proteins, including core, E2, NS4B and NS5A. These clustered structures appeared to be inactive assembly platforms, likely owing to loss of functional connection with replication complexes. Daclatasvir greatly reduced delivery of viral genomes to these core clusters without altering HCV RNA colocalization with NS5A. In contrast, daclatasvir neither induced clustered structures nor inhibited HCV assembly in cells infected with a daclatasvir-resistant mutant (NS5A-Y93H), indicating that daclatasvir targets a mutual, specific function of NS5A inhibiting both processes.In addition to inhibiting replication complex biogenesis, daclatasvir prevents viral assembly by blocking transfer of the viral genome to assembly sites. This leads to clustering of HCV proteins, because viral particles and replication complex vesicles cannot form and/or egress. This dual mode of action of daclatasvir could explain its efficacy in blocking HCV replication in cultured cells and in treatment of patients with HCV infection