Functions of PIWI Proteins in Gene Regulation: New Arrows Added to the piRNA Quiver

International audienc

Shaping of Drosophila neural cell lineages through coordination of cell proliferation and cell fate by the BTB-ZF transcription factor Tramtrack-69

International audienceCell diversity in multicellular organisms relies on coordination between cell proliferation and the acquisition of cell identity. The equilibrium between these two processes is essential to assure the correct number of determined cells at a given time at a given place. Using genetic approaches and correlative microscopy, we show that Tramtrack-69 (Ttk69, a Broad-complex, Tramtrack and Bric-à-brac - Zinc Finger (BTB-ZF) transcription factor ortholog of the human promyelocytic leukemia zinc finger factor) plays an essential role in controlling this balance. In the Drosophila bristle cell lineage, which produces the external sensory organs composed by a neuron and accessory cells, we show that ttk69 loss-of-function leads to supplementary neural-type cells at the expense of accessory cells. Our data indicate that Ttk69 (1) promotes cell cycle exit of newborn terminal cells by downregulating CycE, the principal cyclin involved in S-phase entry, and (2) regulates cell-fate acquisition and terminal differentiation, by downregulating the expression of hamlet and upregulating that of Suppressor of Hairless, two transcription factors involved in neural-fate acquisition and accessory cell differentiation, respectively. Thus, Ttk69 plays a central role in shaping neural cell lineages by integrating molecular mechanisms that regulate progenitor cell cycle exit and cell-fate commitment

Modélisation de la cascade de l’azote dans les sites

Modélisation de la cascade de l’azote dans les sites. Séminaire de clôture ANR ESCAPADE " Evaluation de scénarios sur la cascade de l'azote dans les paysages agricoles et modélisation territoriale

The PIWI protein Aubergine recruits eIF3 to activate translation in the germ plasm

International audiencePiwi-interacting RNAs (piRNAs) and PIWI proteins are essential in germ cells to repress transposons and regulate mRNAs. In Drosophila, piRNAs bound to the PIWI protein Aubergine (Aub) are transferred maternally to the embryo and regulate maternal mRNA stability through two opposite roles. They target mRNAs by incomplete base pairing, leading to their destabilization in the soma and stabilization in the germ plasm. Here, we report a function of Aub in translation. Aub is required for translational activation of nanos mRNA, a key determinant of the germ plasm. Aub physically interacts with the poly(A)-binding protein (PABP) and the translation initiation factor eIF3. Polysome gradient profiling reveals the role of Aub at the initiation step of translation. In the germ plasm, PABP and eIF3d assemble in foci that surround Aub-containing germ granules, and Aub acts with eIF3d to promote nanos translation. These results identify translational activation as a new mode of mRNA regulation by Aub, highlighting the versatility of PIWI proteins in mRNA regulation

Théâtre et politique

Tout en s’inscrivant dans le cadre général de la réflexion sur le rapport entre esthétique et éthique dans des pièces de théâtre où est abordé un sujet politique, l’ambition de ce volume est de dépasser une approche qui regarde les œuvres sous l’angle exclusif de l’engagement ou du désengagement. Il fait, à cette fin, le pari de l’ouverture à d’autres périodes et d’autres champs culturels, proposant, en complémentarité, quelques études sur des théâtres politiques de jadis et d’ailleurs. Chemin faisant, les articles soulèvent la question de l’acceptabilité du politique au théâtre. Dans quelle mesure le public est-il prêt à entendre un « sens politique » derrière ce qui se livre parfois comme un innocent divertissement, quelles sont les époques ou les conjonctures où il se montre plus ou moins volontaire pour coopérer à son avènement ? Si les articles ne proposent pas, à proprement parler, d’études culturelles, ou des analyses des mentalités explicitant les raisons pour lesquelles le « politique » entre plus ou moins dans un horizon d’attente donné, ils apportent des informations sur la façon dont les auteurs abordés perçoivent eux-mêmes (et se positionnent par rapport à) cet implicite de la relation théâtrale. Certains travaux décrivent ainsi des stratégies de légitimation des sujets politiques, surtout dans les situations où la contrainte du pouvoir rend l’exercice dangereux. D’autres décryptent la volonté ou le génie de certains auteurs de ne pas être, politiquement, exactement là où le public attend que le texte se place. Tous dessinent un ensemble plus riche en lignes de fuite qu’en lignes de force, ouvrant des champs dans lesquels le lecteur poussera, en fonction de ses intérêts, ses propres explorations

ESCAPADE to quantify nitrogen losses in territories and assess mitigation and adaptation strategies

oral communication, abstractAgriculture is facing to the challenge of maintaining or even increasing production while limiting the use of nitrogen inputs. The introduction of mineral nitrogen in agroecosystems feeds a cascade of processes and losses to the environment at each stage of the cascade with many environmental and societal impacts (degradation of air, water and soil quality, impacts on greenhouse gas balance, biodiversity and human health…). Since classical approaches at plot or farm scale do not make possible to control all impacts, levers must also be sought at larger scales. The overall objective of the interdisciplinary project ESCAPADE (ANR-12-AGRO-0003, 2013-2017) is to build and assess innovative solutions to reduce nitrogen losses in the environment or adapt production systems. It aims at understanding and hierarchizing the processes involved in the nitrogen cascade and nitrogen losses to the environment, as well as integrating them by taking into account spatial and temporal interactions within landscape mosaics. The project mainly focuses on rural sites from a few km2 to a few tens of km2 and also on larger territories from hundreds to thousands of km2. Modelling approaches are associated with inventories and observations to quantify flows of different forms of reactive nitrogen (NO3-, NH3, NOx, N2O…). Agro-environmental scenarios of nitrogen and landscape management in sites and larger territories are co-constructed and assessed from models. Results produced from the models, the observations and inventories, as well as from the scenarios will be used to propose innovative strategies to mitigate nitrogen losses and adapt production systems to the new agricultural contexts