Séminaire IBIP
Les séminaires ont lieu sur le Campus Montpellier SupAgro/INRA de La Gaillarde (2, place P. Viala Montpellier)

Jeudi 20 juin 2013
Salle 204 (Château) à 14h

Mechanisms of transcriptional gene silencing and heterochromatin formation in Arabidopsis thaliana: roles of the RNA-directed DNA methylation (RdDM) pathway and more surprises!

Thierry Lagrange
Laboratoire Génome et Développement des Plantes – Perpignan

Heterochromatin, whose formation requires conserved pathways of histone and DNA modifications, participates in numerous nuclear processes, including centromere function, gene silencing and nuclear organization. An important recent breakthrough was the discovery that the RNA-interference pathway (RNAi) is implicated in heterochromatin assembly and transcriptional gene silencing (TGS) in eukaryotes. Indeed, mutations affecting various RNAi components, including Argonaute proteins, have been shown to impair heterochromatin assembly and TGS at repeated sequences in fungi and plants. Moreover, numerous short-interfering RNAs have been identified that correspond to these sequences, suggesting that siRNAs are responsible for targeting heterochromatin modification to specific genomic locations. Recent studies performed in plants have added another level of complexity to this pathway by showing the existence of plant-specific homologs of DNA-dependent RNA polymerase II, PolIV and PolV, that mediate siRNA accumulation and DNA methylation-dependent silencing of endogenous repeated sequences. Recent results concerning the function of these novel polymerases in the pathway of RNA-directed DNA methylation in Arabidopsis will be presented.

Contact : Laurence Lejay-Lefèbvre

Contacts IBIP :
Sabine Zimmermann
Philippe Nacry
Christine Granier
Chantal Baracco