Doctorate thesis of Montpellier University
Thusday, December 10, 2020

at 2 PM –Campus de La Gaillarde- BPMP library room without audience in videoconference.

 Doctorale school : GAIA – Biodiversité, Agriculture, Alimentation, Environnement, Terre, Eau
Spéciality : BIDAP – Biologie, Interactions, Diversité Adaptative des Plantes
Montpellier university

Team: Integration of nutrient signaling pathways
Epigenetic and chromatin regulations controlling nitrate starvation responsive gene expressions in Arabidopsis thaliana

jury :

Antoine MARTIN CR1 BPMP Directeur de thèse
Hervé VAUCHERET Directeur de recherche IJPB Rapporteur
Aline PROBST Directeur de recherche GReD Rapporteur
Cécile RAYNAUD Directeur de recherche IPS2 Examinateur
Andreas NIEBEL Directeur de recherche LIPM Examinateur
Christian DUBOS Directeur de recherche BPMP Examinateur


Epigenetic and chromatin regulations control DNA accessibility for the transcriptional machinery by altering the DNA itself, histones constituting nucleosomes or the density of nucleosome around which the DNA is folded. Chromatin modifications largely influence gene expression levels, and allow the coordination of developmental and environmental responses. Studies from the last decades allowed the discovery and characterization of a large number of these regulations. However, few studies focused on their involvement in metabolic processes. Since nitrogen starvation is an important plant growth limiting factor, this thesis purpose was to unravel chromatin related transcriptional regulations controlling the expression of high affinity root nitrate transporters of the NRT2 family. In the first part, we could show that Polycomb complexes targeting NRT2.1 are preserving expression levels of their transcriptionnaly active target genes. Studying the double mutant clf-29 lhp1-4, in which both PRC1 and PRC2 are impaired, allowed us to assess the redundancy between these two factors et identify, at the genome scale, a new role for Polycomb complexes in the preservation of transcripts integrity. In a second part, we also show that, in N sufficient conditions, two transcription factor and chromatin regulator modules participate to repress NRT2. On one hand, LBD/BRM represses NRT2.1 by increasing its nucleosome density while HDAC/NIGT could be involved in the repression of NRT2.1, NRT2.4 and NRT2.5 by histone acetylation withdrawal. Therefore this work allowed us to shed light on new original mechanisms, based on chromatin dynamic, responsible for the regulation of major genes involved in nitrate responses, and, more broadly, involved in plant metabolism