Doctorant : Xue ZHAO
Équipe : Epigénomique des microalgues et interactions avec l’environnement
Directeur de thèse : Leila TIRICHINE , Directrice de recherche CNRS
Financement : Chinese Scholarship Council (CSC)
Date de la soutenance : mardi 15 décembre 2020, 09h00
Modalité :
  • Lieu : Salle de réunion, bâtiment 25, campus Lombarderie
Jury :
  • Président de jury : Marianne Delarue, Professeure, Université Paris Sud
  • Rapporteur : Célia Barroux, Professeure, Université de Zurich
  • Rapporteur : Jean-Luc Mouget, Professeur, Université du Mans
  • Examinateur : Jean-Marc Celton, Maître de Conférences, Université d'Angers
  • Directeur de thèse : Leila TIRICHINE , Directrice de recherche CNRS

Diatoms are one of the ecologically most successful eukaryotic phytoplankton in the world. They are abundant in a wide range of habitats, their physiology, plasticity and fast adaptation to different environmental conditions help them dominate modern Oceans. Compared to genetic regulation, epigenetic changes can be flexible and reversible and histone modifications are one of the epigenetic mechanisms which can impact gene expression. Phaeodactylum tricornutum (P. tricornutum) is one of the model diatom species, also the first unicellular organism with a full repertoire of post-translational modifications of histones, which makes it an ideal species to study epigenetic regulation in single celled organisms. In this thesis manuscript, I focus on histone modification mechanisms in P. tricornutum, utilize classical reverse genetic method: knockout of candidate genes to identify the catalytic enzyme which is responsible of the deposition of histone modifications. Polycomb group protein (PcG) complexes are evolutionarily conserved epigenetic regulatory components that act antagonistically with Trithorax (TrxG) complexes to regulate genes which are involved in cell differentiation and development. In the first chapter we investigated the diversity of PcG and TrxG genes in marine unicellular species, report the correlation of these epigenetic modifiers and environmental factor for the first time, also emphasise the unique co-occurrence pattern of histone marks in P. tricornutum. Based on those discoveries, further study with chapter two and three focused on two PcG complexes, PRC2 and PRC1. In total, three core components of PcG protein were identified in PRC1 and PRC2 complex respectively, the second part of thesis explored the unique function of PRC2 and its associated mark H3K27me3 which I report related to morphology in P. tricornutum. Chapter three discussed the crosstalk between H3K27me3 and H2AK119Ubi which is deposited by PRC1. The last chapter describes a novel histone modification detected in P. tricornutum was found conserved among eukaryotes. The last chapter reports the characterization of this novel mark and identification of the histone writer.



Zhao, Xue; Rastogi, Achal; Cabanillas, Anne Flore Deton; Mohamed, Ouardia Ait; Cantrel, Catherine; Lombard, Berangère; Murik, Omer; Genovesio, Auguste; Bowler, Chris; Bouyer, Daniel; Loew, Damarys; Lin, Xin; Veluchamy, Alaguraj; Vieira, Fabio Rocha Jimenez; Tirichine, Leila

Genome wide natural variation of H3K27me3 selectively marks genes predicted to be important for cell differentiation in Phaeodactylum tricornutum Article de journal

Dans: New Phytologist, p. nph.17129, 2021, ISSN: 0028-646X.

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Ait-Mohamed, Ouardia; Vanclová, Anna M G Novák; Joli, Nathalie; Liang, Yue; Zhao, Xue; Genovesio, Auguste; Tirichine, Leila; Bowler, Chris; Dorrell, Richard G

PhaeoNet: A Holistic RNAseq-Based Portrait of Transcriptional Coordination in the Model Diatom Phaeodactylum tricornutum Article de journal

Dans: Frontiers in Plant Science, vol. 11, 2020, ISSN: 1664462X.

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Zhao, Xue; Hoguin, Antoine; Chaumier, Timothée; Tirichine, Leila

Epigenetic control of diatom genomes: An overview from in Silico characterisation to functional studies Chapitre d'ouvrage

Dans: The molecular life of diatoms, Springer Nature Switzerland AG, 2020.


Zhao, Xue; Cabanillas, Anne Flore Deton; Veluchamy, Alaguraj; Bowler, Chris; Vieira, Fabio Rocha Jimenez; Tirichine, Leila

Probing the Diversity of Polycomb and Trithorax Proteins in Cultured and Environmentally Sampled Microalgae Article de journal

Dans: Frontiers in Marine Science, vol. 7, p. 189, 2020, ISSN: 2296-7745.

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