Manipulation de protéines à bromodomaine d'Arabidopsis par une acetyltransférase de la famille YopJ de chez Ralstonia solanacearum
Notice bibliographique
Résumé
Epigenetic mechanisms contribute to the regulation of gene expression without changing its sequence by influencing the chromatin structure. Increasing evidence reveal that pathogens display virulence strategies that can interfere with host epigenetic mechanisms. This is particularly well described in animal pathogens but less in plant pathogens. Especially, very few evidence relate such virulence strategies used by plant pathogenic bacteria. Ralstonia solanacearum is the causal agent of the bacterial wilt disease, which can affect more than 250 plant species including major crops and model plants such as Arabidopsis thaliana. As a potent R. solanacearum virulence factor, PopP2 is an acetyltransferase from the YopJ family that dampens basal immune responses by targeting defensive WRKY transcription factors. In order to better understand the virulence activities of PopP2, we searched for PopP2-interacting proteins using a yeast two hybrid assay, and identified the GTE9 and GTE11 proteins from the GTE family (General Transcription factor, group E). GTE proteins possess a bromodomain, a specific protein module allowing interaction with acetylated lysine residues, notably on histones tails suggesting that they could be involved in epigenetic-related processes. GTE9 and GTE11 were previously shown to (i) co-localise and interact with PopP2 in the plant nucleus, and (ii) to be acetylated by PopP2. Also, GTE9 and GTE11 were shown to interact in planta with Histone H4 through their bromodomain, suggesting that they function as epigenetic readers whose manipulation by PopP2 would promote R. solanacearum virulence. In this context, the main objectives of my PhD were to better understand the the function of GTE9 and GTE11, by trying to determine how they can be manipulated by PopP2 and whether these proteins play a role in the plant response to R. solanacearum. Mass-spectrometry-based analysis enabled us to map the lysine residues modified by PopP2 in GTE9 and GTE11. Several of these residues are conserved between the two proteins and localised on either side of their bromodomain. By semi-quantitative FRET-FLIM assay performed in vivo, we demonstrated that GTE9 interaction with Histone H4 is altered by PopP2 acetyltransferase activity suggesting that PopP2 uses acetylation to dissociate GTE9 from chromatin. In addition to GTE9 and GTE11, PopP2 acetylates several other GTE members. Regarding the role of GTE9 and GTE11 in the plant response to R. solanacearum, GTE9 and GTE11 over-expressing lines displayed an enhanced disease response to R. solanacearum that depended on PopP2 enzymatic activity. Overall, these data indicate that GTE9 and GTE11 behave as epigenetic readers that are manipulated by a plant bacterial pathogen through their targeting by a YopJ family acetyltransferase. GTE proteins could represent key virulence targets for R. solanacearum since PopP1, an additional YopJ family acetyltransferase that belongs to its effector repertoire, also interacts with several of these proteins. How the targeting of GTE proteins is mechanistically impacting the overall course of R. solanacearum infection remains elusive. To answer this question, we undertook a ChIP-seq analysis aimed at identifying the chromatin regions targeted by GTE9 and GTE11 (approach in progress). In addition to this approach, we wanted to identify more globally the chromatin sites visited by PopP2 in Arabidopsis. For this, we have initiated a second ChIP-seq analysis using various molecular tools including tagged versions of PopP2 for in planta delivery through a bacterial type III secretion system. Overall, this PhD work allows to progress on the understanding of a virulence strategy used by a plant bacterial pathogen that consist in manipulating host epigenetic components to promote infection.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».