Monday, September 25, 2023 - Thesis defense - Mingshuo XUE

Mingshuo XUE

Team Virology

Thursday, September 25, 2023 - 2:00 pm - Amphithéâtre Colette et Josy Bové - Campus INRAE Villenave d'Ornon

Abstract :

Potyvirus is one of the largest genera of plant RNA viruses responsible for serious diseases in important vegetable and fruit crops. To invade plants, those obligatory parasites have developed tactics to reroute host cellular functions for their own benefits. The completion of the viral cycle results from a complex interplay between virus- and host-encoded factors, also called susceptibility factors. In this scheme, absence or non-adequacy of a single susceptibility factor leads to full or partial resistance to viruses. A detailed analysis of these molecular interactions will provide new susceptibility host factors that can be surveyed for mutations leading to resistance to viruses. In particular, plant viruses utilize their cell-to-cell movement proteins (MPs) to gate plant intercellular connections, the plasmodesmata (PD), and spread between the host cells. Potyviruses exploit both the cellular vesicle trafficking and plasmodesmata (PDs) for their movement in the plants. Besides the involvement of at least five viral proteins, a model for the cell-to-cell transportation of potyviruses still remains very speculative.
The aim of this study is to identify membrane and/or PD proteins that interact with the 6K2 protein, a viral protein involved in the replication and cell-to-cell movement of the turnip mosaic virus (TuMV). A screening approach of a cDNA library of Arabidopsis thaliana using Split Ubiquitin Yeast Two Hybrid (SuY2H) was carried out. An interaction between TuMV 6K2 and AtHVA22a (initially discovered in barley, from the Latin Hordeum vulgare 22a) has been demonstrated. AtHVA22a belongs to a multigene family in Arabidopsis gathering proteins homologous to proteins of the DP1/Yop1 family in yeast and reticulon interactors. The role of HVA22 proteins in plants is not well known although it was shown that AtHVA22a is highly enriched in the Arabidopsis thaliana PD proteome. We confirmed the interaction between 6K2 and AtHVA22a in yeast, as well as in planta using bimolecular fluorescence complementation (BiFC) and showed that the interaction occurs at the level of viral replication complexes (VRCs) during TuMV infection. We showed that TuMV propagation in plants is increased when AtHVA22a is overexpressed but slowed in Arabidopsis CRISPR/Cas9 mutants affected in the C-terminal domain of AtHVA22a. TuMV replication does not appear to be affected in these mutants, suggesting a role of AtHVA22a in TuMV movement. Overall, our results indicate that AtHVA22a plays an agonist effect on TuMV propagation.

Membres du Jury :

Mme GERMAN-RETANA Sylvie, Directeur de recherche, INRAE Directrice de thèse
Mme UZEST Marilyne, Chargée de recherche, INRAE Rapporteur
Mme DESBIEZ Cécile, Chargée de recherche, INRAE Rapporteur
M. GALLOIS Jean-Luc, Directeur de recherche, INRAE Examinateur
M. HERNOULD Michel, Professeur, Université de Bordeaux Examinateur