HVA22a, une protéine de plante homologue aux protéines de courbure du réticulum endoplasmique, est impliquée dans la propagation des potyvirus

Le potyvirus est l'un des plus grands genres de virus à ARN de plantes responsables de maladies graves dans d'importantes cultures maraîchères et fruitières. La réussite de l’infection de ces virus, repose sur une succession d’interactions étroites entre protéines virales et de l’hôte, l’absence ou la mutation d’un facteur essentiel au virus pouvant entraîner une résistance de la plante. Connaître les mécanismes qui gouvernent ces interactions permet donc d’identifier de nouvelles sources de résistance. Lors du mouvement dans la plante, les potyvirus exploitent le trafic vésiculaire cellulaire et les plasmodesmes (PD) en produisant des protéines de mouvement capables de modifier les PD et permettre le passage du génome viral. Pour les potyvirus, les mécanismes impliqués dans cette étape du cycle viral sont très peu connus. Le but de cette étude est d'identifier les protéines membranaires et/ou de PD qui interagissent avec la protéine 6K2, une protéine virale impliquée dans la réplication et le passage de cellule à cellule du virus de la mosaïque du navet (TuMV). Une approche de criblage d’une banque d’ADNc d’Arabidopsis thaliana en Split Ubiquitine double hybride (SuY2H) chez la levure a été menée. Une interaction entre la 6K2 du TuMV et la protéine AtHVA22a (initialement découverte chez l’orge, du latin Hordeum vulgare 22a) a été mise en évidence. AtHVA22a appartient à une famille multigénique chez Arabidopsis rassemblant des protéines homologues aux protéines de la famille DP1/Yop1 chez la levure et les interacteurs des réticulons. Le rôle des protéines HVA22 chez les plantes est très peu connu. Il a de plus été montré qu’AtHVA22a est très fortement enrichie dans le protéome des PD d’Arabidopsis thaliana. Nous avons confirmé l'interaction entre 6K2 et AtHVA22a chez la levure, ainsi qu'in planta en utilisant la complémentation de fluorescence bimoléculaire (BiFC) et montré que l'interaction se produit au niveau des complexes de réplication virale (VRC) lors de l'infection par le TuMV. Nous avons montré que la propagation du TuMV dans les plantes est augmentée lorsque AtHVA22a est surexprimé mais ralentie dans des mutants CRISPR-Cas9 affectés dans le domaine C-terminal d’AtHVA22a. La réplication du TuMV ne semble pas affectée dans ces mutants, suggérant un rôle d’AtHVA22a dans le mouvement du TuMV. Dans l'ensemble, nos résultats indiquent que AtHVA22a joue un effet agoniste sur la propagation du TuMV.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

The mystery remains: How do potyviruses move within and between cells?

Abstract The genus Potyvirus is considered as the largest among plant single‐stranded (positive‐sense) RNA viruses, causing considerable economic damage to vegetable and fruit crops worldwide. Through the coordinated action of four viral proteins and a few identified host factors, potyviruses exploit the endomembrane system of infected cells for their replication and for their intra‐ and intercellular movement to and through plasmodesmata (PDs). Although a significant amount of data concerning potyvirus movement has been published, no synthetic review compiling and integrating all information relevant to our current understanding of potyvirus transport is available. In this review, we highlight the complexity of potyvirus movement pathways and present three potential nonexclusive mechanisms based on (1) the use of the host endomembrane system to produce membranous replication vesicles that are targeted to PDs and move from cell to cell, (2) the movement of extracellular viral vesicles in the apoplasm, and (3) the transport of virion particles or ribonucleoprotein complexes through PDs. We also present and discuss experimental data supporting these different models as well as the aspects that still remain mostly speculative.Facteurs cellulaires recrutés par les potyvirus pour leur transport intercellulaire : de nouvelles sources de résistance des plantes

Downlink MIMO-NOMA System for 6G Internet of Things

This paper proposes a system of 6G Internet of Things (IoT) based on downlink non-orthogonal multiple access (NOMA) technology, where the base station (BS) allows signals of the same frequency to serve users at different distances. In particular, we study a cooperative MIMO-NOMA system based on downlink simultaneous wireless information and power transfer (SWIPT) assistance. To improve the overall performance, we employ machine learning to optimize user-pairing and radio resource allocation. At the end of the paper, the simulation results are obtained, which fully prove that the MIMO-NOMA system constructed in this paper is correct in theory and can be realized in practice

Plasmodesmal Components Involved in Cell-to-cell Transport of Potyviruses---Focus on HVA22a candidate

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HVA22a and HVA22c, two candidate proteins involved in potyvirus replication and movement

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AtHVA22a, a plant-specific homologue of Reep/DP1/Yop1 family proteins is involved in turnip mosaic virus propagation

The movement of potyviruses, the largest genus of single-stranded, positive-sense RNA viruses responsible for serious diseases in crops, is very complex. As potyviruses developed strategies to hijack the host secretory pathway and plasmodesmata (PD) for their transport, the goal of this study was to identify membrane and/or PD-proteins that interact with the 6K2 protein, a potyviral protein involved in replication and cell-to-cell movement of turnip mosaic virus (TuMV). Using split-ubiquitin membrane yeast two-hybrid assays, we screened an Arabidopsis cDNA library for interactors of TuMV6K2. We isolated AtHVA22a (Hordeum vulgare abscisic acid responsive gene 22), which belongs to a multigenic family of transmembrane proteins, homologous to Receptor expression-enhancing protein (Reep)/Deleted in polyposis (DP1)/Yop1 family proteins in animal and yeast. HVA22/DP1/Yop1 family genes are widely distributed in eukaryotes, but the role of HVA22 proteins in plants is still not well known, although proteomics analysis of PD fractions purified from Arabidopsis suspension cells showed that AtHVA22a is highly enriched in a PD proteome. We confirmed the interaction between TuMV6K2 and AtHVA22a in yeast, as well as in planta by using bimolecular fluorescence complementation and showed that TuMV6K2/AtHVA22a interaction occurs at the level of the viral replication compartment during TuMV infection. Finally, we showed that the propagation of TuMV is increased when AtHVA22a is overexpressed in planta but slowed down upon mutagenesis of AtHVA22a by CRISPR-Cas9. Altogether, our results indicate that AtHVA22a plays an agonistic effect on TuMV propagation and that the C-terminal tail of the protein is important in this process.</p