Establishment and analysis of a reference transcriptome for Spodoptera frugiperda

International audienceBackground Spodoptera frugiperda (Noctuidae) is a major agricultural pest throughout the American continent. The highly polyphagous larvae are frequently devastating crops of importance such as corn, sorghum, cotton and grass. In addition, the Sf9 cell line, widely used in biochemistry for in vitro protein production, is derived from S. frugiperda tissues. Many research groups are using S. frugiperda as a model organism to investigate questions such as plant adaptation, pest behavior or resistance to pesticides.ResultsIn this study, we constructed a reference transcriptome assembly (Sf_TR2012b) of RNA sequences obtained from more than 35 S. frugiperda developmental time-points and tissue samples. We assessed the quality of this reference transcriptome by annotating a ubiquitous gene family - ribosomal proteins - as well as gene families that have a more constrained spatio-temporal expression and are involved in development, immunity and olfaction. We also provide a time-course of expression that we used to characterize the transcriptional regulation of the gene families studied.ConclusionWe conclude that the Sf_TR2012b transcriptome is a valid reference transcriptome. While its reliability decreases for the detection and annotation of genes under strong transcriptional constraint we still recover a fair percentage of tissue-specific transcripts. That allowed us to explore the spatial and temporal expression of genes and to observe that some olfactory receptors are expressed in antennae and palps but also in other non related tissues such as fat bodies. Similarly, we observed an interesting interplay of gene families involved in immunity between fat bodies and antennae

Sendai virus particle production: basic requirements and role of the SYWST motif present in HN cytoplasmic tail

Sendai virus (SeV) HN protein is dispensable for virus particle production. HN incorporation into virions strictly depends on a cytoplasmic domain SYWST motif. HNAFYKD, with SYWST replaced with the analogous sequence of measles virus (MeV) H (AFYKD), is not incorporated in virus particles produced by LLCMK2 cells, although it is normally expressed at the plasma membrane. Unlike HNSYWST, HNAFYKD is not internalized to late endosomes, raising the possibility that HN internalization is required for uptake into virus particles. Various mosaic MeV-H containing increasing amounts of the SeV-HN all failed to be taken up in SeV virions. However, when co-expressed with HNAFYKD these MeV-H chimera induced HNAFYKD uptake into virions showing that internalization is not a prerequisite for HN uptake into particles. We propose that HN incorporation in virus particles requires first neutralization by HN of a putative inhibitor of infectious particle formation

Réponse immunitaire de Spodoptera frugiperda (Lepidoptera: Noctuidae) à l'infection par différents organismes entomopathogènes

Spodoptera frugiperda est un lépidoptère ravageur de culture dont la chenille dévore principalement les grandes cultures de maïs. Dans le cadre de la lutte biologique contre ces ravageurs, plusieurs microorganismes pathogènes peuvent être utilisés comme alternative aux pesticides. Le laboratoire DGIMI étudie trois pathogènes capables de tuer les chenilles de Spodoptera. Le complexe némato-bactérien (CNB) Steinernema carpocapsae/Xenorhabdus nematophila est capable de pénétrer dans l'hémolymphe des insectes qu'il contamine de ses bactéries symbiotiques, tuant l'insecte en quelques heures. La guêpe parasitoïde Hyposoter didymator, pour se reproduire, pond un oeuf dans une chenille. Elle co-injecte à ce moment-là un virus (HdIV) dont le génome est intégré au sien et qui est nécessaire au succès parasitaire de la guêpe, notamment en abolissant la réponse immunitaire de la chenille. Finalement, le virus JcDV est un petit virus à ADN spécifique d'insecte qui, lorsqu'il est ingéré par la chenille, traverse la barrière intestinale pour infecter ses tissus cibles et provoquer la mort de l'insecte. Dans ces trois modèles d'infection, nous avons étudié par RNA-seq la réponse transcriptionnelle tissu-spécifique de la chenille face à ses pathogènes, en regardant particulièrement les gènes de l'immunité. Nous avons vu que la chenille est capable de déployer l'ensemble de son arsenal anti-microbien en réponse au CNB ainsi qu'au HdIV, mais pas contre le virus JcDV qui semble passer inaperçu. Cette étude nous a permis de décrire les spécificités du système immunitaire lépidoptère face à différents micro-organismes ainsi que de découvrir de nouveaux peptides anti-microbiens acquis par transfert horizontal de gènes

How pathogenic bacteria and viruses defeat the immune defenses of their Lepidoptera host

How pathogenic bacteria and viruses defeat the immune defenses of their [i]Lepidoptera[/i] host. MicrobiOccitanie 2019- Rencontre des Microbiologistes Région Occitani

The cellular protein TIP47 restricts Respirovirus multiplication leading to decreased virus particle production

International audienc

Can Virus-like Particles Be Used as Synergistic Agent in Pest Management?

Among novel strategies proposed in pest management, synergistic agents are used to improve insecticide efficacy through an elevation of intracellular calcium concentration that activates the calcium-dependent intracellular pathway. This leads to a changed target site conformation and to increased sensitivity to insecticides while reducing their concentrations. Because virus-like particles (VLPs) increase the intracellular calcium concentration, they can be used as a synergistic agent to synergize the effect of insecticides. VLPs are self-assembled viral protein complexes, and by contrast to entomopathogen viruses, they are devoid of genetic material, which makes them non-infectious and safer than viruses. Although VLPs are well-known to be used in human health, we propose in this study the development of a promising strategy based on the use of VLPs as synergistic agents in pest management. This will lead to increased insecticides efficacy while reducing their concentrations

Sendai virus budding in the course of an infection does not require Alix and VPS4A host factors

Closing the Sendai virus C protein open reading frames (rSeV-DeltaC virus) results in the production of virus particles with highly reduced infectivity. Besides, the Sendai virus C proteins interact with Alix/AIP1 and Alix suppression negatively affects Sendai virus like particle (VLP) budding. Similarly, the Sendai virus M protein has been shown to interact with Alix. On this basis, it has been suggested that Sendai virus budding involves recruitment of the multivesicular body formation machinery. We follow, here, the production of SeV particles upon regular virus infection. We find that neither Alix suppression nor dominant negative-VPS4A expression, applied separately or in combination, affects physical or infectious virion production. This contrasts with the observed decrease of SV5 virion production upon dominant negative-VPS4A expression. Finally, we show that suppression of more than 70% of a GFP/C protein in the background of a rSeV-DeltaC virus infection has no effect either on SeV particle production or on virus particle infectivity. Our results contrast with what has been published before. Possible explanations for this discrepancy are discussed

Virus et chercheurs sous le soleil de Montpellier

International audienceLes 26 et 27 avril 2021, Montpellier devait accueillir la communauté des virologistes francophones, en hébergeant pour la première fois les « Journées Francophones de Virologie » (JFV). Tout était prêt : les salles, les panneaux pour les posters, les buffets, le vestiaire, le café… et la banderole JFV 2021 devait se dresser fièrement à l’entrée de la Faculté des Science

Paternal transmission of the Wolbachia CidB toxin underlies cytoplasmic incompatibility

International audienceWolbachia are widespread endosymbiotic bacteria that manipulate the reproduction of arthropods through a diversity of cellular mechanisms. In cytoplasmic incompatibility (CI), a sterility syndrome originally discovered in the mosquito Culex pipiens, uninfected eggs fertilized by sperm from infected males are selectively killed during embryo development following the abortive segregation of paternal chromosomes in the zygote. Despite the recent discovery of Wolbachia CI factor (cif) genes, the mechanism by which they control the fate of paternal chromosomes at fertilization remains unknown. Here, we have analyzed the cytological distribution and cellular impact of CidA and CidB, a pair of Cif proteins from the Culex-infecting Wolbachia strain wPip. We show that expression of CidB in Drosophila S2R+ cells induces apoptosis unless CidA is co-expressed and associated with its partner. In transgenic Drosophila testes, both effectors colocalize in germ cells until the histone-to-protamine transition in which only CidB is retained in maturing spermatid nuclei. We further show that CidB is similarly targeted to maturing sperm of naturally infected Culex mosquitoes. At fertilization, CidB associates with paternal DNA regions exhibiting DNA replication stress, as a likely cause of incomplete replication of paternal chromosomes at the onset of the first mitosis. Importantly, we demonstrate that inactivation of the deubiquitylase activity of CidB does not abolish its cell toxicity or its ability to induce CI in Drosophila. Our study thus demonstrates that CI functions as a transgenerational toxin-antidote system and suggests that CidB acts by poisoning paternal DNA replication in incompatible crosses

Les densovirus : une « massive attaque » chez les arthropodes

Densoviruses (DVs) are parvoviruses of arthropods and causative agents of natural epizootics in insects and crustaceans populations. Structurally simple, these small DNA viruses, display a large diversity of genomic sequences, structures and organizations. Such diversity, together with the diversity of their invertebrate hosts, from shrimps to mosquitoes and recently including sea stars, suggests that DVs are largely unknown and ubiquitous in the environment. Densoviruses are considered as a model of choice to study virus-host interactions and their evolution at different scales, from individuals to populations. This review summarizes the knowledge on densovirus biology obtained through mechanistic and global approaches. Finally, the potential use of these viruses as biological control agents against insect pests and disease-vectors are exposed.Les densovirus (DV) sont des parvovirus d’arthropodes responsables d’épizooties chez les insectes et les crustacés. Structurellement simples, ces petits virus à ADN présentent une grande diversité de séquences et d’organisations génomiques, diversité probablement sous-estimée au regard des récentes découvertes de ces virus dans des hôtes inattendus. Les densovirus représentent un modèle de choix pour étudier à différentes échelles les interactions virus-hôtes et leurs évolutions. Nous proposons de revisiter les connaissances fondamentales sur les densovirus qui ont essentiellement été établies par des approches mécanistiques et envisageons les nouvelles perspectives d’études permises par des approches plus globales. Pour conclure, nous décrivons les applications possibles de ces virus comme outils biologiques, notamment pour le contrôle de populations d’insectes dits « nuisibles »