Pathogenesis of Junonia coenia densovirus in Spodoptera frugiperda: A route of infection that leads to hypoxia

AbstractTo evaluate densovirus potential against lepidopteran pests and their capacity to invade new hosts, we have characterised in vivo the infection and pathogenesis of the Junonia coenia densovirus (JcDNV) in the noctuid pest Spodoptera frugiperda. Here we show that infection starts with the ingestion of viral particles that cross the midgut epithelium without replicating. By quantitative PCR we established the kinetic and the route of infection, from virus ingestion to replication in visceral tracheae and hemocytes. JcDNV has a high particle-to-infection ratio mostly due to the barrier function of the midgut. Pathology and cytopathology suggested that infection of tracheal cells impairs oxygen delivery to demanding tissues leading to cytopathic effects in all the tissues. Finally, larval death results from several physiological shocks, including molting arrest and anoxia

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

Determination and characterization of bovine interleukin-17 cDNA

International audienceInterleukin-17 (IL-17) is a proinflammatory cytokine produced by activated memory T cells, and it appears to play an upstream role in T cell-triggered inflammation by stimulating stromal cells to secrete other cytokines. We hypothesize that IL-17 plays a role in the recruitment of neutrophils in the bovine mammary gland during infection or immune-mediated inflammation. The rapid amplification of cDNA ends (RACE) method was used to obtain a cDNA of bovine IL-17 (BoIL-17) containing a 462-bp open reading frame (ORF) encoding a protein of 153 amino acids (aa) with a molecular mass of 17.2 kDa, a 23-residue NH2-terminal signal peptide, a single potential N-linked glycosylation site, and 6 cysteine residues. BoIL-17 protein shared 73.5% identity with the human protein and 67% with the mouse and rat proteins. Sf9 insect cells were transfected with BoIL-17 cDNA, and supernatant was tested for biologic activity on a primary culture of bovine mammary epithelial cells (MECs). mRNA synthesis of IL-6, IL-8, and growth-related oncogene alpha (Gro alpha) was induced, suggesting a functional role for IL-17 in mammary immunity

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 »

A New Prevalent Densovirus Discovered in Acari. Insight from Metagenomics in Viral Communities Associated with Two-Spotted Mite (Tetranychus urticae) Populations: Metagenomics in Viral Communities Associated with Two-Spotted Mite (Tetranychus urticae) Populations

Viral metagenomics and high throughput sequence mining have revealed unexpected diversity, and the potential presence, of parvoviruses in animals from all phyla. Among arthropods, this diversity highlights the poor knowledge that we have regarding the evolutionary history of densoviruses. The aim of this study was to explore densovirus diversity in a small arthropod pest belonging to Acari, the two-spotted spider mite Tetranychus urticae, while using viral metagenomics based on virus-enrichment. Here, we present the viromes obtained from T. urticae laboratory populations made of contigs that are attributed to nine new potential viral species, including the complete sequence of a novel densovirus. The genome of this densovirus has an ambisens genomic organization and an unusually compact size with particularly small non-structural proteins and a predicted major capsid protein that lacks the typical PLA2 motif that is common to all ambidensoviruses described so far. In addition, we showed that this new densovirus had a wide prevalence across populations of mite species tested and a genomic diversity that likely correlates with the host phylogeny. In particular, we observed a low densovirus genomic diversity between the laboratory and natural populations, which suggests that virus within-species evolution is probably slower than initially thought. Lastly, we showed that this novel densovirus can be inoculated to the host plant following feeding by infected mites, and circulate through the plant vascular system.These findings offer new insights into densovirus prevalence, evolution, and ecology