Multigenic Families in Ichnovirus: A Tissue and Host Specificity Study through Expression Analysis of Vankyrins from Hyposoter didymator Ichnovirus

The viral ankyrin (vankyrin) gene family is represented in all polydnavirus (PDVs) genomes and encodes proteins homologous to I-kappaBs, inhibitors of NF-kappaB transcription factors. The structural similarities led to the hypothesis that vankyrins mimic eukaryotic factors to subvert important physiological pathways in the infected host. Here, we identified nine vankyrin genes in the genome of the Hyposoter didymator Ichnovirus (HdIV). Time-course gene expression experiments indicate that all members are expressed throughout parasitism of Spodoptera frugiperda, as assessed using RNA extracted from whole larvae. To study tissue and/or species specificity transcriptions, the expression of HdIV vankyrin genes were compared between HdIV-injected larvae of S. frugiperda and S. littoralis. The transcriptional profiles were similar in the two species, including the largely predominant expression of Hd27-vank1 in all tissues examined. However, in various insect cell lines, the expression patterns of HdIV vankyrins differed according to species. No clear relationship between vankyrin expression patterns and abundance of vankyrin-bearing genomic segments were found in the lepidopteran cell lines. Moreover, in these cells, the amount of vankyrin-bearing genomic segments differed substantially between cytosol and nuclei of infected cells, implying the existence of an unexpected step regulating the copy number of HdIV segments in cell nuclei. Our in vitro results reveal a host-specific transcriptional profile of vankyrins that may be related to the success of parasitism in different hosts. In Spodoptera hosts, the predominant expression of Hd27-vank1 suggests that this protein might have pleiotropic functions during parasitism of these insect species

Modulation of antiviral immunity by the ichnovirus HdIV in Spodoptera frugiperda

Polydnaviruses (PDVs) are obligatory symbionts found in thousands of endoparasitoid species and essential for successful parasitism. The two genera of PDVs, ichnovirus (IV) and bracovirus (BV), use different sets of virulence factors to ensure successful parasitization of the host. Previous studies have shown that PDVs target apoptosis, one of the innate antiviral responses in many host organisms. However, IV and BV have been shown to have opposite effects on this process. BV induces apoptosis in host cells, whereas some IV proteins have been shown to have anti-apoptotic activity. The different biological contexts in which the assays were performed may account for this difference. In this study, we evaluated the interplay between apoptosis and the ichnovirus HdIV from the parasitoid Hyposoter didymator, in the HdIV-infected hemocytes and fat bodies of S. frugiperda larvae, and in the Sf9 insect cell line challenged with HdIV. We found that HdIV induced cell death in hemocytes and fat bodies, whereas anti-apoptotic activity was observed in HdIV-infected Sf9 cells, with and without stimulation with viral PAMPs or chemical inducers. We also used an RT-qPCR approach to determine the expression profiles of a set of genes known to encode key components of the other main antiviral immune pathways described in insects. The analysis of immune gene transcription highlighted differences in antiviral responses to HdIV as a function of host cell type. However, all these antiviral pathways appeared to be neutralized by low levels of expression for the genes encoding the key components of these pathways, in all biological contexts. Finally, we investigated the effect of HdIV on the general antiviral defenses of the lepidopteran larvae in more detail, by studying the survival of S. frugiperda co-infected with HdIV and the entomopathogenic densovirus JcDV. Coinfected S. frugiperda larvae have increased resistance to JcDV at an early phase of infection, whereas HdIV effects enhance the virulence of the virus at later stages of infection. Overall, these results reveal complex interactions between HdIV and its cellular environment

Identification of differentially expressed long non-coding RNAs (lncRNAs) in response to viral infection in S. frugiperda hemocytes

Identification of differentially expressed long non-coding RNAs (lncRNAs) in response to viral infection in [i]S. frugiperda[/i] hemocytes. 10. International Workshop on Molecular Biology and Genetics of the Lepidopter

Genome-wide identification of lncRNAs associated with viral infection in Spodoptera frugiperda

International audienceThe role of lncRNAs in immune defence has been demonstrated in many multicellular and unicellular organisms. However, investigation of the identification and characterization of long non-coding RNAs (lncRNAs) involved in the insect immune response is still limited. In this study, we used RNA sequencing (RNA-seq) to investigate the expression profiles of lncRNAs and mRNAs in the fall armyworm Spodoptera frugiperda in response to virus infection. To assess the tissue- and virus-specificity of lncRNAs, we analysed and compared their expression profiles in haemocytes and fat body of larvae infected with two entomopathogenic viruses with different lifestyles, i.e. the polydnavirus HdIV ( Hyposoter didymator IchnoVirus) and the densovirus JcDV ( Junonia coenia densovirus). We identified 1883 candidate lncRNAs, of which 529 showed differential expression following viral infection. Expression profiles differed considerably between samples, indicating that many differentially expressed (DE) lncRNAs showed virus- and tissue-specific expression patterns. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and target prediction analyses indicated that DE-LncRNAs were mainly enriched in metabolic process, DNA replication and repair, immune response, metabolism of insect hormone and cell adhesion. In addition, we identified three DE-lncRNAs potentially acting as microRNA host genes, suggesting that they participate in gene regulation by producing miRNAs in response to virus infection. This study provides a catalogue of lncRNAs expressed in two important immune tissues and potential insight into their roles in the antiviral defence in S. frugiperda . The results may help future in-depth functional studies to better understand the biological function of lncRNAs in interaction between viruses and the fall armyworm

Mosquitocidal Bacillus sphaericus: Toxins, Genetics, Mode of Action, Use, and Resistance Mechanisms

International audienc

Cloning and characterization of a gut-specific cathepsin L from the aphid Aphis gossypii

International audienc

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