Genomic characterization of viruses associated with the parasitoid Anagyrus vladimiri (Hymenoptera: Encyrtidae)
Résumé
Knowledge on symbiotic microorganisms of insects has increased dramatically in recent years, yet relatively little data are available regarding non-pathogenic viruses. Here we studied the virome of the parasitoid wasp Anagyrus vladimiri Triapitsyn (Hymenoptera: Encyrtidae), a biocontrol agent of mealybugs. By high-throughput sequencing of viral nucleic acids, we revealed three novel viruses, belonging to the families Reoviridae [provisionally termed AnvRV (Anagyrus vladimiri reovirus)], Iflaviridae (AnvIFV) and Dicistroviridae (AnvDV). Phylogenetic analysis further classified AnvRV in the genus Idnoreovirus , and AnvDV in the genus Triatovirus . The genome of AnvRV comprises 10 distinct genomic segments ranging in length from 1.5 to 4.2 kb, but only two out of the 10 ORFs have a known function. AnvIFV and AnvDV each have one polypeptide ORF, which is typical of iflaviruses but very un-common among dicistroviruses. Five conserved domains were found along both the ORFs of those two viruses. AnvRV was found to be fixed in an A. vladimiri population that was obtained from a mass rearing facility, whereas its prevalence in field-collected A. vladimiri was ~15 %. Similarly, the prevalence of AnvIFV and AnvDV was much higher in the mass rearing population than in the field population. The presence of AnvDV was positively correlated with the presence of Wolbachia in the same individuals. Transmission electron micrographs of females’ ovaries revealed clusters and viroplasms of reovirus-like particles in follicle cells, suggesting that AnvRV is vertically transmitted from mother to offspring. AnvRV was not detected in the mealybugs, supporting the assumption that this virus is truly associated with the wasps. The possible effects of these viruses on A. vladimiri ’s biology, and on biocontrol agents in general, are discussed. Our findings identify RNA viruses as potentially involved in the multitrophic system of mealybugs, their parasitoids and other members of the holobiont.
Mots clés
biocontrol agent dicistrovirus endosymbiont iflavirus mealybug reovirus virome. Abbreviations: AnvDV
Anagyrus vladimiri dicistrovirus AnvIFV
Anagyrus vladimiri iflavirus AnvRV
Anagyrus vladimiri reovirus dsRNA
double strand RNA IRES
internal ribosome entry site MR
mass rearing ObIRV
Operophtera brumata idnoreovirus ORF
open reading frame PDV
polydnavirus RdRP
RNA-dependent RNA polymerase ssRNA
single strand RNA TEM
transmission electron microscopy UTR
untranslated region VNA
viral nucleic acid
biocontrol agent
dicistrovirus
endosymbiont
iflavirus
mealybug
reovirus
virome. Abbreviations: AnvDV
Anagyrus vladimiri dicistrovirus
AnvIFV
Anagyrus vladimiri iflavirus
AnvRV
Anagyrus vladimiri reovirus
dsRNA
double strand RNA
IRES
internal ribosome entry site
MR
mass rearing
ObIRV
Operophtera brumata idnoreovirus
ORF
open reading frame
PDV
polydnavirus
RdRP
RNA-dependent RNA polymerase
ssRNA
single strand RNA
TEM
transmission electron microscopy
UTR
untranslated region
VNA
biocontrol agent dicistrovirus endosymbiont iflavirus mealybug reovirus virome
virome
Domaines
Biodiversité| Origine | Fichiers produits par l'(les) auteur(s) |
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