Genomic characterization of viruses associated with the parasitoid Anagyrus vladimiri (Hymenoptera: Encyrtidae)

Abstract

The knowledge on symbiotic microorganisms of insects has increased in recent years, yet relatively little data is available on non-pathogenic viruses. Here we studied the virome of the parasitoid wasp Anagyrus vladimiri (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 the AnvRV in the genus Idnoreovirus, and the AnvDV in the genus Triatovirus. The genome of AnvRV is comprised of 10 distinct genomic segments ranging in length from 1.5 to 4.2 Kbp, but only two out of the 10 open reading frames (ORFs) have a known function. AnvIFV and AnvDV each have one polypeptide ORF, which is typical to iflaviruses but very un-common among dicistroviruses. AnvRV was found to be fixed in a mass-reared population of A. vladimiri, whereas it’s prevalence in field-collected wasps was ~15%. Similarly, the prevalence of AnvIFV and AnvDV were much higher in the mass rearing population than in the field population. Transmission electron micrographs of females’ ovaries revealed clusters and viroplasms of Reovirus-like particles in follicle cells. AnvRV was not detected in the mealybugs, suggesting 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 potential players involved in the multitrophic system of mealybugs, their parasitoids and other members of the holobiont.