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Bracoviruses (BVs) are domesticated viruses found in braconid parasitoid wasp genomes. They are composed of domesticated genes from a nudivrius, coding viral particles in which wasp DNA circles are packaged. BVs are viewed as possible vectors of horizontal transfer of genetic material (HT) from wasp to their hosts because they are injected, together with wasp eggs, by female wasps into their host larvae, and because they undergo massive chromosomal integration in multiple host tissues. Here, we show that chromosomal integrations of the Cotesia typhae BV (CtBV) persist up to the adult stage in individuals of its natural host, Sesamia nonagrioides, that survived parasitism. However, while reproducing host adults can bear an average of nearly two CtBV integrations per haploid genome, we were unable to retrieve any of these integrations in 500 of their offspring using Illumina sequencing. This suggests either that host gametes are less targeted by CtBVs than somatic cells or that gametes bearing BV integrations are nonfunctional. We further show that CtBV can massively integrate into the chromosomes of other lepidopteran species that are not normally targeted by the wasp in the wild, including one which is divergent by at least 100 million years from the natural host. Cell entry and chromosomal integration of BVs are thus unlikely to be major factors shaping wasp host range. Together, our results shed new light on the conditions under which BV-mediated wasp-to-host HT may occur and provide information that may be helpful to evaluate the potential risks of uncontrolled HT associated with the use of parasitoid wasps as biocontrol agents., (© 2022 John Wiley & Sons Ltd.)

The Mediterranean corn borer (Sesamia nonagrioides, Noctuidae, Lepidoptera) is a major pest of maize in Europe and Africa. Here, we report an assembly of the nuclear and mitochondrial genome of a pool of inbred males and females third-instar larvae, based on short- and long-read sequencing. The complete mitochondrial genome is 15,330 bp and contains all expected 13 and 24 protein-coding and RNA genes, respectively. The nuclear assembly is 1021 Mb, composed of 2553 scaffolds and it has an N50 of 1105 kb. It is more than twice larger than that of all Noctuidae species sequenced to date, mainly due to a higher repeat content. A total of 17,230 protein-coding genes were predicted, including 15,776 with InterPro domains. We provide detailed annotation of genes involved in sex determination (doublesex, insulin-like growth factor 2 mRNA-binding protein, and P-element somatic inhibitor) and of alpha-amylase genes possibly involved in interaction with parasitoid wasps. We found no evidence of recent horizontal transfer of bracovirus genes from parasitoid wasps. These genome assemblies provide a solid molecular basis to study insect genome evolution and to further develop biocontrol strategies against S. nonagrioides., (© The Author(s) 2021. Published by Oxford University Press on behalf of Genetics Society of America.)

For successful parasitization, parasitiods usually depend on the chemosensory cues for the selection of hosts, as well as a variety of virulence factors introduced into their hosts to overcome host immunity and prevent rejection of progeny development. In bracovirus-carrying wasps, the symbiotic polydnaviruses act in manipulating development and immunity of hosts. The endoparasitoid Cotesia chilonis carrying bracovirus as a key host immunosuppressive factor is a superior endoparasitoid of rice stem borer, Chilo suppressalis. So far, genomic information for C. chilonis is not available and transcriptomic data may provide valuable resources for global studying on physiological processes of C. chilonis, including chemosensation and parasitism at molecular level. Here, we performed RNA-seq to characterize the transcriptome of C. chilonis adults. We obtained 27,717,892 reads, assembled into 38,318 unigenes with a mean size of 690 bp. Approximately, 62.1% of the unigenes were annotated using NCBI databases. A large number of chemoreception-related genes encoding proteins including odorant receptors, gustatory receptors, odorant-binding proteins, chemosensory proteins, transient receptor potential ion channels, and sensory neuron membrane proteins were identified in silico. Totally, 72 transcripts possessing high identities with the bracovirus-related genes were identified. We investigated the mRNA expression levels of several transcripts at different developmental stages (including egg, larva, pupae, and adult) by quantitative real-time PCR analysis. The results revealed that some genes had adult-specific expression, indicating their potential significance for mating and parasitism. Overall, these results provide comprehensive insights into transcriptomic data of a polydnavirus-carrying parasitoid of a rice pest., (© 2014 Wiley Periodicals, Inc.)