(1st Place) Beneficial virus gene expression partially mediated by ancestral machinery in parasitoid wasp, Microplitis demolitor

The braconid wasp, Microplitis demolitor, utilizes an endogenized beneficial virus, Microplitis demolitor Bracovirus (MdBV), to combat the immune system of its hosts, Soybean Looper larvae, so that the wasp progeny can safely develop. The MdBV genome is contained within M. demolitor’s genome and replicates in the wasp ovaries during pupation, while MdBV virulence only occurs in the Soybean Looper. The MdBV replication genes include both early and late-transcribed viral genes, where some of the “early” genes encode a conserved viral RNA polymerase. In related, entomopathogenic baculoviruses, the RNA polymerase transcribes “late” genes that are responsible for viral structure so it is hypothesized that this role is maintained in MdBV. This is supported by previous qPCR studies demonstrating that the knockdown of “early” MdBV genes reduces transcription of two “late” MdBV genes in M. demolitor. This talk will characterize genes transcribed by the viral RNA polymerase through RNA-Seq analyses comparing samples with an RNAi-mediated knockdown of all four viral RNA polymerase subunits to control samples. Results find that some late viral genes are generally downregulated after this knockdown, suggesting that these are likely controlled by the viral RNA polymerase and that the viral RNA polymerase role in transcription is at least partially conserved. However, some late viral genes appear unaffected, pointing to co-option of other replication control mechanisms. These findings help explain how MdBV is maintained as a beneficial player in the M. demolitor system and are expected to add knowledge to greater themes of viral control in parasitoid literature.