Intracellular dynamics of polydnavirus innexin homologues

Authors: Hasegawa, Daniel; ZHANG, PENG - Clemson University; TURNBALL, MATTHEW - Clemson University

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2020
Publication Date: 8/7/2020
Citation: Hasegawa, D.K., Zhang, P., Turnball, M.W. 2020. Intracellular dynamics of polydnavirus innexin homologues. Insect Molecular Biology. 29(5):477-489. https://doi.org/10.1111/imb.12657.
DOI: https://doi.org/10.1111/imb.12657

Interpretive Summary: The use of parasitoid wasps is an important tool for insect biological control in agriculture systems. Polydnaviruses are a group of insect viruses that have a symbiotic relationship with parasitoid wasps, which may be used as a biocontrol agent for insect pests. During insect parasitization, polydnaviruses injected by the wasp into a host caterpillar leads to immune suppression and developmental arrest. Here, we studied a polydnavirus gene family to understand its roles in insect parasitism. Using a combination of experimental approaches, including gene expression, microscopy, and application of protein inhibitors, the work characterizes several viral genes that disrupt cell physiology and communication. The data contribute to our understanding of the mechanisms of wasp parasitism of insect hosts, which is fundamental in devising novel and effective biocontrol strategies to manage agricultural pests.

Technical Abstract: Polydnaviruses associated with ichneumonid parasitoid wasps (Ichnoviruses) encode large numbers of genes, often in multigene families. One such gene family is the Vinnexins, which are homologues of the Innexin gene family that encodes insect gap junction proteins. Previous work has demonstrated that Vinnexins are expressed in parasitized caterpillars, along with host Innexins. To provide insight into whether different members of the Vinnexin gene family may interact with host Innexins in a protein-specific fashion, we examined intracellular behaviors of the Vinnexins encoded by the Campoletis sonorensis Ichnovirus (CsIV) alone and in combination with a host Innexin orthologue, Innexin2 (Inx2). QRT-PCR verified that transcription of CsIV vinnexins occurs contemporaneously with host caterpillar inx2, with genes showing an inverse correlation between transcript abundance and previously described channel conductance characteristics. Using confocal immunomicroscopy, we observed cytoplasmic and membrane localization of epitope-tagged Vinnexins, VnxG and VnxQ2, along with Spodoptera frugiperda Inx2 (Sf-Inx2). Surface biotinylation assays verified that the Vinnexins and Sf-Inx2 localize to the cell surface, indicating the potential to form both unapposed hemichannels and gap junctions, while cytochalasin B and nocodazole treatments demonstrated a reliance on actin and microtubule cytoskeletal networks for protein localization. Immunomicroscopy following co-transfection of constructs indicated extensive co-localization of Vinnexins with each other and Sf-Inx2, and live-cell imaging of mCherry-labelled Inx2 supports that Vinnexins may affect Sf-Inx2 distribution in a Vinnexin-specific fashion. Interpreted in light of previous findings, these data support that the Vinnexins may disrupt host cell physiology in a protein-specific manner through altering gap junctional intercellular channel communication, as well as indirectly by affecting multicellular junction characteristics.