Gap Junctions: Regulators of Cellular Immunity and Parasite Manipulation in the Remarkable Tripartite Relationship Involving Insects and Genome-integrated Polydnaviruses

Polydnaviruses are double-stranded DNA viruses associated with some subfamilies of ichneumonoid parasitoid wasps. Polydnavirus virions are delivered during wasp parasitization of a host, and virus gene expression in the host induces alterations of host physiology. Infection of susceptible host caterpillars by the polydnavirus Campoletis sonorensis Ichnovirus (CsIV) leads to expression of virus genes, resulting in immune and developmental disruptions. CsIV encodes four homologues of insect gap junction genes (innexins) termed vinnexins, which are expressed in multiple tissues of infected caterpillars. Previously, we demonstrated that two of these, VinnexinD and VinnexinG, form functional gap junctions in paired Xenopus oocytes. Here we show that VinnexinQ1 and VinnexinQ2, likewise, form junctions in this heterologous system. Moreover, we demonstrate that the vinnexins interact differentially with the Innexin2 orthologue of an Ichnovirus host, Spodoptera frugiperda. Cell pairs co-expressing a vinnexin