Date of Award
Doctor of Philosophy (PhD)
Dr. Matthew Turnbull
Dr. Zhicheng Dou
Dr. Susan Chapman
Dr. Emily Rosowski
Campoletis sonorensis Ichnovirus (CsIV) is produced by the ichneumonid parasitoid Campoletis sonorensis (the primary host). Female parasitoid wasps restrictedly replicate viruses in their ovaries and inject them into a larval lepidopteran (secondary host) during oviposition. This symbiotic virus of C. sonorensis is essential for successful parasitization. CsIV is characterized by having a large, segmented double-stranded DNA genome with a large number of genes, many of which are associated with one of five multigene families. The CsIV vinnexin gene family is one of them and has four members, including CsIV-vnxD and CsIV-vnxG. Vinnexins are homologues of insect Innexins, which form gap junctions (GJs). Functional endogenous gap junctions provide a fundamental gate for intercellular communication, while hemichannels formed by GJ proteins connect the cytoplasm with the extracellular environment. Since all four CsIV Vinnexins are expressed in CsIV-infected hemocytes, it suggests they collaborate in manipulating the immune system of secondary hosts during wasp parasitization by disrupting hemocyte physiology or multicellular signaling between hemocytes and other host cells. This work chose GAL4-UAS transgenic Drosophila melanogaster system to investigate and compare the effects of CsIV-VnxD expression and CsIV-VnxG expression on immune cell profiles and immune responses. Intrinsic GJ-related features of CsIV-VnxD and CsIV-VnxG include their membrane localization and function of altering cell bioelectric patterns. Interestingly, we found CsIV-VnxD additional triggered a robust Imd signaling pathway and partially rescued entomopathogen-infected flies, while CsIV-VnxG predominantly compromised larval melanization activity, both of which theoretically protect wasp offspring from bacterial infection and host immune surveillance. These functional differences, in part, are likely associated with their unique interactome, as CsIV-VnxD, but not CsIV-VnxG, biochemically interacted with the signaling molecule β-catenin and altered the distribution pattern of adhesion protein DEcadherin. We also predicted that the residue variations in the C-terminus of Vinnexins determine the interactors of Vinnexins. Taking observations of Dm-Inx2 physiology into consideration, we concluded that, at the single-cell level, CsIV-VnxD tends to function similarly to closed Dm-Inx2 hemichannel and has non-GJ functions, but CsIV-VnxG resembles open Dm-Inx2 hemichannel and possesses vigorous gap junction intercellular communication. This is the first work focusing on the linkage between Innexin physiology and Vinnexin pathophysiology. More broadly, our results support that Vinnexins are not functionally redundant and Vinnexins play member-specific roles that are physiological-system or cell-type specific, which has implications for Ichnovirus-host evolution.
Zhang, Peng, "Functional Analysis of Two Campoletis Sonorensis Ichnovirus Vinnexins in Drosophila Melanogaster" (2023). All Dissertations. 3393.
Available for download on Saturday, August 31, 2024