Hasegawa Daniel K, Erickson Stephanie L, Hersh Bradley M, Turnbull Matthew W
Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
Department of Biology, Allegheny College, Meadville, PA 16335, USA.
J Insect Physiol. 2017 Apr;98:173-181. doi: 10.1016/j.jinsphys.2017.01.003. Epub 2017 Jan 7.
Polydnaviruses are dsDNA viruses that induce immune and developmental alterations in their caterpillar hosts. Characterization of polydnavirus gene families and family members is necessary to understand mechanisms of pathology and evolution of these viruses, and may aid to elucidate the role of host homologues if present. For example, the polydnavirus vinnexin gene family encodes homologues of insect gap junction genes (innexins) that are expressed in host immune cells (hemocytes). While the roles of Innexin proteins and gap junctions in insect immunity are largely unclear, we previously demonstrated that Vinnexins form functional gap junctions and alter the junctional characteristics of a host Innexin when co-expressed in paired Xenopus oocytes. Here, we test the effect of ectopic vinnexin expression on host cell physiology using both a lepidopteran cell culture model and a dipteran whole organism model. Vinnexin expression in the cell culture system resulted in gene-specific alterations in cell morphology and a slight, but non-statistically significant, reduction in gap junction activity as measured by dye transfer, while ectopic expression of a lepidopteran innexin2 gene led to morphological alterations and increase in gap junction activity. Global ectopic expression in the model dipteran, Drosophila melanogaster, of one vinnexin (vinnexinG) or D. melanogaster innexin2 (Dm-inx2) resulted in embryonic lethality, while expression of the other vinnexin genes had no effect. Furthermore, ectopic expression of vinnexinG, but not other vinnexin genes or Dm-inx2, in D. melanogaster larval gut resulted in developmental arrest in the pupal stage. These data indicate the vinnexins likely have gene-specific roles in host manipulation. They also support the use of Drosophila in further analysis of the role of Vinnexins and other polydnavirus genes in modifying host physiological processes. Finally, our findings suggest the vinnexin genes may be useful to perturb and characterize the physiological functions of insect Innexins.
多分DNA病毒是双链DNA病毒，可在其毛虫宿主中引发免疫和发育变化。对多分DNA病毒基因家族及其家族成员进行表征，对于理解这些病毒的致病机制和进化过程至关重要，并且如果存在宿主同源物的话，可能有助于阐明其作用。例如，多分DNA病毒的vinnexin基因家族编码昆虫间隙连接基因（innexins）的同源物，这些同源物在宿主免疫细胞（血细胞）中表达。虽然Innexin蛋白和间隙连接在昆虫免疫中的作用在很大程度上尚不清楚，但我们之前证明，当在成对的非洲爪蟾卵母细胞中共表达时，Vinnexins会形成功能性间隙连接并改变宿主Innexin的连接特性。在这里，我们使用鳞翅目细胞培养模型和双翅目全生物体模型来测试异位表达vinnexin对宿主细胞生理学的影响。在细胞培养系统中表达Vinnexin会导致细胞形态发生基因特异性改变，并且通过染料转移测量的间隙连接活性略有降低，但无统计学意义，而异位表达鳞翅目innexin2基因则会导致形态改变和间隙连接活性增加。在模式双翅目果蝇中全局异位表达一种vinnexin（vinnexinG）或果蝇innexin2（Dm-inx2）会导致胚胎致死，而表达其他vinnexin基因则没有影响。此外，在果蝇幼虫肠道中异位表达vinnexinG而非其他vinnexin基因或Dm-inx2会导致蛹期发育停滞。这些数据表明，Vinnexins可能在宿主操纵中具有基因特异性作用。它们还支持利用果蝇进一步分析Vinnexins和其他多分DNA病毒基因在改变宿主生理过程中的作用。最后，我们的研究结果表明，vinnexin基因可能有助于干扰和表征昆虫Innexins的生理功能。
