Prevalence of galbut virus in wild Drosophila melanogaster populations and to lab colonization
Authors: Tillie Dunham; Mark Stenglein
Affiliation: Center for Vector-Borne and Infectious Disease, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA
Keywords: u. other (Virus Evolution); k. host/pathogen interactions
Galbut virus is remarkably common in wild Drosophila melanogaster. Every population that has been tested contains some infected individuals. But on average only 60% of flies are infected and there is evidence that some flies are resistant to infection. To better understand galbut virus-host interactions in wild and lab-reared populations, we pursued three avenues of investigation. First, we quantified galbut virus prevalence in wild populations sampled from different geographic locations over 5 years. We found that galbut virus prevalence varied widely from 0-96%, even in populations sampled from nearby geographic locations. We also found that galbut virus load in individual flies can be binned into 3 phenotypes: high positives, with galbut virus RNA levels exceeding that of an abundant host mRNA, low positives, with galbut virus RNA levels >100,000x lower, and negatives, flies with undetectable infection. Second, we performed an experiment to assess whether galbut virus prevalence would change over time in multiple independent wild-caught populations reared in lab. This will allow us to assess possible fitness costs to infection by tracking changes in infection frequency from generation to generation. Finally, to better understand the low positive phenotype, we bleached eggs then placed individual eggs into vials to be reared to adulthood. We did this in parallel with unbleached eggs that were reared together to have a baseline comparison. This experiment will allow us to determine whether the low positive infection phenotype represents legitimate low-level infection or contamination from highly infected flies. Overall, these studies contribute to a fuller understanding of the variability associated with infection by this exceptionally common persistent Drosophila virus.