Tricks Not Treats: Wolbachia’s Manipulation of Sex in Infected D. subquinaria Offspring

Madeline Sheppard, a student at Eckerd College, worked in the lab of Dr. Kelly Dyer

Abstract Wolbachia is a bacteria that is found in up to 60% of all insects, which is transmitted exclusively from mother to offspring through the egg. In many host species Wolbachia infection does not Wolbachia are gram-negative maternally transmitted bacterial endosymbionts that are found in upwards of 60% of arthropods. Here, we aimed to determine the phenotype expressed in D. subquinaria when they are infected with a strain of Wolbachia originally found in a closely related species, D. recens. Wolbachia infection is expressed as one of two phenotypes: Cytoplasmic incompatibility (CI), which causes the deaths of most infected offspring, and Male Killing (MK), which causes the death of the sons of infected males. Additionally, we tested how Wolbachia interacts with the varied genetic backgrounds of D. subquinaria populations, as well as how that would influence which phenotype is displayed in infected offspring. We tested a total of 15 lines of D. subquinaria by taking 2 to 3 infected females and crossing them with 1 uninfected male. The F1 offspring from those crosses were collected, and the sex distribution per line’s offspring was determined. Ten lines produced a significant number of flies (n>10). We tested for Wolbachia infection by using PCR, and determined the F1 generation was positive for Wolbachia. All lines expressed evidence of the MK phenotype, and four lines showed nearly complete MK (98-100% female). The remaining six expressed partial MK (60-84% female). In the future, we aim to determine whether there is a genetic suppressor of the MK phenotype in D. subquinaria, as well as to generalize the results of this project to further understand the population dynamics of Wolbachia-infected flies.