No evidence for transgenerational immune priming in Drosophila melanogaster

In this study, we test for the presence of priming mechanisms in the fruit fly, Drosophila melanogaster, using 10 different bacterial pathogens. We chose to focus exclusively on trans-generational priming and tested for the same using both natural and opportunistic pathogens of Drosophila spanning a range of virulence from 10% to 100%. We infected mothers via septic injury and looked for evidence of trans-generational priming among offspring. We collected four sets of offspring for each bacterial treatment: offspring from mothers that survived infections, those that succumbed to infections, injury controls and unhandled controls. Subsequently, we measured offspring’s ability to survive infection and tested whether offspring from infected mothers performed better in this assay. Additionally, we also compared offspring from mothers that survived infections to those from mothers that succumbed to infections to test whether mothers’ ability to survive infections enabled a greater amount of priming among offspring. We also performed similar analysis on pathogen burden data collected from each set of offspring to test whether they differed in their ability to curtail pathogen growth. Despite the extensive nature of our experimental design and the large number of pathogens used in our study, we found that offspring survival and pathogen loads were statistically equivalent regardless of their mothers’ infection status.