Transgenerational effects microbiome in Drosophila simulans

Environmental signals received by organisms may affect subsequent generations that are not exposed to similar environmental conditions via transgenerational effects. Transgenerational effects can be mediated by several different mechanisms, e.g., epigenetic inheritance and the gut microbiome. Their effect on measured phenotypes can be critical in experimental setups that aim at minimizing the environmental heterogeneity, for example, common garden experiments. Hence, the number of generations spent in a common environment is a crucial parameter determining the effect of transgenerational effects. Typically, Drosophila studies conduct only two generations of common garden experiments. In this study, we examined diet-induced transgenerational effects on reproductive dormancy in Drosophila simulans. Flies were exposed to a diet change from a sugar-rich to a sugar-poor diet and phenotyped for dormancy at different numbers of generations after the diet change. Control flies were not exposed to a diet change and fed only with the sugar-poor diet. Consistent with a decreasing transgenerational effect, we observed a striking gradual decrease in dormancy incidence with an increasing number of generations on the new, sugar-poor diet. Transgenerational effects were removed only after four generations when dormancy incidence dropped to control levels. Our results show that two generations are not enough to erase transgenerational effects. We further examined whether these transgenerational effects are mediated through the microbiome, but did not detect any effect of it.