Constant light impairs memory processing transgenerationally in D. melanogaster
Environmental perturbations can have profound effects on our physiology and behavior, but their long-lasting impact remains debatable. We discovered that changes in standard light-dark conditions, such as exposure to constant light or simulated chronic jetlag, causes loss of associative memory in appetitive and aversive conditioning paradigms in D. melanogaster, and this behavior persists through three generations despite transfer of progeny to a standard light-dark cycle. Impaired memory is transmitted through females and is independent of any changes in fitness, brain or mushroom body architecture, or sensing acuity. Mechanistically, effects of constant light on memory are mediated by increased PIWI/piRNA pathway expression in the germline and its H3K9me3 writing capabilities, acting through altered expression of the Dopamine-1-like Receptor 1 (Dop1R1) in the brain. These findings suggest that irregular exposure to light, such as nighttime light pollution, can have negative consequences across generations.