Hypergravity increases resistance to heat in dFOXO Drosophila melanogaster mutants and can lower FOXO translocation in wild-type males.

Severe stresses have deleterious effects, but mild stresses can have beneficial effects called hormetic effects. This study observed survival time of wild-type Drosophila melanogaster flies and dFOXO mutants exposed to 37 °C, a severe stress for flies, after they lived or not for 2 weeks in hypergravity (3 or 5 g), a mild stress with hormetic effects in flies. Hypergravity increased survival time of the mutants, this effect being less observed in wild-type flies. The heat stress increased dFOXO translocation similarly in all gravity groups in a wild-type strain, and hypergravity decreased dFOXO translocation similarly in heat-stressed or not heat-stressed males, no clear effect of the gravity level being observed in females. Because hypergravity increases resistance to heat in dFOXO mutants and the translocation is not tightly dependent on the gravity level, one can conclude that dFOXO does not mediate the effect of hypergravity on resistance to heat. A previous study showed that another mild stress, the cold, can increase survival time at 37 °C of wild-type D. melanogaster flies, but this was not observed in dFOXO mutants. Therefore, two mild stresses, cold and hypergravity, can increase resistance to heat but the pathways mediating this effect are seemingly different, as cold does not increase resistance in dFOXO mutants while hypergravity increases it.