Direct selection for paraquat resistance in Drosophila results in a different extended longevity phenotype

When normal-lived Ra strain Drosophila were indirectly selected for longevi ty, they gave rise to long-lived La strain animals with lower oxidized prot ein and lipid levels that were temporally coincident with higher antioxidan t activities. We wanted to determine whether it was possible to create long -lived animals by a direct selection for increased antioxidant activities. Using the same Ra strain, we selected them over 24 generations for increase d resistance to paraquat. Selection was successful: the paraquat-resistant flies had a fourfold increase in their LT50 (mean lethal time) values. Thei r extended longevity pattern differs from that of the La strain. The paraqu at-resistant animals also have a lower level of antioxidant activity, an in creased total P450 enzyme activity level, an altered pattern of energy meta bolism, and a significantly lower developmental viability. We interpret the se findings as suggesting that similar stress response phenotypes may be ge nerated by different molecular mechanisms, some of which may generate very different types of extended longevity phenotypes.