Experimental Selection for Drosophila Survival in Extremely High O2 Environments

Abstract

Although oxidative stress is deleterious to mammals, the mechanisms underlying oxidant susceptibility or tolerance remain to be elucidated. In this study, through a long-term laboratory selection over many generations, we generated a Drosophila melanogaster strain that can live and reproduce in very high O2 environments (90% O2), a lethal condition to naïve flies. We demonstrated that tolerance to hyperoxia was heritable in these flies and that these hyperoxia-selected flies exhibited phenotypic differences from naïve flies, such as a larger body size and increased weight by 20%. Gene expression profiling revealed that 227 genes were significantly altered in expression and two third of these genes were down-regulated. Using a mutant screen strategy, we studied the role of some altered genes (up- or down-regulated in the microarrays) by testing the survival of available corresponding P-element or UAS construct lines under hyperoxic conditions. We report that down-regulation of several candidate genes including Tropomyosin 1, Glycerol 3 phosphate dehydrogenase, CG33129, and UGP as well as up-regulation of Diptericin and Attacin conferred tolerance to severe hyperoxia. In conclusion, we identified several genes that were not only altered in hyperoxia-selected flies but we also prove that these play an important role in hyperoxia survival. Thus our study provides a molecular basis for understanding the mechanisms of hyperoxia tolerance.

Antimicrobial Peptides Increase Tolerance to Oxidant Stress in Drosophila melanogaster

“…1A, we found that ϳ50% of the pupae of the da-Gal4 ϫ UAS-Dpt progeny (da-Gal4ϾUAS-Dpt) were able to eclose in 90% O 2 , which was significantly higher than the da-Gal4 (no survival) and UAS-Dpt (26%, p Ͻ 0.05) control flies, suggesting that overexpression of Dpt plays a critical role in the survival of hyperoxia. Furthermore, our previous data have shown that flies with decreased Dpt expression using RNA interference cannot eclose in 90% O 2 compared with an eclosion rate of ϳ10% in control flies (15), again supporting the idea that overexpression of Dpt contributes to the survival in hyperoxia. The life span of adult flies in hyperoxia was also determined.…”

“…We have further demonstrated that overexpression of even one AMP gene at a time (e.g. Diptericin (Dpt)) allows wild-type flies to survive much better in hyperoxia (15). To our knowledge, this is the first study to show that Dpt has a protective role against oxidative stress.…”

“…RNA Extraction and Microarray Analysis-Total RNA was extracted as described previously (15). Affymetrix Drosophila Genome 2.0 arrays (Affymetrix, Santa Clara, CA) were used, and probe labeling, array hybridization, and image scanning were performed following the standard protocol according to the manufacturer's instructions.…”

“…Microarray analysis has shown us additionally that the AMP family of genes (e.g. Dpt) is significantly up-regulated in these flies and that this upregulation is not due to the presence of microbes (15). Here, using a UAS/Gal4 system, we overexpressed Dpt by crossing da-Gal4 with UAS-Dpt flies and then exposed the progeny to hyperoxia with 90% O 2 .…”

Does Hyperoxia Selection Cause Adaptive Alterations of Mitochondrial Electron Transport Chain Activity Leading to a Reduction of Superoxide Production?

“…Our laboratory has previously generated Drosophila melanogaster flies that tolerate extreme oxidative stress (90%-95% O 2 ), a lethal condition for naive flies, through a long-term laboratory selection over many generations (8,9). In the current study, we are using this unique Drosophila model to investigate the molecular basis of hyperoxia tolerance.…”