Ionizing radiation generates oxidative stress, which is thought to be a major cause of aging. Although living organisms are constantly exposed to low levels of radiation, most studies examining the effect of radiation have focused on accelerated aging and diminished life span that result from high-dose radiation. On the other hand, several studies have suggested that low-dose radiation enhances the longevity of Drosophila melanogaster. Therefore, investigation of the biological effects of low-dose radiation could contribute to a more comprehensive understanding of the aging process. In this study, microarray and quantitative real time-PCR were used to measure genome-wide changes in transcript levels in low-dose irradiated fruit flies that showed enhanced longevity. In response to radiation, approximately 13% of the genome exhibited changes in gene expression, and a number of aging-related genes were significantly regulated. These data were compared with quantitative trait loci affecting life-span to identify candidate genes involved in enhanced longevity induced by low-dose radiation. This genome-wide survey revealed novel information about changes in transcript levels in low-dose irradiated flies and identified 39 new candidate genes for molecular markers of extended longevity induced by ionizing radiation. In addition, this study also suggests a mechanism by which low-dose radiation extends longevity.

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Ionizing radiation is one of the most extensively studied carcinogens. In contrast to the detrimental effects of high‐dose radiation in carcinogenesis, the biological effects of low‐dose radiation remains poorly understood. In this study, we introduced adult wts/ + heterozygotes of Drosophila melanogaster as transgenic model organisms to determine the tumorigenic activity of low‐dose radiation. The warts (wts) gene is a tumor suppressor gene in mice and humans that is directly involved in cell cycle regulation. Fruit flies at the first larval stage were subjected to ionizing radiation, and then tumorigenic activity was evaluated as the frequency of observed warts tumorous mosaic clones in adult flies. Low‐dose irradiation alone did not cause tumorigenesis in our system. In combined treatment with a chemical carcinogen, chronic irradiation at 0.2 Gy decreased the frequency of tumorous clones induced by cisplatin. These results suggest that low‐dose radiation alone is not deleterious but beneficial in tumorigenesis induced by a chemical carcinogen.