Evidences of radioresistance in Drosophila melanogaster from Northeastern Brazil

Background: Ionizing radiation can inflict cellular damage, the severity of which is determined by the dose, exposure duration, and its capacity to penetrate cells. Some studies have demonstrated that genetic and epigenetic mechanisms have enabled organisms to develop adaptive traits and enhance their ability to repair DNA damage. Northeastern Brazil, a region containing rocky outcrops rich in uranium and thorium, is an ideal scenario to study natural radiation and its effects on natural populations. This study presents evidence of radioresistance in the offspring of a natural strain of Drosophila melanogaster resident in the municipality of Cerro Corá (CC-res), an environment with high levels of radon-222.

Material and methods: Genotoxicity was assessed using the comet assay in offspring of the CC-res and Oregon-R (OR), the control group, both reared under the same laboratory conditions for between 7 and 13 months. The adults and their offspring larvae were exposed to the Cerro Corá environment for 6 days during the dry and wet seasons. Low damage index and frequency were observed only in the CC-res. To confirm the radioresistance, the same strains were exposed after 16 months of cultivation to controlled doses of gamma radiation.

Results and conclusions: CC-res exhibited significantly lower levels of damage compared to the OR strain, with a clear dose-response effect to the irradiation observed exclusively in the OR group. The results support the occurrence of radioresistance in the CC-res strain and underscore the need for further in vivo studies investigations into the impact of Brazil's natural environmental radiation.