Data from: Elevated mitochondrial genome variation after 50 generations of radiation exposure in a wild rodent

Currently, the effects of chronic, continuous low dose environmental irradiation on the mitochondrial genome of resident small mammals are unknown. Using the bank vole (Myodes glareolus) as a model system, we tested the hypothesis that approximately 50 generations of exposure to the Chernobyl environment has significantly altered genetic diversity of the mitochondrial genome. Using deep sequencing, we compared mitochondrial genomes from 131 individuals from reference sites with radioactive contamination comparable to that present in Northern Ukraine before the April 26, 1986 meltdown, to populations where substantial fallout was deposited following the nuclear accident. Population genetic variables revealed significant differences among populations from contaminated and uncontaminated localities. Therefore, we rejected the null hypothesis of no significant genetic effect from 50 generations of exposure to the environment created by the Chernobyl meltdown. Samples from contaminated localities exhibited significantly higher numbers of haplotypes and polymorphic loci, elevated genetic diversity, and a significantly higher average number of substitutions-per-site across mitochondrial gene regions. Observed genetic variation was dominated by synonymous mutations, which may indicate a history of purify selection against nonsynonymous or insertion/deletion mutations. These significant differences were not attributable to sample size artifacts. The observed increase in mitochondrial genomic diversity in voles from radioactive sites is consistent with the possibility that chronic, continuous irradiation resulting from the Chernobyl disaster has produced an accelerated mutation rate in this species over the last 25 years. Our results, being the first to demonstrate this phenomenon in a wild mammalian species, are important for understanding genetic consequences of exposure to low-dose radiation sources.

目前，长期持续低剂量环境辐射对栖息小型哺乳动物的线粒体基因组（mitochondrial genome）的影响尚不明确。本研究以银行田鼠（Myodes glareolus）为模式生物，验证了如下假说：暴露于切尔诺贝利环境约50代的种群，其线粒体基因组的遗传多样性已发生显著改变。本研究采用深度测序（deep sequencing）技术，对131个个体的线粒体基因组进行比对：其中一组采样自对照区域，其放射性污染水平与1986年4月26日切尔诺贝利核事故前的乌克兰北部相当；另一组采样自核事故后大量放射性沉降物沉积的受污染区域。群体遗传学指标显示，受污染区域与未受污染区域的种群间存在显著差异。因此，我们拒绝了“暴露于切尔诺贝利堆芯熔毁所造成的环境达50代后，不会产生显著遗传效应”的零假设。受污染区域的样本表现出显著更多的单倍型与多态位点，遗传多样性更高，且线粒体基因区域内的平均每位点替换率也显著更高。观测到的遗传变异以同义突变为主体，这提示该种群长期受到针对非同义突变及插入/缺失突变的净化选择。上述显著差异并非由样本量偏差所导致。受辐射区域田鼠的线粒体基因组多样性升高，与切尔诺贝利灾难引发的长期持续辐射在近25年间加速了该物种突变率的推测相符。本研究首次在野生哺乳动物中证实了这一现象，其结果对于理解低剂量辐射暴露的遗传效应具有重要意义。