Abstract：
The impact of low-dose-rate radiation on genetics is largely unknown, particularly in natural environments. The Fukushima Dai-ich Nuclear Power Plant disaster resulted in the creation of contaminated natural lands. In this study, de novo mutations (DNMs) in germ line cells were surveyed from double-digest RADseq fragments in Japanese cedar and flowering cherry trees exposed to ambient dose rates ranging from 0.08 to 6.86 μGy h-1. These two species are among the most widely cultivated Japanese gymnosperm and angiosperm trees for forestry and horticultural purpose, respectively. For Japanese flowering cherry, open crossings were performed to produce seedlings, and only two candidate DNMs were detected from uncontaminated area. For Japanese cedar, the haploid megagametophytes were used as next generation samples. The use of megagametophytes from open crossing for next generation mutation screening had many advantages such as reducing exposure to radiation in contaminated areas because artificial crossings are not needed and the ease of data analysis owing to the haploid nature of megagametophytes. A direct comparison of the nucleotide sequences of parents and megagametophytes revealed an average of 1.4 candidate DNMs per megagametophyte sample (range: 0-40) after filtering procedures were optimized based on the validation of DNMs via Sanger sequencing. There was no relationship between the observed mutations and the ambient dose rate in the growing area or the concentration of 137Cs in cedar branches. The present results also suggest that mutation rates differ among lineages and that the growing environment has a relatively large influence on these mutation rates. These results suggested there was no significant increase in the mutation rate of the germplasm of Japanese cedar and flowering cherry trees growing in the contaminated areas.
摘要：
低剂量率辐射对遗传学的影响在很大程度上是未知的,特别是在自然环境中。福岛第一核电站灾难导致了受污染的自然土地的产生。在这项研究中,从暴露于0.08至6.86μGyh-1的环境剂量率的日本雪松和开花樱桃树的双消化RADseq片段中，对种系细胞中的从头突变（DNM）进行了调查。这两个物种是最广泛种植的日本裸子植物和被子植物树之一，用于林业和园艺目的，分别。对于日本开花的樱桃，进行露天杂交以产生幼苗，在未受污染的地区仅检测到两个候选DNM。对于日本雪松，单倍体巨型配子体被用作下一代样品。使用来自开放杂交的巨型配子体进行下一代突变筛选具有许多优点，例如由于不需要人工杂交而减少了受污染地区的辐射暴露，并且由于巨型配子体的单倍体性质而易于进行数据分析。亲本和巨型配子体的核苷酸序列的直接比较显示，在基于通过Sanger测序对DNM的验证优化过滤程序后，每个巨型配子体样品平均有1.4个候选DNM（范围：0-40）。观察到的突变与生长区域的环境剂量率或雪松分支中137Cs的浓度之间没有关系。本结果还表明，谱系之间的突变率不同，并且生长环境对这些突变率有相对较大的影响。这些结果表明，在污染地区生长的日本雪松和开花樱桃树的种质的突变率没有显着增加。
