Adaptation of the gymnosperms to the conditions of irradiation in the Chernobyl zone: from morphological abnormalities to the molecular genetic consequences

Rapid survey of de novo mutations in naturally growing tree species following the March 2011 disaster in Fukushima: The effect of low-dose-rate radiation

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.

A strategy for bioremediation of nuclear contaminants in the environment

Radionuclides released from nuclear contamination harm the environment and human health. Nuclear pollution spread over large areas and the costs associated with decontamination is high. Traditional remediation methods include both chemical and physical, however, these are expensive and unsuitable for large-scale restoration. Bioremediation is the use of plants or microorganisms to remove pollutants from the environment having a lower cost and can be upscaled to eliminate contamination from soil, water and air. It is a cheap, efficient, ecologically, and friendly restoration technology. Here we review the sources of radionuclides, bioremediation methods, mechanisms of plant resistance to radionuclides and the effects on the efficiency of biological adsorption. Uptake of radionuclides by plants can be facilitated by the addition of appropriate chemical accelerators and agronomic management, such as citric acid and intercropping. Future research should accelerate the use of genetic engineering and breeding techniques to screen high-enrichment plants. In addition, field experiments should be carried out to ensure that this technology can be applied to the remediation of nuclear contaminated sites as soon as possible.

Effect of chronic radiation on the flax (Linum usitatissimum L.) genome grown for six consecutive generations in the radioactive Chernobyl area

The growth of plants under chronic radiation stress in the Chernobyl area may cause changes in the genome of plants. To assess the extent of genetic and epigenetic changes in nuclear DNA, seeds of the annual crop flax (Linum usitatissimum L.) of the Kyivskyi variety, sown 21 years after the accident and grown for six generations in radioactive (RAD) and remediated (REM) fields were analysed. Flaxseed used for sowing first generation, which served as a reference (REF), was also analysed. The AFLP (Amplified Fragment Length Polymorphism) revealed a higher number of specific EcoRI-MseI loci (3.4-fold) in pooled flaxseed samples harvested from the RAD field compared with the REM field, indicating a link between the mutation process in the flax genome and the ongoing adaptation process. MSAP (Methylation-Sensitive Amplified Polymorphism) detecting EcoRI-MspI and EcoRI-HpaII loci in flax nuclear DNA genome showed no significant differences in methylation level, reaching about 33% in each of the groups studied. On the other hand, significant changes in the DNA methylation pattern of flaxseed samples harvested from the RAD field compared with controls were detected. Pairwise F_ST comparison revealed within both, EcoRI-MspI and transformed methylation-Sensitive data sets more than a 3-fold increase of genetic divergence in the RAD field compared with both controls. These results indicate that the nuclear genome of flax exposed to chronic radiation for six generations has more mutations and uses DNA methylation as one of the adaptation mechanisms for sustainability under adverse conditions.