Convergent evolution of SWS2 opsin facilitates adaptive radiation of threespine stickleback into different light environments.

Repeated adaptation to a new environment often leads to convergent phenotypic changes whose underlying genetic mechanisms are rarely known. Here, we study adaptation of color vision in threespine stickleback during the repeated postglacial colonization of clearwater and blackwater lakes in the Haida Gwaii archipelago. We use whole genomes from 16 clearwater and 12 blackwater populations, and a selection experiment, in which stickleback were transplanted from a blackwater lake into an uninhabited clearwater pond and resampled after 19 y to test for selection on cone opsin genes. Patterns of haplotype homozygosity, genetic diversity, site frequency spectra, and allele-frequency change support a selective sweep centered on the adjacent blue- and red-light sensitive opsins SWS2 and LWS. The haplotype under selection carries seven amino acid changes in SWS2, including two changes known to cause a red-shift in light absorption, and is favored in blackwater lakes but disfavored in the clearwater habitat of the transplant population. Remarkably, the same red-shifting amino acid changes occurred after the duplication of SWS2 198 million years ago, in the ancestor of most spiny-rayed fish. Two distantly related fish species, bluefin killifish and black bream, express these old paralogs divergently in black- and clearwater habitats, while sticklebacks lost one paralog. Our study thus shows that convergent adaptation to the same environment can involve the same genetic changes on very different evolutionary time scales by reevolving lost mutations and reusing them repeatedly from standing genetic variation.

Absolute quantification of acetylation and phosphorylation of the histone variant H2AX upon ionizing radiation reveals distinct cellular responses in two cancer cell lines.

Histone modifications change upon the cellular response to ionizing radiation, and their cellular amounts could reflect the DNA damage response activity. We previously reported a sensitive and reliable method for the absolute quantification of γH2AX within cells, using liquid chromatography-tandem mass spectrometry (LC/MS/MS). The technique has broad adaptability to a variety of biological systems and can quantitate different modifications of histones. In this study, we applied it to quantitate the levels of γH2AX and K5-acetylated H2AX, and to compare the radiation responses between two cancer cell lines: HeLa and U-2 OS. The two cell lines have distinct properties in terms of their H2AX modifications. HeLa cells have relatively high γH2AX (3.1 %) against the total H2AX even in un-irradiated cells, while U-2 OS cells have an essentially undetectable level (nearly 0 %) of γH2AX. In contrast, the amounts of acetylated histones are lower in HeLa cells (9.3 %) and higher in U-2 OS cells (24.2 %) under un-irradiated conditions. Furthermore, after ionizing radiation exposure, the time-dependent increases and decreases in the amounts of histone modifications differed between the two cell lines, especially at the early time points. These results suggest that each biological system has distinct kinase/phosphatase and/or acetylase/deacetylase activities. In conclusion, for the first time, we have succeeded in simultaneously monitoring the absolute amounts of phosphorylated and acetylated cellular H2AX after ionizing radiation exposure. This multi-criteria assessment enables precise comparisons of the effects of radiation between any biological systems.

Increasing genetic variability in black oats using gamma irradiation.

The black oat (Avena strigosa Schreb) is commonly used for forage, soil cover, and green manure. Despite its importance, little improvement has been made to this species, leading to high levels of genotypic disuniformity within commercial cultivars. The objective of this study was to evaluate the efficiency of different doses of gamma rays [(60)Co] applied to black oat seeds on the increase of genetic variability of agronomic traits. We applied doses of 0, 10, 50, 100, and 200 Gy to the genotype ALPHA 94087 through exposure to [(60)Co]. Two experiments were conducted in the winter of 2008. The first aimed to test forage trait measurements such as plant height, dry matter yield, number of surviving tillers, and seedling stand. The second test assessed seed traits, such as yield and dormancy levels. Gamma irradiation seems not to increase seed yield in black oats, but it was effective in generating variability for the other traits. Tiller number and plant height are important selection traits to increase dry matter yield. Selection in advanced generations of mutant populations can increase the probability of identifying superior genotypes.

Radiation hybrid QTL mapping of Tdes2 involved in the first meiotic division of wheat.

Since the dawn of wheat cytogenetics, chromosome 3B has been known to harbor a gene(s) that, when removed, causes chromosome desynapsis and gametic sterility. The lack of natural genetic diversity for this gene(s) has prevented any attempt to fine map and further characterize it. Here, gamma radiation treatment was used to create artificial diversity for this locus. A total of 696 radiation hybrid lines were genotyped with a custom mini array of 140 DArT markers, selected to evenly span the whole 3B chromosome. The resulting map spanned 2,852 centi Ray with a calculated resolution of 0.384 Mb. Phenotyping for the occurrence of meiotic desynapsis was conducted by measuring the level of gametic sterility as seeds produced per spikelet and pollen viability at booting. Composite interval mapping revealed a single QTL with LOD of 16.2 and r (2) of 25.6 % between markers wmc326 and wPt-8983 on the long arm of chromosome 3B. By independent analysis, the location of the QTL was confirmed to be within the deletion bin 3BL7-0.63-1.00 and to correspond to a single gene located ~1.4 Mb away from wPt-8983. The meiotic behavior of lines lacking this gene was characterized cytogenetically to reveal striking similarities with mutants for the dy locus, located on the syntenic chromosome 3 of maize. This represents the first example to date of employing radiation hybrids for QTL analysis. The success achieved by this approach provides an ideal starting point for the final cloning of this interesting gene involved in meiosis of cereals.

The receptor-like kinase ERECTA contributes to the shade-avoidance syndrome in a background-dependent manner.

BACKGROUND AND AIMS: Plants growing at high densities perceive a decrease in the red to far-red (R/FR) ratio of incoming light. These changes in light quality trigger a suite of responses collectively known as the shade-avoidance syndrome (SAS) including hypocotyl and stem elongation, inhibition of branching and acceleration of flowering. METHODS: Quantitative trait loci (QTLs) were mapped for hypocotyl length to end-of-day far-red (EOD), a simulated shade-avoidance response, in recombinant inbred line (RIL) populations of Arabidopsis thaliana seedlings, derived from Landsberg erecta (Ler) and three accessions (Columbia, Col; Nossen, No-0; and Cape Verde Islands, Cvi-0). KEY RESULTS: Five loci were identified as being responsible for the EOD response, with a positive contribution of Ler alleles on the phenotype independently of the RIL population. Quantitative complementation analysis and transgenic lines showed that PHYB is the candidate gene for EODRATIO5 in the Ler × Cvi-0 RIL population, but not for two co-localized QTLs, EODRATIO1 and EODRATIO2 mapped in the Ler × No-0 and Ler × Col RIL populations, respectively. The ERECTA gene was also implicated in the SAS in a background-dependent manner. For hypocotyl length EOD response, a positive contribution of erecta alleles was found in Col and Van-0, but not in Ler, Cvi-0, Hir-1 or Ws. Furthermore, pleiotropic effects of ERECTA in the EOD response were also detected for petiole and lamina elongation, hyponastic growth, and flowering time. CONCLUSIONS: The results show that the analysis of multiple mapping populations leads to a better understanding of the SAS genetic architecture. Moreover, the background- and trait-dependent contribution of ERECTA in the SAS suggest that its function in shaded natural environments may be relevant for some populations in different phases of plant development. It is proposed that ERECTA is involved in canalization processes buffering the genetic variation of the SAS against environmental light fluctuations.

[Variability of DNA simple sequence repeats in peripheral blood of humans subjected to prolonged exposures of ionizing radiation].

Long-term post-radiation changes in the level of microsatellite DNA polymorphism in peripheral blood of the male "Mayak" employees (Ozyorsk, Russia), who had been exposed to prolonged gamma-irradiation during professional activities, were studied. DNA samples were obtained from the Radiobiology Repository of Human Tissue (Southern-Urals Biophysics Institute FMBA) and used as templates for arbitrarily primed PCR. Comparative analysis of the obtained samples of DNA fragments showed a significant increase in the number of high-molecular fragments and reduction in the number of amplified low molecular weight DNA fragments in comparison with the control. However, a direct correlation of the level of DNA polymorphism with the accumulated total dose of radiation was not found. The study of the polymorphism of microsatellite DNA repeats can be used for qualitative assessment of the levels of genetic variability.

[Increased genomic instability in somatic cells of the progeny of female mice exposed to acute X-radiation in the preconceptional period].

The level of genome instability (GI) was studied in the progeny of female mice exposed in the preconceptional period to radiation doses of 0.5, 1, and 2 Gy in comparison to that in the progeny of the same parent pairs born before irradiation of the females. To assess the level of genome instability, we analyzed polymorphism of DNA fragments from postmitotic (blood and brain) and proliferating (spleen and tail tip) tissues amplified by AP-PCR (PCR amplification with an arbitrary primer). It was found that polymorphism of the spectrum of AP-PCR products, which is a multilocus genetic marker (MGM), in the genome of somatic cells in the progeny of female mice exposed to 2 Gy was higher than in the progeny of male mice exposed to the same doses. In the progenies of female mice born before and after irradiation, tissue-specific variations in the level of DNA polymorphism were detected. The maximum value of this polymorphism (with respect to the frequency of "nonparental bands") was determined for peripheral blood DNA in comparison with the other tissues. Estimations of the MGM polymorphism with the AP-PCR method demonstrate an increased level of genome instability in somatic cells of offsprings from female mice exposed to a single acute dose of X-rays (0.5, 1, and 2 Gy) in the pre-conceptional period. Radiation-induced transgenerational genome instability with an increase in the dose of preconceptional irradiation of female mice was more pronounced in DNA of the postmitotic tissues (blood and brain DNA) than in DNA of the proliferating tissues (spleen and tail tip epithelium).

[Dynamics and ecological-genetic variability of cytogenetic disturbances in Scots pine populations experiencing technogenic impact].

Scots pine (Pinus sylvestris L.) populations in the vicinity of nuclear industry facilities were monitored. Aberrant cells occurrence in root meristem of germinated seeds from the impacted pine populations was found to be significantly above the reference level during all six years of observations. In the reference population, changes of cytogenetic disturbances with time appeared to be cyclic while in the impacted populations, technogenic stress was strong enough to destroy the natural regularities. The increase in cytogenetic disturbances was accompanied by growth of fluctuations magnitude; deviations of basic oscillation parameters from the reference values rose along with technogenic impact level. Variability in cytogenetic response increased under technogenic stress. Inter-family component of variability predominated, though its contribution slightly decreased in impacted populations. A tendency for destabilization of a repetition coefficient dynamics was found under technogenic impact. A portion of the seeds was exposed to 15 Gy of gamma-rays, and higher radio-resistance in the impacted populations was observed. In the reference population, a family-related analysis of cytogenetic variability components after acute y-exposure revealed significant contributions of "family" and "germination conditions" factors as well as their interactions. On the contrary, in populations existing under chronic stress, considerable modifications in the structure of ecological-genetic variability were found, their degree increasing with technogenic impact severity.

Induced mutation in Agaricus bisporus by gamma ray to improve genetic variability, degradation enzyme activity, and yield.

PURPOSE: Genetic variability in white button mushroom cultivars is very low due to the life cycle. Induction mutations using gamma irradiation is a useful way to generate diversity in white button mushrooms to obtain genotype(s) with desirable traits. METHODS: Gamma irradiation Cobalt-60 was used for inducting genetic diversity in white button mushroom to obtain genotype(s) with desirable traits. Gamma irradiation with doses of 0-500 Gy was conducted on spores on Potato Dextrose Agar medium. RESULTS: The results showed significant differences in days to pin production and harvest, fruit body number, fresh and dry weight, yield, laccase, and manganese peroxidase enzyme activity. After isolating variants, 15 variants were selected on the base of their high yield and enzyme degradation activity. Their genetic variation was confirmed by Sequence Related Amplified Polymorphism (SRAP) markers, and then incubated on three types of substrates (50:50, 75:25, and 100:0 % compost: raw straw). The results showed that all variants, except GR18, colonized in 75:25, and GR3, GR4, GR9, GR61, GR72, and GR74 variants colonized in 50:50. In 100:0 substrate, GR55 and GR63 were the earliest variants, and GR9 produced the highest fruit body number. In 75:25 substrate, GR9, GR3, GR61, GR4, GR74, GR4, GR61, and GR72 showed higher yields. The highest laccase and manganese peroxidase activity were recorded in GR3, GR4, GR9, GR72, and GR61. The isolated 15 variants were clustered into two main groups by cluster analysis and genetic variation was confirmed by SRAP markers. CONCLUSION: The results showed that the diversity in the white button mushroom could be improved using gamma rays, and the variation would be useful for the development of future breeding programs.

Effect of Ionizing Radiation on the Transcript Variants Expression of p21 Gene.

PURPOSE: CDK1A is one of the most important genes that have different key roles in cell lines. This gene has several transcript variants. Investigating of expression of each one actually can be so important because any one of them may have a separate unknown role in cancer cells so can be used to increase therapeutic efficacy. METHODS: A549, MDA-MB-231 and Hek-AD cell lines were used in this study. Firstly, three primers for variants of p21 gene were designed by Snapgene and BLAST software. Secondly, the variants expression was checked for each cell lines by RT-qPCR technique, separately. Then the variants that expressed in the cells were selected for more investigation. Finally 2 Gy irradiation was used to evaluate the effect of that on variants expression. RESULTS: The results show that for all cell lines, primer num1 and 3 expressed before any stimuli. After irradiation, for MDA-MB-231 and A549, the expression of primer num3 was decreased, while for Hek-AD no change was observed. The primer num1 expression after the irradiation was different for the cells, V1 expression was decreased in A549 by fold of 0.03 while expression of this for MDA-MB-231 cells was not changed after 2Gy irradiation. CONCLUSION: It is very necessary to pay attention to the function of each splice variant as well as the response to external stimuli. Understanding the role of each variant in a gene is critical and researchers can use that to improve radiotherapy as well.

Phenotypic Response to Light Versus Shade Associated with DNA Methylation Changes in Snapdragon Plants (Antirrhinum majus).

The phenotypic plasticity of plants in response to change in their light environment, and in particularly, to shade is a schoolbook example of ecologically relevant phenotypic plasticity with evolutionary adaptive implications. Epigenetic variation is known to potentially underlie plant phenotypic plasticity. Yet, little is known about its role in ecologically and evolutionary relevant mechanisms shaping the diversity of plant populations in nature. Here we used a reference-free reduced representation bisulfite sequencing method for non-model organisms (epiGBS) to investigate changes in DNA methylation patterns across the genome in snapdragon plants (Antirrhinum majus L.). We exposed plants to sunlight versus artificially induced shade in four highly inbred lines to exclude genetic confounding effects. Our results showed that phenotypic plasticity in response to light versus shade shaped vegetative traits. They also showed that DNA methylation patterns were modified under light versus shade, with a trend towards global effects over the genome but with large effects found on a restricted portion. We also detected the existence of a correlation between phenotypic and epigenetic variation that neither supported nor rejected its potential role in plasticity. While our findings imply epigenetic changes in response to light versus shade environments in snapdragon plants, whether these changes are directly involved in the phenotypic plastic response of plants remains to be investigated. Our approach contributed to this new finding but illustrates the limits in terms of sample size and statistical power of population epigenetic approaches in non-model organisms. Pushing this boundary will be necessary before the relationship between environmentally induced epigenetic changes and phenotypic plasticity is clarified for ecologically relevant mechanisms with evolutionary implications.

Ionizing Radiation Alters the Transition/Transversion Ratio in the Exome of Human Gingiva Fibroblasts.

Little is known about the mutational impact of ionizing radiation (IR) exposure on a genome-wide level in mammalian tissues. Recent advancements in sequencing technology have provided powerful tools to perform exome-wide analyses of genetic variation. This also opened up new avenues for studying and characterizing global genomic IR-induced effects. However, genotypes generated by next generation sequencing (NGS) studies can contain errors, which may significantly impact the power to detect signals in common and rare variant analyses. These genotyping errors are not explicitly detected by the standard Genotype Analysis ToolKit (GATK) and Variant Quality Score Recalibration (VQSR) tool and thus remain a potential source of false-positive variants in whole exome sequencing (WES) datasets. In this context, the transition-transversion ratio (Ti/Tv) is commonly used as an additional quality check. In case of IR experiments, this is problematic when Ti/Tv itself might be influenced by IR treatment. It was the aim of this study to determine a suitable threshold for variant filters for NGS datasets from irradiated cells in order to achieve high data quality using Ti/Tv, while at the same time being able to investigate radiation-specific effects on the Ti/Tv ratio for different radiation doses. By testing a variety of filter settings and comparing the obtained results with publicly available datasets, we observe that a coverage filter setting of depth (DP) 3 and genotype quality (GQ) 20 is sufficient for high quality single nucleotide variants (SNVs) calling in an analysis combining GATK and VSQR and that Ti/Tv values are a consistent and useful indicator for data quality assessment for all tested NGS platforms. Furthermore, we report a reduction in Ti/Tv in IR-induced mutations in primary human gingiva fibroblasts (HGFs), which points to an elevated proportion of transversions among IR-induced SNVs and thus might imply that mismatch repair (MMR) plays a role in the cellular damage response to IR-induced DNA lesions.

The intergenic region of Arabidopsis thaliana cab1 and cab2 divergent genes functions as a bidirectional promoter.

Genetic engineering plays a unique role in fundamental plant biology studies and in improving crop traits. These efforts often necessitate introduction and expression of multiple genes using promoters from a very limited repertoire. Current common practice of expressing multiple genes is the repeated use of the same or similar promoters. This practice causes more frequent transgene silencing due to a high degree of sequence homology and a greater chance of rearrangement among repeatedly used promoter sequences. Therefore, availability and use of natural bidirectional promoters to minimize gene silencing and achieve desirable expression pattern of transgenes is a critical issue in the field of plant genetic engineering. Here we describe the use of a single natural bidirectional promoter to drive the expression of two reporter genes in onion epidermal cells and in transgenic tobacco plants. We show that (1) the promoter drives the simultaneous expression of GUS and GFP reporter genes after transient expression and stable transformation, (2) the transcription is equally strong in both directions, (3) immediate upstream regions in each direction control transcription independently from each other, and (4) the reporter genes are expressed in leaves and stems but not in roots, as expected from the fact that the endogenous promoter controls the expression of two photosynthetic genes in Arabidopsis. Hence, use of bidirectional promoters in heterologous background provides a means to express multiple genes in transgenic plants and aids genetic engineering-based crop improvement.

Transcriptomic comparison in the leaves of two aspen genotypes having similar carbon assimilation rates but different partitioning patterns under elevated [CO2].

This study compared the leaf transcription profiles, physiological characteristics and primary metabolites of two Populus tremuloides genotypes (clones 216 and 271) known to differ in their responses to long-term elevated [CO2] (e[CO2]) at the Aspen free-air CO2 enrichment site near Rhinelander, WI, USA. The physiological responses of these clones were similar in terms of photosynthesis, stomatal conductance and leaf area index under e[CO2], yet very different in terms of growth enhancement (0-10% in clone 216; 40-50% in clone 271). Although few genes responded to long-term exposure to e[CO2], the transcriptional activity of leaf e[CO2]-responsive genes was distinctly different between the clones, differentially impacting multiple pathways during both early and late growing seasons. An analysis of transcript abundance and carbon/nitrogen biochemistry suggested that the CO2-responsive clone (271) partitions carbon into pathways associated with active defense/response to stress, carbohydrate/starch biosynthesis and subsequent growth. The CO2-unresponsive clone (216) partitions carbon into pathways associated with passive defense (e.g. lignin, phenylpropanoid) and cell wall thickening. This study indicates that there is significant variation in expression patterns between different tree genotypes in response to long-term exposure to e[CO2]. Consequently, future efforts to improve productivity or other advantageous traits for carbon sequestration should include an examination of genetic variability in CO2 responsiveness.

[The dynamics of variability of the genotype of experimental populations of Drosophila melanogaster by chronic radiation exposure].

The reaction on the irradiation in a dose 3 Gy of experimental populations of Drosophila melanogaster, differing on mobile genetic element patterns, chronically irradiated in low doses ionising radiation was investigated. Received results testify that the effect of radioadaptation is found out only in populations with an initial genotype and is not revealed at populations containing P-mobile elements. It is shown, that in chronically irradiated populations D. melanogaster with an initial genotype, decrease in frequency recessive lethal mutations after a sharp irradiation in a dose 3 Gy is observed. The analysis of frequency of dominant lethal mutations and gonads atrophy such tendency has not revealed. It is supposed, that the mechanisms participating in formation of the adaptive answer, induced with an irradiation and transpositions activity of mobile elements differ.

Scots pine as a promising indicator organism for biomonitoring of the polluted environment: A case study on chronically irradiated populations.

In this paper the main results of long-term (2003-2016) observations on Scots pine populations inhabiting sites affected by the Chernobyl accident are presented. Populations growing for many years under chronic radiation exposure are characterized by the enhanced mutation rates, increased genetic diversity, changes in the gene expression and in the level of genome-wide methylation, alterations in the temporal dynamics of cytogenetic abnormalities and genetic structure of populations. However, significant changes at the genetic level had no effects on enzymatic activity, morphological abnormalities, and reproductive ability of pine trees. The results presented increase our understanding of the long-term effects of chronic radiation exposure on plant populations in the wild nature and provide important information for the management and monitoring of radioactively contaminated territories.

Induced polygenic variations through γ -rays irradiation and selection of novel genotype in chamomile (Chamomilla recutita [L.] Rauschert).

Purpose: To develop elite mutants in chamomile (Chamomilla recutita [L.] Rauschert) for increasing the quantity and quality of essential oil rich in acetylenic compound (2Z,8Z)-matricaria acid methyl ester by applying γ -rays irradiation. Molecular and chemical analysis was performed for ithe dentification/differentiation of mutant genotype. Materials and methods: Chamomile (Chamomilla recutita [L.] Rauschert) variety Vallary seeds were irradiated by applying γ -rays irradiation at 100, 200, 300, 400, 500, 600, 700, 800, 900 and1000 Gy doses at a dose rate of 55 Gy/min and mutants were isolated and analyzed for the quantity and quality of essential oil. The oil was found to be rich in acetylenic compound (2Z,8Z)-matricaria acid methyl ester and the results obtained were validated using gas chromatography (GC) coupled with either Flame Ionization detection (GC-FID) or mass spectrometer (GC-MS), and nuclear magnetic resonance (NMR). Results: The selected mutant SELM-1 (Selection Mutant-1) showed the production potential of 7.00-7.50 q ha-1 dry flowers and 6.00-6.50 kg ha-1 essential oil yield. Essential oil of mutant SELM-1 contained in [(2Z,8Z)-matricaria acid methyl ester] (76-80%) useful in cosmetic, perfumery, and pharmaceutical industries. Conclusion:γ -rays irradiation method is a very efficient mutation breeding method for chamomile crop. GC-FID or GC-MS and NMR methods are found to be the most powerful methods for screening of essential oil chemical compounds isolated from the mutants. The novel mutant (SELM-1) is very promising in terms of high flower and essential oil yield rich in acetylenic compound (2Z,8Z)-matricaria acid methyl ester (76-80%), hence, it was released as variety in Council of Scientific & Industrial Research (CSIR)-Central Institute of Medicinal and Aromatic Plant (CIMAP), Lucknow U.P. (India) named as CIM-Ujjwala for commercial cultivation.

Cytological Effect of Gamma Radiation on Selected Mutants of Wheat Triticum aestivum L. in M3 Generation.

BACKGROUND AND OBJECTIVE: Wheat (Triticum aestivum L.) offers some unique opportunities for the induction and exploitation of agronomic value. The use of gamma radiation has been proven to be an effective method to induce genetic variation in crops. We aimed to determine genetically stable mutants of wheat which could be utilized for breeding purposes. MATERIALS AND METHODS: We did a cytological investigation of induced mutant's behavior and chiasma frequency. Selected mutant types induced in dry and soaked seeds were treated with different doses of gamma rays. Each treated sample and control were subjected to cytological examination of the fixed pollen mother cells in various meiotic stages. RESULTS: The percentage of the total abnormal cells significantly increased in one mutant and significantly decreased in the other mutant. The percentage of total abnormal cells did not diminish from the first to the second meiotic division. The types of meiotic anomalies found included laggards (56.51%), univalent (9.43%), stickiness (45.45%) and bridges (19.32%). There were genotypic differences in the frequency of occurrence of multivalent (trivalent and quadrivalents). A marked reduction in the number of rod and ring bivalent/cell in some genotypes were noticed. The frequency of chiasmata per pollen mother cell was reduced subsequently. Depression index of mutants was negative compared with controls or treatments except for a few genotypes. CONCLUSION: Selected mutants of wheat tend to be cytologically stable and can therefore, be utilized for breeding purposes.

Chronic radiation exposure as an ecological factor: Hypermethylation and genetic differentiation in irradiated Scots pine populations.

Genetic and epigenetic changes were investigated in chronically irradiated Scots pine (Pinus sylvestris L.) populations from territories that were heavily contaminated by radionuclides as result of the Chernobyl Nuclear Power Plant accident. In comparison to the reference site, the genetic diversity revealed by electrophoretic mobility of AFLPs was found to be significantly higher at the radioactively contaminated areas. In addition, the genome of pine trees was significantly hypermethylated at 4 of the 7 affected sites.

Transmission of genomic instability from a single irradiated human chromosome to the progeny of unirradiated cells.

Ionizing radiation can induce chromosome instability that is transmitted over many generations after irradiation in the progeny of surviving cells, but it remains unclear why this instability can be transmitted to the progeny. To acquire knowledge about the transmissible nature of genomic instability, we transferred an irradiated human chromosome into unirradiated mouse recipient cells by microcell fusion and examined the stability of the transferred human chromosome in the microcell hybrids. The transferred chromosome was stable in all six microcell hybrids in which an unirradiated human chromosome had been introduced. In contrast, the transferred chromosome was unstable in four out of five microcell hybrids in which an irradiated human chromosome had been introduced. The aberrations included changes in the irradiated chromosome itself and rearrangements with recipient mouse chromosomes. Thus the present study demonstrates that genomic instability can be transmitted to the progeny of unirradiated cells by a chromosome exposed to ionizing radiation, implying that the instability is caused by the irradiated chromosome itself and also that the instability is induced by the nontargeted effect of radiation.