• Journal of Radiation Protection and Research
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• v.23 no.1
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• pp.17-23
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• 1998

Dose response relationships for one of biological end-points (gene mutation) in somatic cells of Tradescantia 4430 clones were studied using neutrons coming out of a californium-252 isotopic source. And the relative biological effectiveness (RBE) of neutrons in relation to X-rays in the induction of TSH pink mutations was assessed. Inflorescences were irradiated with X-ray from X-ray generator and neutrons from $^{252}Cf$ source. Irradiated cuttings were incubated with aeration in neutrient solution under the controlled condition. For more than 4 weeks after irradiation cell mutations were scored. Pink mutation frequencies were calculated from the pooled data for the peak interval (days 6 to 13 post-irradiation). Somatic cell mutations in TSH showed linear dose response relationships in the range of neutron doses available for the experiment. The RBE values estimated for neutrons in relation to X-rays were in the range 3.1 to 6.8, which were much lower than normally recognized value.

• Microbiology and Biotechnology Letters
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• v.40 no.1
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• pp.70-75
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• 2012

In Salmonella enterica, many genes encoded within Salmonella pathogenicity islands (SPI) 1 and 2 are required to cause a range of diseases in a variety of hosts. The SPI1-encoded regulator HilD activates both the SPI1 and 2 genes at different times during growth in Luria-Bertani (LB) media. In this study, the expression levels of hilD during growth in LB were investigated. The data suggest that hilD expression is induced in the early stationary phase and decreases in the late stationary phase, when sseA, an SPI2 gene, is maximally expressed. However, HilD could act as an activator of sseA expression in the late stationary phase despite being present at low levels. SseA expression was investigated in SPI1 regulator mutant strains, hilA, hilD and invF mutants. As expected, hilD mutation decreased sseA expression. However, we found that invF mutation caused a 1.5-fold increase in sseA expression in not only LB but also M9 minimal media, which is thought to resemble an intracellular environment. InvF overexpression restored sseA expression to wild-type levels in an invF mutant but did not cause an additional reduction in sseA expression. These results suggest that SPI1 controls SPI2 expression either positively or negatively.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.4
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• pp.318-323
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• 1981

This study was conducted to establish an effective radiation treatment and selection method for induced mutants in M_1 population of soybean treated with gamma-ray. About 64% of total M_1 plants was reduced in plant height up to 50 - 60% and among which 60 - 70% of the plants were contained mutations in M_2 generation. About 60% of the MI plants have born 6 - 15 seeds per plant and 50 - 60% of their progenies produced mutants in M_2 generation. Positive correlation between plant height and number of seeds per plant in M_1 population was found. Higher visible macro-mutation rate in M_2 was observed in the groups of reduced plant height and seed number in the M_1 generation, whereas the frequency of chlorophyll mutation was increased in the group of less damaged plants. The size of mutation sector was increased with reduction in number of seeds per M_1 plant and the mutants were occurred at random in all the parts of M_1 plants. For the effective selection of mutants in soybean mutation breeding, the M_1 seeds should be harvested from the radiation damaged M_1 plants with the application of higher doses of mutagens, and handling M_2 generation by bulk population method is recommendable.

• Journal of Radiation Industry
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• v.6 no.3
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• pp.223-229
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• 2012

In this study, we investigated the biological damage and stress responses induced by ion beam (proton beam) irradiation as a basis for the development of protective measures against space radiation. We examined the biological effects of proton beam produced by MC-50 cyclotron at KIRAMS on the cultured cells and mice. The proton beam energy used in this study was 34.9 MeV and the absorption dose rate for cells and mice were $0.509Gy\;sec^{-1}$ and $0.65Gy\;sec^{-1}$, respectively. The cell survival rates measured by plating efficiency showed the different sensitivity and dose-relationship between CHO cells and Balb/3T3 cells. HGPRT gene mutation frequency in Balb/3T3 was $15{\times}10^{-6}Gy^{-1}$, which was similar to the reported value of X-ray. When stress signaling proteins were examined in Balb/3T3 cells, $I{\kappa}B-{\alpha}$ decreased markedly whereas p53, phospho-p53, and Rb increased after proton beam irradiation, which implied that the stress signaling pathways were activated by proton beam irradiation. In addition, cellular senescence was induced in IMR-90 cells. In the experiments with C57BL/6 mouse, the immune cells (white blood cells, lymphocytes) in the peripheral blood were greatly reduced following proton beam irradiation whereas red blood cells and platelets showed relatively little change. These results can be utilized as basic data for studying the biological effects of proton beam using MC-50 cyclotron with respect to proton therapy research as well as space radiation research.

• Molecules and Cells
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• v.39 no.8
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• pp.594-602
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• 2016

Alkyl hydroperoxide reductase subunit C from Pseudomonas aeruginosa PAO1 (PaAhpC) is a member of the 2-Cys peroxiredoxin family. Here, we examined the peroxidase and molecular chaperone functions of PaAhpC using a site-directed mutagenesis approach by substitution of Ser and Thr residues with Cys at positions 78 and 105 located between two catalytic cysteines. Substitution of Ser with Cys at position 78 enhanced the chaperone activity of the mutant (S78C-PaAhpC) by approximately 9-fold compared with that of the wild-type protein (WT-PaAhpC). This increased activity may have been associated with the proportionate increase in the high-molecular-weight (HMW) fraction and enhanced hydrophobicity of S78C-PaAhpC. Homology modeling revealed that mutation of $Ser^{78}$ to $Cys^{78}$ resulted in a more compact decameric structure than that observed in WT-PaAhpC and decreased the atomic distance between the two neighboring sulfur atoms of $Cys^{78}$ in the dimer-dimer interface of S78C-PaAhpC, which could be responsible for the enhanced hydrophobic interaction at the dimer-dimer interface. Furthermore, complementation assays showed that S78C-PaAhpC exhibited greatly improved the heat tolerance, resulting in enhanced1 survival under thermal stress. Thus, addition of Cys at position 78 in PaAhpC modulated the functional shifting of this protein from a peroxidase to a chaperone.

• Korean Journal of Breeding Science
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• v.42 no.3
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• pp.222-225
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• 2010

'Seoritae' is a very famous variety of black soybean for mixed cooking with rice in Korea. However, it has a couple of bad traits such as late flowering and maturity. To improve these characteristics, seeds of original 'Seoritae' were irradiated using a 250 Gy gamma ray in 1994. Some mutants were identified and finally a new soybean variety 'Josaengseori' was developed in 2005. This variety has a few distinguishable characteristics such as smaller grain size, early maturity and high yielding compared to the 'Seoritae'. The flowering period of 'Josaengseori' is 57 days after seeding (DAS), which is 10 days earlier than that of 'Seoritae' (67 DAS). The maturation period of 'Josaengseori' is 130 DAS, which is 34 days earlier than 'Seoritae' (164 DAS). And the total yield of the new variety with 179 kg/10a is 2.4 times higher than that of 'Seoritae' with 74 kg/10a. 100 grain weight of 'Josaengseori' is 32.8 g, which is 20% lower than that of 'Seoritae' with 40.1 g.

• Journal of Animal Environmental Science
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• v.19 no.1
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• pp.63-68
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• 2013

In vitro culture and radiation techniques were used for obtaining mutants tin tall fescue. Endophyte free and friendly tall fescue cultivars Kentucky-31 and Jesup were used for induction of genetic variability through in-vitro mutagenesis. Mature seeds was used for callus induction on 6 mg/L 2,4-D. Actively growing and compact callus was treated with three different doses of gamma rays (10 Gy, 30 Gy and 50 Gy). Maximum proliferation and plantlets regeneration growth was observed in control and minimum at 10 Gy. Furthermore, the maximum number of tiller in the irradiated population was observed in 10 Gy. The treatments 30 Gy and 50 Gy exhibited negative impact on the tillering potential of the tall fescue plant. The object of this study was to develop protocols for mutation breeding in tall fescue through radiation techniques.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.9-9
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• 2021

Mutation breeding is useful for improving agronomic characteristics of various crops. In this study, we constructed soybean Mutant Diversity Pool (MDP) from 1,695 gamma-irradiated mutants through two selection phases over M1 to M12 generations; we selected 523 mutant lines exhibiting at least 30% superior agricultural characteristics, and, second, we eliminated redundant morphological phenotypes in the M12 generation. Finally, we constructed 208 MDP lines and investigated 11 agronomic traits. We then assessed the genetic diversity and inter-relationships of these MDP lines using target region amplification polymorphism (TRAP) markers. Among the different TRAP primer combinations, polymorphism levels and PIC values averaged 59.71% and 0.15, respectively. Dendrogram and population structure analyses divided the MDP lines into four major groups. According to an analysis of AMOVA, the percentage of inter-population variation among mutants was 11.320 (20.6%), whereas mutant inter-population variation ranged from 0.231 (0.4%) to 14.324 (26.1%). Overall, the genetic similarity of each cultivar and its mutants were higher than within other mutant populations. In an analysis of the genome-wide association study (GWAS) using based on the genotyping-by-sequencing (GBS), we detected 66 SNPs located on 13 different chromosomes were found to be highly associated with four agronomic traits: days of flowering (33 SNPs), flower color (16 SNPs), node number (6 SNPs), and seed coat color (11 SNPs). These results are consistent with those previously reported for other genetic resource populations, including natural accessions and recombinant inbred line. Our observations suggest that genomic changes in mutant individuals induced by gamma rays occurred at the same loci as those of natural soybean population. This study has demonstrated that the integration of GBS and GWAS can serve as a powerful complementary approach to gamma-ray mutation for the dissection of complex traits in soybean.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2004.10a
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• pp.29-34
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• 2004

Reduction in stratospheric ozone layer increases the amount of ultraviolet-B radiation (UVB: 280-320 nm) that reaches the earth ’ s surface. UVB radiationcan damage plants, resulting in decrease in growth and productivity. UVB-augmentation studies have indicated that the sensitivity to UVB radiation in plants varies among the species and cultivars. However. there are no definitive answers for the mechanisms of UVB-resistance in higher plants and for bioengineering design and development of UVB-tolerant plants. We have been studying physiological and biochemical aspects of the effects of UVB radiation on growth and yield of rice COryza sativa LJ. aiming to clarify the mechanism of resistance to UVB radiationin rice. At this meeting. weintroduce our research as followed: (1) supplementary UVB radiation has inhibitory effects on the growth. yield and grain development of rice; (2) UVB sensitivity of rice varies widely among cultivars; (3) among Japanese rice cultivars. Sasanishiki. a leading variety in northeast Japan. is more resistant to UVB. while Norin 1. a progenitor of Sasanishiki. is less resistant; (4)UV-sensitive Norin 1 cultivar is deficient in photorepair of UVB-induced cyclobutane pyrimidine dimer (CPD). and this deficiency results from one amino acid residue alteration of CPD photolyase. These results suggest that spontaneously occurring mutation in CPD photolyase gene could lead to difference in UVB sensitivity in rice. and that CPD photolyase might be a useful target for improving UVB-sensitivity in rice by selective breeding or bioengineering of UVB-tolerant rice.

• The Korean Journal of Zoology
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• v.25 no.1
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• pp.29-29
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• 1982

Carcinogenesis is extremely complex. Therefore, it is paradoxical but nonetheless important in cancer research if, in an animal whose parental strains are normally sensitive to cancer induction, we could find mutant strains which are resistant to various carcinogens as a result of mutations in one or two genes. No such mutants have been reported so far as I am aware but we do know that at early stages in their development, fish, mice, and humans are highly resistant to cancer induction by chemicals and radiation. I will give a brief overview of the stage-dependent resistance of fish, mice and humans to cancer induction and discuss the stem-cell mutation theory to explain the cancer-resistant stages. Finally, the latent period of induced neoplasms will be discussed in relation to the stem-cell mutation theory.