• 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.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.287-294
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• 2008

Three amino acid residues (His119, Glu164, and Glu338) in the active site of Thermus caldophilus GK24 ${\beta}$-glycosidase (Tca ${\beta}$-glycosidase), a family 1 glycosyl hydrolase, were mutated by site-directed mutagenesis. To verify the key catalytic residues, Glu164 and Glu338 were changed to Gly and Gln, respectively. The E164G mutation resulted in drastic reductions of both ${\beta}$-galactosidase and ${\beta}$-glucosidase activities, and the E338Q mutation caused complete loss of activity, confirming that the two residues are essential for the reaction process of glycosidic linkage hydrolysis. To investigate the role of His119 in substrate binding and enzyme activity, the residue was substituted with Gly. The H119G mutant showed 53-fold reduced activity on 5mM p-nitrophenyl ${\beta}$-D-galactopyranoside, when compared with the wild type; however, both the wild-type and mutant enzymes showed similar activity on 5mM p-nitrophenyl ${\beta}$-D-glucopyranoside at $75^{\circ}C$. Kinetic analysis with p-nitrophenyl ${\beta}$-D-galactopyranoside revealed that the $k_{cat}$ value of the H119G mutant was 76.3-fold lower than that of the wild type, but the $K_m$ of the mutant was 15.3-fold higher than that of the wild type owing to the much lower affinity of the mutant. Thus, the catalytic efficiency $(k_{cat}/K_m)$ of the mutant decreased to 0.08% to that of the wild type. The $k_{cat}$ value of the H119G mutant for p-nitrophenyl ${\beta}$-D-glucopyranoside was 5.l-fold higher than that of the wild type, but the catalytic efficiency of the mutant was 2.5% of that of the wild type. The H119G mutation gave rise to changes in optima pH (from 5.5-6.5 to 5.5) and temperature (from $90^{\circ}C\;to\;80-85^{\circ}C$). This difference of temperature optima originated in the decrease of H119G's thermostability. These results indicate that His119 is a crucial residue in ${\beta}$-galactosidase and ${\beta}$-glucosidase activities and also influences the enzyme's substrate binding affinity and thermostability.

• KSBB Journal
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• v.15 no.2
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• pp.113-119
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• 2000

In order to produce xylitol with high yield, experiments were carried out to develope xylitol dehydrogenase (XDH) defective m mutant from Pichia stipitis and to investigate the xylit이 fermentation characteristics of mutant strain. After treatment of P s stipitis with EMS, mutant PXM-4 was selected based on the XDH activity and xylitol production capability. Among the tested c cosubstrates, galactose was selected as an adequate cosubstrate on xyl뻐I production of mutant PXM-4. With the increase of galactose concentration, xylitol production was decreased because the transport of xylose into cell was inhibited by g galactose. The optimal concentration of galactose for the production of xylitol using 20 g/L xylose was 20 g/L. Under this c condition, maximum concentration of xylitol and yield were 14.4 g/L and 97%, respectively. In order to prevent the inhibitory e effect of xylose transport by galactose, galactose was fed with low concentration and the concentration of xylitol produced w was increased up to 25 g/L. In the fermentation of corn cob hydrolyzate by mutant PXM-4, xylose was completely converted t to xylit이 with a 100% yield in 4 days culture.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.2
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• pp.657-662
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• 2014

Background: The epidermal growth factor receptor (EGFR) mutation status of lung cancer is important because it means that EGFR-tyrosine kinase inhibitor treatment is indicated. The purpose of this prospective study is to determine whether EGFR mutation status could be identified with reference to preoperative factors. Materials and Methods: One hundred-forty eight patients with lung cancer (111 adenocarcinomas, 25 squamous cell carcinomas and 12 other cell types) were enrolled in this study. The EGFR mutation status of each lung cancer was analyzed postoperatively. Results: There were 58 patients with mutant EGFR lung cancers (mutant LC) and 90 patients with wild-type EGFR lung cancers (wild-type LC). There were significant differences in gender, smoking status, maximum tumor diameter in chest CT, type of tumor shadow, clinical stage between mutant LC and wild-type LC. EGFR mutations were detected only in adenocarcinomas. Maximum standardized uptake value (SUVmax:$3.66{\pm}4.53$) in positron emission tomography-computed tomography of mutant LC was significantly lower than that ($8.26{\pm}6.11$) of wild-type LC (p<0.0001). Concerning type of tumor shadow, the percentage of mutant LC was 85.7% (6/7) in lung cancers with pure ground glass opacity (GGO), 65.3%(32/49) in lung cancers with mixed GGO and 21.7%(20/92) in lung cancers with solid shadow (p<0.0001). For the results of discriminant analysis, type of tumor shadow (p=0.00036) was most significantly associated with mutant EGFR. Tumor histology (p=0.0028), smoking status (p=0.0051) and maximum diameter of tumor shadow in chest CT (p=0.047) were also significantly associated with mutant EGFR. The accuracy for evaluating EGFR mutation status by discriminant analysis was 77.0% (114/148). Conclusions: Mutant EGFR is significantly associated with lung cancer with pure or mixed GGO, adenocarcinoma, never-smoker, smaller tumor diameter in chest CT. Preoperatively, EGFR mutation status can be identified correctly in about 77 % of lung cancers.

• Korean Journal of Plant Resources
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• v.24 no.1
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• pp.17-22
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• 2011

This study was for developing leaf chlorophyll mutant cultivars of Cymbidium goeringii by ethyl-methanesulfonate(EMS) treatment. Chlorophyll mutant rhizomes were easily produced by 0.2% EMS treatment in this genus. Among the mutants, they became dark brown about 50% of the rhizomes. When the dark-brown rhizomes were cultured in a solidified MS medium, new rhizomes were formed from part of the old ones. Chlorophyll mutant rhizomes were obtained from subcultured meristem tissues of newly-formed rhizomes. The rhizomes were cut and subcultured for a year and then became mutant plants. As the results, they produced 4 kinds of leaf mutant cultivars; zigzag-striped, comb-striped, net-striped, and dwarf types, indicating that the EMS treatment in the rhizome could produce versatile leaf chlorophyll regulating mutants. These results suggest that our method is useful for developing leaf mutant cultivars of this planta which they are estimated as higher commercial values.

• Journal of Crop Science and Biotechnology
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• v.11 no.3
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• pp.181-186
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• 2008

To assess the potential as biofortified rice varieties, new endosperm and grain mutant lines were selected from $M_4$ generation seeds of the rice cultivar Shindongjin, which were either $\gamma$-irradiated or treated with N-methyl-N-nitrosourea(MNU) and lipid, sugar, and tocopherol content were analyzed. Amylose content in non-waxy mutants ranged from 8.8% in SM-4, a dull-type mutant, to 29.5% in SM-51, compared to 18.9% in the parental variety, Shindongjin. SM-23, a floury-type mutant, contained 0.09 ${\mu}g/g$ $\alpha$-tocopherol(40.9% of total tocopherol), was three times higher than in the parental variety. SM-32, a giant embryo-type mutant, had a 2.2-fold higher total tocopherol content, 2.1-fold higher $\alpha$-tocopherol, and 5.5-fold higher $\delta$-tocopherol content(47.3% of total tocopherol) than the parental variety(0.13 ${\mu}g/g$). Total free sugar content was elevated in all selected mutants and 1.2-8.6 times higher than in the parental variety(11.38 ${\mu}g/g$). These increased sugar levels were due to increase in sucrose concentration. SM-23(floury-type mutant) and SM-51(high amylose-type mutant) had 4.6 and 7.0 times more sugar, respectively, than the parental variety(11.38 ${\mu}g/g$). With relatively high concentrations, most mutants showed elevated fatty acid content in the SM 32(giant embryo-type) and SM-51(high amylose-type) mutants, at 124.56 and 89.59 mg/g, respectively. All selected mutants displayed valuable characteristics for the development of new varieties in rice-breeding programs.

• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.373-381
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• 2019

Site-directed mutagenesis was employed to generate five different triple point mutations in the double mutant (C295A/I86A) of Thermoanaerobacter ethanolicus alcohol dehydrogenase (TeSADH) by computer-aided modeling with the aim of widening the small alkyl-binding pocket. TeSADH engineering enables the enzyme to accept sterically hindered substrates that could not be accepted by the wild-type enzyme. The underline in the mutations highlights the additional point mutation on the double mutant TeSADH introduced in this work. The catalytic efficiency ($k_{cat}/K_M$) of the ${\underline{M151A}}$/C295A/I86A triple TeSADH mutant for acetophenone increased about 4.8-fold higher than that of the double mutant. A 2.4-fold increase in conversion of 3'-methylacetophenone to (R)-1-(3-methylphenyl)-ethanol with a yield of 87% was obtained by using ${\underline{V115A}}$/C295A/I86A mutant in asymmetric reduction. The ${\underline{A85G}}$/C295A/I86A mutant also produced (R)-1-(3-methylphenyl)-ethanol (1.7-fold) from 3'-methylacetophenone and (R)-1-(3-methoxyphenyl)-ethanol (1.2-fold) from 3'-methoxyacetophenone, with improved yield. In terms of thermal stability, the ${\underline{M151A}}$/C295A/I86A and ${\underline{V115A}}$/C295A/I86A mutants significantly increased ${\Delta}T_{1/2}$ by $+6.8^{\circ}C$ and $+2.4^{\circ}C$, respectively, with thermal deactivation constant ($k_d$) close to the wild-type enzyme. The ${\underline{M151A}}$/C295A/I86A mutant reacts optimally at $70^{\circ}C$ with almost 4 times more residual activity than the wild type. Considering broad substrate tolerance and thermal stability together, it would be promising to produce (R)-1-(3-methylphenyl)-ethanol from 3'-methylacetophenone by ${\underline{V115A}}$/C295A/I86A, and (R)-1-phenylethanol from acetophenone by ${\underline{M151A}}$/C295A/I86A mutant, in large-scale bioreduction processes.

• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.324-332
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• 1985

Aspergillus niger B-15 with strong Endo-polygalacturonase (Endo-PG) activities was selected out from a total of 1,573 fungal strains isolated from various testing materials. A mutant strain, U-46, was obtained from the Aspergillus niger B-15 by repeated irradition of ultra-violet light. The objectives of the study were to investigate the fungal properties of the parental and mutant strains obtained and to study the condition of enzyme production and reaction. The results obtained are summarized as follows: 1. The size of conidial head of the U-46 mutant was smaller than that of the parental strains, B-15 and the length of the conidiophore was also shorter than that of the parental strains. 2. The optimum conditions for the Endo-PG production of the parental B-15 strain in the wheat bran Koji were obtained when 40% of water was added to the wheat bran and the temperature was 30 to $35^{\circ}C$. However, the best condition for the mutant U-46 strain was attained when 60 to 70% of water was added and the temperature was $35^{\circ}C$. The optimum growing periods were two to three days for both parental and mutant strains. 3. Under the optimum producing conditions of each strains, the enzymatic activity of the mutant U-46 was 20 times higher than the Endo-PG of the parental strain, B-15. 4. When both strains were cultured in the wheat bran Koji containing 60% of water at $35^{\circ}C$ for three days, the mutant strain. U-46, was about 46 times higher in the Endo-PG activity and about 18 times greater in Exo-PG activity than the parental strain, B-15. The activities of cellulase, $\alpha$-amylase, and glucoamylase were also highly increased in the mutant strain. 5. The mutant strain, U-46, increased its Endo-PG activity up to 20% over that of ordinary case when 1.2 to 1.5% of ammonium sulphate was added to the wheat bran. 6. The optimum condition for Endo-PG activity of crude enzyme of the mutant strain, U-46, was attained when pH of reaction solution was 4.0 to 4.5 and the temperature was $50^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.26 no.6
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• pp.476-482
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• 1998

Growth sensitivity of bifidobacteria on oxygen hindered their industrial applications so that it was necessary to select oxygen-tolerant strains. Studies on their responses to oxygen might facilitate the effective utilization of bifidobacteria in industry. Oxygen-tolerant strain of Bifidobacterium longum JI-1 was able to remove 3% dissolved oxygen within 10 min whilst oxygen-sensitive strain of B. adolescentis, slime non-former, was not. The ability to remove environmental oxygen seemed to be related to the oxygen-tolerance of bifidobacteria. Mutant B. longum ADJ-1 was induced from the B. longum JI-1 under microaerobic atmosphere. There were no differences in sugar utilization pattern, NADH oxidative enzymes and cellular fatty acid compositions between them. The maximal cell density of the mutant was a little bit reduced to 81% of that of the mother strain. However, the mutant formed thick slime layer around its cell. The layer visualized with confocal scanning laser microscopy from the mutant was 6 ${\mu}{\textrm}{m}$ in diameter but that from the mother strain was only 3 ${\mu}{\textrm}{m}$. Therefore, the improved tolerances of the mutant might come from the slime layer, indicating the increase of the layer might be one of oxygen tolerance mechanisms for bifidobacteria.

• Microbiology and Biotechnology Letters
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• v.18 no.5
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• pp.535-540
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• 1990

Bacitlus sphaericus ts-Dl290 was characterized comparatively with the wild type strain 1593 by themeasurements of the biosynthesis of total DNA, RNA and protein on the temperature-shift culturesat permissive temperature of $30^{\circ}C$ and at nonpermissive temperature of $42^{\circ}C$. The growth patterns of the wild type strain and ts-Dl290 were similar at $30^{\circ}C$, but at 4Z C the mutant almost did not grow (temperature-sensitivity). When the growth temperatures of both stains were shifted-up from $30^{\circ}C$ to $42^{\circ}C$ after a 4 hour culture, their growths were normal, but when shifted-down from $42^{\circ}C$ to $30^{\circ}C$ after a 4 h culture, the mutant did not grow. When shifted up from $30^{\circ}C$ to $42^{\circ}C$ after a 4 hculture, the DNA syntheses of the two strains were at a normal rate for 1 h, but after 1 h the biosynthesesdecreased. The rate of DNA synthesis of the wild type strain at the nonpermissive temperature was about 93%, and that of the mutant was about 50% of the ratio of the wild type strain, and the RNA synthesis of the wild type strain was maintained for 3 h, and that of the mutant for 2 h. Thereafter the RNA synthesis decreased, and the synthesis of proteins in the both strains were similarlykept high for 8 h. The reversibility of the DNA synthesis of the mutant at $42^{\circ}C$ was lessened whenthe culture times were increased.re times were increased.