• Journal of Plant Biotechnology
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• v.42 no.1
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• pp.19-24
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• 2015

Glycine betaine (GB) is one of the compatible solutes that accumulate in the chloroplasts of certain halotolerant plants under salt or cold stress. The codA gene for choline oxidase, the enzyme that converts choline into GB, has been cloned from a soil bacterium Arthrobacter globiformis. We generated transgenic sweetpotato plants [Ipomoea batatas (L.) Lam] expressing codA gene in chloroplasts under the control of the SWPA2 promoter (referred to as SC plants) and evaluated SC plants under oxidative and drought stresses. SC plants showed enhanced tolerance to methyl viologen (MV)-mediated oxidative stress and drought stress due to induced expression of codA. At $5{\mu}M$ of MV treatment, all SC plants showed enhanced tolerance to MV-mediated oxidative stress through maintaining low ion leakage and increased GB levels compared to wild type plants. When plants were subjected to drought conditions, SC plants showed enhanced tolerance to drought stress through maintaining high relative water contents and increased codA expression compared to wild type plants. These results suggest that the SC plants generated in this study will be useful for enhanced biomass production on global marginal lands.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2010.10a
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• pp.14-14
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• 2010

Vitamin C (ascorbic acid) is an essential component for collagen biosynthesis and also for the proper functioning of the cardiovascular system in humans. Unlike most of the animals, humans lack the ability to synthesize ascorbic acid on their own due to a mutation in the gene encoding the last enzyme of ascorbate biosynthesis. As a result, vitamin C must be obtained from dietary sources like plants. In this study, we have developed two different kinds of transgenic potato plants (Solanumtuberosum L. cv. Taedong Valley) overexpressing strawberry GalUR and mouse GLoase gene under the control of CaMV 35S promoter with increased ascorbic acid levels. Integration of the these genes in the plant genome was confirmed by PCR and Southern blotting. Ascorbic acid(AsA) levels in transgenic tubers were determined by high-performance liquid chromatography(HPLC). The over-expression of these genes resulted in 2-4 folds increase in AsA intransgenic potato and the levels of AsA were positively correlated with increased geneactivity. The transgenic lines with enhanced vitamin C content showed enhanced tolerance to abiotic stresses induced by methyl viologen(MV), NaCl or mannitol as compared to untransformed control plants. The leaf disc senescence assay showed better tolerance in transgenic lines by retaining higher chlorophyll as compared to the untransformed control plants. Present study demonstrated that the over-expression of these gene enhanced the level of AsA in potato tubers and these transgenics performed better under different abiotic stresses as compared to untransformed control. We have also investigated the mechanism of the abiotic stress tolerance upon enhancing the level of the ascorbate in transgenic potato. The transgenic potato plants overexpressing GalUR gene with enhanced accumulation of ascorbate were investigated to analyze the antioxidants activity of enzymes involved in the ascorbate-glutathione cycle and their tolerance mechanism against different abiotic stresses under invitro conditions. Transformed potato tubers subjected to various abiotic stresses induced by methyl viologen, sodium chloride and zinc chloride showed significant increase in the activities of superoxide dismutase(SOD, EC 1.15.1.1), catalase, enzymes of ascorbate-glutathione cycle enzymes such as ascorbate peroxidase(APX, EC 1.11.1.11), dehydroascorbate reductase(DHAR, EC 1.8.5.1), and glutathione reductase(GR, EC 1.8.1.7) as well as the levels of ascorbate, GSH and proline when compared to the untransformed tubers. The increased enzyme activities correlated with their mRNA transcript accumulation in the stressed transgenic tubers. Pronounced differences in redox status were also observed in stressed transgenic potato tubers that showed more tolerance to abiotic stresses when compared to untransformed tubers. From the present study, it is evident that improved to lerance against abiotic stresses in transgenic tubers is due to the increased activity of enzymes involved in the antioxidant system together with enhanced ascorbate accumulated in transformed tubers when compared to untransformed tubers. At moment we also investigating the role of enhanced reduced glutathione level for the maintenance of the methylglyoxal level as it is evident that methylglyoxal is a potent cytotoxic compound produced under the abiotic stress and the maintenance of the methylglyoxal level is important to survive the plant under stress conditions.

• Journal of Life Science
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• v.27 no.12
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• pp.1415-1420
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• 2017

The metallothionein (MT) gene (IbMT3) was selected from an EST library of suspension-cultured sweet potato cells. The MT gene, which is one of abundant ESTs in the library, is involved in stress regulation of cells and tissues. A full-length IbMT3 cDNA was obtained and analysis of its nucleotide sequence revealed that IbMT3 encoded a type 3 MT protein, based on its structural characteristics. The function of type 3 MT in plants is not yet known. Northern blot analysis showed stronger expression of IbMT3 in suspension-cultured cells than in sweet potato plant leaves. Since cell culture is known to impose a state of oxidative stress on cells, sweet potato plants were subjected to oxidative stress to investigate the transcriptional regulation of IbMT3. When the herbicide methyl viologen (MV) was administered for 6, 12, and 24 hr, IbMT3 transcription rapidly increased at 6 hr and then decreased. A cold treatment at $15^{\circ}C$ for 24 and 48 hr resulted in a gradual increase in IbMT3 expression. These findings indicate that IbMT3 expression is regulated in response to environmental and oxidative stress. IbMT3 isoform is expected to have antioxidant effects in sweet potato plants and may play an important role in cellular adaptation to oxidative stress.

• Molecules and Cells
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• v.23 no.1
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• pp.108-114
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• 2007

The mitogen-activated protein kinase (MAPK) signaling cascade is critical for regulating plant defense systems against various kinds of pathogen and environmental stresses. One component of this cascade, the MAP kinase kinases (MAPKK), has not yet been shown to be induced in plants following biotic attacks, such as those by insects and fungi. We describe here a gene coding for a blast (Magnaporthe grisea)- and insect (Nilaparvata lugens)-responsive putative MAPK kinase, OmMKK1 (Oryza minuta MAPKK 1), which was identified in a library of O. minuta expressed sequence tags (ESTs). Two copies of OmMKK1 are present in the O. minuta genome. They encode a predicted protein with molecular mass 39 kDa and pI of 6.2. Transcript patterns following imbibition of plant hormones such as methyl jasmonic acid (MeJA), ethephone, salicylic acid (SA) and abscisic acid (ABA), as well as exposure to methyl viologen (MV), revealed that the expression of OmMKK1 is related to defense response signaling pathways. A comparative analysis of OmMKK1 and its O. sativa ortholog OsMKK1 showed that both were induced by stress-related hormones and biotic stresses, but that the kinetics of their responses differed despite their high amino acid sequence identity (96%).

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.983-985
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• 2004

PMMA-coated CdS nanorod was prepared by encapsulation of CdS nanorod through the polymerization process of PMMA on the surface of CdS nanorod. PMMA organic nanotube was then obtained from the elimination of the CdS nanorod by the photocorrosion. For the photocorrosion reaction of the CdS nanorod, monochromatic light was irradiated to the oxygen-saturated aqueous methyl viologen solution with PMMAcoated CdS nanorod. Photocorrosion reactions of PMMA-coated CdS nanorod were investigated and characterized by utilizing UV-Vis absorption, X-ray diffraction (XRD) and scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1122-1126
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• 2009

The exogenously added cadaverine is effective in protecting Vibrio vulnificus from methyl viologen (MV)-induced superoxide stress at pH 8.5. Such a protective effect by cadaverine was not observed at pH 7.5. Consistently, the accumulated level of intracellular cadaverine at pH 8.5 is approximately four times as much as that of the control cell at pH 7.5. Cadaverine accumulation is not affected by MV. The protection of V. vulnificus by cadaverine from superoxide stress was abolished when cadB coding for the lysine-cadaverine antiporter was interrupted. However, the cadaverine-mediated protection was complemented with cadB DNA. Therefore, CadB of V. vulnificus not only acts as a lysine-cadaverine antiporter at acid pH to neutralize the external medium, but also mediates cadaverine uptake at alkaline pH to result in cell protection from superoxide stress.

• Journal of Microbiology and Biotechnology
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• v.2 no.4
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• pp.248-254
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• 1992

The initial growth of Clostridium acetobutylicum was not inhibited by 1 atm of H$_2$ while H$_2$ reduced glucose consumption in a solventogenic culture of a phosphate limited 2-stage chemostat. Under 1 atm of H$_2$, a solventogenic culture consumed hydrogen, but an acidogenic culture produced hydrogen. H$_2$ consumption by the solventogenic culture was enhanced by the addition of 5 mM neutral red, an artificial electron carrier with a redox potential of -325 mV. Hydrogenase activity, measured in both directions of production and consumption, showed that activity coupled with methyl viologen is higher in an acidogenic culture than in a solventogenic culture, and that the two cultures have similar activities for methylene blue reduction. The solventogenic culture showed a higher activity coupled with neutral red than the acidogenic culture. From these results, it is hypothesized that hydrogen producing hydrogenase activity is high during the acidogenic phase, and decreases as solventogenesis starts, and that the solventogenic culture produces a second hydrogenase which uses an electron carrier other than ferredoxin. This hypothesis was supported by the fact that enzyme activities involved in electron flow can be coupled to neutral red, indepedent of ferredoxin, and that neutral red addition to the fermentation system increased butanol yield, with a decrease in production of less reduced fermentation products, and $H^2$.

• Journal of Microbiology and Biotechnology
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• v.16 no.5
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• pp.678-682
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• 2006

To remove nitrate from wastewater, a novel bioelectrochemical denitrification system is introduced. In this proposed system, biological reactions are coupled with reactions on the electrode, whereby the electrons are transferred to the bacterial enzymes via a mediator as an electron carrier. The denitrification reaction was achieved with permeabilized Ochrobactrum anthropi SY509 containing denitrifying enzymes, such as nitrate reductase, nitrite reductase, and nitrous oxide reductase, and methyl viologen was used as the mediator. The electron transfer from the electrode to the enzymes in the bacterial cells was confirmed using cyclic voltammetry. A high removal efficiency of nitrate was achieved when the bioelectrochemical system was used with the permeabilized cells. Furthermore, when the permeabilized cells were immobilized to a graphite felt electrode using a calcium alginate matrix containing graphite powder, a high removal efficiency was achieved (4.38 nmol/min mg cell) that was comparable to the result when using the free permeabilized cells.

• Korean Journal of Plant Resources
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• v.23 no.6
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• pp.535-540
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• 2010

Phenylalanine ammonia-lyase (PAL), a key enzyme of the phenylpropanoid biosynthesis pathway, is activated by a number of developmental and environmental cues. The coding region of the NtPAL4 gene was 2,154 bp in length, and its deduced protein was composed of 717 amino acids. Sequence analysis of NtPAL4 cDNA from tobacco (Nicotiana tabacum L.) revealed high structural similarity to PAL genes of other plant species. The NtPAL4 gene exists as a single copy in the tobacco plant, and its transcripts were strongly expressed in flowers and leaves. NtPAL4 expression was significantly induced in response to NaCl, mannitol, and cold treatments, but it was not induced by abscisic acid (ABA). NtPAL4 expression decreased gradually after treatment with ABA and $H_2O_2$; however, NtPAL4 transcripts accumulated after treatment with methyl viologen (MV). Our results suggest that the NtPAL4 gene may function in response to abiotic stresses.

• Journal of the Korean Applied Science and Technology
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• v.16 no.3
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• pp.249-254
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• 1999

The N-docosyl N'-methyl viologen-$(TCNQ)_2$, (DMVT) was synthesized. We investigated the ${\pi}-A$ isotherm of DMVT to find the optimal deposition condition. Temperature-dependent current-voltage characteristics of the DMVT LB films shows that there is an increase in conductivity at 330K or so. The in-plane electrical conductivity at room temperature is in the range of $10^{-7}{\sim}10^{-6}S/cm$. From the plot of logarithmic conductivity as a function of reciprocal temperature, two types of activation energies, 0.04eV and 0.73eV, were obtained depending on the temperature range. The Ohmic behaviour was observed below 0.6V and the Schottky effect was confirmed at $2.5{\sim}6V$, when the I-V characteristics was measured with Al/LB film/Al structure. I-V measurement for Al/LB film/ITO structure showed the asymmetrical I-V relationship, which resulted from the rectification property.