• Proceedings of the Korean Society of Grassland Science Conference
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• 2002.09a
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• pp.18-18
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• 2002

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.273-282
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• 2008

The relationship between water deficit stress and monodehydroascorbate reductase (MDHAR) activity was determined in lettuce (Lactuca sativa L.) leaves under water stress condition imposed by with-holding water for 72 hrs. Relative water content determined in water deficit stressed lettuce leaves gradually reduced from 91.29% to 74.58%, and water content of medium drastically decreased 4.73% after quitting of irrigation. Hydrogen peroxide content in leaves subjected to water deficit stress rapidly increased, but soluble protein content rapidly decreased when those were compared to control plant. The relationship between relative water content and hydrogen peroxide content in stressed leaves positively correlated with $R^2$=0.8851, but soluble protein content reversely correlated with $R^2$=0.9826. Total chlorophyll content in stressed plant leaves was higher than that of control plant, and increased rapidly in early stage of treatment of both stressed and control plants. Carotenoid content was higher than that of control plant, and the ratio of carotenoid to total chlorophyll in stressed plant was higher as compared to control plant. As water deficit stress continued progressively, total ascorbate content in stressed plant leaves was a little higher than that of control plant. But dehydroascorbate (DHA) content within 6 hr of water deficit stress was higher than that of control plant, and then, content of control plant in 12 hr of stress treatment higher than that of stressed leaves. The activity of monodehydroascorbate reductase of cytosolic and chloroplastic tractions increased dramatically, and mRNA of MDHAR was highly detected by probing $^{32}P$-labeled single stranded MDHAR RNA of lettuce plant leaves subjected to water deficit stress. Relationship between MDHAR activity and relative water content and hydrogen peroxide highly correlated with $R^2$=0.9937 and 0.8645, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.1
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• pp.32-39
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• 2013

The relationship between relative water contents of lettuce leaves and biochemical activities in lettuce was examined in this study to explore an adaptation response of lettuce to water stress from soils. Soil water contents and relative water contents of leaves were positively related to show $R^2$=0.8728. Hydrogen peroxide contents of leaves rapidly increased with reduction of soil water content, whereas soluble protein contents and dry matters rapidly decreased. And chlorophyll a and b contents of leaves decreased with increase in carotenoid content. Furthermore, the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) increased dramatically, and mRNA transcript levels of APX, MDHAR and DHAR also increased. Relationship of relative water content of lettuce leaves to hydrogen peroxide, to ascorbate peroxidase activity, to dehydroascorbate reductase activity, and to monodehydroascorbate reductase activity was shown to be positively correlated. It is highly plausible from this study that these enzyme activities could be developed as an indicator of water states in soils.

• Journal of Plant Biotechnology
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• v.41 no.4
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• pp.194-200
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• 2014

Monodehydroascorbate reductase (MDHAR) is an important enzyme that plays a role in the detoxification of reactive oxygen species (ROS) by maintaining reduced pool of ascorbate through recycling the oxidized form of ascorbate. In this study, we isolated a PagMDHAR1 gene from Populus alba ${\times}$ P. glandulosa, and investigated its expression characteristics. The PagMDHAR1 cDNA encodes a putative 434 amino acids containing FAD- and NAD(P)H-binding domains. Southern blot analysis indicated that a single nuclear gene encodes this enzyme. Northern hybridization analysis revealed that PagMDHAR1 is highly expressed in both suspension cells and flower tissues, while its expression levels were enhanced by drought, salt, cold, wounding and ABA. Therefore, PagMDHAR1 might be expressed in response to abiotic stress through the ABA-mediated signaling pathway in this poplar species, suggesting that the PagMDHAR1 plays an important role in the defense mechanisms against oxidative stress.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.164-170
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• 1999

This experiment was carried out to elucidate change of antioxidant enzymes activities subjected to water stresses in soybean plant. In this study, we measured the activities of ascorbate peroxidase(APDX), monodehydroascorbate reductase(MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase(GR) subjected to drought or flooding stresses for 4days and following recovery for 3days. Leaves of two soybean lines subjected to drought or flooding showed premature senescence as evidenced by the decrease in water content and total soluble protein content but those of soybean leaves was increased when stresses were recovered for 3days. The activities of APDX and GR subjected to drought or flooding were the decrease but those of enzymes were recovered when water stress was recovered. The activities of MDHAR with drought or flooding were on the decrease, whereas those of DHAR were increased, respectively. Antioxidant contents decreased continually subjected to drought or flooding but it recovered after 3 days subjected to water stresses.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.249-249
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• 2005

• Journal of Life Science
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• v.21 no.3
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• pp.368-374
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• 2011

The relationship between MDHA reductase activity and ascorbate, dehydroascorbate, and hydrogen peroxide content was evaluated, and this experiment was conducted to determine the change of MDHA reductase activity and the level of steady-state mRNA abundance of MDHA reductase in lettuce leaves subjected to low temperature stress. MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to $4^{\circ}C$ for 24 hr increased, followed by a steady decrease during the duration of recovery to $20^{\circ}C$ for 48 hr. The content of ascorbate slowly increased during low temperature treatment, followed by a rapid increase during the duration of recovery to $20^{\circ}C$ for 48 hr, while dehydroascorbate content rapidly decreased. The relationship between MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to $4^{\circ}C$ and ascorbate content correlated positively ($R^2$=0.9240, 0.9108, respectively), but MDHA reductase activity of chloroplastic and cytosolic fraction and dehydroascorbate were reversely correlated ($R^2$=0.8638, 0.8980, respectively). Hydrogen peroxide content and MDHA reductase activity of chloroplastic and cytosolic fraction in lettuce leaves subjected to $4^{\circ}C$ correlated positively ($R^2$=0.9443, 0.9647, respectively). Northern blot analysis showed that the level of mRNA transcript of MDHA reductase was similar to total activity of MDHA reductase, and also that the level of mRNA of MDHA reductase after recovery to $20^{\circ}C$ for 24 hr decreased.

• Journal of Environmental Science International
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• v.7 no.5
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• pp.633-638
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• 1998

To determine whether the enhanced UV-B causes oxidative stress, and to test the relationship between plant growth response and biochemical defense response to UV-B, two soybean plants, Keunolkong, a highly UV-B susceptible cultivar, and Danyeubkong, a less UV-B susceptible cultivar, were subjected to the enhanced UV-B [daily dose : 0.06 (control) and 11.32 (enhanced UV-B) kJ $m^{-2}$ ; $UV-B_{BE}$] for 3 weeks. Contents of malondialdehyde and total carotenold were increased in Keunolkong compared with Danyeubkong by UV-B. In control plants, ascorbate level of Danyeubkong was 3 times higher than that of Keunolkong. The ratio of dehydroascorbate/ascorbate was highly increased in Keunolkong by UV-B . The activities of antioxidative enzyme such as superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase and glutathione reductase were increased in both cultivars by UV-B. This results indicate that enhanced UV-B caused oxidative stress in both two cultivars, especially in Keunolkong. Susceptibility of two soybean cultivars to UV-B is closely related to the levels of antioxidants such as carotenoid and ascorbate.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.235-235
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• 2017

Chromium (Cr) toxicity is hazardous to the seed germination, growth, and development of plants. ${\gamma}$-Aminobutyric acid (GABA) is a non-protein amino acid and is involved in stress tolerance in plants. To investigate the effects of GABA in alleviating Cr toxicity, we treated eight-d-old mustard (Brassica juncea L.) seedlings with Cr (0.15 mM and 0.3 mM $K_2CrO_4$, 5 days) alone and in combination with GABA ($125{\mu}M$) in a semi-hydroponic medium. The roots and shoots of the seedlings accumulated Cr in a dose-dependent manner, which led to an increase in oxidative damage [lipid peroxidation; hydrogen peroxide ($H_2O_2$) content; superoxide ($O{_2}^{{\cdot}-}$) generation; lipoxygenase (LOX) activity], MG content, and disrupted antioxidant defense and glyoxalase systems. Chromium stress also reduced growth, leaf relative water content (RWC), and chlorophyll (chl) content but increased phytochelatin (PC) and proline (Pro) content. Furthermore, supplementing the Cr-treated seedlings with GABA reduced Cr uptake and upregulated the non-enzymatic antioxidants (ascorbate, AsA; glutathione, GSH) and the activities of the enzymatic antioxidants including ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II), and finally reduced oxidative damage. Adding GABA also increased leaf RWC and chl content, decreased Pro and PC content, and restored plant growth. These findings shed light on the effect of GABA in improving the physiological mechanisms of mustard seedlings in response to Cr stress.

• Journal of Ginseng Research
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• v.41 no.3
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• pp.307-315
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• 2017

Background: Red-skin root disease has seriously decreased the quality and production of Panax ginseng (ginseng). Methods: To explore the disease's origin, comparative analysis was performed in different parts of the plant, particularly the epidermis, cortex, and/or fibrous roots of 5-yr-old healthy and diseased red-skin ginseng. The inorganic element composition, phenolic compound concentration, reactive oxidation system, antioxidant concentrations such as ascorbate and glutathione, activities of enzymes related to phenolic metabolism and oxidation, and antioxidative system particularly the ascorbate-glutathione cycle were examined using conventional methods. Results: Aluminum (Al), iron (Fe), magnesium, and phosphorus were increased, whereas manganese was unchanged and calcium was decreased in the epidermis and fibrous root of red-skin ginseng, which also contained higher levels of phenolic compounds, higher activities of the phenolic compound-synthesizing enzyme phenylalanine ammonia-lyase and the phenolic compound oxidation-related enzymes guaiacol peroxidase and polyphenoloxidase. As the substrate of guaiacol peroxidase, higher levels of $H_2O_2$ and correspondingly higher activities of superoxide dismutase and catalase were found in red-skin ginseng. Increased levels of ascorbate and glutathione; increased activities of $\text\tiny L$-galactose 1-dehydrogenase, ascorbate peroxidase, ascorbic acid oxidase, and glutathione reductase; and lower activities of dehydroascorbate reductase, monodehydroascorbate reductase, and glutathione peroxidase were found in red-skin ginseng. Glutathione-S-transferase activity remained constant. Conclusion: Hence, higher element accumulation, particularly Al and Fe, activated multiple enzymes related to accumulation of phenolic compounds and their oxidation. This might contribute to red-skin symptoms in ginseng. It is proposed that antioxidant and antioxidative enzymes, especially those involved in ascorbate-glutathione cycles, are activated to protect against phenolic compound oxidation.