• Proceedings of the Korean Society of Grassland Science Conference
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• 2002.09a
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• pp.19.1-19
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• 2002

• Journal of Plant Biotechnology
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• v.43 no.2
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• pp.223-230
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• 2016

Ascorbic acid (AsA) is a strong antioxidant/reducing agent that can be converted to dehydroascorbate (DHA) by oxidation in plants. DHA, a very short-lived chemical, is recycled to AsA by dehydroascorbate reductase (DHAR). Previously, DHAR cDNA was isolated from the hairy roots of the sesame plant, and DHAR-overexpressing transgenic potato plants were generated under the control of the CaMV35S promoter (CaMV35S::DHAR). An increase in transgene expression and ascorbate levels were observed in the transgenic plants. In the present study, proteomic analysis revealed that transgenic plants not only accumulated DHAR in their cells, but also induced several other antioxidant enzyme-related proteins during plant growth. These results suggest that DHAR is important for stress tolerance via induction of antioxidant proteins, and could improve stress tolerance in transgenic potato plants.

• 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.

• 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.

• Proceedings of the Korean Society of Grassland Science Conference
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• 2005.06a
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• pp.174-175
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• 2005

• BMB Reports
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• v.34 no.4
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• pp.316-321
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• 2001

Dehydroascorbate (DHA) reductase (DHAR, EC 1.8.5.1) catalyzes the reduction of DHA to reduced ascorbate (AsA) using glutathione (GSH) as the electron donor in order to maintain an appropriate level of ascorbate in plant cells. To analyze the physiological role of DHAR in environmental stress adaptation, we developed transgenic tobacco (Nicotiana tabacum cv. Xanthi) plants that express a human DHAR gene isolated from the human fetal liver cDNA library in the chloroplasts. We also investigated the DHAR activity, levels of ascorbate, and GSH. Two transgenic plants were successfully developed by Agrobacterium-mediated transformation and were confirmed by PCR and Southern blot analysis. DHAR activity and AsA content in mature leaves of transgenic plants were approximately 1.41 and 1.95 times higher than in the non-transgenic (NT) plants, respectively In addition, the content of oxidized glutathione (GSSG) in transgenic plants was approximately 2.95 times higher than in the NT plants. The ratios of AsA to DHA and GSSG to GSH were changed by overexpression of DHAR, as expected, even though the total content of ascorbate and glutathione was not significantly changed. When tobacco leaf discs were subjected to methyl viologen at $5\;{\mu}M$, $T_0$ transgenic plants showed about a 50% reduction in membrane damage compared to the NT plants.

• BMB Reports
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• v.32 no.6
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• pp.605-609
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• 1999

Thioltransferase, also called glutaredoxin, is a general GSH-disulfide reductase of importance for redox regulation. Previously, the protein thioltransferase, now called S-type thioltransferase, was purified and characterized from Arabidopsis thaliana seed. In the present study, a second thioltransferase, called L-type thioltransferase, was purified to homogeneity from Arabidopsis thaliana leaves. The purification procedures included DEAE-cellulose ion-exchange chromatography, Sephadex G-50 gel filtration, and glutathione-agarose affinity chromatography. The purified enzyme was confirmed to show a unique band on SDS-PAGE and its molecular weight was estimated to be 26.6 kDa, which appeared to be atypical compared with those of most other thioltransferase. It could utilize 2-hydroxyethyl disulfide, S-sulfocysteine, and insulin as substrates, and also contained dehydroascorbate reductase activity. Its optimum pH was 8.5 and its activity was greatly activated by L-cysteine. When it was kept for 30 min, it appeared to be very stable up to $70^{\circ}C$. It was activated by $MgCl_2$ and, on the contrary, inhibited by $ZnCl_2$, $MnCl_2$, and $AlCl_3$.

• 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.

• Journal of Life Science
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• v.18 no.12
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• pp.1705-1711
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• 2008

To investigate the relationship between cold stress and the activity of ascorbate peroxidase(APX), dehydroascorbate reductase (DHAR), mRNA expression level of two enzymes, hydrogen peroxide content was studied in lettuce leaves under stress condition imposed by cold stress at $4^{\circ}C$ for 24 hr in the dark and following recovery at $20^{\circ}C$ from cold stress. Hydrogen peroxide content increased gradually in lettuce leaves during cold stress, but decreased slightly following recovery from cold stress. Soluble protein content, however, decreased gradually during cold stress, and then rapidly returned to normal levels following recovery. Total chlorophyll content decreased gradually during cold stress, and then keep constant following recovery. The patterns of chlorophyll a and b content similar to that of total chlorophyll content, and carotenoid content didn't change. The ratio of chlorophyll a and total chlorophyll was increased during cold stress, but decreased with rapid during cold stress, and then the ratio returned to normal levels following recovery. During cold stress, the activity of APX and DHAR in the lettuce leaves increased dramatically, and also transcript levels of mRNA of APX and DHAR, as determined by probing 32P-labeled single stranded RNA of APX and DHAR, highly increased and returned to normal levels following recovery, respectively. Relationship between APX and DHAR activity and hydrogen peroxide highly related ($R^2$=0.8715 and 0.8643), whereas between hydrogen peroxide and total chlorophyll content and soluble content related reversely ($R^2$=0.5021 and 0.8915).

• Molecules and Cells
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• v.26 no.6
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• pp.616-620
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• 2008

Maintaining redox balance is one of the crucial requirements for a cell to endure stress from the outside. Dehydroascorbate reductase (DHAR; EC 1.8.5.1) plays an important role in the ascorbate-glutathione cycle; one of the major ROS scavenging systems in most known biological systems. A cDNA clone of the DHAR gene from Oryza sativa (OsDHAR) was isolated and overexpressed in Escherichia coli BL21 (DE3) strain from the pET-28a(+) expression vector. The OsDHAR transformed E. coli cells showed significantly higher DHAR activity and a lower level of ROS than the E. coli cells transformed by an empty pET-28a(+) vector. Also, the DHAR-overexpressing E. coli strain was more tolerant to oxidant- and heavy metal-mediated stress conditions than the control E. coli strain. The results suggest that the overexpressed rice DHAR gene effectively functions in a prokaryotic system and provide protection to various oxidative stresses.