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J.D. Chung, B.J. Lee, H.S. Lee, and C.K. Kim

Lettuce (Lactuca sativa L.) were transformed using microparticle bombardment with two different genes, alpha-glucuronidase (GUS) gene and Chinese cabbage Glutathione Reductase (GR) gene. The adventitious shoots of cotyledonary explant from 4-day-old seedlings were formed (46.7%) in MS basal media supplemented with 5.0 μm IAA and 1.0 μm 2ip. When 1100 psi helium pressure, 9 target distance, and coating with tungsten 10 microparticles were used and explants were treated with osmoticum-conditioning medium (0.6M sorbitol/mannitol), 4 h prior to and 16 h after bombardment, it was identified by GUS assay that these conditions were the most efficient for transformation of foreign genes into cotyledon tissue of lettuce with particle bombardment. PCR confirmed that the band observed in the transgenic plants were originated from T-DNA tranfer with strong hybridization. The genomic Southern analysis showed that the 1.5-kbp fragment was hybridized with radiolabeled 1.5-kbp GR probe. To know whether the expression of the GR gene can be stably maintained in the next generation, when T2 selfing seeds that were obtained from the transformed mother plants were sowed on MS medium supplemented with 200 μm kanamycin, 70% of seedlings were revealed resistance to kanamycin.

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Suping Zhou, Roger J. Sauvé, Margaret T. Mmbaga, and Chaim Frenkel

Leucanthemum maximum `Silver Princess' plants, that were gradually acclimated for 7 days at 10 °C followed by 28 days at 7 °C, were subjected to the following cold treatments: 30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C to identify cold inducible proteins that may be responsible for cold tolerance in this cold tolerant species. Change in antioxidant enzymes activity in fully expanded leaves was assessed after each treatment. Catalase activity began to increase after 30 days at 4 °C and reached its peak after a 5-day exposure to 0 °C. The activity of cellular glutathione peroxidase and glutathione reductase significantly increased after a 4-day exposure to 0 °C. Changes in activity of four active superoxide dismutase isoforms, one basic guaiacol peroxidase and two o-dianisine peroxidase isoforms were also detected following the full series of cold treatments (30 days at 4 °C; 4 or 5 days at 0 °C and for 3 hours at –1 °C).

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Lailiang Cheng and Fengwang Ma

Xanthophyll cycle conversion and the antioxidant system in the peel of apple fruit (Malus ×domestica Borkh. `Liberty') were monitored in the field over a diurnal course at about 3 months after full bloom. Compared with leaves, sun-exposed peel of apple fruit had much lower photosystem II operating efficiency at any given photon flux density (PFD) and a larger xanthophyll cycle pool size on a chlorophyll basis. Zeaxanthin (Z) level increased with rising PFD in the morning, reached the highest level during midday, and then decreased with falling PFD for the rest of the day. At noon, Z accounted for >90% of the xanthophyll cycle pool in the fruit peel compared with only 53% in leaves. Efficiency of excitation transfer to PSII reaction centers (F v′/F m′) was negatively related to the level of Z in fruit peel and leaves throughout the day. In fruit peel, the antioxidant enzymes in the ascorbate-glutathione cycle, ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) showed a diurnal pattern similar to that of incident PFD. In contrast, the activities of APX and GR in leaves did not change significantly during the day although activities of both MDAR and DHAR were higher in the afternoon than in the morning. In both fruit peel and leaves, superoxide dismutase activity did not change significantly during the day; catalase activity showed a diurnal pattern opposite to that of PFD with much lower activity in fruit peel than in leaves. The total ascorbate pool was much smaller in fruit peel than in leaves on an area basis, but the ratio of reduced ascorbate to oxidized ascorbate reached a maximum in the early afternoon in both fruit peel and leaves. The total glutathione pool, reduced glutathione and the ratio of reduced glutathione to oxidized glutathione in both fruit peel and leaves also peaked in the early afternoon. We conclude that the antioxidant system as well as the xanthophyll cycle responds to changing PFD over the course of a day to protect fruit peel from photooxidative damage.

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Shiow Y. Wang and Miklos Faust

The ability of low and high temperatures and S-containing compounds to overcome endo- and paradormancy along with the possible mechanisms involved in these treatments for breaking `Anna' apple bud dormancy were studied. All three treatments induced budbreak in paradormant (July) and endodormant (October) buds. Cold, heat, and allyl disulfide increased ascorbic acid, the reduced form of glutathione (GSH), total glutathione, total nonprotein thiol (NPSH), and nonglutathione thiol (RSH), whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased. The treatments also increased the ratios of ascorbic acid: dehydroascorbate and GSH: GSSG and the activities of ascorbate free-radical reductase (AFR, EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), ascorbate oxidase (AAO, EC 1.10.3.3), and glutathione reductase (GR, EC 1.6.4.2) in the buds. These results indicate that budbreak induced by cold, heat, and allyl disulfide is associated with the removal of free radicals through activated peroxide-scavenging systems.

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Priscila L. Gratão, Carolina C. Monteiro, Lázaro E.P. Peres, and Ricardo Antunes Azevedo

have concentrated our attention on some of the key antioxidant enzymes such as catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), glutathione reductase (GR), and superoxide dismutase (SOD). The Micro-Tom cultivar was kindly

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Yong In Kuk and Ji San Shin

peroxidase (APX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6), and an ascorbate–glutathione cycle that includes glutathione reductase (GR; EC 1.6.4.2). Several small antioxidant molecules, such as ascorbic acid, glutathione, α-tocopherol, carotenoids, and

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Shiow Y. Wang, Kim S. Lewers, Linda Bowman, and Min Ding

glutathione reductase (GR), with ascorbic acid (AsA) and glutathione (GSH) as important nonenzyme components. Strawberry extracts also exhibited chemopreventive and chemotherapeutic activities in vitro and in vivo ( Carlton et al., 2001 ; Meyers et al

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Sarunya Yimyong, Tatsiana U. Datsenka, Avtar K. Handa, and Kanogwan Seraypheap

inferior ripening or inability to ripen after LTS ( Sala and Lafuente, 2004 ). Induction of ROS scavenging enzymes such as ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR) has been suggested as a mechanism to protect cells under

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Shuai-Ping Gao, Kang-Di Hu, Lan-Ying Hu, Yan-Hong Li, Yi Han, Hui-Li Wang, Kai Lv, Yong-Sheng Liu, and Hua Zhang

than water controls. Glutathione reductase, which catalyzes the regeneration of reduced glutathione, was measured as another indicator of ROS. GR activity in both NaHS and water treatments increased dramatically on Day 1, but the level of GR activity in

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Naveen Kumar and Robert C. Ebel

oxidative enzymes superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APOD), and glutathione reductase (GR) and causes generation of reactive oxygen species (ROS) including hydrogen peroxide (H 2 O 2 ), hydroxyl radical (OH · ), superoxide