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Misael O. Vega-García, Greici López-Espinoza, Jeanett Chávez Ontiveros, José J. Caro-Corrales, Francisco Delgado Vargas, and José A. López-Valenzuela

., 2009 ). An oxidative stress response has been related to the appearance of the CI symptoms, suggesting that the antioxidant system, including superoxide dismutases (SOD), peroxidases, catalases (CAT), and glutathione reductase (GR), confers protection

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Pedro Novillo, Alejandra Salvador, Pilar Navarro, and Cristina Besada

accumulation and subsequent up-regulation of CAT, APX, and LOX enzymes) reveal that the fruit underwent progressive oxidative stress associated with low-temperature exposure, which was not reduced by the 1-MCP treatment. Contrarily to that observed at cold

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Sukhvinder Pal Singh and Zora Singh

Postharvest oxidative stress is a phenomenon caused by an imbalance in the production and scavenging of reactive oxygen species (ROS) in the fruit during postharvest handling and storage ( Hodges et al., 2004 ). ROS such as superoxide anion (O 2

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Sukhdeep Singh, Taylor Livingston, Lisa Tang, and Tripti Vashisth

, and oxidative stress was determined using real-time quantitative polymerase chain reaction (qRT-PCR). The primer sequences for specific genes were designed using Primer BLAST (NCBI; ) and are listed in

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Yueju Wang, Michael Wisniewski, Richard Meilan, Minggang Cui, Robert Webb, and Leslie Fuchigami

Ascorbate peroxidase (APX) plays an important role in the metabolism of hydrogen peroxide in higher plants, affording them protection against oxidative stress. We studied the effect of overexpressing a cytosolic ascorbate peroxidase (cAPX) gene—derived from pea (Pisum sativum L.)—in transgenic tomato plants (Lycopersicon esculentum L.). Transformants were selected in vitro using kanamycin resistance and confirmed by polymerase chain reaction (PCR) and northern analyses. An APX native-gel assay indicated that, in the absence of stress, APX activity in transgenic plants was several times greater than that measured in wild-type (WT) plants. Several independently transformed lines were propagated and evaluated for resistance to chilling and salt stress. After placing seeds at 9 °C for 5 weeks, percent germination was greater for seeds obtained from transgenic lines (26% to 37%) compared to the WT (3%). Plants from transgenic lines also had lower electrolyte leakage (20% to 23%) than WT (44%) after exposure to 4 °C. Visual assessment of transgenic and WT lines exposed to salinity stress (200 or 250 mm) confirmed that overexpression of APX minimized leaf damage. Moreover, APX activity was nearly 25- and 10-fold higher in the leaves of transgenic plants in response to chilling and salt stresses, respectively. Our results substantiate that increased levels of APX activity brought about by overexpression of a cytosolic APX gene may play an important role in ameliorating oxidative injury induced by chilling and salt stress.

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D. Mark Hodges and Charles F. Forney

Rapidly declining levels of ascorbate (vitamin C) have been associated with advancing senescence and postharvest quality loss in spinach (Spinacia oleracea L.). To further explore the association between ascorbate metabolism and senescence, two cultivars of spinach previously shown to differ in their postharvest senescence rates were grown under controlled conditions (18 °C, 14 light: 10 dark photocycle) and harvested 6 weeks after planting. Detached leaves of `Spokane F1' (relatively fast senescence rate) and `BJ412 Sponsor'(relatively slow senescence rate) were bagged and placed in the dark at 10 °C. Samples were removed on days 0, 7, 14, 21, and 28, and analyzed for activities of L-galactono-γ-lactone dehydrogenase (GLDH), ascorbate peroxidase (ASPX), ascorbate oxidase (AAO), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR), and levels of ascorbate [reduced (AsA) and oxidized (DHA)] and malondialdehyde (MDA) (estimator of lipid peroxidation). Oxidative stress, as estimated by MDA levels, steadily increased in both spinach cultivars during storage, but increased more in `Spokane'than in `Sponsor'. GLDH activities peaked on day 14 for both cultivars and leveled off thereafter, while activities of ASPX, DHAR, and MDHAR declined during storage. ASPX activities were lower in `Spokane'than in `Sponsor'after day 21. No difference in AAO activities was noted between `Sponsor'and `Spokane'during storage. Total ascorbate concentrations declined in both cultivars on day 14 after which no further decreases were noted, while DHA/AsA ratios increased during storage. Early in the storage regime (days 0 and 7), ascorbate levels were lower in `Spokane'than in `Sponsor. GLDH activities may have increased as part of a strategy to maintain the ascorbate pool during escalating oxidative stress. However, decreased levels of ascorbate suggests that, even though ascorbate biosynthesis was increased, ascorbate was being degraded, possibly through hydrolysis of DHA to 2,3-diketogulonate. Initially lower levels of ascorbate (days 0 and 7) and lower activities of ASPX (day 28) in `Spokane' may have resulted in comparatively greater susceptibility of this cultivar to oxidative stress than `Sponsor'.

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Rocío Leyva, Christian Constán-Aguilar, Begoña Blasco, Eva Sánchez-Rodríguez, Teresa Soriano, and Juan M. Ruíz

and adenosine-5′-triphosphate (ATP) production ( Lawlor, 1995 ). In addition, PDH activity could act as an effective response mechanism against oxidative stress, directly participating in detoxifying ROS and reducing their formation ( Rosales et al

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Chen Chen, Meng-Ke Zhang, Kang-Di Hu, Ke-Ke Sun, Yan-Hong Li, Lan-Ying Hu, Xiao-Yan Chen, Ying Yang, Feng Yang, Jun Tang, He-Ping Liu, and Hua Zhang

selectable markers ( Delmas et al., 2014 ). In this work, we constructed the deletion mutant Δ sodC by homologous recombination. Then, the role of sodC gene in fungal resistance to oxidative stress was examined, and the infection ability of Δ sodC mutant