ascorbic-acid and ethylene

Plant bioregulators play an important role in managing oxidative stress tolerance in plants. Utilizing their ability in stress sensitive crops through genetic engineering will be a meaningful approach to manage food production under the threat of climate change. Exploitation of the plant defense system against oxidative stress to engineer tolerant plants in the climate change scenario is a sustainable and meaningful strategy. Plant bioregulators (PBRs), which are important biotic factors, are known to play a vital role not only in the development of plants, but also in inducing tolerance in plants against various environmental extremes. These bioregulators include auxins, gibberellins, cytokinins, abscisic acid, brassinosteroids, polyamines, strigolactones, and ascorbic acid and provide protection against the oxidative stress-associated reactive oxygen species through modulation or activation of a plant's antioxidant system. Therefore, exploitation of their functioning and accumulation is of considerable significance for the development of plants more tolerant of harsh environmental conditions in order to tackle the issue of food security under the threat of climate change. Therefore, this review summarizes a new line of evidence that how PBRs act as inducers of oxidative stress resistance in plants and how they could be modulated in transgenic crops via introgression of genes. Reactive oxygen species production during oxidative stress events and their neutralization through an efficient antioxidants system is comprehensively detailed. Further, the use of exogenously applied PBRs in the induction of oxidative stress resistance is discussed. Recent advances in engineering transgenic plants with modified PBR gene expression to exploit the plant defense system against oxidative stress are discussed from an agricultural perspective.

Topics: Antioxidants; Ascorbic Acid; Brassinosteroids; Climate Change; Crops, Agricultural; Cytokinins; Ethylenes; Gene Expression Regulation, Plant; Gibberellins; Indoleacetic Acids; Oxidation-Reduction; Oxidative Stress; Plant Physiological Phenomena; Polyamines; Reactive Oxygen Species; Tocopherols

Stomatal numbers are tightly controlled by environmental signals including light intensity and atmospheric CO(2) partial pressure. This requires control of epidermal cell development during the early phase of leaf growth and involves changes in both the density of cells on the leaf surface and the proportion of cells that adopt a stomatal fate. This paper reviews the current understanding of how stomata develop and describes recent advances that have given insights into the regulatory mechanisms involved using mutant Arabidopsis plants that implicates a role for long-chain fatty acids in cell-to-cell communication. Evidence is presented which indicates that long-distance signalling from mature to newly developing leaves forms part of the mechanism by which stomatal development responds to environmental cues. Analysis of mutant plants suggests that the plant hormones abscisic acid, ethylene and jasmonates are implicated in the long-distance signalling pathway and that the action may be mediated by reactive oxygen species.

Topics: Ascorbic Acid; Carbohydrate Metabolism; Carbon Dioxide; Cell Differentiation; Cell Division; Cyclopentanes; Ecosystem; Ethylenes; Mutation; Oxylipins; Plant Epidermis; Plant Growth Regulators; Plant Leaves; Reactive Oxygen Species; Signal Transduction

The current status of research on the use of ionizing radiation for shelf life improvement and disinfestation of fresh tropical fruits like bananas, mangoes, and papayas are reviewed. The aspects covered are influence of maturity and physiological state of the fruits on delayed ripening and tolerance to radiation; varietal responses; changes in chemical constituents, volatiles, respiration, and ethylene evolution; biochemical mechanisms of delayed ripening and browning of irradiated fruits; and organoleptic quality. The efficacy of the combination of hot water dip and radiation treatments for control of postharvest fungal diseases are considered. The immediate potential of radiation as a quarantine treatment, in place of the currently used chemical fumigants, for disinfestation of fruit flies and mango seed weevil are discussed. Future prospects for irradiation of tropical fruits are discussed in the light of experience gained from studies conducted in different countries.

Topics: Amino Acids; Antifungal Agents; Ascorbic Acid; Carbohydrates; Carbon Dioxide; Catechol Oxidase; Ethylenes; Food Handling; Food Irradiation; Fruit; Fungi; Gamma Rays; Hot Temperature; Insect Control; Lipids; Nutritive Value; Oxidation-Reduction; Plant Diseases; Time Factors; Tropical Climate; Vitamins

ETHYLENE-INSENSITIVE 3/ETHYLENE-INSENSITIVE 3-LIKEs (EIN3/EILs) are important ethylene response factors during fruit ripening. Here, we discovered that EIL2 controls carotenoid metabolism and ascorbic acid (AsA) biosynthesis in tomato (Solanum lycopersicum). In contrast to the red fruits presented in the wild type (WT) 45 d after pollination, the fruits of CRISPR/Cas9 eil2 mutants and SlEIL2 RNA interference lines (ERIs) showed yellow or orange fruits. Correlation analysis of transcriptome and metabolome data for the ERI and WT ripe fruits revealed that SlEIL2 is involved in β-carotene and AsA accumulation. ETHYLENE RESPONSE FACTORs (ERFs) are the typical components downstream of EIN3 in the ethylene response pathway. Through a comprehensive screening of ERF family members, we determined that SlEIL2 directly regulates the expression of 4 SlERFs. Two of these, SlERF.H30 and SlERF.G6, encode proteins that participate in the regulation of LYCOPENE-β-CYCLASE 2 (SlLCYB2), encoding an enzyme that mediates the conversion of lycopene to carotene in fruits. In addition, SlEIL2 transcriptionally repressed L-GALACTOSE 1-PHOSPHATE PHOSPHATASE 3 (SlGPP3) and MYO-INOSITOL OXYGENASE 1 (SlMIOX1) expression, which resulted in a 1.62-fold increase of AsA via both the L-galactose and myoinositol pathways. Overall, we demonstrated that SlEIL2 functions in controlling β-carotene and AsA levels, providing a potential strategy for genetic engineering to improve the nutritional value and quality of tomato fruit.

Topics: Ascorbic Acid; beta Carotene; Ethylenes; Fruit; Galactose; Gene Expression Regulation, Plant; Lycopene; Plant Proteins; Solanum lycopersicum

The objective of the present study was to explore the effect of folic acid on the postharvest physiology of broccoli placed in storage. Broccoli heads were immersed in 5 mg L

Topics: Antioxidants; Ascorbic Acid; Brassica; Catalase; Ethylenes; Flavonoids; Folic Acid; Food Storage; Gene Expression; Malondialdehyde; Peroxidases; Phenols; Plant Proteins; Reactive Oxygen Species; Temperature

This study examined the ability of l-arginine, l-cysteine and l-methionine, to inhibit postharvest senescence of broccoli. Florets were dipped in aqueous solutions of the amino acids at concentrations from 1.0 to 100 mM and stored at 10 °C. A 5 mM dip was found to be optimal in delaying senescence as measured by retention of green colour, vitamin C and antioxidant activity, and a lower level of ethylene production, respiration, weight loss, phenylalanine ammonia lyase (PAL) activity and ion leakage with the benefits being similar for all three amino acids. Arginine, cysteine and methionine have Generally Recognised As Safe (GRAS) status and should have few impediments in obtaining regulatory approval for commercial use if similar effects were found for other leafy vegetables.

Topics: Ammonia-Lyases; Antioxidants; Arginine; Ascorbic Acid; Brassica; Cysteine; Ethylenes; Methionine; Plant Proteins; Time Factors

Nitrogen (N), phosphorus (P), and potassium (K) are three essential macro-elements for plant growth and development. Used to improve yield in agricultural production, the excessive use of chemical fertilizers often leads to increased production costs and ecological environmental pollution. Vitamins C and E are antioxidants that play an important role in alleviating abiotic stress. However, there are few studies on alleviating oxidative stress caused by macro-element deficiency. Here, we used Arabidopsis vitamin E synthesis-deficient mutant

Topics: Antioxidants; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Chlorophyll; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Malondialdehyde; Oxidative Stress; Oxylipins; Plant Diseases; Plant Leaves; Reactive Oxygen Species; Seedlings; Seeds; Signal Transduction; Time Factors; Vitamin E

During plant growth and development, ethylene and abscisic acid (ABA) play important roles and exert synergistic or antagonistic effects on various biological processes, but the detailed mechanism underlying the interaction of the two phytohormones, especially in the regulation of the accumulation of reactive oxygen species (ROS), is largely unclear. Here, we report that ethylene inhibits but ABA promotes the accumulation of ROS in Arabidopsis (

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; DNA-Binding Proteins; Ethylenes; Gene Expression Regulation, Plant; Nuclear Proteins; Phosphoric Monoester Hydrolases; Plant Growth Regulators; Reactive Oxygen Species; Transcription Factors

Sweet cherries rapidly depreciate in market value owing to decay and the quick loss of fruit quality after harvest. Therefore, optimum postharvest treatment is crucial for maintaining the qualities of cherries during storage. Here, we tested a new method of postharvest treatment by immersing sweet cherries in nitric oxide-releasing chitosan nanoparticles (GSNO-CS NPs), storing them at 0 °C and evaluating fruit quality over time. The results indicated that GSNO-CS NPs more effectively preserved the quality of cherries during cold storage compared to other methods. Specifically, GSNO-CS NPs reduced fruit weight loss, respiration rate and ethylene production and increased soluble solids content. Additionally, GSNO-CS NPs reduced reactive oxygen species, increased the antioxidant enzyme activity in direct and indirect antioxidant systems, and increased the levels of ascorbic acid and reduced glutathione. Overall, results suggest that treatment with GSNO-CS NPs can effectively preserve the quality of cherries and enhance antioxidant capacity during cold storage.

Topics: Antioxidants; Ascorbic Acid; Chitosan; Ethylenes; Food Storage; Fruit; Glutathione; Nanoparticles; Nitric Oxide; Oxidoreductases; Prunus avium; Reactive Oxygen Species; Temperature

The objective of the present study was to investigate the effectiveness of lysozyme coatings and 1-MCP on storage and preservation of kiwifruit stored at 4 ± 1 °C and 90-95% RH for 20 d. Ethylene production, respiratory rate, decay incidence, weight loss, firmness, chlorophyll, soluble solid, titratable acid, ascorbic acid, total bacterial count, ascorbate peroxidase (APX), superoxide dismutase (SOD) and catalase (CAT) activity of treated kiwifruit were examined. The results showed that lysozyme coatings or 1-MCP treatment inhibited ethylene production and respiratory rate, delayed the increase of decay incidence, weight loss, soluble solid and total bacterial count, improved firmness, chlorophyll, titratable acid, ascorbic acid content, APX, SOD and CAT activity during the storage compared with the untreated kiwifruit in different degree. Moreover, the combined effect of lysozyme coatings and 1-MCP was more excellent than that of lysozyme coatings or 1-MCP alone. In conclusion, our present results indicated that the combined treatment of lysozyme coatings and 1-MCP may be an efficient way to improve the postharvest quality and prolong the shelf life of kiwifruit.

Topics: Actinidia; Ascorbate Peroxidases; Ascorbic Acid; Catalase; Chlorophyll; Cyclopropanes; Ethylenes; Food Preservation; Muramidase; Superoxide Dismutase

The first transcriptome coupled to metabolite analyses reveals major trends during acerola fruit ripening and shed lights on ascorbate, ethylene signalling, cellular respiration, sugar accumulation, and softening key regulatory genes. Acerola is a fast growing and ripening fruit that exhibits high amounts of ascorbate. During ripening, the fruit experience high respiratory rates leading to ascorbate depletion and a quickly fragile and perishable state. Despite its growing economic importance, understanding of its developmental metabolism remains obscure due to the absence of genomic and transcriptomic data. We performed an acerola transcriptome sequencing that generated over 600 million reads, 40,830 contigs, and provided the annotation of 25,298 unique transcripts. Overall, this study revealed the main metabolic changes that occur in the acerola ripening. This transcriptional profile linked to metabolite measurements, allowed us to focus on ascorbate, ethylene, respiration, sugar, and firmness, the major metabolism indicators for acerola quality. Our results suggest a cooperative role of several genes involved in AsA biosynthesis (PMM, GMP1 and 3, GME1 and 2, GGP1 and 2), translocation (NAT3, 4, 6 and 6-like) and recycling (MDHAR2 and DHAR1) pathways for AsA accumulation in unripe fruits. Moreover, the association of metabolites with transcript profiles provided a comprehensive understanding of ethylene signalling, respiration, sugar accumulation and softening of acerola, shedding light on promising key regulatory genes. Overall, this study provides a foundation for further examination of the functional significance of these genes to improve fruit quality traits.

Topics: Ascorbic Acid; Ethylenes; Fruit; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Malpighiaceae; Plant Proteins; Principal Component Analysis; Signal Transduction; Transcriptome

To reduce the postharvest loss and improve apricot quality attributes, near freezing temperature (NFT) technology was applied to store apricot cultivars (var. "Xiaobai" and "Daliguang"). The NFT storage temperatures for the "Xiaobai" apricot and "Daliguang" apricot were determined as -1.9 to -2.3°C and -1.2 to -1.6°C, respectively. Storage at NFT significantly improved the storage quality of apricots by suppressing respiration rate, ethylene production, decay rate, internal browning index, membrane permeability, and malondialdehyde content. Apricots stored at NFT maintained higher firmness, total soluble solids, titrable acid, total phenolics, total flavonoids, and ascorbic acid content than those stored at 0-1°C. Additionally, NFT storage enhanced the capacity of radical scavenging and metal chelating, antioxidant properties in apricots compared to those stored at 0-1°C. Hence, NFT storage proved to be an effective method to improve the quality and antioxidant attributes of apricots. PRACTICAL APPLICATIONS: This study explored the effect of storage at near freezing temperature (NFT) on the postharvest quality of two cultivars of apricot (var. "Xiaobai" and "Daliguang"). We found that storage for 70 days at NFT resulted in better edible quality compared to storage at 0-1°C and 4-6°C. Apricot quality was determined in terms of respiration rate, ethylene production, decay rate, internal browning index, membrane permeability, malondialdehyde content, firmness, total soluble solids, titrable acid, total phenolics, total flavonoids, and ascorbic acid content. The antioxidant properties of the fruits were also retained during storage at NFT. We believe that our study makes a significant contribution to the preservative industry because it demonstrates the superiority of NFT storage over low temperature for apricots.

Topics: Antioxidants; Ascorbic Acid; Cold Temperature; Ethylenes; Flavonoids; Food Storage; Free Radical Scavengers; Fruit; Malondialdehyde; Phenols; Prunus armeniaca; Respiratory Rate

The effect of tree age on physicochemical quality attributes and storage behaviour of Amrapali mango fruit was evaluated. Physiologically mature fruits were harvested from 6-, 18- and 30-year-old trees and kept for ripening under ambient conditions (temperature 35 ± 3 °C, relative humidity 60 ± 5%). Observations were recorded at 3-day intervals.. Highest total soluble solids and total sugars were found in the fruit sourced from 18-year-old trees. At the end of storage, least titratable acidity (0.17%) and higher carotenoids (10.86 mg 100 g. Higher total soluble solids and total sugars were found in fruit harvested from middle-age-group (18-year-old) trees during the entire storage period of 9 days. Most of the functional parameters, such as TP, AC and AA, were observed to be higher in fruits from younger (6-year-old) trees. The obtained results revealed that produce from middle-age-group (18-year-old) Amrapali mango orchards suit consumers' and processors' requirements. © 2017 Society of Chemical Industry.

Topics: Antioxidants; Ascorbic Acid; Carboxylic Ester Hydrolases; Carotenoids; Chemical Phenomena; Ethylenes; Food Preservation; Fruit; Mangifera; Phenols; Polygalacturonase; Sugars; Time Factors; Trees

Ascorbic acid (AA) is a major redox buffer in plant cells. The role of ethylene in the redox signaling pathways that influence photosynthesis and growth was explored in two independent AA deficient Arabidopsis thaliana mutants (vtc2-1 and vtc2-4). Both mutants, which are defective in the AA biosynthesis gene GDP-L-galactose phosphorylase, produce higher amounts of ethylene than wt plants. In contrast to the wt, the inhibition of ethylene signaling increased leaf conductance, photosynthesis and dry weight in both vtc2 mutant lines. The AA-deficient mutants showed altered expression of genes encoding proteins involved in the synthesis/responses to phytohormones that control growth, particularly auxin, cytokinins, abscisic acid, brassinosterioids, ethylene and salicylic acid. These results demonstrate that AA deficiency modifies hormone signaling in plants, redox-ethylene interactions providing a regulatory node controlling shoot biomass accumulation.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Biomass; Ethylenes; Gene Expression Regulation, Plant; Mutation; Oxidation-Reduction; Phosphoric Monoester Hydrolases; Photosynthesis; Plant Growth Regulators; Salicylic Acid; Signal Transduction

The feasibility of active packaging from chitosan (CS) and chitosan containing nanosized titanium dioxide (CT) to maintain quality and extend storage life of climacteric fruit was investigated. The CT nanocomposite film and CS film were fabricated using a solution casting method and used as active packaging to delay ripening process of cherry tomatoes. Changes in firmness, weight loss, a*/b* color, lycopene content, total soluble solid, ascorbic acid, and concentration of ethylene and carbon dioxide of the tomatoes packaged in CT film, CS film, and control (without CT or CS films) were monitored during storage at 20°C. Classification of fruit quality as a function of different packaging treatments was visualized using linear discriminant analysis. Tomatoes packaged in the CT film evolved lower quality changes than those in the CS film and control. The results suggested that the CT film exhibited ethylene photodegradation activity when exposed to UV light and consequently delayed the ripening process and changes in the quality of the tomatoes.

Topics: Ascorbic Acid; Carbon Dioxide; Chitosan; Ethylenes; Food Packaging; Food Preservation; Food Storage; Nanocomposites; Solanum lycopersicum; Titanium

In modified atmosphere packaging of guava, moisture scavenger (MS) sachet containing 30-50 g of coarse silica gel and ethylene scavenger (ES) sachet containing 0-4 g of potassium permanganate was added as per central composite rotatable design. The headspace O

Topics: Ascorbic Acid; Atmosphere; Color; Ethylenes; Food Packaging; Food Storage; Fruit; Phenols; Psidium; Temperature

Biochemical and physiological traits of two soybean [Glycine max (L.) Merr.] genotypes differing in sensitivity to ozone (O3 ) were investigated to determine the possible basis for the differential response. Fiskeby III (O3 -tolerant) and Mandarin (Ottawa) (O3 -sensitive) were grown in a greenhouse with charcoal-filtered air for 4 weeks, then treated with O3 for 7 h·day(-1) in greenhouse chambers. Mandarin (Ottawa) showed significantly more leaf injury and hydrogen peroxide (H2 O2 ) and superoxide (O2 (-) ) production compared with Fiskeby III. Peroxidase activity in Mandarin (Ottawa) was 31% higher with O3 but was not significantly different in Fiskeby III. Ozone did not affect superoxide dismutase or glutathione reductase activities, or leaf concentrations of glutathione or ascorbic acid. Thus, variation in O3 response between Fiskeby III and Mandarin (Ottawa) was not explained by differences in antioxidant enzymes and metabolites tested. Ethylene emission from leaves declined in Fiskeby III following O3 exposure but not in Mandarin (Ottawa). Ozone exposure reduced quantum yield (ΦPSII ), electron transport rate (ETR) and photochemical quenching (qp ) in Mandarin (Ottawa) more than in Fiskeby III, indicating that efficiency of energy conversion of PSII and photosynthetic electron transport was altered differently in the two genotypes. Short-term exposure to O3 had minimal effects on net carbon exchange rates of both soybean cultivars. A trend toward higher stomatal conductance in Mandarin (Ottawa) suggested stomatal exclusion might contribute to differential O3 sensitivity of the two genotypes. Increased sensitivity of Mandarin (Ottawa) to O3 was associated with higher H2 O2 and O2 (-) production compared with Fiskeby III, possibly associated with genotype differences in stomatal function or regulation of ethylene during the initial phases of O3 response.

Topics: Antioxidants; Ascorbic Acid; Electron Transport; Ethylenes; Genotype; Glutathione; Glutathione Reductase; Glycine max; Hydrogen Peroxide; Oxidation-Reduction; Ozone; Photosynthesis; Physiological Phenomena; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plant Transpiration; Superoxide Dismutase

Controlling storage atmosphere is a key factor for delaying postharvest fruit quality loss. The objective of this study is to evaluate its influence on physico-chemical, sensorial and nutritional quality attributes of two tomato fruit cultivars (Delizia and Pitenza) that respectively have a short- and long-storage life. To that end, the effect of two types of bags with different gas permeability, combined or not with an ethylene sorbent, on tomato organoleptic and nutritional properties were compared during fruit storage at 13°C. CO2 and O2 were critical factors for controlling tomato postharvest behaviour. Weight loss, firmness, color and visual quality were only affected by bag permeability just as total sugar content and acidity for Pitenza tomatoes. (trans)-2-Hexenal also appears to be related with CO2 and O2 levels. Lycopene, total phenols (TP) and ascorbic acid (AA) contents were also affected by the packaging form and the storage length. Ethylene removal in combination with MAP led to a higher content in TP and AA in the short-life tomato cultivar.

Topics: Ascorbic Acid; Color; Ethylenes; Fruit; Humans; Nutritive Value; Phenols; Solanum lycopersicum; Taste

We investigated the effects of different concentrations (0, 1, 2 and 4 mM) of putrescine on chilling injury, fruit quality, ethylene production rate, fatty acid composition and the antioxidant system of cold-stored kiwifruit (Actinidia chinensis Planch. var. chinensis 'Hongyang'). We achieved a significant decrease in ethylene production, maintained fruit quality and alleviated chilling injury during storage via treatment with 2 mM putrescine. Furthermore, putrescine treatment inhibited increases in superoxide anion production rate and H2O2 concentration, while maintaining higher membrane lipid unsaturation as well as increased activities of superoxide dismutase and catalase. In addition, putrescine treatment enhanced the activities of antioxidant enzymes related to the ascorbate-glutathione cycle while causing higher levels of ascorbic acid and reduced glutathione. Our results suggest that induced tolerance against chilling injury via putrescine treatment in cold-stored kiwifruit may be due to enhanced antioxidant activity, increased unsaturation of membrane lipids, and inhibited ethylene production.

Topics: Actinidia; Antioxidants; Ascorbic Acid; Catalase; Cold Temperature; Ethylenes; Fatty Acids; Fruit; Glutathione; Hydrogen Peroxide; Principal Component Analysis; Putrescine; Superoxide Dismutase; Superoxides

Ready-to-eat fresh cut produce are exposed to pre- and postharvest abiotic stresses during the production chain. Our work aimed to identify stress responsive genes as new molecular markers of quality that can be widely applied to leaves and fruits and easily determined at any stage of the production chain. Stress responsive genes associated with quality losses were isolated in rocket and melon fresh-cut produce and their expression levels analyzed by quantitative real time PCR (qRT-PCR) at different time points after harvest at 20 °C and 4 °C. qRT-PCR results were supported by correlation analysis with physiological and biochemical determinations evaluated at the same conditions such as chlorophyll a fluorescence indices, total, reducing sugars, sucrose, ethylene, ascorbic acid, lipid peroxidation and reactive oxygen species. In both species the putative molecular markers increased their expression soon after harvest suggesting a possible use as novel and objective quality markers of fresh-cut produces.

Topics: Ascorbic Acid; Carbohydrates; Chlorophyll; Chlorophyll A; Cucurbitaceae; Ethylenes; Food Quality; Fruit; Lipid Peroxidation; Oxidative Stress; Plant Leaves; RNA, Plant; Thiobarbituric Acid Reactive Substances

Mature-green cherry tomato fruits (Lycopersicon esculentum cv. Jinyu) were exposed to different power densities of ultrasound (66.64, 106.19, and 145.74 W/L) at 25 °C to study ultrasound non-thermal effects on the storage properties. Among the three levels of ultrasound irradiation, 106.19 W/L ultrasound was effective in reducing the spoilage microorganisms, delaying postharvest ripening through inhibiting ethylene production and respiration rates, and consequently maintaining fruit firmness, flavor, enzyme activities, antioxidants (total phenolics, total flavonoids), and the total antioxidant capacity of cherry tomatoes. The 66.64 W/L ultrasound had similar effects but to a lesser extent. Meanwhile, although 145.74 W/L ultrasound resulted in higher content of ascorbic acid (AA), it showed many negative effects on the storage quality of fruits. These results demonstrated that ultrasound of appropriate power density had great potentials in inhibiting decay, maintaining flavor and nutritional quality of cherry tomatoes.. Recently, ultrasound has been considered as a multifunctional pretreatment method for the preservation of postharvest fruits and vegetables. Although the preservation effects were slight because of the screening of the thermal effects, its non-thermal effects presented potentials in improving storage quality of cherry tomato. Further studies are needed to explore the combinations between ultrasound with heating as well as other postharvest preservation technologies to enhance the effects of ultrasound. These explorations would facilitate the large-scale application of ultrasound in the preservation of fresh fruits and vegetables.

Topics: Antioxidants; Ascorbic Acid; Ethylenes; Flavonoids; Food Handling; Food Preservation; Food Storage; Fruit; Hardness; High-Energy Shock Waves; Humans; Nutritive Value; Phenols; Solanum lycopersicum; Taste; Temperature; Ultrasonics

Plant steroid hormones brassinosteroids (BRs) and the gaseous hormone ethylene (ET) alter the ascorbic acid-glutathione (AA-GSH) levels in tomato (Solanum lycopersicum L.) plants. The interaction of these hormones in regulating antioxidant metabolism is however unknown. The combined use of genetics (BR-mutants) and chemical application (BR/ET-related chemicals) shows that BRs and ET signalling pathways interact, to regulate leaf AA content and synthesis. BR-deficient (d(x)) leaves display low total AA but BR-accumulating (35S:D) leaves show normal total AA content. Leaves with either BR levels lower or higher than wild type plants showed a higher oxidised AA redox state. The activity of L-galactono-1,4-lactone dehydrogenase (L-GalLDH), the mitochondrial enzyme that catalyses the last step in AA synthesis is lower in d(x) and higher in 35S:D plants. BR-deficient mutants show higher ET production but it is restored to normal levels when BR content is increased in 35S:D plants. Suppression of ET signalling using 1-methylcyclopropene in d(x) and 35S:D plants restored leaf AA content and L-GalLDH activity, to the values observed in wild type. The suppression of ET action in d(x) and 35S:D leaves leads to the respective decreasing and increasing respiration, indicating an opposite response compared to AA synthesis. This inverse relationship is lacking in ET suppressed d(x) plants in response to external BRs. The modifications in the in vivo activity of L-GalLDH activity do not correlate with changes in the level of the enzyme. Taken together, these data suggest that ET suppresses and BRs promote AA synthesis and accumulation.

Topics: Ascorbic Acid; Brassinosteroids; Ethylenes; Glutathione; Oxidation-Reduction; Plant Leaves; Solanum lycopersicum

Exogenous hydrogen sulfide (H₂S) treatment can prolong the postharvest life of cut flowers and strawberries. Little work has been done to explore the effects of H₂S on respiratory climacteric fruits such as kiwifruits during storage. Therefore the aim of the present study was to evaluate the effects of H₂S treatment at concentrations of 15–1000 µmol L⁻¹ on the postharvest life of kiwifruit during 25 °C storage and the role of H₂S in regulating the antioxidant defensive system of kiwifruit.. Treatments with 45 and 90 µmol L⁻¹ H₂S significantly inhibited the increase in soluble sugar content and the decrease in vitamin C (Vit C), chlorophyll content and firmness, inhibited ethylene production and both superoxide production rate (O(·2)⁻) and hydrogen peroxide content. Kiwifruits with 45 and 90 µmol L⁻¹ H₂S exhibited significantly higher activities of superoxide dismutase, catalase and peroxidase. Treatment with 180 µmol L⁻¹ H₂S promoted the ripening of kiwifruits.. Treatments with 45 and 90 µmol L⁻¹ H₂S could delay the maturation and senescence of kiwifruits and maintain higher titratable acid (TA) and Vit C during eating-ripe storage by inhibiting ethylene production, improving protective enzyme activities and decreasing the accumulation of reactive oxygen species to protect the cell membrane during storage.

Topics: Actinidia; Ascorbic Acid; Cell Membrane Permeability; Chemical Phenomena; China; Chlorophyll; Dietary Sucrose; Ethylenes; Food Preservatives; Food Quality; Food Storage; Fruit; Hydrogen Peroxide; Hydrogen Sulfide; Mechanical Phenomena; Oxidoreductases; Plant Proteins; Solubility; Superoxides; Up-Regulation

Ethephon, an ethylene releasing compound, promoted leaf senescence, H2O2 elevation, and senescence-associated gene expression in sweet potato. It also affected the glutathione and ascorbate levels, which in turn perturbed H2O2 homeostasis. The decrease of reduced glutathione and the accumulation of dehydroascorbate correlated with leaf senescence and H2O2 elevation at 72h in ethephon-treated leaves. Exogenous application of reduced glutathione caused quicker and significant increase of its intracellular level and resulted in the attenuation of leaf senescence and H2O2 elevation. A small H2O2 peak produced within the first 4h after ethephon application was also eliminated by reduced glutathione. Diphenyleneiodonium (DPI), an NADPH oxidase inhibitor, delayed leaf senescence and H2O2 elevation at 72h, and its influence was effective only within the first 4h after ethephon treatment. Ethephon-induced senescence-associated gene expression was repressed by DPI and reduced glutathione at 72h in pretreated leaves. Leaves treated with l-buthionine sulfoximine, an endogenous glutathione synthetase inhibitor, did enhance senescence-associated gene expression, and the activation was strongly repressed by reduced glutathione. In conclusion, ethephon-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression are all alleviated by reduced glutathione and NADPH oxidase inhibitor DPI. The speed and the amount of intracellular reduced glutathione accumulation influence its effectiveness of protection against ethephon-mediated effects. Reactive oxygen species generated from NADPH oxidase likely serves as an oxidative stress signal and participates in ethephon signaling. The possible roles of NADPH oxidase and reduced glutathione in the regulation of oxidative stress signal in ethephon are discussed.

Topics: Ascorbic Acid; Buthionine Sulfoximine; Cellular Senescence; Chlorophyll; Ethylenes; Gene Expression Regulation, Plant; Glutathione; Hydrogen Peroxide; Ipomoea batatas; NADPH Oxidases; Onium Compounds; Organophosphorus Compounds; Plant Leaves

Ascorbic acid (AsA) is an important antioxidant in plants, and its biosynthesis is finely regulated through developmental and environmental cues; however, the regulatory mechanism remains unclear. In this report, the knockout and knockdown mutants of Arabidopsis AtERF98 decreased the AsA level, whereas the overexpression of AtERF98 increased it, which suggests that AtERF98 plays an important role in regulating AsA biosynthesis. AtERF98-overexpressing plants showed enhanced expression of AsA synthesis genes in the d-mannose/l-galactose (d-Man/l-Gal) pathway and the myo-inositol pathway gene MIOX4, as well as of AsA turnover genes. In contrast, AtERF98 mutants showed decreased expression of AsA synthesis genes in the d-Man/l-Gal pathway but not of the myo-inositol pathway gene or AsA turnover genes. In addition, the role of AtERF98 in regulating AsA production was significantly impaired in the d-Man/l-Gal pathway mutant vtc1-1, but the expression of the myo-inositol pathway gene or AsA turnover genes was not affected, which indicates that the regulation of AtERF98 in AsA synthesis is primarily mediated by the d-Man/l-Gal pathway. Transient expression and chromatin immunoprecipitation assays further showed that AtERF98 binds to the promoter of VTC1, which indicates that AtERF98 modulates AsA biosynthesis by directly regulating the expression of the AsA synthesis genes. Moreover, the knockout mutant aterf98-1 displayed decreased salt-induced AsA synthesis and reduced tolerance to salt. The supplementation of exogenous AsA increased the salt tolerance of aterf98-1; coincidently, the enhanced salt tolerance of AtERF98-overexpressing plants was impaired in vtc1-1. Thus, our data provide evidence that the regulation of AtERF98 in AsA biosynthesis contributes to enhanced salt tolerance in Arabidopsis.

Topics: Amino Acid Sequence; Antioxidants; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Ethylenes; Galactose; Gene Expression Regulation, Plant; Inositol Oxygenase; Mannose; Molecular Sequence Data; Mutation; Nicotiana; Oxidative Stress; Plant Growth Regulators; Plant Leaves; Plants, Genetically Modified; Reactive Oxygen Species; Salt Tolerance; Seedlings; Stress, Physiological; Transcription Factors; Transcriptional Activation

The plant hormone, ethylene, is an important regulator which involved in regulating fruit ripening and flower senescence. In this study, RNA interference (RNAi) technology was employed to silence the genes involved in ethylene biosynthetic pathway. This was achieved by blocking the expression of specific gene encoding the ACC oxidase. Initially, cDNA corresponding to ACO1 of lowland tomato cultivar (MT1), which has high identity with ACO1 of Solanum lycopersicum in GenBank, was cloned through RT-PCR. Using a partial coding region of ACO1, one hpRNAi transformation vector was constructed and expressed ectopically under the 35S promoter. Results showed that transgenic lines harboring the hpRNA-ACO1 construct had lower ethylene production and a longer shelf life of 32 days as compared to 10 days for wild-type fruits. Changes in cell wall degrading enzyme activities were also investigated in cases where the transgenic fruits exhibited reduced rates of firmness loss, which can be associated with a decrease in pectin methylesterase (PME) and polygalacturonase (PG) activities. However, no significant change was detected in both transgenic and wild-type fruits in terms of β-galactosidase (β-Gal) activity and levels of total soluble solid, titratable acid and ascorbic acid.

Topics: Amino Acid Oxidoreductases; Ascorbic Acid; Base Sequence; beta-Galactosidase; Carboxylic Ester Hydrolases; DNA Primers; Ethylenes; Genes, Plant; Plants, Genetically Modified; Polygalacturonase; RNA Interference; Solanum lycopersicum

In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4-D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl-CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over-accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4-D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues.

Topics: 2,4-Dichlorophenoxyacetic Acid; Antioxidants; Ascorbic Acid; Biomarkers; Ethylenes; Gene Expression Regulation, Plant; Glutathione; Hydrogen Peroxide; Models, Biological; Oxidative Stress; Phenotype; Pisum sativum; Plant Leaves; Plant Proteins; Reactive Oxygen Species

Ascorbic acid (AA) is an antioxidant fulfilling a multitude of cellular functions. Given its pivotal role in maintaining the rate of cell growth and division in the quiescent centre of the root, it was hypothesized that the AA-deficient Arabidopsis thaliana mutants vtc1-1, vtc2-1, vtc3-1, and vtc4-1 have altered root growth. To test this hypothesis, root development was studied in the wild type and vtc mutants grown on Murashige and Skoog medium. It was discovered, however, that only the vtc1-1 mutant has strongly retarded root growth, while the other vtc mutants exhibit a wild-type root phenotype. It is demonstrated that the short-root phenotype in vtc1-1 is independent of AA deficiency and oxidative stress. Instead, vtc1-1 is conditionally hypersensitive to ammonium (NH(4)(+)). To provide new insights into the mechanism of NH(4)(+) sensitivity in vtc1-1, root development, NH(4)(+) content, glutamine synthetase (GS) activity, glutamate dehydrogenase activity, and glutamine content were assessed in wild-type and vtc1-1 mutant plants grown in the presence and absence of high NH(4)(+) and the GS inhibitor MSO. Since VTC1 encodes a GDP-mannose pyrophosphorylase, an enzyme generating GDP-mannose for AA biosynthesis and protein N-glycosylation, it was also tested whether protein N-glycosylation is affected in vtc1-1. Furthermore, since root development requires the action of a variety of hormones, it was investigated whether hormone homeostasis is linked to NH(4)(+) sensitivity in vtc1-1. Our data suggest that NH(4)(+) hypersensitivity in vtc1-1 is caused by disturbed N-glycosylation and that it is associated with auxin and ethylene homeostasis and/or nitric oxide signalling.

Topics: Arabidopsis; Ascorbic Acid; Down-Regulation; Ethylenes; Glycosylation; Indoleacetic Acids; Nucleotidyltransferases; Plant Growth Regulators; Plant Roots; Quaternary Ammonium Compounds

Consumption of minimally processed fruit and vegetables has increased significantly in the past few years due to the consumers' life style. The aim of this study was to evaluate the effect of treatment with ascorbic acid or calcium chloride on the quality parameters of fresh-cut kiwifruit prepared from fruit previously stored for 3 months, either treated or not treated with 1-methylcyclopropene (1-MCP) before storage. Harvested fruit were treated with 1 microL L(-1) 1-MCP for 20 h at room temperature ( approximately 20 degrees C) (MCP) or had no treatment (C) and were then stored at 0 degrees C. After 3 months, fruit were removed from storage, peeled, and cut longitudinally in quarters, dipped in 2% ascorbic acid (Asc), 2% calcium chloride (Ca), or just water (cont), and kept at 2 degrees C for 8 days. Measurements of firmness, soluble solids content (SSC) ( degrees Brix), color (CIE L*, a*, b*), electrolyte leakage, sugars, organic acids, total phenolics, and antioxidant activity (DPPH and ABTS) were performed at 0, 4, and 8 days. A taste panel was performed on the seventh shelf life day. It was shown that whole MCP-treated kiwifruit kept better than the control through the 3 months storage, this effect being lost through the fresh-cut shelf life period. Furthermore, the postcut dip on 2% CaCl(2) was effective on delaying softening and browning of fresh-cut kiwifruit, which were also the fruit preferred by panelists. Both ascorbic acid and CaCl(2) were effective on preserving or improving nutritional properties (phenolics, ascorbic acid, DPPH, and ABTS) mainly in the first 4 days of shelf life. The CaCl(2) had a further beneficial effect until 8 shelf life days. It is suggested that CaCl(2) is better in keeping overall quality through 8 days of shelf life at 2 degrees C in fresh-cut kiwifruit followed by Asc, and 1-MCP has negligible effect in the conditions of this experiment.

Topics: Actinidia; Antioxidants; Ascorbic Acid; Calcium Chloride; Carbohydrates; Carboxylic Acids; Cyclopropanes; Ethylenes; Food Handling; Food Preservation; Fruit; Humans; Nutritive Value; Phenols; Quality Control; Sensation

High levels of ascorbic acid (AsA) in tomato fruits provide health benefits for humans and also play an important role in several aspects of plant life. Although AsA metabolism has been characterized in detail, the genetic mechanisms controlling AsA accumulation in tomatoes are poorly understood. The transcriptional control of AsA levels in fruits can be investigated by combining the advanced genetic and genomic resources currently available for tomato. A comparative transcriptomic analysis of fruit tissues was carried out on an introgression line containing a QTL promoting AsA accumulation in the fruit, using a parental cultivar with lower AsA levels as a reference.. Introgression line IL 12-4 (S. pennellii in a S. lycopersicum background) was selected for transcriptomic analysis because it maintained differences in AsA levels compared to the parental genotypes M82 and S. pennellii over three consecutive trials. Comparative microarray analysis of IL 12-4 and M82 fruits over a 2-year period allowed 253 differentially-expressed genes to be identified, suggesting that AsA accumulation in IL 12-4 may be caused by a combination of increased metabolic flux and reduced utilization of AsA. In particular, the upregulation of a pectinesterase and two polygalacturonases suggests that AsA accumulation in IL12-4 fruit is mainly achieved by increasing flux through the L-galactonic acid pathway, which is driven by pectin degradation and may be triggered by ethylene.. Based on functional annotation, gene ontology classification and hierarchical clustering, a subset of the 253 differentially-expressed transcripts was used to develop a model to explain the higher AsA content in IL 12-4 fruits in terms of metabolic flux, precursor availability, demand for antioxidants, abundance of reactive oxygen species and ethylene signaling.

Topics: Ascorbic Acid; Carbohydrate Metabolism; Ethylenes; Fruit; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Glutathione; Humans; Pectins; Solanum lycopersicum

L-ascorbate (the reduced form of vitamin C) participates in diverse biological processes including pathogen defence mechanisms, and the modulation of plant growth and morphology, and also acts as an enzyme cofactor and redox status indicator. One of its chief biological functions is as an antioxidant. L-ascorbate intake has been implicated in the prevention/alleviation of varied human ailments and diseases including cancer. To study the regulation of accumulation of this important nutraceutical in fruit, the expression of 24 tomato (Solanum lycopersicon) genes involved in the biosynthesis, oxidation, and recycling of L-ascorbate during the development and ripening of fruit have been characterized. Taken together with L-ascorbate abundance data, the results show distinct changes in the expression profiles for these genes, implicating them in nodal regulatory roles during the process of L-ascorbate accumulation in tomato fruit. The expression of these genes was further studied in the context of abiotic and post-harvest stress, including the effects of heat, cold, wounding, oxygen supply, and ethylene. Important aspects of the hypoxic and post-anoxic response in tomato fruit are discussed. The data suggest that L-galactose-1-phosphate phosphatase could play an important role in regulating ascorbic acid accumulation during tomato fruit development and ripening.

Topics: Anaerobiosis; Ascorbic Acid; Ethylenes; Fruit; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Oxidation-Reduction; Promoter Regions, Genetic; Solanum lycopersicum; Stress, Physiological

MA-ACS1 and MA-ACO1 are the two major ripening genes in banana and play crucial role in the regulation of ethylene production during ripening. Here, we report a comparative ripening pattern in five different naturally occurring banana cultivars namely Cavendish (AAA), Rasthali (AAB), Kanthali (AB), Poovan (AAB) and Monthan (ABB), which have distinct genome composition. We found a distinct variation in the climacteric ethylene production and in-vivo ACC oxidase activity level during the ripening stages in the five cultivars. We identified the cDNAs for MA-ACS1 and MA-ACO1 from the five cultivars and studied the transcript accumulation patterns of the two genes, which correlated well with the differential timing in the expression of these two genes during ripening. The GCC-box is one of the ethylene-responsive elements (EREs) found in the promoters of many ethylene-inducible genes. We have identified a GCC-box motif (putative ERE) in the promoters of MA-ACS1 and MA-ACO1 in banana cultivars. DNA-protein interaction studies revealed the presence of a GCC-box-specific DNA-binding activity in the fruit nuclear extract and such DNA-binding activity was enhanced following ethylene treatment. South-Western blotting revealed a 25-kDa nuclear protein that binds specifically to GCC-box DNA in the climacteric banana fruit. Together, these results indicate the probable involvement of the GCC-box motif as the cis-acting ERE in the regulation of MA-ACS1 and MA-ACO1 during ripening in banana fruits via binding of specific ERE-binding protein.

Topics: Amino Acid Oxidoreductases; Ascorbic Acid; Base Sequence; Binding Sites; Blotting, Southwestern; DNA-Binding Proteins; Ethylenes; Gene Expression Regulation, Plant; Iron; Lyases; Musa; Plant Proteins; Reverse Transcriptase Polymerase Chain Reaction

Transcriptome profiling via cDNA microarray analysis identified 869 genes that are differentially expressed in developing tomato (Solanum lycopersicum) pericarp. Parallel phenotypic and targeted metabolite comparisons were employed to inform the expression analysis. Transcript accumulation in tomato fruit was observed to be extensively coordinated and often completely dependent on ethylene. Mutation of an ethylene receptor (Never-ripe [Nr]), which reduces ethylene sensitivity and inhibits ripening, alters the expression of 37% of these 869 genes. Nr also influences fruit morphology, seed number, ascorbate accumulation, carotenoid biosynthesis, ethylene evolution, and the expression of many genes during fruit maturation, indicating that ethylene governs multiple aspects of development both prior to and during fruit ripening in tomato. Of the 869 genes identified, 628 share homology (E-value < or = 1 x 10(-10)) with known gene products or known protein domains. Of these 628 loci, 72 share homology with previously described signal transduction or transcription factors, suggesting complex regulatory control. These results demonstrate multiple points of ethylene regulatory control during tomato fruit development and provide new insights into the molecular basis of ethylene-mediated ripening.

Topics: Ascorbic Acid; Carotenoids; Ethylenes; Fruit; Gene Expression Regulation, Plant; Genome, Plant; Mutation; Oligonucleotide Array Sequence Analysis; Plant Proteins; Receptors, Cell Surface; Regulatory Elements, Transcriptional; RNA, Plant; Sequence Homology, Nucleic Acid; Solanum lycopersicum; Transcription Factors; Transcriptional Activation

Fresh peppers (Capsicum annuum L., variety California) in their green and red ripe stages were stored at 20 degrees C for 7 and 19 days to determine the effects of storage on whole fruit antioxidant capacity (TAA) and ascorbate (ASC) content, as well as on some antioxidant enzyme activities, such as catalase (CAT), superoxide dismutase (SOD), and those of the ASC-glutathione cycle. At least one Mn-SOD, two Fe-SODs, and three CuZn-SODs were detected in the fruit extract after native polyacrylamide gel electrophoresis. All of the SOD isozymes and glutathione reductase had higher activity levels in the red control fruits than in the green fruits, whereas the activities of monodehydroascorbate and dehydroascorbate reductase were higher in green fruits. Ascorbate peroxidase (APX) was found to be similar in both fruits. SODs, CAT, and APX seem to be involved in pepper fruit ripening and senescence during storage at 20 degrees C, perhaps influencing the active oxygen species levels in the fruit. TAA, as well as the ASC content, was higher in red peppers than in green, and storage increased the ASC in both green and red fruits.

Topics: Antioxidants; Ascorbic Acid; Capsicum; Carbon Dioxide; Catalase; Cold Temperature; Electrophoresis, Polyacrylamide Gel; Ethylenes; Food Preservation; Fruit; Glutathione; Glutathione Reductase; Isoenzymes; Plant Extracts; Plant Proteins; Superoxide Dismutase

Brassinosteroids are now considered as the sixth group of hormones in plants. As brassinosteroids influence varied growth and development processes such as growth, germination of seeds, rhizogenesis, flowering, senescence and abscission, they are considered as plant hormones with pleiotropic effects. The effect of 28-homobrassinolide and 24-epibrassinolide on ripening of tomato pericarp discs was studied. Application of brassinosteroids to pericarp discs resulted in elevated levels of lycopene and lowered chlorophyll levels. In addition brassinosteroid-treated pericarp discs exhibited decreased ascorbic acid and increased carbohydrate contents. Fruit ripening as induced by brassinosteroids was associated with increase in ethylene production. The study revealed the ability of brassinosteroids in accelerating fruit-senescence.

Topics: Ascorbic Acid; Brassinosteroids; Carbohydrates; Carotenoids; Chlorophyll; Cholestanols; Ethylenes; Lycopene; Plant Growth Regulators; Solanum lycopersicum; Steroids, Heterocyclic; Time Factors

1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO) catalyzes the last step in the biosynthesis of the gaseous plant hormone ethylene, which is involved in development, including germination, fruit ripening, and senescence. ACCO is a mononuclear non-heme ferrous enzyme that couples the oxidation of the cosubstrate ascorbate to the oxidation of substrate ACC by dioxygen. In addition to substrate and cosubstrate, ACCO requires the activator CO(2) for continuous turnover. NIR circular dichroism and magnetic circular dichroism spectroscopies have been used to probe the geometric and electronic structure of the ferrous active site in ACCO to obtain molecular-level insight into its catalytic mechanism. Resting ACCO/Fe(II) is coordinatively saturated (six-coordinate). In the presence of CO(2), one ferrous ligand is displaced to yield a five-coordinate site only when both the substrate ACC and cosubstrate ascorbate are bound to the enzyme. The open coordination position allows rapid O(2) activation for the oxidation of both substrates. In the absence of CO(2), ACC binding alone converts the site to five-coordinate, which would react with O(2) in the absence of ascorbate and quickly deactivate the enzyme. These studies show that ACCO employs a general strategy similar to other non-heme iron enzymes in terms of opening iron coordination sites at the appropriate time in the reaction cycle and define the role of CO(2) as stabilizing the six-coordinate ACCO/Fe(II)/ACC complex, thus preventing the uncoupled reaction that inactivates the enzyme.

Topics: Amino Acid Oxidoreductases; Ascorbic Acid; Binding Sites; Carbon Dioxide; Catalysis; Circular Dichroism; Escherichia coli; Ethylenes; Ferrous Compounds; Ketoglutaric Acids; Spectroscopy, Near-Infrared

It has been suggested that antioxidants play a role in regulating or modulating senescence dynamics of plant tissues. Ethylene has been shown to promote early plant senescence while controlled atmospheres (CA; reduced O2 levels and elevated CO2 levels) can delay its onset and/or severity. In order to examine the possible importance of various antioxidants in the regulation of senescence, detached spinach (Spinacia oleracea L.) leaves were stored for 35 d at 10 degrees C in one of three different atmospheres: (1) ambient air (0.3% CO2, 21.5% O2, 78.5% N2), (2) ambient air + 10 ppm ethylene to promote senescence, or (3) CA (10% CO2, 0.8% O2 and 89.2% N2) to delay senescence. At weekly intervals, material was assessed for activities of the antioxidant enzymes ascorbate peroxidase (ASPX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6), dehydroascorbate reductase (DHAR; EC 1.8.5.4), glutathione reductase (GR; EC 1.6.4.2), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and superoxide dismutase (SOD; EC 1.15.1.1), and concentrations of the water-soluble antioxidant compounds ascorbate and glutathione. Indicators of the rate and severity of senescence (lipid peroxidation, chlorophyll, and soluble protein levels) were also determined. Results indicated that the rate and severity of senescence was similar between the leaves stored in ambient air or CA until day 35, at which point the ambient air-stored leaves exhibited a sharp increase in lipid peroxidation. Tissues under both storage regimes demonstrated significant declines only in levels of ASPX, CAT, and ascorbate. Glutathione content in the CA-stored tissue also significantly dropped, but only on day 35. In contrast, spinach leaves stored in ambient air + ethylene experienced a rapid decrease in levels of all the antioxidants assessed except SOD. Declines in levels of ASPX, CAT, and ascorbate over the 35 d storage period regardless of the composition of the storage atmosphere suggests that regulation of H2O2 levels plays an important role in both the dynamics and severity of post-harvest senescence of spinach.

Topics: Antioxidants; Ascorbic Acid; Carbon Dioxide; Catalase; Chlorophyll; Ethylenes; Glutathione; Lipid Peroxidation; Oxidoreductases; Oxygen; Plant Growth Regulators; Plant Leaves; Plant Proteins; Spinacia oleracea

Herein, we report a new, rapid,and reliable method for measuring the protective antioxidant potential of pure antioxidant solutions or biological tissues. Peroxyl radicals generated by thermal homolysis of 2,2'-azobis-amidinopropane (ABAP) cause the oxidation of alpha-keto-gamma-methiolbutyric acid (KMBA) to ethylene; ethylene formation is monitored by gas chromatographic analysis of head space from the reaction vessel. The partial inhibition of ethylene formation in the presence of antioxidants that compete with KMBA for oxyradicals is the basis of the Total Oxyradical Scavenging Capacity Assay (TOSCA). The assay is shown to be reliable for quantifying ROS scavenging potential. The quantifiable parameters are consistent with the relative order of those predicted by the fluorescence- and oxygen electrode-based assays reported in the literature. Antioxidants competing for peroxyl radicals influenced the rate of KMBA oxidation in different ways, but the calculation of TOSC was not affected by such variations. Responses were linear over a wide range of sample concentrations and the TOSC values of classical soluble antioxidants showed the following relative order: Trolox > uric acid > ascorbic acid > GSH. The KMBA method was reliable for biological tissues; the TOSC for 1 microg rat liver cytosolic protein was 0.40 +/- 0.02 and for the microsomal membrane, 0.15 +/- 0.03. Soluble antioxidants accounted for 77% of the protective antioxidant potential in rat liver cytosol. When incorporated into the microsomal membrane, alpha-tocopherol markedly enhances antioxidant protection against peroxyl radical; thus, the assay is suitable for the assessment of fat-soluble antioxidants.

Topics: Animals; Antioxidants; Ascorbic Acid; Body Fluids; Butyrates; Chromans; Chromatography, Gas; Cytosol; Ethylenes; Free Radical Scavengers; Glutathione; Kinetics; Liver; Microsomes; Peroxides; Rats; Solutions; Sulfhydryl Compounds; Uric Acid; Vitamin E

Aqueous solutions of engine exhaust condensation products were derived from cars powered by diesel or four-stroke gasoline engines (with and without three-way catalytic converter). The cars were operated on a static test platform. Samples of the different exhaust solutions accumulated in a Grimmer-type distillation trap (VDI 3872) during standard test programs (Federal Test Procedure) were incubated with important biomolecules. As indicators of reactive oxygen species or oxidative destruction, ascorbic acid, cysteine, glutathione, serum albumin, the enzymes glycerinaldehyde phosphate dehydrogenase and xanthine oxidase, and the oxygen free-radical indicator keto-methylthiobutyrate were used. During and after the incubations, oxygen activation (consumption) and oxidative destruction were determined. Comparison of the oxidative activities of the different types of exhaust condensates clearly showed that the exhaust condensate derived from the four-stroke car equipped with a three-way catalytic converter exhibited by far the lowest oxidative and destructive power.

Topics: Antioxidants; Ascorbic Acid; Automobiles; Carotenoids; Ethylenes; Gasoline; Glyceraldehyde-3-Phosphate Dehydrogenases; Methionine; Oxidation-Reduction; Reactive Oxygen Species; Serum Albumin, Bovine; Sulfhydryl Compounds; Vehicle Emissions; Xanthine Oxidase

Incubation of free, but not of peptide-bound methionine in an iron/ascorbate system resulted in ethylene generation, which was inhibited by glutathione. Leucine and isoleucine, however, when incubated in an iron/ascorbate/GSH system, released small amounts of propane and ethane, respectively. Peptide-bound leucine additionally yielded butane, as did bovine serum albumin or casein. Hydrocarbon generation from amino acids was inhibited by hydroxyl radical scavengers, but catalase and superoxide dismutase were more efficient. Additionally, ethane and propane generation in this system was optimal at pH 6.2 suggesting the involvement of protonated superoxide besides OH-radicals which attack the side chains of Leu and Ile and very probably produce carbon-centered radicals, which should abstract a hydrogen atom from the thiol group of GSH resulting in the formation of saturated hydrocarbons.

Topics: Amino Acids; Ascorbic Acid; Butanes; Chemical Phenomena; Chemistry; Ethane; Ethylenes; Gases; Glutathione; Hydrocarbons; Iron; Models, Chemical; Propane; Proteins

Accidental poisoning by oral iron preparations is a serious problem in young children. We investigated the formation of hydroxyl radicals (.OH) in rats after intragastric instillation of ferrous sulfate. .OH was detected via its reaction with intragastrically administered 2-keto-4-methylthiobutyrate to generate ethylene gas. Ascorbic acid is typically present in oral iron preparations in order to facilitate absorption by maintaining iron in the reduced state. However, ascorbate possesses two properties that can affect .OH, recycling of oxidized iron to the ferrous state augments .OH production, while ascorbate in high concentration scavenges .OH. In experiments conducted in vitro, both actions were evident, depending upon the concentration of ascorbate. In parallel experiments conducted in vivo, the scavenging action of ascorbate was more prominent. Experiments in vitro with .OH-scavengers (dimethylsulfoxide, ethanol) and with the enzyme, catalase, confirmed both the presence of .OH and its dependence upon generated hydrogen peroxide during the oxidation of ferrous salt by molecular oxygen. Hydroxyl radicals (and/or reactive higher oxidation states of iron) may play a role in tissue damage after accidental overdose of oral iron.

Topics: Administration, Oral; Animals; Ascorbic Acid; Catalase; Dimethyl Sulfoxide; Ethanol; Ethylenes; Female; Ferrous Compounds; Hydrogen Peroxide; Hydroxides; Hydroxyl Radical; In Vitro Techniques; Rats; Rats, Inbred Strains

Topics: Administration, Oral; Animals; Ascorbic Acid; Ethylenes; Female; Ferrous Compounds; Free Radicals; Hydroxides; Hydroxyl Radical; Iron; Methionine; Oxidation-Reduction; Rats; Rats, Inbred Strains

Experiments were carried out to evaluate the production of hydroxyl radical-like species by intact rat liver cells by assaying for the production of ethylene from alpha-keto-4-thiomethylbutyric acid in the absence and presence of added iron. In the absence of iron, a low rate of ethylene production, which was not sensitive to superoxide dismutase, catalase, or competitive scavengers was observed. Ethylene was produced when KMBA was incubated with perfusates of rat liver or the suspension medium obtained after incubating liver cells for varying periods of time, followed by removal of the liver cells. Boiling the perfusate or suspension medium had no effect on ethylene production. This ethylene production does not appear to reflect an oxygen radical-mediated event. The addition of ferric-EDTA, but not ferric-desferrioxamine, increased ethylene production by the hepatocyte suspensions in a reaction sensitive to inhibition by catalase, ascorbate oxidase, and competitive scavengers, but not superoxide dismutase. The sensitivity to externally added catalase and ascorbate oxidase suggested that the ethylene production reflected an extracellular oxygen radical generating system. Ferric alone and several ferric chelates, for example, ferric-ATP, ADP, AMP, histidine, and citrate stimulated ethylene production using perfusates of liver or suspension medium after removal of the hepatocytes. The sensitivity of the added iron system to ascorbate oxidase suggested that during perfusion or incubation of liver cells, efflux of ascorbate occurs, followed by reduction of the iron and subsequently, extracellular production of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Ascorbic Acid; Butyrates; Ethylenes; Free Radicals; Hydroxides; Hydroxyl Radical; In Vitro Techniques; Iron; Liver; Male; Oxidation-Reduction; Perfusion; Rats; Rats, Inbred Strains; Sulfhydryl Compounds