Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.3 (ascorbate oxidase)
 778 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ascorbate content declined rapidly in broccoli (Brassica oleracea L. var. italica) florets, but not in the stem tissue, during post-harvest senescence. Ascorbate peroxidase (APX), ascorbate oxidase (AO), l-galactono-1,4-lactone dehydrogenase (GLDH), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were investigated in gene expression after harvest in both florets and the stem tissue of broccoli. Cytosolic gene expressions (BO-APX 1, BO-APX 2, BO-AO, BO-MDAR 2, and BO-GR) were stimulated actively in broccoli florets after harvest. By contrast, it was observed that mRNA levels of chloroplastic APX, BO-sAPX and BO-tbAPX, had decreased by 12 h after harvest in broccoli florets, suggesting that the active oxygen species (AOS) scavenging system in chloroplasts was largely abolished in florets during the early hours of the post-harvest period. In addition, gene expressions in GLDH and other chloroplastic enzymes such as BO-MDAR 1 and BO-DHAR decreased rapidly within 24 h after harvest. Ethylene treatment had no effect on the ascorbate level and the expression of all genes investigated. The expressions of BO-GLDH and chloroplastic genes (BO-sAPX, BO-tbAPX, BO-MDAR 1, and BO-DHAR) mRNA were suppressed by treatment with methyl jasmonate (MJ) and abscisic acid (ABA) and were accompanied by the acceleration of ascorbate degradation. These data suggest that ascorbate metabolism tends to be inactivated in chloroplasts by transcriptional regulation, but not in the cytosol, when ascorbate decreases under stress conditions.
J Exp Bot 2003 Nov
PMID:Ascorbate metabolism in harvested broccoli. 1451 88

Ascorbate levels and redox state, as well as the activities of the ascorbate related enzymes, have been analysed both in the apoplastic and symplastic spaces of etiolated pea (Pisum sativum L.) shoots during cellular differentiation. The ascorbate pool and the ascorbate oxidizing enzymes, namely ascorbate oxidase and ascorbate peroxidase, were present in both pea apoplast and symplast, whereas ascorbate free radical reductase and dehydroascorbate reductase were only present in the symplastic fractions. During cell differentiation the ascorbate redox enzymes changed in different ways, since a decrease in ascorbate levels, ascorbate peroxidase and ascorbate free radical reductase occurred from meristematic to differentiated cells, whereas ascorbate oxidase and dehydroascorbate reductase increased. The activity of secretory peroxidases has also been followed in the apoplast of meristematic and differentiating cells. These peroxidases increased their activity during differentiation. This behaviour was accompanied by changes in their isoenzymatic profiles. The analysis of the kinetic characteristics of the different peroxidases present in the apoplast suggests that the presence of ascorbate and ascorbate peroxidase in the cell wall could play a critical role in regulating the wall stiffening process during cell differentiation by interfering with the activity of secretory peroxidases.
J Exp Bot 2004 Dec
PMID:Changes in the ascorbate metabolism of apoplastic and symplastic spaces are associated with cell differentiation. 1547 79

Transgenic tobacco plants expressing the ascorbate oxidase (AAO) gene in sense and antisense orientations, and an Arabidopsis mutant in which the T-DNA was inserted into a putative AAO gene, were used to examine the potential roles of AAO for salt-stress tolerance in plants. AAO activities in the transgenic tobacco plants expressing the gene in sense and antisense orientations were, respectively, about 16-fold and 0.2-fold of those in the wild type. Under normal growth conditions, no significant differences in phenotypes were observed, except for a delay in flowering time in the antisense plants. However, at high salinity, the percentage germination, photosynthetic activity, and seed yields were higher in antisense plants, with progressively lower levels in the wild type and the sense plants. The redox state of apoplastic ascorbate in sense plants was very low even under normal growth conditions. Upon salt stress, the redox state of symplastic and apoplastic ascorbate decreased among the three types of plants, but was lowest in the sense plants. The hydrogen peroxide contents in the symplastic and apoplastic spaces were higher in sense plants, progressively lower in the wild type, followed by the antisense plants. The Arabidopsis T-DNA inserted mutant exhibited very low ascorbate oxidase activity, and its phenotype was similar to that of antisense tobacco plants. These results suggest that the suppressed expression of apoplastic AAO under salt-stress conditions leads to a relatively low level of hydrogen peroxide accumulation and a high redox state of symplastic and apoplastic ascorbate which, in turn, permits a higher seed yield.
J Exp Bot 2005 Jul
PMID:Suppressed expression of the apoplastic ascorbate oxidase gene increases salt tolerance in tobacco and Arabidopsis plants. 1588 31

Control of stomatal aperture is of paramount importance for plant adaptation to the surrounding environment. Here, we report on several parameters related to stomatal dynamics and performance in transgenic tobacco plants (Nicotiana tabacum L., cv. Xanthi) over-expressing cucumber ascorbate oxidase (AO), a cell wall-localized enzyme of uncertain biological function that oxidizes ascorbic acid (AA) to monodehydroascorbic acid which dismutates yielding AA and dehydroascorbic acid (DHA). In comparison to WT plants, leaves of AO over-expressing plants exhibited reduced stomatal conductance (due to partial stomatal closure), higher water content, and reduced rates of water loss on detachment. Transgenic plants also exhibited elevated levels of hydrogen peroxide and a decline in hydrogen peroxide-scavenging enzyme activity. Leaf ABA content was also higher in AO over-expressing plants. Treatment of epidermal strips with either 1 mM DHA or 100 microM hydrogen peroxide resulted in rapid stomatal closure in WT plants, but not in AO-over-expressing plants. This suggests that signal perception and/or transduction associated with stomatal closure is altered by AO over-expression. These data support a specific role for cell wall-localized AA in the perception of environmental cues, and suggest that DHA acts as a regulator of stomatal dynamics.
J Exp Bot 2008
PMID:Altered stomatal dynamics in ascorbate oxidase over-expressing tobacco plants suggest a role for dehydroascorbate signalling. 1834 48

In plant cells, antioxidants keep reactive oxygen species at low concentrations, avoiding oxidative damage while allowing them to play crucial functions in signal transduction. However, little is known about the role of antioxidants during fruit maturation, especially in legumes. Snap pea (Pisum sativum) plants, which have edible fruits, were grown under nodulating and non-nodulating conditions. Fruits were classified in three maturity stages and antioxidants were determined in the seeds and seedless pods. Maturation or prolonged storage of fruits at 25 degrees C led to a decline in antioxidant activities and metabolites and in gamma-glutamylcysteine synthetase protein. Notable exceptions were superoxide dismutase activity and glutathione peroxidase protein, which increased in one or both of these processes. During maturation, cytosolic peroxiredoxin decreased in seeds but increased in pods, and ascorbate oxidase activity was largely reduced in seeds. In stored fruits, ascorbate oxidase activity was nearly abolished in seeds but doubled in pods. It is concluded that symbiotic nitrogen fixation is as effective as nitrogen fertilization in maintaining the antioxidant capacity of pea fruits and that, contrary to climacteric fruits, a general decrease in antioxidants during maturation does not involve oxidative stress. Results underscore the importance of the antioxidant system in reproductive organs and point to ascorbate-glutathione metabolism and cytosolic peroxiredoxin as key players in pea fruit development.
J Exp Bot 2010
PMID:Function of antioxidant enzymes and metabolites during maturation of pea fruits. 1982 34

High surface ozone concentration is increasingly being recognized as a factor that negatively affects crop yields in Asia. However, little progress has been made in developing ozone-tolerant genotypes of rice-Asia's major staple crop. This study aimed to identify possible tolerance mechanisms by characterizing two quantitative trait loci (QTLs) that were previously shown to influence visible leaf symptoms under ozone exposure (120 nl l(-1), 7 h d(-1), 13 d). Two chromosome segment substitution lines (SL15 and SL41) that carried introgressions of the QTLs OzT3 and OzT9, respectively, were exposed to ozone at 120 nl l(-1) along with their parent Nipponbare. In accordance with the expected QTL effect, SL15 showed stronger visible symptoms of ozone damage than Nipponbare, whereas SL41 had fewer symptoms. Gene expression profiling by microarray hybridization yielded 470 probes that were differentially expressed in SL15 and 314 in SL41. Potential tolerance mechanisms were evaluated by investigating changes in gene expression in three general categories. (i) Processes involved in programmed cell death, in which a number of genes related to ethylene or jasmonic acid metabolism or general disease resistance were identified that were differentially regulated in one of the substitution lines. (ii) Biosynthesis of antioxidants. Testing this hypothesis did not reveal any genes differentially regulated between genotypes, and it was thus rejected. (iii) Turnover of antioxidants and enzymatic detoxification of radical oxygen species (ROS), in which a number of differentially regulated genes were also identified. Genes encoding antioxidant enzymes (catalase and peroxidases) tended to be more strongly expressed in SL15. A potential tolerance gene which encodes a putative ascorbate oxidase was identified within the QTL introgression in SL41. This gene showed consistently lower expression in SL41 under ozone exposure across different points in time within independent experiments. Its expression may be involved in mechanisms leading to enhanced ascorbic acid status in SL41 under ozone exposure, and may be linked to a higher concentration of total apoplastic ascorbic acid in SL41 that was observed in an independent experiment.
J Exp Bot 2010 Mar
PMID:Mechanisms of ozone tolerance in rice: characterization of two QTLs affecting leaf bronzing by gene expression profiling and biochemical analyses. 2016 44

Ascorbic acid (AA) is the major antioxidant buffer produced in the shoot tissue of plants. Previous studies on root-knot nematode (RKN; Meloidogyne graminicola)-infected rice (Oryza sativa) plants showed differential expression of AA-recycling genes, although their functional role was unknown. Our results confirmed increased dehydroascorbate (DHA) levels in nematode-induced root galls, while AA mutants were significantly more susceptible to nematode infection. External applications of ascorbate oxidase (AO), DHA, or reduced AA, revealed systemic effects of ascorbate oxidation on rice defence versus RKN, associated with a primed accumulation of H2O2 upon nematode infection. To confirm and further investigate these systemic effects, a transcriptome analysis was done on roots of foliar AO-treated plants, revealing activation of the ethylene (ET) response and jasmonic acid (JA) biosynthesis pathways in roots, which was confirmed by hormone measurements. Activation of these pathways by methyl-JA, or ethephon treatment can complement the susceptibility phenotype of the rice Vitamin C (vtc1) mutant. Experiments on the jasmonate signalling (jar1) mutant or using chemical JA/ET inhibitors confirm that the effects of ascorbate oxidation are dependent on both the JA and ET pathways. Collectively, our data reveal a novel pathway in which ascorbate oxidation induces systemic defence against RKNs.
J Exp Bot 2020 Jul 06
PMID:Ascorbate oxidation activates systemic defence against root-knot nematode Meloidogyne graminicola in rice. 3224 24