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Ascorbate degradation in tomato leads to accumulation of oxalate, threonate and oxalyl threonate

Author:
Truffault, Vincent, Fry, Stephen C., Stevens, Rebecca G., Gautier, Hélène
Source:
The plant journal 2017 v.89 no.5 pp. 996-1008
ISSN:
0960-7412
Subject:
carbon, dehydroascorbic acid, fruits, leaves, models, monodehydroascorbate reductase (NADH), oxalates, radionuclides, recycling, tartaric acid, tomatoes
Abstract:
Ascorbate content in plants is controlled by its synthesis from carbohydrates, recycling of the oxidized forms and degradation. Of these pathways, ascorbate degradation is the least studied and represents a lack of knowledge that could impair improvement of ascorbate content in fruits and vegetables as degradation is non‐reversible and leads to a depletion of the ascorbate pool. The present study revealed the nature of degradation products using [¹⁴C]ascorbate labelling in tomato, a model plant for fleshy fruits; oxalate and threonate are accumulated in leaves, as is oxalyl threonate. Carboxypentonates coming from diketogulonate degradation were detected in relatively insoluble (cell wall‐rich) leaf material. No [¹⁴C]tartaric acid was found in tomato leaves. Ascorbate degradation was stimulated by darkness, and the degradation rate was evaluated at 63% of the ascorbate pool per day, a percentage that was constant and independent of the initial ascorbate or dehydroascorbic acid concentration over periods of 24 h or more. Furthermore, degradation could be partially affected by the ascorbate recycling pathway, as lines under‐expressing monodehydroascorbate reductase showed a slight decrease in degradation product accumulation.
Agid:
5721880