title: Ascorbate degradation in tomato leads to accumulation of oxalate, threonate and oxalyl threonate.
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.
authors.affiliation: INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France.|INRA, UR-1115, Plantes et Systèmes de culture Horticoles, CS40509, 84914 Avignon Cedex 9, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Truffault
authors.affiliation: The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Daniel Rutherford Building, The King's Building, Edinburgh, EH9 3BF, UK.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Fry
authors.affiliation: INRA, UR-1052, Génétique et Amélioration des Fruits et Légumes, CS60094, 84143, Montfavet, France.
authors.forename: Rebecca G
authors.initials: RG
authors.lastname: Stevens
authors.affiliation: INRA, UR-1115, Plantes et Systèmes de culture Horticoles, CS40509, 84914 Avignon Cedex 9, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Gautier
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism*; D002087:Butyrates / Q000378:metabolism*; D005638:Fruit / Q000378:metabolism / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000528:radiation effects; D008027:Light; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010070:Oxalates / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects
chemical_list: D002087:Butyrates; D010070:Oxalates; D009247:NADH, NADPH Oxidoreductases; C023927:monodehydroascorbate reductase (NADH); C011369:threonic acid; D001205:Ascorbic Acid
keywords: 
  Solanum lycopersicum
  ; [14C]ascorbate labelling; ascorbate degradation; high-voltage paper electrophoresis; light environment; monodehydroascorbate reductase; tomato