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Oxydation et dégradation de l'ascorbate chez la tomate et impact sur la croissance et le métabolisme

Abstract : Ascorbate metabolism and particularly ascorbate redox status are involved in stress tolerance and growth processes of plant cells. The concentration of ascorbate and its redox status are under control of (i) its biosynthetic pathways, (ii) the ascorbate-glutathione cycle allowing recycling of semi-oxidized and oxidized forms of ascorbate and (iii) its degradation rate. These processes are under environmental control. Transgenic lines modified for the activity of monodehydroascorbate reductase (involved in ascorbate-glutathione cycle) and ascorbate oxidase were generated in cherry and large-fruited genotypes of tomato. Physiological and metabolic modifications related to the modification of these enzyme activities were studied. We observed large phenotypic alterations that affected fruit yield under both stress conditions and normal growth conditions. Links between ascorbate recycling and sugar metabolism, photosynthesis and stomatal conductance were also revealed. An imbalance between the oxidizing and reducing activities of these enzymes is the first step leading to ascorbate degradation. We have shown that the degradation rate was very low under light, whereas under darkness the degradation compounds oxalate, threonate and oxalyl-threonate accumulated in tomato leaves. Also, the degradation rate is correlated with MDHAR activity. These results highlight the crucial role of the redox status of the ascorbate / monodehydroascorbate couple in growth processes and yield stability in tomato, and the impact on ascorbate degradation.
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Submitted on : Friday, June 5, 2020 - 5:22:29 PM
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  • HAL Id : tel-02799194, version 1
  • PRODINRA : 354124



Vincent Truffault. Oxydation et dégradation de l'ascorbate chez la tomate et impact sur la croissance et le métabolisme. Sciences agricoles. Université d'Avignon et des Pays de Vaucluse, 2015. Français. ⟨tel-02799194⟩



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