Identification de gènes impliqués dans la synthèse des apocaroténoïdes chez la tomate et la violette odorante

Authors: Bulot, Blandine
Advisor: Goulet, Charles
Abstract: Volatile apocarotenoids are molecules with a fruity aroma that have a significant impact on the flavor of fruits and the fragrance of flowers. Despite their importance, the regulation of their synthesis in plants in still not fully understood. The main objective of this thesis was to identify key genes involved in the apocarotenoid pathway in order to ultimately improve the aroma of fruits. In tomatoes, SlCCD1 (Carotenoid Cleavage Dioxygenase 1), even if localized in cytosol, was considered the enzyme responsible for the oxidative cleavage of plastid-localized carotenoids. Analyses of transgenic tomato lines and Viola odorata flowers demonstrate that CCD1 is not a key enzyme in apocarotenoid synthesis in flowers and fruits, and that plastidial enzymes are associated with the production of apocarotenoid volatiles. In tomato, the lipoxygenase C co-oxidizes carotenoids while performing fatty acid oxidation. In V. odorata flowers, the considerable production of ionones correlates with the high expression of plastid-localized CCDs such as VoCCD4 and VoCCD1-like. Since carotenoid accumulation in plastid has an important impact on the nature of the apocarotenoids produced, our attention was also drawn to their synthesis. Genetic analysis of tomatoes that show unusual lycopene accumulation demonstrated the importance of the phytoene synthase 1 (PSY1) gene in the pathway, and the way different structural variation in its promoter or coding sequences can affect fruits color. Bicolor cultivars phenotype is notably due to a likely decrease of PSY1 translation efficiency caused by a deletion in the PSY1 5’UTR region. Similarly, yellow cultivars are the result of structural variations in the first or last exon of PSY1. This knowledge on carotenoid and apocarotenoid synthesis will be useful in order to improve the flavor of tomatoes and many other cultivated species.
Document Type: Mémoire de maîtrise
Issue Date: 2019
Open Access Date: 14 February 2020
Grantor: Université Laval
Collection:Thèses et mémoires

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