Biosynthesis of lipophilic compounds in tomato fruit

Abstract

Metabolic engineering approaches to increasing lycopene contents in tomato fruit have always led to moderate increases of this metabolite. This reflects, at least in part, the lack of knowledge about the mechanisms underlying the regulation of carotenoid biosynthesis and accumulation as well as the rest of metabolic processes operating in the chromoplasts. A study performed with chromoplasts to know the origin of the precursors for carotenoids biosynthesis using a variety of ¹⁴C-labelled precursors showed that the most important incorporation was found in lipids. This study aims to understand the biochemical and metabolic processes operating during tomato fruit ripening. Labelling studies showed an efficient incorporation of ¹⁴Cacetate not only into fatty acids and sterols (as expected) but also into lycopene, suggesting that the cytosolic mevalonate pathway was also contributing to carotenoid biosynthesis during fruit ripening. This observation has been confirmed using ¹⁴C-mevalonate, which served as a precursor for the synthesis of sterols and carotenoids.

Keywords: Carotenoid, sterol, labelling assay, pericarp, chromoplasts.