Insights into carotenoid sequestration mechanisms in Tomato fruit (Solanum lycopersicum) and the effect of ectopic expression approaches on carotenoid biosynthesis

Martin Klompmaker

Research output: ThesisDoctoral Thesis

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Carotenoids are involved in a wide range of plant processes varying from development to defence, pollination and seed dispersal. The consumption benefits of carotenoids for human health and nutrition have led to development of an interest in the industrial application of carotenoids in food, feed and cosmetics. Tomato (Solanum lycopersicum) is the model plant for carotenoids related studies with its fruits which contain high levels of carotenoids.
Carotenoid sequestration is an important process linked to carotenoid biosynthesis which requires further elucidation. A selection of tomato lines perturbed in carotenoid biosynthesis was studied for their differences in sequestration mechanisms. Premature accumulation of carotenes in a tomato line constitutively expressing PSY1 led to the differentiation of chloroplasts to chromoplast in immature fruit to create a higher capacity for carotenoid accumulation. Tomato lines rr, ogC and tan, knock out lines for PSY1, LCY-B and CRT-ISO respectively, demonstrated different distributions between plastoglobules and crystalline membrane structures associated with cis-carotenes and trans-carotenes. The role of carotenoid accumulation and changes in carotenoid profiles suggests the plastid can adapt to changes in carotenoid content through plastid differentiation and preferential sequestration.
Ectopic expression of the MEP and bacterial carotenoid (crtE, crtB, crtI) pathway in the cytosol has hereby been attempted to enhance carotenoid content as an alternative to metabolic engineering of endogenous key enzymes. The isoprenoid biosynthesis clusters are spread over various cellular compartments in plants. A modular cloning system (GB Cloning) was used for the assembly of vectors with the genes of the MEP and bacterial carotenoid pathway in single or multi gene combinations. The ectopic expression of crtB led to the accumulation of phytoene (14-fold), phytofluene and lycopene, and increased levels of lutein and β-carotene. The impact of the enzyme on pathway intermediates beyond its function suggest a signalling cascade based on cytosolic apocarotenoids derived from the CRTB activity.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Fraser, Paul, Supervisor
Publication statusUnpublished - 2018



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