Optimisation of high-value isoprenoid production in plants: Potential strategies and insights into carotenoid sequestration

Research output: ThesisDoctoral Thesis

406 Downloads (Pure)


Carotenoids and ketocarotenoids are isoprenoid molecules, which represent one of the most widespread classes of natural pigments, found in animals, plants and
microorganisms. Moreover, they have valuable antioxidant properties. Their health
benefits and colorant aspects have led to attempts to elevate their level in foodstuffs.
In the present study, several metabolic engineering strategies were tested in order to enhance the levels of high-value carotenoid and ketocarotenoid compounds, such as lycopene, -carotene, canthaxanthin and astaxanthin, in tomato and tobacco plants.
Biosynthetic bacterial pathway genes have been overexpressed independently
(GGPP synthase (CrtE), phytoene synthase (CrtB) and phytoene desaturase (CrtI))
and in combination (CrtE+B, CrtE+I, CrtB+I and -carotene hydroxylase and
ketolase (CrtZ+W)), with different promoters (for CrtB, CrtI and CrtB+I) or in
association with transcription factors (Phytochrome-interacting factor 5
(CrtZ+W+PIF5) and Arabidopsis Response Regulator 14 (CrtZ+W+ARR14)). The
effects of these different strategies on the plant metabolism and especially on
carotenoid formation, sequestration and the activation of regulation mechanisms
were studied.
The combination of the two genes CrtB and CrtI, in their hemizygous state, had a
synergistic effect on the production of carotenoids and the expression of
CrtZ+W+ARR14 increased the levels of ketocarotenoids in the plants. The important
features for the design of metabolic engineering strategies were highlighted.
Moreover, regulatory mechanisms that operate across multiple levels of cellular
regulation, including transcription, protein localisation, metabolite levels, cell or
tissue type, and organelle/sub-organelle structure and organisation were revealed. It was demonstrated how changes to chromoplast and sub-chromoplast structures, such as crystal formation, plastoglobule and membrane composition/structures can arise in response to changes in metabolites. A new carotenoid regulation mechanism at the sub-organellar level was discovered and a schematic model was proposed.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Fraser, Paul, Supervisor
  • Bramley, Peter, Supervisor
  • Devoto, Alessandra, Advisor
Thesis sponsors
Award date1 Jan 2014
Publication statusUnpublished - 2013


  • carotenoid
  • ketocarotenoid
  • sequestration

Cite this