Differential contribution of the first two enzymes of the MEP pathway to the supply of metabolic precursors for carotenoid and chlorophyll biosynthesis in carrot (Daucus carota)
Simpson, Kevin (Universidad de Chile. Departamento de Biología)
Quiroz, Luis F. (Universidad de Chile. Departamento de Biología)
Rodríguez Concepción, Manuel (Centre de Recerca en Agrigenòmica)
Stange, Claudia R. (Universidad de Chile. Departamento de Biología)

Data:	2016
Resum:	Carotenoids and chlorophylls are photosynthetic pigments synthesized in plastids from metabolic precursors provided by the methylerythritol 4-phosphate (MEP) pathway. The first two steps in the MEP pathway are catalyzed by the deoxyxylulose 5-phosphate synthase (DXS) and reductoisomerase (DXR) enzymes. While DXS has been recently shown to be the main flux-controlling step of the MEP pathway, both DXS and DXR enzymes have been proven to be able to promote an increase in MEP-derived products when overproduced in diverse plant systems. Carrot (Daucus carota) produces photosynthetic pigments (carotenoids and chlorophylls) in leaves and in light-exposed roots, whereas only carotenoids (mainly α- and β-carotene) accumulate in the storage root in darkness. To evaluate whether DXS and DXR activities influence the production of carotenoids and chlorophylls in carrot leaves and roots, the corresponding Arabidopsis thaliana genes were constitutively expressed in transgenic carrot plants. Our results suggest that DXS is limiting for the production of both carotenoids and chlorophylls in roots and leaves, whereas the regulatory role of DXR appeared to be minor. Interestingly, increased levels of DXS (but not of DXR) resulted in higher transcript abundance of endogenous carrot genes encoding phytoene synthase, the main rate-determining enzyme of the carotenoid pathway. These results support a central role for DXS on modulating the production of MEP-derived precursors to synthesize carotenoids and chlorophylls in carrot, confirming the pivotal relevance of this enzyme to engineer healthier, carotenoid-enriched products.
Ajuts:	Ministerio de Economía y Competitividad SEV2015/0533 Ministerio de Economía y Competitividad BIO2014/59092-P Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-1434
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Carrot ; Storage root ; Deoxyxylulose 5-phosphate synthase (DXS) ; Deoxyxylulose 5-phosphate reductoisomerase (DXR) ; Carotenoids ; Chlorophylls
Publicat a:	Frontiers in plant science, Vol. 7 (Aug. 2016) , art. 1344, ISSN 1664-462X

DOI: 10.3389/fpls.2016.01344
PMID: 27630663

10 p, 2.0 MB

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