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JXB Advance Access published online on September 18, 2009
Journal of Experimental Botany, doi:10.1093/jxb/erp283
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© The Author [2009]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

RESEARCH PAPER

The expression of a chromoplast-specific lycopene beta cyclase gene is involved in the high production of saffron's apocarotenoid precursors

Oussama Ahrazem1, Angela Rubio-Moraga1, Raquel Castillo López2 and Lourdes Gómez-Gómez1,*

1Departamento de Ciencia y Tecnología Agroforestal y Genética, ETSIA, Universidad de Castilla-La Mancha, Campus Universitario s/n, E-02071 Albacete, Spain
2VITAB Laboratorios, Polígono Industrial Garysol C/ Pino, parcela 53, La Gineta, E-02110 Albacete, Spain

* To whom correspondence should be addressed: E-mail: marialourdes.gomez{at}uclm.es

Crocus sativus is a triploid sterile plant characterized by its long red stigmas, which produce and store significant quantities of carotenoid derivatives formed from the oxidative cleavage of β-carotene and zeaxanthin. The present study reports on the genomic structures of two lycopene-β-cyclase genes, CstLcyB1 and CstLcyB2a, and on their transcription patterns in different C. sativus tissues. Phylogenetic analysis showed that both proteins are located in different groups: CstLcyB2a encodes chromoplast-specific lycopene cyclases, with an expression analysis showing strongly in flower stigmas where it activates and boosts β-carotene accumulation. The CstLcyB1 transcript, however, was present in leaves, tepals, and stigmas at lower levels. In vivo assays in transgenic Arabidopsis demonstrated lycopene β-cyclase activity of CstLcyB2a. CstLcyB2a is a CstLcyB1 paralogue derived through a gene duplication event, while promoter analysis showed that both genes have diverged in their regulatory sequences after duplication. Furthermore, it was found that the CstLcyB2a gene was absent from Crocus kotschyanus and, although present in C. goulimyi and C. cancellatus, the absence of transcripts suggests that transcriptional regulation of CstLcyB2a is responsible for the low apocarotenoid content in these species.

Key words: Apocarotenoids, Crocus sativus, gene expression, lycopene, lycopene β-cyclase, promoter, stigma

Received 11 June 2009; Revised 27 August 2009 Accepted 30 August 2009


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