Journal Article

Evolutionarily distinct carotenoid cleavage dioxygenases are responsible for crocetin production in <i>Buddleja davidii</i>

Oussama Ahrazem, Gianfranco Diretto, Javier Argandoña, Ángela Rubio-Moraga, José Manuel Julve, Diego Orzáez, Antonio Granell and Lourdes Gómez-Gómez

Edited by Qiao Zhao

in Journal Of Experimental Botany

Volume 68, issue 16, pages 4663-4677
Published in print July 2017 | ISSN: 0022-0957
Published online August 2017 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erx277
Evolutionarily distinct carotenoid cleavage dioxygenases are responsible for crocetin production in Buddleja davidii

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Abstract

Crocetin, one of the few colored apocarotenoids known in nature, is present in flowers and fruits and has long been used medicinally and as a colorant. Saffron is the main source of crocetin, although a few other plants produce lower amounts of this apocarotenoid. Notably, Buddleja davidii accumulates crocetin in its flowers. Recently, a carotenoid dioxygenase cleavage enzyme, CCD2, has been characterized as responsible for crocetin production in Crocus species. We searched for CCD2 homologues in B. davidii and identified several CCD enzymes from the CCD1 and CCD4 subfamilies. Unexpectedly, two out of the three CCD4 enzymes, namely BdCCD4.1 and BdCCD4.3, showed 7,8;7′,8′ activity in vitro and in vivo over zeaxanthin. In silico analyses of these enzymes and CCD2 allowed the determination of key residues for this activity. Both BdCCD4 genes are highly expressed during flower development and transcripts levels parallel the accumulation of crocins in the petals. Phylogenetic analysis showed that BdCCD4.2 grouped with almost all the characterized CCD4 enzymes, while BdCCD4.1 and BdCCD4.3 form a new sub-cluster together with CCD4 enzymes from certain Lamiales species. The present study indicates that convergent evolution led to the acquisition of 7,8;7′,8′ apocarotenoid cleavage activity in two separate CCD enzyme families.

Keywords: Carotenoid dioxygenase cleavage; crocetin; flowers; Lamiales; zeaxanthin

Journal Article.  9006 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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