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J Exp Bot. 2016 Nov;67(21):5993-6005. Epub 2016 Oct 6.

Enzymatic study on AtCCD4 and AtCCD7 and their potential to form acyclic regulatory metabolites.

Author information

1
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
2
Albert-Ludwigs University of Freiburg, Department of Physics, Hermann-Herder-Str. 3a, D-79104 Freiburg, Germany.
3
Albert-Ludwigs University of Freiburg, BIOSS Center for Biological Signalling Studies, Schaenzlestr. 18, D-79104 Freiburg, Germany.
4
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany salim.babili@kaust.edu.sa.
5
King Abdullah University of Science and Technology (KAUST), BESE Division, Center for Desert Agriculture, 23955-6900 Thuwal, Saudi Arabia.

Abstract

The Arabidopsis carotenoid cleavage dioxygenase 4 (AtCCD4) is a negative regulator of the carotenoid content of seeds and has recently been suggested as a candidate for the generation of retrograde signals that are thought to derive from the cleavage of poly-cis-configured carotene desaturation intermediates. In this work, we investigated the activity of AtCCD4 in vitro and used dynamic modeling to determine its substrate preference. Our results document strict regional specificity for cleavage at the C9-C10 double bond in carotenoids and apocarotenoids, with preference for carotenoid substrates and an obstructing effect on hydroxyl functions, and demonstrate the specificity for all-trans-configured carotenes and xanthophylls. AtCCD4 cleaved substrates with at least one ionone ring and did not convert acyclic carotene desaturation intermediates, independent of their isomeric states. These results do not support a direct involvement of AtCCD4 in generating the supposed regulatory metabolites. In contrast, the strigolactone biosynthetic enzyme AtCCD7 converted 9-cis-configured acyclic carotenes, such as 9-cis-ζ-carotene, 9'-cis-neurosporene, and 9-cis-lycopene, yielding 9-cis-configured products and indicating that AtCCD7, rather than AtCCD4, is the candidate for forming acyclic retrograde signals.

KEYWORDS:

Apocarotenoids; CCD4; CCD7; carotenoid cleavage dioxygenase; carotenoids; retrograde signaling

PMID:
27811075
PMCID:
PMC5100015
DOI:
10.1093/jxb/erw356
[Indexed for MEDLINE]
Free PMC Article

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