Enzymatic study on AtCCD4 and AtCCD7 and their potential to form acyclic regulatory metabolites.
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.
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Mark
M
Bruno
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Julian
J
Koschmieder
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Florian
F
Wuest
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Patrick
P
Schaub
Albert-Ludwigs University of Freiburg, Department of Physics, Hermann-Herder-Str. 3a, D-79104 Freiburg, Germany.
Mirjam
M
Fehling-Kaschek
Albert-Ludwigs University of Freiburg, Department of Physics, Hermann-Herder-Str. 3a, D-79104 Freiburg, Germany.|Albert-Ludwigs University of Freiburg, BIOSS Center for Biological Signalling Studies, Schaenzlestr. 18, D-79104 Freiburg, Germany.
Jens
J
Timmer
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Peter
P
Beyer
Albert-Ludwigs University of Freiburg, Faculty of Biology, Schaenzlestr. 1, D-79104 Freiburg, Germany salim.babili@kaust.edu.sa.|King Abdullah University of Science and Technology (KAUST), BESE Division, Center for Desert Agriculture, 23955-6900 Thuwal, Saudi Arabia.
Salim
S
Al-Babili
D017360:Arabidopsis / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D002338:Carotenoids / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D049308:Dioxygenases / Q000378:metabolism / Q000502:physiology*; D013058:Mass Spectrometry; D013379:Substrate Specificity; D024341:Xanthophylls / Q000378:metabolism
D029681:Arabidopsis Proteins; D024341:Xanthophylls; D002338:Carotenoids; C000592331:CCD4 protein, Arabidopsis; C494441:CCD7 protein, Arabidopsis; D049308:Dioxygenases
Apocarotenoids; CCD4; CCD7; carotenoid cleavage dioxygenase; carotenoids; retrograde signaling