beta-apo-10--carotenal and carlactone

Strigolactones are a new class of phytohormones synthesized from carotenoids via carlactone. The complex structure of carlactone is not easily deducible from its precursor, a cis-configured β-carotene cleavage product, and is thus formed via a poorly understood series of reactions and molecular rearrangements, all catalyzed by only one enzyme, the carotenoid cleavage dioxygenase 8 (CCD8). Moreover, the reactions leading to carlactone are expected to form a second, yet unidentified product. In this study, we used

Topics: beta Carotene; Biocatalysis; Carbon Isotopes; Carotenoids; Dioxygenases; Escherichia coli; Gene Expression; Lactones; Oxygen Isotopes; Pisum sativum; Plant Growth Regulators; Plant Proteins; Recombinant Proteins

Strigolactones, phytohormones with diverse signaling activities, have a common structure consisting of two lactones connected by an enol-ether bridge. Strigolactones derive from carotenoids via a pathway involving the carotenoid cleavage dioxygenases 7 and 8 (CCD7 and CCD8) and the iron-binding protein D27. We show that D27 is a β-carotene isomerase that converts all-trans-β-carotene into 9-cis-β-carotene, which is cleaved by CCD7 into a 9-cis-configured aldehyde. CCD8 incorporates three oxygens into 9-cis-β-apo-10'-carotenal and performs molecular rearrangement, linking carotenoids with strigolactones and producing carlactone, a compound with strigolactone-like biological activities. Knowledge of the structure of carlactone will be crucial for understanding the biology of strigolactones and may have applications in combating parasitic weeds.

Topics: Arabidopsis; Arabidopsis Proteins; beta Carotene; Biosynthetic Pathways; Carotenoids; Dioxygenases; Germination; Isomerases; Lactones; Molecular Structure; Mutation; Oryza; Phenotype; Pisum sativum; Plant Growth Regulators; Plant Proteins; Stereoisomerism; Striga