title: 4-Deoxyaurone formation in Bidens ferulifolia (Jacq.) DC.
abstract: The formation of 4-deoxyaurones, which serve as UV nectar guides in Bidens ferulifolia (Jacq.) DC., was established by combination of UV photography, mass spectrometry, and biochemical assays and the key step in aurone formation was studied. The yellow flowering ornamental plant accumulates deoxy type anthochlor pigments (6'-deoxychalcones and the corresponding 4-deoxyaurones) in the basal part of the flower surface whilst the apex contains only yellow carotenoids. For UV sensitive pollinating insects, this appears as a bicoloured floral pattern which can be visualized in situ by specific ammonia staining of the anthochlor pigments. The petal back side, in contrast, shows a faintly UV absorbing centre and UV absorbing rays along the otherwise UV reflecting petal apex. Matrix-free UV laser desorption/ionisation mass spectrometric imaging (LDI-MSI) indicated the presence of 9 anthochlors in the UV absorbing areas. The prevalent pigments were derivatives of okanin and maritimetin. Enzyme preparations from flowers, leaves, stems and roots of B. ferulifolia and from plants, which do not accumulate aurones e.g. Arabidopsis thaliana, were able to convert chalcones to aurones. Thus, aurone formation could be catalyzed by a widespread enzyme and seems to depend mainly on a specific biochemical background, which favours the formation of aurones at the expense of flavonoids. In contrast to 4-hydroxyaurone formation, hydroxylation and oxidative cyclization to the 4-deoxyaurones does not occur in one single step but is catalyzed by two separate enzymes, chalcone 3-hydroxylase and aurone synthase (catechol oxidase reaction). Aurone formation shows an optimum at pH 7.5 or above, which is another striking contrast to 4-hydroxyaurone formation in Antirrhinum majus L. This is the first example of a plant catechol oxidase type enzyme being involved in the flavonoid pathway and in an anabolic reaction in general.
authors.affiliation: Institut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften, Technische Universität Wien, Wien, Austria.
authors.forename: Silvija
authors.initials: S
authors.lastname: Miosic
authors.forename: Katrin
authors.initials: K
authors.lastname: Knop
authors.forename: Dirk
authors.initials: D
authors.lastname: Hölscher
authors.forename: Jürgen
authors.initials: J
authors.lastname: Greiner
authors.forename: Christian
authors.initials: C
authors.lastname: Gosch
authors.forename: Jana
authors.initials: J
authors.lastname: Thill
authors.forename: Marco
authors.initials: M
authors.lastname: Kai
authors.forename: Binita Kumari
authors.initials: BK
authors.lastname: Shrestha
authors.forename: Bernd
authors.initials: B
authors.lastname: Schneider
authors.forename: Anna C
authors.initials: AC
authors.lastname: Crecelius
authors.forename: Ulrich S
authors.initials: US
authors.lastname: Schubert
authors.forename: Aleš
authors.initials: A
authors.lastname: Svatoš
authors.forename: Karl
authors.initials: K
authors.lastname: Stich
authors.forename: Heidi
authors.initials: H
authors.lastname: Halbwirth
mesh_terms: D001572:Benzofurans / Q000032:analysis* / Q000378:metabolism*; D031176:Bidens / Q000737:chemistry*; D002338:Carotenoids / Q000737:chemistry; D004156:Catechol Oxidase / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005419:Flavonoids / Q000378:metabolism; D035264:Flowers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010860:Pigments, Biological / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014466:Ultraviolet Rays
chemical_list: D001572:Benzofurans; D005419:Flavonoids; D010860:Pigments, Biological; C486837:aurone; D002338:Carotenoids; D004156:Catechol Oxidase