Identification of Flavonoids in Leaves of a Labile Bicolor Flowering Dahlia (<i>Dahlia variabilis</i>) ‘Yuino’

Abstract

Bicolor flowering dahlias are a group of cultivars that produce inflorescences with bicolored petals characterized by a colored basal part and a white tip. However, they frequently produce single-colored petals, even if they are vegetatively propagated. In a previous study, strong relationships between inflorescence color and leaf phenotype were observed in a red-white bicolor flowering dahlia 'Yuino'; red petal-producing individuals accumulate flavonoids in leaves, whereas only bicolor petal-producing individuals tend not to accumulate them in leaves. Flavonoids in leaves are assumed to be chalcones. In this study, we investigated flavonoids in the leaves of 'Yuino' by nuclear magnetic resonance analysis and identified six caffeoyl esters, four flavonol derivatives, and three novel butein derivatives in the flavonoid-rich leaves of 'Yuino'. The three novel compounds were butein 4',4-O-di-[2-O-(β-glucopyranosyl)-β-glucopyranoside], butein 4'-O-[2-O-(β-glucopyranosyl)-β-glucopyranoside]-4-O-β-glucopyranoside, and butein 4'-[6-O-(3-hydroxy-3-methylglutaryl)-β-glucopyranoside]-4-O-β-glucopyranoside.On the other hand, only caffeoyl esters were detected in flavonoidpoor leaves. These data demonstrated that flavonoid-rich leaves accumulated the flavonoids of butein and flavonol derivatives. The common enzyme for the biosynthesis of butein and flavonol derivatives is chalcone synthase; thus, the importance of chalcone synthase for phenotypic lability in 'Yuino' was confirmed.

Post-transcriptional silencing of chalcone synthase is involved in phenotypic lability in petals and leaves of bicolor dahlia (Dahlia variabilis) ‘Yuino’

“…7b) suggesting PTGS of CHS was suppressed in red petals. (Ohno et al 2017). In the present study, only DvCHS2 had lower expression in flavonoidpoor leaves than in flavonoid-rich leaves, whereas other flavonoid biosynthetic genes had almost the same expression levels (Fig.…”

“…the loss of expression of DvCHS2 in petals results in the loss of anthocyanin, flavone and butein synthesis (Ohno et al 2011b; Fig. 3), and the loss of expression of DvCHS2 in leaves results in the loss of flavonol and butein synthesis (Ohno et al 2016(Ohno et al , 2017. Therefore, it appears that the DvCHS2 protein may be the functional CHS enzyme in both petals and leaves, and so is associated with all flavonoid biosynthesis in dahlia.…”

Identification of Chalcones and their Contribution to Yellow Coloration in Dahlia (<i>Dahlia variabilis</i>) Ray Florets

“…Yellow flower cultivars accumulate chalcones and flavones in their ray florets (Ohno et al, 2013a). Butein accumulation is found in dahlia leaves (Ohno et al, 2018) and in flowers of some limited species such as two Coreopsis species (C. douglasii and C. gigantea) (Geissman, 1941a;Geissman, 1941b), Cosmos sulphureus (Geissman, 1942) and Bidens (Scogin and Zakar, 1976). Alhough butein itself functions as a yellow pigment, but it is also used as a precursor of aurone in Coreopsis grandiflora, in which the step is catalyzed by polyphenol oxidase (Kaintz et al, 2014;Molitor et al, 2016).…”

Identification of a novel chalcone reductase gene for isoliquiritigenin biosynthesis in dahlia (Dahlia variabilis)

“…The pigment contributes to yellow flower color in dahlia is a butein (Price, 1939), and the final products were determined as butein 4'-malonylsophoroside and butein 4'-malonylglucoside (Harborne et al, 1990). Butein derivatives were also detected in leaves (Ohno et al, 2018b).…”

“…The pigment contributes to yellow flower color in dahlia is a butein (Price, 1939), and the final products were determined as butein 4’-malonylsophoroside and butein 4’-malonylglucoside (Harborne et al, 1990). Butein derivatives were also detected in leaves (Ohno et al, 2018b). In dahlia, butein always co-accumulates with isoliquiritigenin, suggesting CHR is the determinant factor for butein biosynthesis (Ohno et al, 2013a).…”