Disequilibrium of Flavonol Synthase and Dihydroflavonol-4-Reductase Expression Associated Tightly to White vs. Red Color Flower Formation in Plants

Abstract

Flower color is the main character throughout the plant kingdom. Though substantial information exists regarding the structural and regulatory genes involved in anthocyanin and flavonol biosynthesis, little is known that what make a diverse white vs. red color flower in natural species. Here, the contents of pigments in seven species from varied phylogenetic location in plants with red and white flowers were determined. Flavonols could be detected in red and white flowers, but anthocyanins were almost undetectable in the white cultivar. Comparisons of expression patterns of gene related to the flavonoid biosynthesis indicated that disequilibrium expression of flavonol synthase (FLS) and dihydroflavonol-4-reductase (DFR) genes determined the accumulation of flavonols and anothcyanins in both red and white flowers of seven species. To further investigate the role of such common regulatory patterns in determining flower color, FLS genes were isolated from Rosa rugosa (RrFLS1), Prunus persica (PpFLS), and Petunia hybrida (PhFLS), and DFR genes were isolated from Rosa rugosa (RrDFR1) and Petunia hybrida (PhDFR). Heterologous expression of the FLS genes within tobacco host plants demonstrated conservation of function, with the transgenes promoting flavonol biosynthesis and inhibiting anthocyanin accumulation, so resulting in white flowers. Conversely, overexpression of DFR genes in tobacco displayed down-regulation of the endogenous NtFLS gene, and the promotion of anthocyanin synthesis. On this basis, we propose a model in which FLS and DFR gene-products compete for common substrates in order to direct the biosynthesis of flavonols and anthocyanins, respectively, thereby determining white vs. red coloration of flowers.

Dihydroflavonol 4-Reductase Genes from Freesia hybrida Play Important and Partially Overlapping Roles in the Biosynthesis of Flavonoids

“…In addition, it seemed reasonable to deduce that the lack of myricetin in F. hybrida flowers might result from the substrate selectivity of FLS ( Figure 8 ). Thus, it was interesting to conclude that FLS and DFR competed for common substrates in order to direct the biosynthesis of flavonols and anthocyanins, respectively, which was also illustrated by Luo et al (2015) earlier. Actually, several other plant species, such as Petunia hybrida, Cymbidium hybrida, Angelonia angustifolia, Agapanthus praecox ssp.…”

Metabolome and Transcriptome Analysis Reveals Putative Genes Involved in Anthocyanin Accumulation and Coloration in White and Pink Tea (Camellia sinensis) Flower

“…FLS catalyzes dihydroflavonols into flavonols, which competes at a key branch point with DFR in the anthocyanin pathway [36]. Luo Ping et al [37] proposed that disequilibrium in the expression of FLS and DFR genes modulated the accumulation of anthocyanins and flavonols in both white and red flowers of different species. Their deduction has already been verified using heterologous expression of the FLS genes in tobacco, in which transgenes inhibiting the expression of DFR promoted flavonol accumulation, resulting in white flowers.…”

Flavones Produced by Mulberry Flavone Synthase Type I Constitute a Defense Line against the Ultraviolet-B Stress

“…The concentration of anthocyanins was calculated using the formula: Q Anthocyanins = (A 530 − 0.25 × A 657 ) × M −1 as described by Luo et al [49]. For flavones quantification, 12 volumes of acid methanol (1% [v/v] HCl in methanol) were used to extract the sample powder for 8 h, and then 12 volumes of chloroform and 6 volumes of water were used for the second extraction.…”