Flower colour and cytochromes P450

Abstract

Cytochromes P450 play important roles in biosynthesis of flavonoids and their coloured class of compounds, anthocyanins, both of which are major floral pigments. The number of hydroxyl groups on the B-ring of anthocyanidins (the chromophores and precursors of anthocyanins) impact the anthocyanin colour, the more the bluer. The hydroxylation pattern is determined by two cytochromes P450, flavonoid 3′-hydroxylase (F3′H) and flavonoid 3′,5′-hydroxylase (F3′5′H) and thus they play a crucial role in the determination of flower colour. F3′H and F3′5′H mostly belong to CYP75B and CYP75A, respectively, except for the F3′5′Hs in Compositae that were derived from gene duplication of CYP75B and neofunctionalization. Roses and carnations lack blue/violet flower colours owing to the deficiency of F3′5′H and therefore lack the B-ring-trihydroxylated anthocyanins based upon delphinidin. Successful redirection of the anthocyanin biosynthesis pathway to delphinidin was achieved by expressing F3′5′H coding regions resulting in carnations and roses with novel blue hues that have been commercialized. Suppression of F3′5′H and F3′H in delphinidin-producing plants reduced the number of hydroxyl groups on the anthocyanidin B-ring resulting in the production of monohydroxylated anthocyanins based on pelargonidin with a shift in flower colour to orange/red. Pelargonidin biosynthesis is enhanced by additional expression of a dihydroflavonol 4-reductase that can use the monohydroxylated dihydrokaempferol (the pelargonidin precursor). Flavone synthase II (FNSII)-catalysing flavone biosynthesis from flavanones is also a P450 (CYP93B) and contributes to flower colour, because flavones act as co-pigments to anthocyanins and can cause blueing and darkening of colour. However, transgenic plants expression of a FNSII gene yielded paler flowers owing to a reduction of anthocyanins because flavanones are precursors of anthocyanins and flavones.

Metabolic and molecular analyses of white mutant Vaccinium berries show down-regulation of MYBPA1-type R2R3 MYB regulatory factor

“…F 0 3 0 5H catalyzes two hydroxylations in the 3 0 and 5 0 -positions of flavonoids which are needed in formation of myricetin and delphinidin derived anthocyanins. Earlier studies with flowers of various species and, e.g., grape berries have shown consistency in accumulation of 3,4,5,-hydroxylated anthocyanins and function of F 0 3 0 5H (Shimada et al 1999;Castellarin and Di Gaspero 2007;Tanaka and Brugliera 2013). Our results suggest that in bog bilberry, VuF3 0 5 0 H is regulated separately from the other flavonoid pathway genes analyzed in the current study.…”

Isolation and molecular characterisation of flavonoid 3′-hydroxylase and flavonoid 3′, 5′-hydroxylase genes from a traditional Chinese medicinal plant, Epimedium sagittatum

“…The F3′H and F3′5′H genes, both of which belong to the cytochrome P450 superfamily, catalyse hydroxylation at the 3′ and 3′, 5′ positions of the B-ring of the flavonoids. This leads to the production of the red cyanidin-based pigments and the blue/violet delphinidin-based pigments, respectively (Ayabe and Akashi, 2006;Tanaka, 2006). In addition to the hydroxylation of anthocyanidins, both genes also catalyse the hydroxylation of flavanones, flavones and flavonols.…”

Functional analysis of Antirrhinum kelloggii flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylase genes; critical role in flower color and evolution in the genus Antirrhinum

“…Phylogenetic analysis of F3 0 H and F3 0 5 0 H indicates that genes encoding the enzymes diverted before speciation of flowering plants ( Fig. 2) (Tanaka 2006). Although most flowering plants produce cyanidin, many plant species such as Arabidopsis, rose and carnation do not produce delphinidin due to deficiency of F3 0 5 0 H activity.…”

“…Flavonoid 3 0 -hydroxylase (F3 0 H) and flavonoid 3 0 ,5 0 -hydroxylase (F3 0 5 0 H) determine the hydroxylation pattern of the B-ring and are essential to biosynthesize cyanidin (typically conferring red/magenta color) and delphinidin based anthocyanins, respectively ( Fig. 1) (Tanaka 2006). Both of these enzymes belong to the cytochrome P450 superfamily where members are classified into family and subfamily on the basis of their amino acid sequences (Nelson and Werck-Reichhart 2011).…”