Phytochemistry Reviews

, Volume 5, Issue 2–3, pp 283–291

Flower colour and cytochromes P450

Original Paper

Abstract

Flavonoids are major constituents of flower colour. Plants accumulate specific flavonoids and thus every species often exhibits a limited flower colour range. Three cytochromes P450 play critical roles in the flavonoid biosynthetic pathway. Flavonoid 3′-hydroxylase (F3′H, CYP75B) and flavonoid 3′,5′-hydroxylase (F3′5′H, CYP75A) catalyze the hydroxylation of the B-ring of flavonoids and are necessary to biosynthesize cyanidin-(red to magenta) and delphinidin-(violet to blue) based anthocyanins, respectively. Pelargonidin-based anthocyanins (orange to red) are synthesized in their absence. Some species such as roses, carnations and chrysanthemums do not have violet/blue flower colour due to deficiency of F3′5′H. Successful expression of heterologous F3′5′H genes in roses and carnations results in delphinidin production, causing a novel blue/violet flower colour. Down-regulation of F3′H and F3′5′H genes has yielded orange petunia and pink torenia colour that accumulate pelargonidin-based anthocyanins. Flavone synthase II (CYP93B) catalyzes the synthesis of flavones that contribute to the bluing of flower colour, and modulation of FNSII gene expression in petunia and tobacco changes their flower colour. Extensive engineering of the anthocyanin pathway is therefore now possible, and can be expected to enhance the range of flower colours.

Keywords

Anthocyanin Cytochrome P450 Flavonoid Flavone Flower colour Cyanidin Delphinidin Dihydroflavonol 4-reductase Flavonoid 3′-hydroxylase Flavonoid 3′,5′-hydroxylase Flavone synthase II Flavonol hydroxylase Monooxygenase Pelargonidin 

Abbreviations

DFR

dihydroflavonol 4-reductase

DHK

dihydrokaempferol

DHQ

dihydroquercetin

DHM

dihydromyricetin

F3H

flavanone 3-hydroxylase

F3′H

flavonoid 3′-hydroxylase

F3′5′H

flavonoid 3′,5′-hydroxylase

FLS

flavonol synthase

FNS

flavone synthase

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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  1. 1.Institute for Advanced Core TechnologySuntory Ltd.Shimamoto-cho, Mishima-gunJapan

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