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Flower colour and cytochromes P450.
Yoshikazu Tanaka1, Filippa Brugliera
1Institute for Plant Science, Suntory Business Expert Ltd., Shimamoto, Osaka 618-8503, Japan. yoshikazu_tanaka@suntory.co.jp
Summary
Flower colour is determined by specific P450 enzymes controlling anthocyanin hydroxylation. Modifying flavonoid 3
Area of Science:
- Plant biochemistry and genetics
- Floral pigment biosynthesis
- Enzyme function in secondary metabolism
Background:
- Cytochromes P450 are key enzymes in the biosynthesis of floral pigments, including flavonoids and anthocyanins.
- The hydroxylation pattern of anthocyanidins, particularly on the B-ring, dictates anthocyanin color, with more hydroxyl groups leading to bluer hues.
- Flavonoid 3'-hydroxylase (F3'H) and flavonoid 3',5'-hydroxylase (F3'5'H) are crucial P450 enzymes that control this hydroxylation pattern and thus flower color.
Purpose of the Study:
- To investigate the role of specific cytochrome P450 enzymes, F3'H and F3'5'H, in determining flower color by controlling anthocyanin B-ring hydroxylation.
- To explore the potential for manipulating flower color through genetic modification of these P450 enzymes.
- To understand the contribution of flavone synthase II (FNSII) to flower color as a co-pigment.
Main Methods:
- Analysis of cytochrome P450 gene families (CYP75B for F3'H, CYP75A for F3'5'H) and their roles in anthocyanin biosynthesis.
- Genetic modification of plants, including the expression of F3'5'H to achieve blue hues in roses and carnations.
- Suppression of F3'H and F3'5'H to alter hydroxylation patterns and resulting pigment production.
- Investigating the effect of expressing Flavone synthase II (FNSII, CYP93B) on flower color and anthocyanin levels.
Main Results:
- Roses and carnations lack blue/violet colors due to the absence of functional F3'5'H, preventing delphinidin-based anthocyanin production.
- Expression of F3'5'H in roses and carnations successfully introduced blue hues, leading to commercialization.
- Suppression of F3'5'H and F3'H resulted in pelargonidin-based (red/orange) pigments due to reduced B-ring hydroxylation.
- Enhanced expression of dihydroflavonol 4-reductase further promoted pelargonidin biosynthesis.
- Transgenic expression of FNSII led to paler flowers due to reduced anthocyanin levels, despite flavones acting as co-pigments.
Conclusions:
- Flavonoid hydroxylases (F3'H, F3'5'H) are critical determinants of flower color by controlling anthocyanin structure.
- Genetic engineering of F3'5'H is a viable strategy for developing novel blue-flowered cultivars.
- The balance between anthocyanin and flavone biosynthesis, influenced by enzymes like FNSII, impacts overall flower pigmentation.
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