Abstract
The anthocyanins found in the cyanic ray-florets of chrysanthemum (Chrysanthemum morifolium) flower are only cyanidin-based anthocyanins. Because chrysanthemums do not accumulate delphinidin-based anthocyanins, they have no violet- or blue-flowered cultivars. This is due to the deficiency of flavonoid 3',5'-hydroxylase (F3'5'H), the key enzyme for delphinidin biosynthesis. In order to modify flower color toward bluer color by genetic engineering, we tried to express heterologous F3'5'H and make chrysanthemums to accumulate delphinidin-based anthocyanins. Through evaluation of ability to synthesize delphinidin of binary vectors contained pansy F3'5'H driven by various promoters, we found that combination of petal-specific flavanone 3-hydroxylase gene (CmF3H) promoter from chrysanthemum and translational enhancer NtADH-5'UTR was appropriate to delphinidin synthesis. We then tried to introduce various F3'5'H genes controlled by CmF3H promoter combined with NtADH-5'UTR. Dramatic increase of delphinidin-based anthocyanins (up to 75%) was achieved by bellflower (Campanula medium) F3'5'H expression. The flowers of some transgenic plants changed from red to purple/violet hue.
