Genetic engineering of the anthocyanin biosynthetic pathway with flavonoid-3′,5′-hydroxylase: specific switching of the pathway in petunia

Abstract.

Flavonoid-3′,5′-hydroxylase (F3′5′H) is the key enzyme in the synthesis of 3′,5′-hydroxylated anthocyanins, which are generally required for the expression of blue or purple flower color. It has been predicted that the introduction of this enzyme into a plant species that lacks it would enable the production of blue or purple flowers by altering the anthocyanin composition. We present here the results of the genetic engineering of petunia flower color, pigmentation patterns and anthocyanin composition with sense or antisense constructs of the F3 ′ 5 ′ H gene under the control of the CaMV 35S promoter. When sense constructs were introduced into pink flower varieties that are deficient in the enzyme, transgenic plants showed flower color changes from pink to magenta along with changes in anthocyanin composition. Some transgenic plants showed novel pigmentation patterns, e.g. a star-shaped pattern. When sense constructs were introduced into blue flower petunia varieties, the flower color of the transgenic plants changed from deep blue to pale blue or even pale pink. Pigment composition analysis of the transgenic plants suggested that the F3 ′ 5 ′ H transgene not only created or inhibited the biosynthetic pathway to 3′,5′-hydroxylated anthocyanins but switched the pathway to 3′,5′-hydroxylated or 3′-hydroxylated anthocyanins.