Flower color modification of Petunia hybrida commercial varieties by metabolic engineering

Petunia flower colors are mainly due to flavonoids. The flower color of commercial varieties of Petunia hybrida was successfully modified by the suppression of endogenous flavonoid biosynthetic genes, the expression of a hetelorogous flavonoid biosynthetic gene, and the combination of both. Flower color changed from purple to almost white or from purple to red by the suppression of the endogenous gene expression, from red to orange by the down-regulation of the flavonoid 3′-hydroxylase gene and the expression of the rose dihydroflavonol 4-reductase gene, and from violet to pale violet by the expression of the flavonol synthase or flavone synthase gene. These results clearly indicate the usefulness of metabolic engineering of the flavonoid biosynthetic pathway to modify flower color. Only a few of the transgenic petunia exhibited phenotypic stability. For commercialisation, it is necessary to generate many independent transgenic lines, select elite lines with stable phenotypes and maintain them in tissue culture.