The study of the anthocyanidin synthase (ANS) gene, one of the late structural genes in the anthocyanin pathway, was undertaken in Forsythia x intermedia cv. 'Spring Glory'. Previous molecular and biochemical studies had demonstrated expression and activity of genes and enzymes upstream of ans. The ans gene was cloned and shown to be present in two copies in the Forsythia genome. Expression analyses carried out on flower organs showed that ans was expressed exclusively in anthocyanin-containing sepals and not in anthocyaninless anthers and petals. ans expression in sepals showed induction of transcription at early flower developmental stages. Inspection of the ans promoter region as far as 790 bp upstream of the start codon revealed several potential DNA-protein binding motifs. The results from this paper, combined with previous data, show that the lack of ans expression should be the major cause of the absence of anthocyanins in Forsythia petals, thus providing directions for genetic engineering of flower color in this ornamental species.

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