Identification of the <i>glutathione</i> S-<i>transferase</i> gene responsible for flower color intensity in carnations

Abstract

Two cDNAs with homology to glutathione S-transferase (GST) were isolated from the carnation (Dianthus caryophyllus); these cDNAs are termed here DcGSTF1 and DcGSTF2. Phylogenetic analysis suggested that both DcGSTF1 and DcGSTF2 belonged to the Phi class of GSTs. DcGSTF2 showed high levels of transcription at late stages of petal development when anthocyanin biosynthesis is most active. Sequencing of DcGSTF2 indicated that it consisted of three exons and two introns. A truncated DcGSTF2 gene, resulting from the insertion of a CACTA-type transposable element, was found in the genome of a mutable flower line bearing deep pink sectors on pale pink petals. A full length DcGSTF2 gene driven by a continuous expression promoter was introduced into the epidermal cells of carnations with pale pink petals. The transformed cells were deep pink. These results suggest that the DcGSTF2 gene is responsible for flower color intensity in carnations.