Sequence variations in the flavonoid 3′,5′-hydroxylase gene associated with reddish flower phenotypes in three delphinium varieties

Abstract

Although delphiniums are famed for their blue flowers, a few varieties display reddish flowers, such the pale-pink garden varieties ‘Ehime Kou 9 (Kou 9)’ and ‘F₁ Super Happy Pink (SHP),’ and the orange-red flowered species Delphinium nudicaule (NDC). Blue delphinium flowers contain a delphinidin-derived anthocyanin, whereas the three varieties mentioned above have anthocyanins derived from the aglycone pelargonidin in their sepals. As flavonoid 3′,5′-hydroxylase (F3′5′H) is known to be the key enzyme in biosynthesis of delphinidin, we compared the structure and function of the F3′5′H gene in three varieties of delphiniums with reddish flowers to one that has blue flowers. We found that the F3′5′H gene of ‘Kou 9’ had a point mutation that generated a stop codon in the first exon. Genomic PCR analysis indicated that the ‘SHP’ variety lacked F3′5′H. Although the nucleotide sequence of the F3′5′H open reading frame was identical in ‘NDC’ to that of the wild type, it lacked an intron and no F3′5′H transcripts could be detected in this variety. We conclude that the red flower phenotypes of these delphiniums derive from independent mutations of the F3′5′H gene. This is the first report on the delphinium F3′5′H gene. At a practical level, these mutations should be of value for breeding new pink and red flower varieties.