Flower color patterning in pansy ( Viola × wittrockiana Gams.) is caused by the differential expression of three genes from the anthocyanin pathway in acyanic and cyanic flower areas

The petals of pansy (Viola × wittrockiana Gams.) ‘Mengdie’ exhibit a cyanic blotched pigmentation pattern. The accumulation of anthocyanins, cyanidin and delphinidin, was detected in the upper epidermal cells of the cyanic blotches. In order to elucidate the mechanism by which cyanic blotches are formed in pansy petal, the expression level of genes involved in anthocyanin synthesis was measured and compared between cyanic blotches and acyanic areas of the flower. The use of primers in conserved regions allowed the successful isolation of six cDNA clones encoding putative anthocyanin enzymes from pansy petals. The clones isolated encoded chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), flavonoid 3′-hydroxylase (F3′H), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS). The transcription patterns of seven genes (VwCHS, VwCHI, VwF3H, VwF3′H, VwDFR, VwF3′5′H, and VwANS) in cyanic blotches and acyanic areas of the petals at seven stages of flower development were determined by real-time quantitative PCR. Transcription of VwF3′5′H, VwDFR and VwANS was significantly increased in cyanic blotches at stages III–V of flower development, implicating these genes in the pigmentation of Viola × wittrockiana Gams. petals.