Floral pigmentation pattern in Oriental hybrid lily (Lilium spp.) cultivar 'Dizzy' is caused by transcriptional regulation of anthocyanin biosynthesis genes.

Flower color patterns are the result of spatially and temporally restricted pigment deposition, and clarifying the mechanisms responsible for restricted pigment deposition is a topic of broad interest for both theoretical and practical reasons. The Oriental hybrid lily cultivar 'Dizzy' develops red stripes along the tepal midribs; in order to clarify the genetic basis of these stripes, we isolated most of the genes related to anthocyanin accumulation from 'Dizzy' tepals and compared their expression levels between the red stripe region and the white marginal region of the tepals. RNA-seq revealed a complete set of genes necessary for anthocyanin biosynthesis and transport, including anthocyanidin 3-O-glucosyltransferase and glutathione S-transferase. Most of these genes were expressed at higher rates in the red stripe region than in the white region, suggesting that transcriptional regulation of these genes is primarily responsible for the spatially restricted anthocyanin deposition in 'Dizzy' tepals. Subgroup 6 R2R3-MYB is a major factor regulating anthocyanin biosynthesis: RNA-seq clarified three subgroup 6 R2R3-MYB genes expressed in 'Dizzy' tepals, of which MYB12 was predominantly expressed. Expression of MYB12 was six-fold higher in the red-pigmented region than in the white region. Thus, MYB12 is more likely to be involved in the regulation of the restricted anthocyanin deposition in 'Dizzy', even though MYB12 is expressed in the entire tepal region of many Oriental hybrid lily cultivars. Diversity of the expression profiles of MYB12 among lily cultivars and species is also discussed.