Oriental hybrid lily Sorbonne homologue of LhMYB12 regulates anthocyanin biosyntheses in flower tepals and tepal spots

Anthocyanins are the predominant visible pigments in flowers of the Oriental hybrid lily (Lilium spp.). To understand the regulatory mechanisms of flower coloration in this hybrid lily, full-length cDNA of the R2R3-MYB gene, LhSorMYB12, was isolated from anthocyanin-accumulating tepals of the cultivar Sorbonne. The deduced amino acid sequence of LhSorMYB12 showed 85% (209/246) identity, including a gap of seven amino acids, with an amino acid sequence in LhMonMYB12 that regulates anthocyanin biosynthesis in the Asiatic hybrid lily. Transcripts of LhSorMYB12 accumulated in anthocyanin-accumulating tepals of three cultivars but not in white tepals of two other cultivars. The white-tepal cultivar Rialto showed LhMYB12 transcription in tepals, but the Rialto sequence contained amino acid replacements in the R2 repeat, resulting in reduced transcription of anthocyanin biosynthesis genes and in no pigmentation. Spatial and temporal transcription of LhSorMYB12 showed that transcription of LhMYB12 corresponded well with transcription of anthocyanin biosynthesis genes in tepal regions where anthocyanins accumulated and in anthocyanin spots on tepals. These results indicate that LhSorMYB12 definitely regulates anthocyanin biosynthesis and is responsible for the tepal color difference between Oriental hybrid lily cultivars.