Pigment accumulation and transcription of LhMYB12 and anthocyanin biosynthesis genes during flower development in the Asiatic hybrid lily (Lilium spp.)

Anthocyanin biosynthesis is often regulated by MYB transcription factors that are classified into AN2 and C1 subgroups. The AN2 subgroup regulates the late genes in the anthocyanin biosynthesis pathway of eudicots, whereas the C1 subgroup controls both early and late genes in monocots. Anthocyanin is a major pigment in Asiatic hybrid lilies (Lilium spp.), with LhMYB12 being the first AN2 subgroup in monocots. In this study, the accumulation of pigments and gene transcripts during flower bud development was evaluated to determine the genes regulated by LhMYB12. LhMYB12 and anthocyanin biosynthesis genes showed the same transcription profiles, with LhMYB12 directly activating the promoters of chalcone synthase and dihydroflavonol 4-reductase. This indicates that LhMYB12 regulates both early and late genes, despite belonging to the AN2 subgroup. The cultivar Landini accumulated anthocyanin and flavonol. The contents of these pigments increased during the late stages of flower bud development; this might result from the coordinated expression of early and late genes. During the early stages of flower bud development, the tepals contained no flavonoids but accumulated cinnamic acid derivatives. These results indicate that the profiles of pigment accumulation and gene transcription in lily tepals are unique among angiosperm flowers.

► The lily LhMYB12 is the first AN2 homologue among monocots. ► LhMYB12 and anthocyanin biosynthesis genes showed the same transcription profiles. ► LhMYB12 directly activated LhCHS and LhDFR promoters. ► Hence, LhMYB12 regulates early and late genes required for anthocyanin biosynthesis. ► Profiles of pigment accumulation were also unique to lily tepals.