Article ID: UTD-373
The lily MYB12 gene, a positive regulator of anthocyanin biosynthesis, is targeted by microRNA828 (miR828). In bicolor tepals of Asiatic hybrid lilies with white lower halves and pigmented upper halves, accumulation levels of miR828 are higher in the lower halves than in the upper halves, and action of MYB12 is suppressed in the lower halves, resulting in bicolor tepal development. This is a newly identified mechanism of color pattern development in flowers. However, which wild species has donated the miR828-mediated bicolor tepal traits to these hybrid lilies is uncertain, and whether miR828-dependent pattern development occurs in species other than Lilium and is responsible for other types of color patterns is unknown. In this study, miR828 accumulation levels were compared between anthocyanin pigmented and unpigmented regions of flowers in lilies and other species. Lilium dauricum is among the parental wild species of Asiatic hybrid lilies. Lilium dauricum showed bicolor tepals, in which anthocyanins highly accumulated in the upper halves, and miR828 accumulation was more than 10 times higher in the lower halves than in the upper halves. Thus, the profile of miR828 accumulation was similar to that found in bicolor cultivars of Asiatic hybrid lilies. It is possible that the miR828-mediated bicolor tepal trait in Asiatic hybrid lilies is derived from L. dauricum. In L. cernuum var. album and an Oriental hybrid lily ‘Dizzy’, the suppression of MYB12 expression causes unpigmented tepals or tepal regions, but the unpigmented regions are spatially different from those in bicolor tepals of Asiatic hybrid lilies. MiR828 accumulation levels were similar between white and pink flowers of L. cernuum, and rather higher in pigmented regions than white regions of ‘Dizzy’ tepals, suggesting little involvement of miR828 in MYB12 expression suppression. MiR828 accumulation levels were evaluated in bicolor flowers of cherry sage, tulip, and Alstroemeria, but differences in miR828 accumulation were not detected between red and white petal/tepal regions, indicating that the mechanisms by which the bicolor flowers developed in these species are likely different from that occurring in Asiatic hybrid lilies and L. dauricum. Thus, the miR828/R2R3-MYB module is likely responsible for color only in lily flowers and only for the color pattern that consists of lower un-pigmented and upper pigmented regions.
