Expression of anthocyanin biosynthesis-related genes during flower development in Lilium spp.

Sterility of hybrids produced from interspecific hybridization in lilies (Lilium, Liliaceae) is a great limitation in the breeding program, especially for Lilium longiflorum, which only has white-flowered cultivars. Because modification of flower colour in L. longiflorum by conventional breeding is limited by pre- and post-fertilization barriers, we think genetic modification could be used as an alternative in the future. For this, we need to understand what determines white colouration in L. longiflorum and other species and identify the molecular mechanisms regulating flower colour. In this study, we determined the accumulation of anthocyanins and related compounds in flower tissues during flower developmental stages in L. longiflorum cultivar ‘Lincoln’ and in the Oriental hybrid lily cultivars ‘Rialto’, ‘Perth’ and ‘Gran Tourismo’, respectively with white, pink and red flowers. Furthermore, the presence/absence and the expression of eight structural genes (CHSa, CHSb, CHIa, CHIb, F3H, F3’H, DFR, ANS) and three transcription factor genes (MYB12, MYB15, bHLH2) in flower tissues were investigated. Two structural genes (LlLinF3’H and LlLinDFR) and one transcription factor gene (LlLinbHLH2) were not detected in ‘Lincoln’ flowers. In ‘Rialto’, an amino acid substitution in the R2 repeat of LhRiaMYB12 which was previously reported to be responsible for the white flower colour is also found in the LhPerMYB12 of the pink ‘Perth’ flowers. Moreover, LhRiaDFR is present but not expressed in ‘Rialto’ flowers. Accumulation of cyanidin was observed in the flowers of ‘Perth’ and ‘Gran Tourismo’. High amounts of dihydrokaempferol accumulated in flowers of all four lily cultivars confirming the expression and functionality of early structural genes in the pathway. The elevated expression of the structural genes is strongly correlated with the expression of LhMYB12 and LhMYB15. This information can be used in the future to generate new L. longiflorum or Oriental lily hybrid cultivars with novel flower colours

The ROSEA1 and DELILA transcription factors control anthocyanin biosynthesis in Nicotiana benthamiana and Lilium flowers

The activity of anthocyanin biosynthesis genes is regulated at the transcriptional level, thus manipulation of transcription factors (TFs) is an ideal strategy to alter the expression of multiple target genes. In this study, we investigated the effect of introducing ROSEA1 (ROS1, a MYB-type) and DELILA (DEL, a bHLH-type) TFs from snapdragon under control of a flower specific promoter, Floral Binding Protein 1 (FBP1) from petunia into Nicotiana benthamiana flowers and Lilium tepals. The usefulness of the FBP1 promoter was demonstrated by the generation of purplish flowers in otherwise normal-growing plants of N. benthamiana, while the expression by the 35S promoter led to the development of stunted plants with anthocyanins in all parts. N. benthamiana was successfully transformed by ROS1 alone and by a combination of ROS1 + DEL. The observed accumulation of delphinidin corresponded to the expression of NbCHS, NbF3H, NbDFR and NbANS. The effect of ROS1 + DEL on Lilium flower colour was investigated using agroinfiltration. A higher cyanidin accumulation was observed in tepals of the Oriental hybrid lily cv. ‘Perth’ resulting in deeper pink colouration at the infiltrated area. Nevertheless, the introduction of ROS1 + DEL did not produce any phenotypic changes to the white-flowered L. longiflorum cv. ‘Lincoln’ and the white Oriental hybrid lily cv. ‘Rialto’ due to other deficiencies in their anthocyanin biosynthetic pathway. Co-expression of ROS1 + DEL under control of the FBP1 promoter together with active structural anthocyanin biosynthetic genes can result in modification of Lilium flower colour.</p