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.