Novel R2R3-MYB transcription factors from Prunus americana regulate differential patterns of anthocyanin accumulation in tobacco and citrus.

The level of anthocyanins in plants vary widely among cultivars, developmental stages and environmental stimuli. Previous studies have reported that the expression of various MYBs regulate anthocyanin pigmentation during growth and development. Here we examine the activity of 3 novel R2R3-MYB transcription factor (TF) genes,PamMybA.1, PamMybA.3andPamMybA.5fromPrunus americana. The anthocyanin accumulation patterns mediated byCaMV double35Spromoter (db35Sp) controlled expression of the TFs in transgenic tobacco were compared with citrus-MoroMybA, Arabidopsis-AtMybA1and grapevine-VvMybA1transgenics during their entire growth cycles. Thedb35Sp-PamMybA.1anddb35Sp-PamMybA.5 constructs induced high levels of anthocyanin accumulation in both transformed tobacco calli and the regenerated plants. The red/purple color pigmentation induced in thePamMybA.1andPamMybA.5 lines was not uniformly distributed, but appeared as patches in the leaves, whereas the flowers showed intense uniform pigmentation similar to theVvMybA1expressing lines.MoroMybAandAtMybA1showed more uniform pink coloration in both vegetative and reproductive tissues. Plant morphology, anthocyanin content, seed viability, and transgene inheritance were examined for thePamMybA.5transgenic plants and compared with the controls. We conclude that these TFs alone are sufficient for activating anthocyanin production in plants and may be used as visible reporter genes for plant transformation. Evaluating these TFs in a heterologous crop species such as citrus further validated that these genes can be useful for the metabolic engineering of anthocyanin production and cultivar enhancement. [ABSTRACT FROM AUTHOR]