|DASGUPTA, KATSURI - University Of California|
|Thomson, James - Jim|
Submitted to: GM Crops & Food
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 1/4/2017
Citation: Dasgupta, K., Thilmony, R.L., Stover, E.W., Oliveira, M.L., Thomson, J.G. 2017. Novel R2R3-MYB transcription factors from Prunus americana regulate differential patterns of anthocyanin accumulation in tobacco and citrus. GM Crops & Food. 8:85-105. https://doi.org/10.1080/21645698.2016.1267897.
Interpretive Summary: Anthocyanins are typically red/purple plant pigments that commonly color fruits or flowers and have antioxidant properties. To increase the levels of these beneficial nutrients in foods, we isolated three novel regulatory genes from plum trees that encode protein switches with the potential ability to activate the production of anthocyanins in plants. We also synthesized a fourth gene, modeling it on the equivalent gene from citrus trees. When we transformed these genes into tobacco plants, we found that three of these genes elicited the accumulation of anthocyanin pigments. Interestingly, each produced distinctly different patterns and intensities of anthocyanin accumulation within various organs of the plants. The plants with the highest levels of pigments had reduced seed production. Expression of these novel plum genes may be useful for activating the desirable production of anthocyanins in fruits to enhance their color and nutritional quality. These genes could also be used as simple and non-destructive visual markers for plant transformation.
Technical Abstract: 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 three novel R2R3-MYB transcription factor (TF) genes, PamMybA.1, PamMybA.3 and PamMybA.5 from Prunus americana. The anthocyanin accumulation patterns mediated by CaMV double35S promoter driving expression of TFs in transgenic tobacco were compared to citrus-MoroMybA, Arabidopsis-AtMybA1 and grapevine-VvMybA1 transgenics during their entire growth cycles. The db35Sp-PamMybA.1 and db35Sp-PamMybA.5 constructs induced high levels of anthocyanin accumulation in both transformed tobacco calli and the regenerated plants. PamMybA.3 on the other hand failed to accumulate any anthocyanin in regenerated tobacco plants. This is consistent with the conclusion that PamMybA.3 is an inactive pseudogene. The red/purple color pigmentation induced in the PamMybA.1 and PamMybA.5 lines was not uniformly distributed, but appeared as patches in the leaves, whereas the flowers showed intense uniform pigmentation similar to VvMybA1 expressing lines. MoroMybA and AtMybA1 showed more uniform pink coloration in both vegetative and reproductive tissues. Plant morphology, anthocyanin content, seed viability, and transgene inheritance were examined for the PamMybA.5 transgenic plants and compared to 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.