RESUMEN
To produce beneficial phenolic acids for medical and commercial purposes, researchers are interested in improving the normally low levels of salvianolic acid B (Sal B) produced by Salvia miltiorrhiza. Here, we present a strategy of combinational genetic manipulation to enrich the precursors available for Sal B biosynthesis. This approach, involving the lignin pathway, requires simultaneous, ectopic expression of an Arabidopsis Production of Anthocyanin Pigment 1 transcription factor (AtPAP1) plus co-suppression of two endogenous, key enzyme genes: cinnamoyl-CoA reductase (SmCCR) and caffeic acid O-methyltransferase (SmCOMT). Compared with the untransformed control, we achieved a greater accumulation of Sal B (up to 3-fold higher) along with a reduced lignin concentration. This high-Sal B phenotype was stable in roots during vegetative growth and was closely correlated with increased antioxidant capacity for the corresponding plant extracts. Although no outward change in phenotype was apparent, we characterized the molecular phenotype through integrated analysis of transcriptome and metabolome profiling. Our results demonstrated the far-reaching consequences of phenolic pathway perturbations on carbohydrate metabolism, respiration, photo-respiration, and stress responses. This report is the first to describe the production of valuable end products through combinational genetic manipulation in S. miltiorrhiza plants. Our strategy will be effective in efforts to metabolically engineer multi-branch pathway(s), such as the phenylpropanoid pathway, in economically significant medicinal plants.
Asunto(s)
Benzofuranos/metabolismo , Ingeniería Metabólica , Plantas Modificadas Genéticamente , Salvia miltiorrhiza , Aldehído Oxidorreductasas/biosíntesis , Aldehído Oxidorreductasas/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/biosíntesis , Proteínas de Arabidopsis/genética , Metiltransferasas/biosíntesis , Metiltransferasas/genética , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Salvia miltiorrhiza/genética , Salvia miltiorrhiza/metabolismo , Factores de Transcripción/biosíntesis , Factores de Transcripción/genéticaRESUMEN
Phenolic acids are health-promoting but low content secondary metabolites in Salvia miltiorrhiza. Here, the Arabidopsis transcription factor Production of Anthocyanin Pigment 1 (AtPAP1) was expressed in S. miltiorrhiza and improved the antioxidant capacity in transgenic plants up to 3-fold. Salvianolic acid B (Sal B) biosynthesis was strongly induced (10-fold higher) in 1 month old transgenic plantlets, a growth stage not normally characterized by significant levels of phenolic acids. This high-Sal B phenotype was stable in roots during vegetative growth, with tissues accumulating approximately 73.27 mg/g of dry weight. Total phenolics, total flavonoids, anthocyanin, and lignin were also significantly enhanced. Consistent with these biological and phytochemical changes, expression of phenolic acid biosynthetic genes was stimulated. Our results demonstrate that AtPAP1 has an additional, previously unknown, role as a transcriptional activator of phenolic acid biosynthesis in S. miltiorrhiza. The results provide a promising strategy for engineering phenolics production in economically significant medicinal plants.