Concerning the role of cinnamoyl CoA reductase gene in phenolic acids biosynthesis in Salvia miltiorrhiza

Salvia miltiorrhiza Bunge produces salvianolic acid, a water-soluble phenolic acid that is widely used in treating cardiovascular disease. The objective of this study is to employ AtPAP1 (Production of Anthocyanin Pigmentation) and SmCCR1 (cinnamoyl CoA reductase) for improving the phenolic acids of S. miltiorrhiza. First, results showed that AtPAP1 significantly increased the promoter activities of SmCCR1 by transient transformation of tobacco. To enrich the precursors available for phenolic acid biosynthesis, we present a strategy of combinational genetic manipulation by Agrobacterium tumefaciens-mediated gene transfer that simultaneously over-expressed AtPAP1 and down-regulated SmCCR1. Compared with the control, the amount of lignin was significantly reduced and its composition was changed in transgenic plants. While, the main phenolic acids, including salvianolic acid B and rosmarinic acid, were induced 2.0- and 1.8-fold compared with control lines in two-month-old plants. Meanwhile, the contents of total phenolics and total flavonoids were significantly improved in transformed plants. Expression of related genes throughout the phenylpropanoid pathways were altered, following the same trends as shown for their products, i.e., phenolic acids accumulation and lignin reduction. These results demonstrate that such methods for genetic modification, which increase the expression of transcription factors while suppressing that of branch genes, are of great value when genetically engineering plants for other secondary products.