Overexpression of LeMYB1 enhances shikonin formation by up-regulating key shikonin biosynthesis-related genes in Lithospermum erythrorhizon

We previously reported that LeMYB1 might be a crucial transcription factor in regulating shikonin formation in Lithospermum erythrorhizon. In this study, by overexpressing LeMYB1 under the control of CaMV35S promoter in L. erythrorhizon hairy roots, we further clarified the role of LeMYB1 in the shikonin formation and its regulation. The LeMYB1-overexpressing transgenic hairy roots were successfully induced by infecting seedling nodes with Agrobacterium rhizogenes strain ATCC15834 that carried the pBI121-LeMYB1 vector. The LeMYB1 transcripts were significantly up-regulated in the transgenic hairy root lines compared with the wild type lines, and the total content of shikonin and its derivatives was dramatically enhanced by the LeMYB1 overexpression. Real-time PCR results reveal that the enhanced shikonin biosynthesis in the overexpressing lines were mainly caused by a highly up-regulated expression of genes coding key enzymes (PAL, HMGR, and PGT) and key regulators (LeDI-2 and LePS-2) involved in the shikonin biosynthesis. Overall, our results suggest that LeMYB1 plays a positive role in regulating the shikonin biosynthesis in L. erythrorhizon.