Project description:Shikonins represent a class of valuable naphthoquinone derivatives with significant pharmaceutical potential. To date, investigations into their biosynthetic regulation have mainly focused on Lithospermum erythrorhizon, a species constrained by a long growth cycle and low genetic transformation efficiency. In contrast, Echium plantagineum efficiently produces shikonins in its roots, grows rapidly and enables highly efficient transgenic hairy root induction, thereby constituting an ideal system for studying shikonin biosynthesis and cloning key regulatory genes. Here, we performed a genome-wide identification of the MYB transcription factor family in E. plantagineum, identifying 244 members. Among these, we focused on EpMYB71, a 2R-MYB gene that is phylogenetically close to LeMYB1 (a previously characterized regulator in L. erythrorhizon) and closely associated with shikonin biosynthesis. Expression analysis showed that EpMYB71 transcripts were strongly induced by methyl jasmonate (MeJA) yet significantly suppressed by 2,4-dichlorophenoxyacetic acid (2,4-D). Overexpression of EpMYB71 in hairy roots led to a significant increase in shikonin production, whereas CRISPR-Cas9 knockout lines exhibited the opposite phenotype. Transcriptome profiling identified 992 differentially expressed genes with significant enrichment in the phenylpropanoid biosynthesis pathway. Among these, the key enzyme gene p-hydroxybenzoate:geranyltransferase (PGT) (EC 2.5.1.-) displayed an 18.4‑fold upregulation, as confirmed by qPCR analysis. Dual-luciferase reporter assays further demonstrated that EpMYB71 directly binds to the PGT promoter and activates its transcription. Collectively, these results establish EpMYB71 as a positive regulator of shikonin biosynthesis in E. plantagineum, providing a valuable target for metabolic engineering of shikonin production.
Project description:Genome-wide Identification of MYB Family and Functional Analysis of EpMYB71 as the Key Regulator of Shikonin Biosynthesis in Echium plantagineum