Heterologous Expression of SoMYB1 Derived from Syringa oblata Enhances Cyanidin Biosynthesis in Tobacco

Syringa oblata is a renowned flowering shrub, yet the functional studies on the regulatory factors governing its flower color formation remain limited. In this study, a new MYB transcription factor, named SoMYB1, was isolated from the petals of Syringa oblata by the homologous cloning technique. The open reading frames of SoMYB1 was 705 bp in length. Amino acid sequence analysis showed that SoMYB1 contained the highly conserved R2 and R3 MYB domains. A quantitative real-time PCR analysis revealed that SoMYB1 was expressed tissue specifically in flowers. Ectopic expression of SoMYB1 induced anthocyanins accumulation in both vegetative and reproductive tissues of transgenic tobacco lines. Overexpression of SoMYB1 in tobacco enhanced the expression of NtAN2 (MYB) and NtAN1b (bHLH), and the expression of structural genes NtCHS, NtCHI, NtF3H, NtF3′H, NtDFR, NtANS, NtUFGT, and Nt3RT increased remarkably. The UPLC-MS/MS analysis of transgenic tobacco leaves showed that the heterologous expression of SoMYB1 significantly promoted the accumulation of anthocyanin metabolites, especially cyanidin, which accounted for more than 50% of the total anthocyanins in the transgenic tobacco lines. This study elucidates the molecular mechanism by which SoMYB1 positively regulates anthocyanin biosynthesis in S. oblata, providing theoretical and technical support for developing plant resources rich in cyanidin.