SbMYB3 transcription factor promotes root-specific flavone biosynthesis in Scutellaria baicalensis

Abstract

Scutellaria baicalensis Georgi produces abundant root-specific flavones (RSFs), which provide various benefits to human health. We have elucidated the complete biosynthetic pathways of baicalein and wogonin. However, the transcriptional regulation of flavone biosynthesis in S. baicalensis remains unclear. We show that the SbMYB3 transcription factor functions as a transcriptional activator involved in the biosynthesis of RSFs in S. baicalensis. Yeast one-hybrid and transcriptional activation assays showed that SbMYB3 binds to the promoter of flavone synthase II-2 ( SbFNSII-2) and enhances its transcription. In S. baicalensis hairy roots, RNAi of SbMYB3 reduced the accumulation of baicalin and wogonoside, and SbMYB3 knockout decreased the biosynthesis of baicalein, baicalin, wogonin, and wogonoside, whereas SbMYB3 overexpression enhanced the contents of baicalein, baicalin, wogonin, and wogonoside. Transcript profiling by qRT–PCR demonstrated that SbMYB3 activates SbFNSII-2 expression directly, thus leading to more abundant accumulation of RSFs. This study provides a potential target for metabolic engineering of RSFs.

Acknowledgements

This work was supported by the National Key R&D Program of China (2018YFC1706200), the National Natural Science Foundation of China (31870282 and 31700268), the Chenshan Special Fund for Shanghai Landscaping Administration Bureau Program (G182401, G192419, and G212401), and the Youth Innovation Promotion Association, Chinese Academy of Sciences. Q.Z. is also supported by a Sanofi-SIBS scholarship and C.M. is supported by the CAS/JIC Centre of Excellence for Plant and Microbial Sciences (CEPAMS) joint foundation. We thank Dr Ping Xu, Dr Lei Yang, and Dr Jingjing Xu from Chenshan Plant Science Research Center for their advice on the experiments.

Author contributions

Q.Z. and Y.M.F. conceived and designed the study; Y.M.F. and C.M. performed bioinformatics analyses; Y.M.F., J.L., M.M.Z., S.M.Z., T.L.P., M.Y.C., L.J.C., and H.W.X. performed the experiments; Y.M.F., Q.Z., J.Y., and C.M. analyzed and interpreted the data; Y.M.F., Q.Z., and C.M. wrote the paper with significant input from all authors.

Data availability

The sequences of the genes isolated in this study have been submitted to the Nucbank database (https://ngdc.cncb.ac.cn/nucbank/) with the accession numbers SbMYB1, C_AA001102.1; SbMYB2, C_AA001103.1; SbMYB3, C_AA001104.1; SbMYB4, C_AA001105.1; SbMYB5, C_AA001106.1; and SbMYB6, C_AA001107.1.

Conflict of interest

The authors have declared no conflicts of interest.

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