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

Abstract

Scutellaria baicalensis Georgi (S. baicalensis ) 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.

miR828a-CsMYB114 Module Negatively Regulates the Biosynthesis of Theobromine in Camellia sinensis

“…Yeast cells were cultured on a triple-deficiency medium (SD/-His/-Leu/-Trp), both with and without the addition of 3-AT. These cultures were prepared in a series of dilutions, reducing the concentration by factors of 10, 100, and 1000 respectively, and then incubated at 28 °C for 3 days . The presence of white colonies in the experimental group, in contrast with their absence in the control group (which utilized self-activation), would indicate effective trans-activation.…”

Molecular regulation of the key specialized metabolism pathways in medicinal plants

“…Based on the fact that abundant flavonoids were produced in roots and could be enhanced by JA treatment, candidate MYB TFs were screened. Y1H assay results revealed that only SbMYB3 could bind to the flavone synthase (Fang et al, 2022). Lightinduced SbMYB45 and SbMYB86.1 were positive baicalin regulators promoting CHI expression (Fang et al, 2023a).…”

“…Flavonoids in S. baicalensis S. baicalensis, a well-known Chinese medicine named Huang-Qin, has been used for over 2,000 years (Zhao et al, 2016). Abundant flavonoids are produced in aerial parts and roots, such as scutellarein and scutellarin, mainly in the aerial organs, and baicalein, baicalin, wogonin, and wogonoside (RSFs) in roots (Fang et al, 2022;Zhang, et al, 2022b). Like many other plants, MYB TFs regulating flavonoids brought about widespread attention.…”

“…Further study revealed that overexpression of SbMYB3 in S. baicalensis hairy roots enhanced RSF content by activating transcription of SbFNSII‐2 , while RNAi of SbMYB3 decreased the baicalin and wogonoside accumulation (Fang et al, 2022). Light‐induced SbMYB45 and SbMYB86.1 were positive baicalin regulators promoting CHI expression (Fang et al, 2023a). In addition, SbWRKY75 accelerated baicalin biosynthesis by directly regulating the flavonoid biosynthetic gene SbCLL‐7 , and SbWRKY41 directly targeted SbF6H , UDP‐glucosyl transferase ( UGT ), and SbWRKY75 , to increase the content of baicalin (Fang et al, 2023b).…”

“…Y1H assay results revealed that only SbMYB3 could bind to the flavone synthase II‐2 ( SbFNSII‐2 ) promoter. Further study revealed that overexpression of SbMYB3 in S. baicalensis hairy roots enhanced RSF content by activating transcription of SbFNSII‐2 , while RNAi of SbMYB3 decreased the baicalin and wogonoside accumulation (Fang et al, 2022). Light‐induced SbMYB45 and SbMYB86.1 were positive baicalin regulators promoting CHI expression (Fang et al, 2023a).…”