SmMYC2b Enhances Tanshinone Accumulation in Salvia miltiorrhiza by Activating Pathway Genes and Promoting Lateral Root Development.

Yangyun Zhou,Jingxian Feng,Zongyou Lv,Junfeng Chen,Qing Li,Wansheng Chen,Zenan Du,Ying Xiao,Xiao Chen,Doudou Huang,Yonglong Han

doi:10.3389/fpls.2020.559438

Abstract

Salvia miltiorrhiza Bunge (Lamiaceae) is an economically important medicinal plant as well as an emerging model plant. Our previous studies indicate that SmMYC2b is a positive transcription factor that can affect the biosynthesis of phenolic acids and tanshinones in S. miltiorrhiza. Moreover, MYC2s are well known to induce the development of lateral roots. As tanshinones are mainly distributed in the periderm, the promotion of lateral root development probably leads to increased accumulation of tanshinones. In this paper, we firstly discovered that SmMYC2b played a dual regulatory role in effectively enhancing the tanshinone accumulation by activating tanshinone biosynthetic pathway and promoting lateral root development. The expression levels of the previously studied pathway genes SmCPS1, SmKSL1, SmCYP76AH1, SmCYP76AH3, and SmCYP76AK1 dramatically increased. In addition, SmMYC2b was proved to exhibit a similar function as other homologs in promoting lateral root development, which increased the tanshinone produced tissue and further enhanced the biosynthesis of tanshinones. RNA-seq assays revealed that SmMYC2b-regulated genes comprised 30.6% (1,901 of 6,210) of JA-responsive genes, confirming that SmMYC2b played a crucial role in transcriptional regulation of JA-regulated genes. Overall, we concluded that SmMYC2b could enhance tanshinone accumulation by activating the tanshinone biosynthetic pathway and promoting lateral root development. Our study provides an effective approach to enhance the production of desired tanshinones and enriches our knowledge of the related regulatory network.

Highlights

Salvia miltiorrhiza Bunge (Lamiaceae) is a perennial herb that is a source of the famous traditional Chinese medicine (TCM) Danshen
We showed that SmMYC2b could promote the biosynthesis of tanshinone biosynthesis genes (SmCPS1, SmKSL1, SmCYP76AH1, SmCYP76AH3, and SmCYP76AK1)
Compared with CK, we surprisingly found that MYC2b overexpression (MYC2bOE) plants exhibited a much more developed root systems (Figures 1C, D)

Summary

Introduction

Salvia miltiorrhiza Bunge (Lamiaceae) is a perennial herb that is a source of the famous traditional Chinese medicine (TCM) Danshen. The biosynthesis of terpenoids consists of three stages: isoprene precursor biosynthesis, direct skeleton precursor generation, and the biosynthesis of various tanshinones (Chen et al, 2011; Chang et al, 2019; Xue et al, 2019). The first stage mainly generates isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) derived from the mevalonate (MVA) pathway and the methylerythritol phosphate (MEP) pathway (Vranová et al, 2013; Zhao et al, 2013). The second stage is the generation of farnesyl diphosphate (FPP), geranyl diphosphate (GPP) and geranylgeranyl diphosphate (GGPP), which further form the precursors of monoterpenes, sesquiterpenes, and diterpenes respectively (Liang et al, 2002; Szkopińska and Płochocka, 2005). The first two stages have been studied clearly and are shared by all terpenes. The third stage involves a variety of terpenoid synthases and modifying enzymes, which determine the structural diversity of terpenoids and are species specific (Keeling et al, 2008; Degenhardt et al, 2009)

Methods

Results

Conclusion