Water Deficit Affected Flavonoid Accumulation by Regulating Hormone Metabolism in Scutellaria baicalensis Georgi Roots

Yuan Yuan,Luqi Huang,Shuangshuang Qin,Zhaochun Yang,Shunqin Chen,Zhouyong Wang,Yunjun Liu,Chong Wu,Keqiang Wu

doi:10.1371/journal.pone.0042946

Abstract

The content of flavonoids especially baicalin and baicalein determined the medical quality of Scutellaria baicalensis which is a Chinese traditional medicinal plant. Here, we investigated the mechanism responsible for the content and composition of flavonoids in S. baicalensis under water deficit condition. The transcription levels of several genes which are involved in flavonoid biosynthesis were stimulated by water deficit. Under water deficit condition, fifteen up-regulated proteins, three down-regulated proteins and other six proteins were detected by proteomic analysis. The identified proteins include three gibberellin (GA)- or indoleacetic acid (IAA)-related proteins. Decreased endogenous GAs level and increased IAA level were observed in leaves of S. baicalensis which was treated with water deficit. Exogenous application of GA or α-naphthalene acelic acid (NAA) to plants grown under water deficit conditions led to the increase of endogenous GAs and the decrease of IAA and flavonoids, respectively. When the synthesis pathway of GA or IAA in plants was inhibited by application with the inhibitors, flavonoid levels were recovered. These results indicate that water deficit affected flavonoid accumulation might through regulating hormone metabolism in S. baicalensis Georgi.

Highlights

Flavonoids are important plant secondary metabolites which have important effect on plant physiology [1]
S. baicalensis plants grow in the north of Control of Pharmaceutical and Biological Products (China) where 15–20% of soil water content (SWC) is usually suitable for crop growth, whereas 12–15% SWC and 8–12% SWC is considered as mild and moderate drought stress, respectively
By blasting in GenBank with the known gene sequence of Arabidopsis, we found the S. baicalensis EST sequences encoding for phenylalanine ammonialyase (PAL) (EF501766), chalcone synthase (CHS) (AB008748), UBGAT (EF512580) and GUS (AB040072)

Summary

Introduction

Flavonoids are important plant secondary metabolites which have important effect on plant physiology [1]. Plant flavonoids exhibit several medicinal properties, such as antioxidant activity and anti-inflammatory activity [2], and these flavonoids largely determine the quality of medicinal plants. Flavonoids are regarded as one of the most important determinants of quality in red grapes and wine [3]. The active compounds of S. baicalensis include baicalin, baicalein, wogonoside, wogonin, neobaicalein, visidulin I, and oroxylin A, and these compounds exhibit anti-inflammatory, anti-tumor, and anti-HIV activities [5]. These flavonoids, especially baicalin and baicalein, are regarded as the most important determinants of the quality of S. baicalensis [6]. Baicalein can be catalyzed back to baicalin by UDP-glucuronate: baicalein 7-O-glucuronosyltransferase (UBGAT) [10]

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Conclusion