Abstract
The aerial parts of Glycyrrhiza uralensis supply substantial raw material for the extraction of active pharmaceutical ingredients comprehensively utilized in many industries. Our previous study indicated that salt stress increased the content of active ingredients. However, the regulatory mechanism remains unclear. In this study, RNA-sequencing (RNA-seq) of the aerial parts of G. uralensis treated with 150 mM NaCl for 0, 2, 6, and 12 h was performed to identify the key genes and metabolic pathways regulating pharmacological active component accumulation. The main active component detection showed that liquiritin was the major ingredient and exhibited more than a ten-fold significant increase in the 6 h NaCl treatment. Temporal expression analysis of the obtained 4245 differentially expressed genes (DEGs) obtained by RNA-seq revealed two screened profiles that included the significant up-regulated DEGs (UDEGs) at different treatment points. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of these UDEGs identified phenylpropanoid metabolism and flavonoid biosynthesis as the most significantly enriched pathways in 2 h treated materials. Interestingly, the carotenoid biosynthesis pathway that is related to ABA synthesis was also discovered, and the ABA content was significantly promoted after 6 h NaCl treatment. Following ABA stimulation, the content of liquiritin demonstrated a significant and immediate increase after 2 h treatment, with the corresponding consistent expression of genes involved in the pathways of ABA signal transduction and flavonoid biosynthesis, but not in the pathway of glycyrrhizic acid biosynthesis. Our study concludes that salt stress might promote liquiritin accumulation through the ABA-mediated signaling pathway, and provides effective reference for genetic improvement and comprehensive utilization of G. uralensis.
Highlights
As the most widely used Chinese traditional medicinal plant (Kitagawa 2002), licorice has comprehensive pharmacological activities for disease therapy including anti-tumor,1 3 Vol.:(0123456789)Molecular Genetics and Genomics anti-virus, and memory enhancement performed by its active pharmaceutical components (Shim et al 2000; Dhingra et al 2004; Dhingra and Sharma 2006; Kim et al 2006; Lee et al 2007; Nagai et al 2007; Sato et al 2007; Shin et al 2007; Fiore et al 2008; Tohma and Gulcin 2010; Jiang et al 2018)
To identify genes and metabolic pathways regulating the active component accumulation under salt stress, the aerial parts of G. uralensis treated with 150 mM NaCl for 0, 2, 6, and 12 h were used for high throughput sequencing analysis
Based on a comparison of the data of high-quality sequences and mapping to the reference genome of G. uralensis, more than 83.28% of clean reads of the transcriptome data in all samples were uniquely mapped to the genome of G. uralensis (Supplementary Table S4). quantitative real-time PCR (qRT-PCR) validation of seven genes involved in terpenoid backbone biosynthesis, carotenoid biosynthesis, phenylpropanoid biosynthesis, and plant hormone signaling transduction indicated their consistent expression profiles with the RNA-seq data, and combined with the correlation analysis of qRT-PCR and RNA-seq, showed the high reliability of the transcriptome data (Supplementary Fig. S2)
Summary
As the most widely used Chinese traditional medicinal plant (Kitagawa 2002), licorice has comprehensive pharmacological activities for disease therapy including anti-tumor,1 3 Vol.:(0123456789)Molecular Genetics and Genomics anti-virus, and memory enhancement performed by its active pharmaceutical components (Shim et al 2000; Dhingra et al 2004; Dhingra and Sharma 2006; Kim et al 2006; Lee et al 2007; Nagai et al 2007; Sato et al 2007; Shin et al 2007; Fiore et al 2008; Tohma and Gulcin 2010; Jiang et al 2018). As the most widely used Chinese traditional medicinal plant (Kitagawa 2002), licorice has comprehensive pharmacological activities for disease therapy including anti-tumor,. Flavonoid compounds are considered to be the main active ingredients containing liquiritin that has recently been validated to play important roles in inhibiting the replication of novel coronavirus (Zhu et al 2020). These new discoveries of pharmacological function will further enhance the importance of licorice. Licorice provides massive aerial parts annually that include sufficient active pharmaceutical ingredients that are comprehensively utilized in many industries
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