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Digitalis purpurea (D. purpurea) is one of the most important medicinal plants and is well known in the treatment of heart failure because of the cardiac glycosides that are its main active compounds. However, in the absence of strand specific sequencing information, the post-transcriptional mechanism of gene regulation in D. purpurea thus far remains unknown. In this study, a strand-specific RNA-Seq library was constructed and sequenced using Illumina HiSeq platforms to characterize the transcriptome of D. purpurea with a focus on alternative splicing (AS) events and the effect of AS on protein domains. De novo RNA-Seq assembly resulted in 48,475 genes. Based on the assembled transcripts, we reported a list of 3,265 AS genes, including 5,408 AS events in D. purpurea. Interestingly, both glycosyltransferases and monooxygenase, which were involved in the biosynthesis of cardiac glycosides, are regulated by AS. A total of 2,422 AS events occurred in coding regions, and 959 AS events were located in the regions of 882 unique protein domains, which could affect protein function. This D. purpurea transcriptome study substantially increased the expressed sequence resource and presented a better understanding of post-transcriptional regulation to further facilitate the medicinal applications of D. purpurea for human health. [ABSTRACT FROM AUTHOR]

Prenylated flavonol glycosides in Epimedium plants, as key medicinal components, are known to have great pharmaceutical activities for human health. Among the main prenylated flavonol glycosides, the modification mechanism of different sugar moieties is still not well understood. In the current study, a novel prenylated flavonol rhamnoside xylosyltransferase gene (EpF3R2″XylT) was cloned from E. pubescens, and the enzymatic activity of its decoding proteins was examined in vitro with different prenylated flavonol rhamnoside substrates and different 3-O-monosaccharide moieties. Furthermore, the functional and structural domains of EpF3R2″XylT were analyzed by bioinformatic approaches and 3-D protein structure remodeling. In summary, EpF3R2″XylT was shown to cluster with GGT (glycosyltransferase that glycosylates sugar moieties of glycosides) through phylogenetic analysis. In enzymatic analysis, EpF3R2″XylT was proven to transfer xylose moiety from UDP-xylose to prenylated flavonol rhamnoside at the 2″-OH position of rhamnose. The analysis of enzymatic kinetics showed that EpF3R2″XylT had the highest substrate affinity toward icariin with the lowest Km value of 75.96 ± 11.91 mM. Transient expression of EpF3R2″XylT in tobacco leaf showed functional production of EpF3R2″XylT proteins in planta. EpF3R2″XylT was preferably expressed in the leaves of E. pubescens, which is consistent with the accumulation levels of major prenylflavonol 3-O-triglycoside. The discovery of EpF3R2″XylT will provide an economical and efficient alternative way to produce prenylated flavonol trisaccharides through the biosynthetic approach. [ABSTRACT FROM AUTHOR]

Prenylated polyphenols have attracted a lot of interest because of their significant pharmacological activities. The chemoenzymatic synthesis of prenylated polyphenols using prenyltransferase (PT) has been regarded as a promising alternative to chemical synthesis or plant-based production. Psoralea corylifolia L. with abundance of diversified prenylated polyphenol compounds is an ideal material for the discovery of prenyltransferases available in synthetic biology. In this study, we investigated the transcriptomic data from P. corylifolia for prenyltransferases (PcPTs) involved in the biosynthesis of prenylated phenols. Among 11 PcPTs, our yeast expression in vitro survey showed that PcPT11 was able to utilize 23 substrates, including 22 flavonoids and 1 coumarin, and was the one able to use the most substrates. PcPT11 acts in a highly regio-specific way to prenylate flavonoids at the C-6 position to produce compounds with important pharmacological effects such as corylifolinin, wighteone, and bavachin, which are the major ingredients in P. corylifolia. Finally, PcPT11 exhibited strong expression in fruits and leaves, and a GFP-PcPT11 fusion protein was shown to be localized in chloroplasts when expressed in Nicotiana benthamiana. Our study laid a foundation for understanding the biosynthetic pathway of prenylated flavonoids in P. corylifolia , and demonstrated that PcPT11 is a valuable enzyme to produce these pharmaceutically important prenylated polyphenols through biosynthetic approaches. • PcPT11 is a novel prenyltransferase gene with broad substrate promiscuity from Psoralea corylifolia. • PcPT11 has largely contributed to the diverse biosynthesis of secondary compounds in Psoralea corylifolia. • PcPT11 is a potential tool to produce bioactive prenylated compounds. [ABSTRACT FROM AUTHOR]