Abstract
Background Erigeron breviscapus (Vant.) Hand-Mazz. is a famous medicinal plant. Scutellarin and chlorogenic acids are the primary active components in this herb. However, the mechanisms of biosynthesis and regulation for scutellarin and chlorogenic acids in E. breviscapus are considerably unknown. In addition, genomic information of this herb is also unavailable.Principal FindingsUsing Illumina sequencing on GAIIx platform, a total of 64,605,972 raw sequencing reads were generated and assembled into 73,092 non-redundant unigenes. Among them, 44,855 unigenes (61.37%) were annotated in the public databases Nr, Swiss-Prot, KEGG, and COG. The transcripts encoding the known enzymes involved in flavonoids and in chlorogenic acids biosynthesis were discovered in the Illumina dataset. Three candidate cytochrome P450 genes were discovered which might encode flavone 6-hydroase converting apigenin to scutellarein. Furthermore, 4 unigenes encoding the homologues of maize P1 (R2R3-MYB transcription factors) were defined, which might regulate the biosynthesis of scutellarin. Additionally, a total of 11,077 simple sequence repeat (SSR) were identified from 9,255 unigenes. Of SSRs, tri-nucleotide motifs were the most abundant motif. Thirty-six primer pairs for SSRs were randomly selected for validation of the amplification and polymorphism. The result revealed that 34 (94.40%) primer pairs were successfully amplified and 19 (52.78%) primer pairs exhibited polymorphisms.ConclusionUsing next generation sequencing (NGS) technology, this study firstly provides abundant genomic data for E. breviscapus. The candidate genes involved in the biosynthesis and transcriptional regulation of scutellarin and chlorogenic acids were obtained in this study. Additionally, a plenty of genetic makers were generated by identification of SSRs, which is a powerful tool for molecular breeding and genetics applications in this herb.
Highlights
Erigeron breviscapus (Vant.) Hand-Mazz. is a famous medicinal plant
Flavonoid 7-O-glucuronides are commonly detected in plants within the Lamiales order, such as Perilla frutescens, Antirrhinum majus, and Scutellaria baicalensis [6], but the high content of scutellarin is only found in a few Erigeron species, including E. breviscapus and E. multiradiatus [7]
Illumina Sequencing and de novo Assembly In order to find more genes involved in the biosynthesis of scutellarin and chlorogenic acids, total RNA was extracted from the fully-expanded young fresh leaves and the flowers at different stages
Summary
The major active components of E. breviscapus are flavonoid glucuronides [1], mainly scutellarin, along with a small amount of apigenin 7-O-glucuronide and quercetin-3-O-glucuronide [2]. Scutellarin is a kind of flavonoid 7-O-glucuronide, which has neuroprotective effects and cytotoxicity protective action [3,4,5]. Flavonoid 7-O-glucuronides are commonly detected in plants within the Lamiales order, such as Perilla frutescens, Antirrhinum majus, and Scutellaria baicalensis [6], but the high content of scutellarin is only found in a few Erigeron species, including E. breviscapus and E. multiradiatus [7]. The 6-OH is the most important characteristic of scutellarin, suggested that there must be a flavonoid 6-hydroxylase (F6H) in E. breviscapus, which converts apigenin to scutellarein. Scutellarin and chlorogenic acids are the primary active components in this herb. Genomic information of this herb is unavailable
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