De novo Transcriptome Assembly of Rhubarb (Rheum ribes) Roots Identify the Secondary Metabolites Biosynthetic Genes with Emphasis on Antraquinon

Rheum ribes roots contain pharmaceutical compounds. But this plant genetic background has not yet been elucidated. We performed RNA sequencing of R. ribes roots. In result, 82047 transcripts were generated through de novo assembly, 52975 of these transcripts were annotated in public databases and 12,502 transcripts were annotated in the KEGG database. A total of 3296 transcripts were identified as differentially expressed between 4 and 8 years old roots. Functional annotation identified 86 transcripts for 34 critical enzymes associated with terpenoid backbone, 44 transcripts for phenylpropanoid biosynthetic pathway, 26 transcripts for flavonoid biosynthetic pathway, 5 transcripts related to anthraquinone biosynthesis, 59 transcripts for UDP glycosyltransferase and 45 transcripts for cytochrome P450. In addition, 944 transcription factors and 4777 SSR were identified. This is the first report dealing with the R. ribes transcriptome and provides important genetic resources related to the genes involved in the biosynthetic pathways of secondary metabolites.