De novo Assembly and Transcriptome Analysis of Polygonatum odoratum (Mill.) Druce : Detection of Potential Genes Involved in Polysaccharide Synthesis

Abstract Background: Polygonatum odoratum (Mill.) Druceis a well-known traditional Chinese herb. Polysaccharide is one of the main bioactive components from Polygonatum odoratum, with broad pharmacological effects, including improving immunity, and is used in the treatment of rheumatic heart disease, cardiovascular disease, and diabetes. Results: This study identifies potential genes and transcription factors (TFs) that regulate polysaccharide synthesis in Polygonatum odoratum by using RNA sequencing data from leaf, stem and rhizome tissues. A total of 112,443 unigenes were de novo assembled, and 76,714 were annotated in public databases. Differentially expressed gene analysis showed that most upregulated and uniquely expressed unigenes were enriched in rhizome tissue compared with leaf or stem tissue. UV-spectrophotometry results showed that polysaccharide content was the greatest in the rhizome tissue. Additionally, 2,865 unigenes relevant to TF families were predicted, including 73 involved in polysaccharide synthesis. A few key enzyme genes were also verified by quantitative real-time PCR (qRT-PCR). Seven β-fructofuranosidases with different amino acid sequences showed similar spatial structures and all had well-conserved catalytic triads. Conclusion: This study substantially enlarges the public transcriptome datasets of this species, and provides insight into the detection of novel genes involed polysaccharide and other secondary metabolite synthesis. Keywords: Polygonatum odoratum, transcriptome , polysaccharide synthesis, Differentially expressed gene, key enzyme genes