An insight into the genes involved in secoiridoid biosynthesis in Gentiana macrophylla by RNA-seq.

The dried root of Gentiana macrophylla is a well-known traditional Chinese herbal medicine for treating jaundice, hepatitis, and stomachic and choleretic ailments. However, natural sources are now in short supply. A lack of information about its genetic background has been a great hindrance to producing its active constituents via genetic engineering. We performed RNA-seq to obtain 42,918 unigenes (average length = 667 bp) in its transcriptome. Of these, 32,141 (74.89 %) were annotated and 2,339 unigenes were assigned to secondary-metabolite pathways. In all, 114 putative unigenes involved in secoiridoid biosynthesis were identified in our transcriptome library. A Blast X search against the Arabidopsis gene regulatory information server showed that 4,413 unigenes are homologous to transcription factor genes from Arabidopsis. Organ-specific genes and candidate gene expression profiles were also investigated with digital gene expression technology. Quantitative PCR was used to verify the expression patterns of several novel transcripts involved in secoiridoid biosynthesis. Our results not only enrich the gene resource but will also benefit research into the molecular genetics and functional genomics of this species.