Deep sequencing and transcriptome analyses to identify genes involved in iridoid biosynthesis in the medicinal plant Valeriana jatamansi Jones

Abstract

Valeriana jatamansi Jones is utilized for medicinal purposes in China, and is also an important substitute for European Valeriana officinalis. The major active principles are generally called valepotriates, which belong to iridoids compounds. To better understand the iridoid biosynthesis pathway in V. jatamansi, we generated transcriptome sequences from the leaf and root tissues, and performed de novo sequence assembly, a total of 183,524,060 transcripts and 61,876 unigenes for V. jatamansi were obtained from 13.28 Gb clean reads. 56,641 unigenes were annotated by public databases, while 5,235 unigenes remained unannotated. Different unigenes in V. jatamansi were identified by MISA analysis, and 5,195 unigenes containing Simple Sequence Repeat (SSR) were identified. When examining the annotation of transcriptome contigs against the KEGG database, we identified 24 unigenes that could be classified into 24 enzyme categories associated with three metabolic pathways leading to iridoid biosynthesis, 6 genes of MVA pathways, 9 genes of MEP pathways and 9 genes of iridoids pathways. We selected 9 genes encoding key enzymes in the iridoid pathway of V. jatamansi to examine their organ specificity of expression using quantitative real-time PCR (qPCR). In conclusion, we generated a comprehensive transcriptome assembly representing the gene space in V. jatamansi, and the genomic dataset and analyses presented here lay the foundation for further research on this important medicinal plant.

Keywords

• gene expression; iridoid biosynthesis; transcriptome; Valeriana jatamansi