Herbgenomics provides a global platform to explore the genetics and biology of herbs on the genome level. Panax ginseng C.A. Meyer is an important medicinal plant with numerous pharmaceutical effects. Previous reports mainly discussed the transcriptome of ginseng at the organ level. However, based on mass spectrometry imaging analyses, the ginsenosides varied among different tissues. In this work, ginseng root was separated into three tissues—periderm, cortex and stele—each for five duplicates. The chemical analysis and transcriptome analysis were conducted simultaneously. Gene-encoding enzymes involved in ginsenosides biosynthesis and modification were studied based on gene and molecule data. Eight widely-used ginsenosides were distributed unevenly in ginseng roots. A total of 182,881 unigenes were assembled with an N50 contig size of 1374 bp. About 21,000 of these unigenes were positively correlated with the content of ginsenosides. Additionally, we identified 192 transcripts encoding enzymes involved in two triterpenoid biosynthesis pathways and 290 transcripts encoding UDP-glycosyltransferases (UGTs). Of these UGTs, 195 UGTs (67.2%) were more highly expressed in the periderm, and that seven UGTs and one UGT were specifically expressed in the periderm and stele, respectively. This genetic resource will help to improve the interpretation on complex mechanisms of ginsenosides biosynthesis, accumulation, and transportation.

Herb genomics and comparative genomics provide a global platform to explore the genetics and biology of herbs at the genome level. Panax ginseng C.A. Meyer is an important medicinal plant for a variety of bioactive chemical compounds of which the biosynthesis may involve transport of a wide range of substrates mediated by oligopeptide transporters (OPT). However, information about the OPT family in the plant kingdom is still limited. Only 17 and 18 OPT genes have been characterized for Oryza sativa and Arabidopsis thaliana, respectively. Additionally, few comprehensive studies incorporating the phylogeny, gene structure, paralogs evolution, expression profiling, and co-expression network between transcription factors and OPT genes have been reported for ginseng and other species. In the present study, we performed those analyses comprehensively with both online tools and standalone tools. As a result, we identified a total of 268 non-redundant OPT genes from 12 flowering plants of which 37 were from ginseng. These OPT genes were clustered into two distinct clades in which clade-specific motif compositions were considerably conservative. The distribution of OPT paralogs was indicative of segmental duplication and subsequent structural variation. Expression patterns based on two sources of RNA-Sequence datasets suggested that some OPT genes were expressed in both an organ-specific and tissue-specific manner and might be involved in the functional development of plants. Further co-expression analysis of OPT genes and transcription factors indicated 141 positive and 11 negative links, which shows potent regulators for OPT genes. Overall, the data obtained from our study contribute to a better understanding of the complexity of the OPT gene family in ginseng and other flowering plants. This genetic resource will help improve the interpretation on mechanisms of metabolism transportation and signal transduction during plant development for Panax ginseng.

The root of Gentiana macrophylla is a traditional Chinese medicine that has been used for over 2000 years. We introduced seed priming to improve germination performance for this species and found that after ferrous sulphate priming (FeP), seeds presented higher germination under both optimal and adverse environments than non-primed (NP) seeds. Transcriptome analysis conducted on FeP, hydro-primed (HP) and NP seeds was used to identify the key genes involved in metabolism and contribute to understanding of the molecular mechanisms of seed priming. After calculating the gene expression and analysing the differentially-expressed genes (DEGs), a total of 2050 and 914 unigenes were identified as differentially expressed in FeP and HP seeds, respectively, relative to NP seeds. On the basis of the KEGG pathway enrichment analysis results, by analysing and summarising those DEGs related to enzymes during metabolism, enzymes involved in carbohydrate, nucleic acid metabolism, hormone biosynthesis and signal transduction, respiration and energy metabolism, and stress-related metabolism were all regulated after FeP treatment. Their regulated trends exhibited almost similar patterns with the initial germination process, whereas those from HP treatment were weaker than the effect of FeP, where only a small number of enzymes were regulated. Primed seeds are developmentally more advanced towards the completion of germination than NP seeds.