De novo genome assembly of the medicinal plant Gentiana macrophylla provides insights into the genomic evolution and biosynthesis of iridoids.

Gentiana macrophylla is a perennial herb in the Gentianaceae family, whose dried roots are used in traditional Chinese medicine. Here, we assembled a chromosome-level genome of G. macrophylla using a combination of Nanopore, Illumina, and Hi-C scaffolding approaches. The final genome size was ~1.79 Gb (contig N50 = 720.804 kb), and 98.89% of the genome sequences were anchored on 13 pseudochromosomes (scaffold N50 = 122.73 Mb). The genome contained 55,337 protein-coding genes, and 73.47% of the assemblies were repetitive sequences. Genome evolution analysis indicated that G. macrophylla underwent two rounds of whole-genome duplication after the core eudicot γ genome triplication event. We further identified candidate genes related to the biosynthesis of iridoids, and the corresponding gene families mostly expanded in G. macrophylla. In addition, we found that root-specific genes are enriched in pathways involved in defense responses, which may greatly improve the biological adaptability of G. macrophylla. Phylogenomic analyses showed a sister relationship of asterids and rosids, and all Gentianales species formed a monophyletic group. Our study contributes to the understanding of genome evolution and active component biosynthesis in G. macrophylla and provides important genomic resource for the genetic improvement and breeding of G. macrophylla.

A nucleotide signature for the identification of Pinelliae Rhizoma (Banxia) and its products.

BACKGROUND: Ensuring the authenticity of raw materials is a key step prior to producing Chinese patent medicines. Pinellia ternata (Thunb.) Breit. is the botanical origin of Pinelliae Rhizoma (Banxia), a traditional Chinese medicine used to treat cough, insomnia, nausea, inflammation, epilepsy, and so on. Unfortunately, authentic Pinelliae Rhizoma is often adulterated by morphologically indistinguishable plant material due to the insufficient regulatory procedures of processed medicinal plant products. Thus, it is important to develop a molecular assay based on species-specific nucleotide signatures and primers to efficiently distinguish authentic Pinelliae Rhizoma from its adulterants. METHODS AND RESULTS: The ITS2 region of 67 Pinelliae Rhizoma and its common adulterants were sequenced. Eight single nucleotide polymorphisms within a 28-43 bp stretch of ITS2 were used to develop six primer pairs to amplify these species-specific regions. We assayed 56 Pinelliae Rhizoma products sold on the Chinese market, including medicinal slices, powder and Chinese patent medicines, which revealed that about 66% of products were adulterated. The most common adulterants were Pinellia pedatisecta (found in 57% of the assayed products), Arisaema erubescens (9%), Typhonium giganteum (2%) and Typhonium flagelliforme (2%). CONCLUSIONS: A severe adulteration condition was revealed in the traditional medicine market. The species-specific nucleotide assays developed in this study can be applied to reliably identify Pinelliae Rhizoma and its adulterants, aiding in the authentication and quality control of processed products on the herbal market.

Genetic and chemical differentiation characterizes top-geoherb and non-top-geoherb areas in the TCM herb rhubarb.

Medicinal herbs of high quality and with significant clinical effects have been designated as top-geoherbs in traditional Chinese medicine (TCM). However, the validity of this concept using genetic markers has not been widely tested. In this study, we investigated the genetic variation within the Rheum palmatum complex (rhubarb), an important herbal remedy in TCM, using a phylogeographic (six chloroplast DNA regions, five nuclear DNA regions, and 14 nuclear microsatellite loci) and a chemical approach (anthraquinone content). Genetic and chemical data identified two distinct groups in the 38 analysed populations from the R. palmatum complex which geographically coincide with the traditional top-geoherb and non-top-geoherb areas of rhubarb. Molecular dating suggests that the two groups diverged in the Quaternary c. 2.0 million years ago, a time of repeated climate changes and uplift of the Qinghai-Tibetan Plateau. Our results show that the ancient TCM concept of top-geoherb and non-top-geoherb areas corresponds to genetically and chemically differentiated groups in rhubarb.

Authentication of Eleutherococcus and Rhodiola herbal supplement products in the United Kingdom.

Siberian ginseng (Eleutherococcus senticosus, Araliaceae) and roseroot (Rhodiola rosea, Rosaceae) are popular herbal supplements which have been shown to improve resilience to conditions such as stress and exhaustion. Using DNA barcoding methods we tested 25 Siberian ginseng and 14 roseroot products which are widely available to UK customers to test whether the herbal ingredient stated on the label is also in the product. All Siberian ginseng supplements contained E. senticosus, however, 36% also contained an Eleutherococcus species other than E. senticosus. In three out of the 13 roseroot products which produced amplifiable DNA, we could only retrieve sequences matching alfalfa (declared on the product label) and fenugreek (not declared). In the other 10 supplements Rhodiola was detected but only five matched the target species R. rosea. As DNA can get severely degraded during the manufacturing process we did not take the absence of Rhodiola DNA as proof for a compromised product. Contamination could explain the presence of non-target species such as fenugreek but is unlikely to be account for the detection of congeneric Rhodiola species in roseroot preparations. Our results therefore suggest that the substitution or mixing of the target medicinal ingredient in these two popular supplements with other species is common.