Dendrobium officinale Kimura et Migo is a traditional Chinese orchid herb that has both ornamental value and a broad range of therapeutic effects. Here, we report the first de novo assembled 1.35 Gb genome sequences for D. officinale by combining the second-generation Illumina Hiseq 2000 and third-generation PacBio sequencing technologies. We found that orchids have a complete inflorescence gene set and have some specific inflorescence genes. We observed gene expansion in gene families related to fungus symbiosis and drought resistance. We analyzed biosynthesis pathways of medicinal components of D. officinale and found extensive duplication of SPS and SuSy genes, which are related to polysaccharide generation, and that the pathway of D. officinale alkaloid synthesis could be extended to generate 16-epivellosimine. The D. officinale genome assembly demonstrates a new approach to deciphering large complex genomes and, as an important orchid species and a traditional Chinese medicine, the D. officinale genome will facilitate future research on the evolution of orchid plants, as well as the study of medicinal components and potential genetic breeding of the dendrobe.

The flavonoid extract from Erigeron breviscapus, breviscapine, has increasingly been used to treat cardio- and cerebrovascular diseases in China for more than 30 years, and plant supply of E. breviscapus is becoming insufficient to satisfy the growing market demand. Here we report an alternative strategy for the supply of breviscapine by building a yeast cell factory using synthetic biology. We identify two key enzymes in the biosynthetic pathway (flavonoid-7-O-glucuronosyltransferase and flavone-6-hydroxylase) from E. breviscapus genome and engineer yeast to produce breviscapine from glucose. After metabolic engineering and optimization of fed-batch fermentation, scutellarin and apigenin-7-O-glucuronide, two major active ingredients of breviscapine, reach to 108 and 185 mg l–1, respectively. Our study not only introduces an alternative source of these valuable compounds, but also provides an example of integrating genomics and synthetic biology knowledge for metabolic engineering of natural compounds.

Maca (Lepidium meyenii Walp, 2n = 8x = 64), belonging to the Brassicaceae family, is an economic plant cultivated in the central Andes sierra in Peru (4000-4500 m). Considering that the rapid uplift of the central Andes occurred 5-10 million years ago (Ma), an evolutionary question arises regarding how plants such as maca acquire high-altitude adaptation within a short geological period. Here, we report the high-quality genome assembly of maca, in which two closely spaced maca-specific whole-genome duplications (WGDs; ∼6.7 Ma) were identified. Comparative genomic analysis between maca and closely related Brassicaceae species revealed expansions of maca genes and gene families involved in abiotic stress response, hormone signaling pathway, and secondary metabolite biosynthesis via WGDs. The retention and subsequent functional divergence of many duplicated genes may account for the morphological and physiological changes (i.e., small leaf shape and self-fertility) in maca in a high-altitude environment. In addition, some duplicated maca genes were identified with functions in morphological adaptation (i.e., LEAF CURLING RESPONSIVENESS) and abiotic stress response (i.e., GLYCINE-RICH RNA-BINDING PROTEINS and DNA-DAMAGE-REPAIR/TOLERATION 2) under positive selection. Collectively, the maca genome provides useful information to understand the important roles of WGDs in the high-altitude adaptation of plants in the Andes.

BackgroundP. vietnamensis var. fuscidiscus, called “Yesanqi” in Chinese, is a new variety of P. vietnamensis, which was first found in Jinping County, the southern part of Yunnan Province, China. Compared with other Panax plants, this species contains higher content of ocotillol-type saponin, majonoside R2. Despite the pharmacological importance of ocotillol-type saponins, little is known about their biosynthesis in plants. Hence, P. vietnamensis var. fuscidiscus is a suitable medicinal herbal plant species to study biosynthesis of ocotillol-type saponins. In addition, the available genomic information of this important herbal plant is lacking.ResultsTo investigate the P. vietnamensis var. fuscidiscus transcriptome, Illumina HiSeq™ 2000 sequencing platform was employed. We produced 114,703,210 clean reads, assembled into 126,758 unigenes, with an average length of 1,304 bp and N50 of 2,108 bp. Among these 126,758 unigenes, 85,214 unigenes (67.23%) were annotated based on the information available from the public databases. The transcripts encoding the known enzymes involved in triterpenoid saponins biosynthesis were identified in our Illumina dataset. A full-length cDNA of three Squalene epoxidase (SE) genes were obtained using reverse transcription PCR (RT-PCR) and the expression patterns of ten unigenes were analyzed by reverse transcription quantitative real-time PCR (RT-qPCR). Furthermore, 15 candidate cytochrome P450 genes and 17 candidate UDP-glycosyltransferase genes most likely to involve in triterpenoid saponins biosynthesis pathway were discovered from transcriptome sequencing of P. vietnamensis var. fuscidiscus. We further analyzed the data and found 21,320 simple sequence repeats (SSRs), 30 primer pairs for SSRs were randomly selected for validation of the amplification and polymorphism in 13 P. vietnamensis var. fuscidiscus accessions. Meanwhile, five major triterpene saponins in roots of P. vietnamensis var. fuscidicus were determined using high performance liquid chromatography (HPLC) and evaporative light scattering detector (ELSD).ConclusionsThe genomic resources generated from P. vietnamensis var. fuscidiscus provide new insights into the identification of putative genes involved in triterpenoid saponins biosynthesis pathway. This will facilitate our understanding of the biosynthesis of triterpenoid saponins at molecular level. The SSR markers identified and developed in this study show genetic diversity for this important crop and will contribute to marker-assisted breeding for P. vietnamensis var. fuscidiscus.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1332-8) contains supplementary material, which is available to authorized users.

BackgroundDanshen (Salvia miltiorrhiza Bunge), also known as Chinese red sage, is a member of Lamiaceae family. It is valued in traditional Chinese medicine, primarily for the treatment of cardiovascular and cerebrovascular diseases. Because of its pharmacological potential, ongoing research aims to identify novel bioactive compounds in danshen, and their biosynthetic pathways. To date, only expressed sequence tag (EST) and RNA-seq data for this herbal plant are available to the public. We therefore propose that the construction of a reference genome for danshen will help elucidate the biosynthetic pathways of important secondary metabolites, thereby advancing the investigation of novel drugs from this plant.FindingsWe assembled the highly heterozygous danshen genome with the help of 395 × raw read coverage using Illumina technologies and about 10 × raw read coverage by using single molecular sequencing technology. The final draft genome is approximately 641 Mb, with a contig N50 size of 82.8 kb and a scaffold N50 size of 1.2 Mb. Further analyses predicted 34,598 protein-coding genes and 1,644 unique gene families in the danshen genome.ConclusionsThe draft danshen genome will provide a valuable resource for the investigation of novel bioactive compounds in this Chinese herb.Electronic supplementary materialThe online version of this article (doi:10.1186/s13742-015-0104-3) contains supplementary material, which is available to authorized users.