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.

Characterization of the complete chloroplast genome of Hedysarum polybotrys var. alaschanicum (Fabaceae) and its phylogeny.

Hedysarum polybotrys var. alaschanicum is an important medicinal plant and is widely used in traditional Chinese medicine. The complete chloroplast genome of H. polybotrys var. alaschanicum was assembled from Illumina pair-end sequence reads. The whole chloroplast genome is 122,933 bp in length and encodes a total of 110 genes, including 76 protein-coding genes, 30 tRNA genes and 4 rRNA genes. The overall GC content of the cp genome is 35.3%. A maximum likelihood (ML) phylogenetic analysis revealed that H. polybotrys var. alaschanicum was close to Hedysarum semenovii.

Characteristic and phylogenetic analyses of chloroplast genome for Ephedra monosperma (Ephedraceae), an important medicinal species.

Ephedra monosperma is an important medicinal plant of Ephedra (Ephedraceae). The complete chloroplast genome of E. monosperma was assembled from Illumina pair-end sequence reads. The whole chloroplast (cp) genome is 109,548 bp in length and presents a quadripartite structure consisting of two copies of inverted repeat (IR) regions (20,398) separated by a large single copy (LSC) region (60,674 bp) and a small single copy (SSC) region (8078 bp). The cp genome of E. monosperma encodes a total of 118 genes, including 73 protein-coding genes, 37 tRNA genes and 8 rRNA genes. The overall GC content of E. monosperma cp genome is 36.6%. A maximum likelihood (ML) phylogenetic analysis revealed that E. monosperma was close to Ephedra equisetina. The ML tree also showed Ephedraceae appeared more closely related to Gnetaceae than to the other families in Gymnospermae.