Comfrey (Lithospermum erythrorhizon) (Fig. 1) It is a perennial herb of the comfrey genus comfrey in the comfrey family, which has high economic value as part of traditional medicine. Comfrey root has antiviral and wound-healing properties, mainly due to the biologically active compound it contains, comfrey and its derivatives. In recent years, shikonin and its enantiomer comfrey red (alkannin) and several other comfrey/comfrey red derivatives have entered the field of vision as valuable natural pigments and new drug scaffolds. Although comfrey is one of the longest studied natural products of plants, due to the lack of comfrey reference genomes, the elucidation of the comfrey/comfrey metabolic pathway and its evolutionary and ecological significance have lagged behind.
Fig. 1 Shikonin is produced in the roots of Lithospermum erythrorhizon.
Recently, Horticulture Research published a research paper entitled Hybrid de novo genome assembly of red gromwell (Lithospermum erythrorhizon) reveals evolutionary insight into shikonin biosynthesis. The study was done by Robert P. Auber et al. of Purdue University. The first de novo-assembled genome of comfrey was constructed by the long reads generated by Oxford Nanopore Technology (ONT) technology combined with the short reads generated by illumina HiSeq sequencing of an irima HiSeq at Nanjing University in 2008. The comfrey genome is 367.41Mb in size and contains 2465 contigs, the longest contig is 3.44 Mb and the N50 contig is 314.31 kb long. Among them, the amount of ONT data is 7.6Gb, and the coverage rate is about 20 times that of the genome. Based on OrthoFinder, an evolutionary analysis of gene families of different genes, including genes associated with comfrey synthesis, showed that Boraginales was most closely related to a large branch of solanales, gentians, and laminales.
p-hydroxybenzoate:geranyltransferase (PGT) is a key enzyme in comfrey biosynthesis, and in a recent common ancestor of comfrey/comfrey red plants, orthogroup OG0000509 predicted multiple replication events, which contained 13 comfrey genes, including LePGT1, LePGT2, and 11 unreported PGT genes. In order to better analyze the evolutionary history of LePGT1 and LePGT2, the researchers performed a phylogenetic analysis of prenyltransferases in the OG0000509 homologous group (Fig. 2000509). 2), the Leryth_011786 copy is relatively far from other copies and may be the previously reported "missing" ubiquinone isoprenyltransferase in comfrey. In addition, RNAi experiments on LePGT1 in comfrey hairy roots showed that the total content of combonin in the culture medium decreased by more than 95%, further confirming that LePGT1 is indeed the main PGT gene that controls comfrey synthesis. The evolutionary origin analysis of comfrey reference genome and the provided comfrey biosynthesis provided in this study provides some new clues for the evolutionary study of special metabolites of comfrey family and has important guiding significance for the analysis of unknown parts of comfrey biosynthesis pathways.
Fig. 2 Phylogenetic analysis of prenyltransferase homologs in orthogroup OG0000509.
Article links:
https://www.nature.com/articles/s41438-020-0301-9
About Horticultural Research
Horticulture Research is an English-language journal co-founded by Nanjing Agricultural University in collaboration with Nature Publishing Group (now Springer Nature) and is Nature's only special journal in the field of horticulture. All basic and theoretical research on horticultural crops can be submitted. Horticulture Research JCR2018 Impact Factor: 3.640, located in Horticulture Zone 1 (3/36th) and Plant Sciences Region 1 (32nd/228th). 2019 Chinese Academy of Sciences Journal Division (Basic Edition): Located in Horticulture Sub-District 1, Plant Science Sub-Category 1, Agroforestry Science Category 1 (Top Journal).