Transcriptome analyses provide insights into the difference of alkaloids biosynthesis in the Chinese goldthread (Coptis chinensis Franch.) from different biotopes

Coptis chinensis Franch., the Chinese goldthread ('Weilian' in Chinese), one of the most important medicinal plants from the family Ranunculaceae, and its rhizome has been widely used in Traditional Chinese Medicine for centuries. Here, we analyzed the chemical components and the transcriptome of the Chinese goldthread from three biotopes, including Zhenping, Zunyi and Shizhu. We built comprehensive, high-quality de novo transcriptome assemblies of the Chinese goldthread from short-read RNA-Sequencing data, obtaining 155,710 transcripts and 56,071 unigenes. More than 98.39% and 95.97% of core eukaryotic genes were found in the transcripts and unigenes respectively, indicating that this unigene set capture the majority of the coding genes. A total of 520, 462, 493,718, and 507,247 heterozygous SNPs were identified in the three accessions from Zhenping, Zunyi, and Shizhu respectively, indicating high polymorphism in coding regions of the Chinese goldthread (similar to 1%). Chemical analyses of the rhizome identified six major components, including berberine, palmatine, coptisine, epiberberine, columbamine, and jatrorrhizine. Berberine has the highest concentrations, followed by coptisine, palmatine, and epiberberine sequentially for all the three accessions. The drug quality of the accession from Shizhu may be the highest among these accessions. Differential analyses of the transcriptome identified four pivotal candidate enzymes, including aspartate aminotransferaseprotein, polyphenol oxidase, primary-amine oxidase, and tyrosine decarboxylase, were significantly differentially expressed and may be responsible for the difference of alkaloids contents in the accessions from different biotopes.