Phylogenetic analysis of Uncaria species based on internal transcribed spacer (ITS) region and ITS2 secondary structure.
CONTEXT
The plant genus Uncaria (Rubiaceae), also known as Gouteng, is the source of an important traditional Chinese medicine. Misidentification and adulteration of Gouteng affect the safety and efficacy of the medication. Phylogenetic relationships among the species of this genus are unknown.


OBJECTIVE
The present study sought to detect the phylogenetic relationships based on internal transcribed spacer (ITS) region of all 12 species of Uncaria recorded in the Flora of China.


MATERIALS AND METHODS
Accession of seven species of Uncaria served as reference samples. ITS region was used for polymerase chain reaction (PCR) amplification of the reference samples representing 39 specimens. Distance analysis, species discrimination, and secondary structure of ITS2 were used to assess the ability of ITS sequence in authenticating. The phylogenetic relationships were detected using three methods: Bayesian inference (BI), maximum likelihood (ML), and neighbor joining (NJ).


RESULTS
Five species of traditional Chinese medicine Gouteng were well resolved in molecular phylogenetic tree. Besides, Uncaria lancifolia Hutch. was closer to U. rhynchophylloides F.C. How and U. sessilifructus Roxb. was closer to U. laevigata Wall. within the tree. Further, we also found that ITS2 secondary structure can be a candidate tool in distinguishing two closely related species U. yunnanensis K.C.Hsia and U. lanosa Wall. For accurate identification of different species of Uncaria based on species-specific nucleotide sites, a consensus sequences database with all 12 species is established.


DISCUSSIONS AND CONCLUSIONS
The results are able to discriminate Uncaria species and illustrate the phylogenetic relationships, which are essential for the investigation of adulterants and misidentifications of Uncaria.
['Zhu|Shuang|S|', 'Li|Qiwei|Q|http://orcid.org/0000-0002-7674-5565', 'Chen|Shanchong|S|', 'Wang|Yesheng|Y|', 'Zhou|Lin|L|', 'Zeng|Changqing|C|', 'Dong|Jun|J|']
D058893:DNA Barcoding, Taxonomic D018744:DNA, Plant D021903:DNA, Ribosomal Spacer D020459:Genes, rRNA D009690:Nucleic Acid Conformation D010802:Phylogeny D010946:Plants, Medicinal D016133:Polymerase Chain Reaction D032070:Uncaria
discrimination DNA barcoding Molecular phylogeny