Application of deoxyribonucleic acid barcoding in Lauraceae plants

DNA barcoding: an efficient technology to authenticate plant species of traditional Chinese medicine and recent advances

Traditional Chinese medicine (TCM) plays an important role in the global traditional health systems. However, adulterated and counterfeit TCM is on the rise. DNA barcoding is an effective, rapid, and accurate technique for identifying plant species. In this study, we collected manuscripts on DNA barcoding published in the last decade and summarized the use of this technique in identifying 50 common Chinese herbs listed in the Chinese pharmacopoeia. Based on the dataset of the major seven DNA barcodes of plants in the NCBI database, the strengths and limitations of the barcodes and their derivative barcoding technology, including single-locus barcode, multi-locus barcoding, super-barcoding, meta-barcoding, and mini-barcoding, were illustrated. In addition, the advances in DNA barcoding, particularly identifying plant species for TCM using machine learning technology, are also reviewed. Finally, the selection process of an ideal DNA barcoding technique for accurate identification of a given TCM plant species was also outlined.

Essential Oil Composition and DNA Barcode and Identification of Aniba species (Lauraceae) Growing in the Amazon Region

Lauraceae species are widely represented in the Amazon, presenting a significant essential oil yield, large chemical variability, various biological applications, and high economic potential. Its taxonomic classification is difficult due to the accentuated morphological uniformity, even among taxa from a different genus. For this reason, the present work aimed to find chemical and molecular markers to discriminate Aniba species collected in the Pará State (Brazil). The chemical composition of the essential oils from Aniba canelilla, A. parviflora, A. rosaeodora, and A. terminalis were grouped by multivariate statistical analysis. The major compounds were rich in benzenoids and terpenoids such as 1-nitro-2-phenylethane (88.34-70.85%), linalool (15.2-75.3%), α-phellandrene (36.0-51.8%), and β-phellandrene (11.6-25.6%). DNA barcodes were developed using the internal transcribed spacer (ITS) nuclear region, and the matK, psbA-trnH, rbcL, and ycf1 plastid regions. The markers psbA-trnH and ITS showed the best discrimination for the species, and the phylogenic analysis in the three- (rbcL + matK + trnH - psbA and rbcL + matK + ITS) and four-locus (rbcL + matK + trnH - psbA + ITS) combination formed clades with groups strongly supported by the Bayesian inference (BI) (PP:1.00) and maximum likelihood (ML) (BS ≥ 97%). Therefore, based on statistical multivariate and phylogenetic analysis, the results showed a significant correlation between volatile chemical classes and genetic characteristics of Aniba species.

DMSO and betaine significantly enhance the PCR amplification of ITS2 DNA barcodes from plants

ITS2 marker is highly efficient in species discrimination but its application in DNA barcoding is limited due to huge variations in the PCR success rate. We have hypothesized that higher GC content and the resultant secondary structures formed during annealing might hinder the PCR amplification of ITS2. To test this hypothesis, we selected 12 species from 12 different families in which ITS2 was not amplified under standard PCR reaction conditions. In these samples, DMSO, formamide, betaine, and 7-deaza-dGTP were evaluated for their ability to improve the PCR success rate. The highest PCR success rate (91.6%) was observed with 5% DMSO, followed by 1 M betaine (75%), 50 μM 7-deaza-dGTP (33.3%), and 3% formamide (16.6%). The one sample that did not amplify with DMSO was amplified by adding 1 M betaine. However, combining DMSO and betaine in the same reaction did not improve the PCR. Therefore, to achieve the highest PCR success rate for ITS2, it is recommended to include 5% DMSO by default and substitute it with 1 M betaine only in the case of failed reactions. When this strategy was tested in 50 species from 43 genera and 29 families, the PCR success rate of ITS2 increased from 42% to 100%.

Comparative chloroplast genomics and phylogenetics of nine Lindera species (Lauraceae)

Lindera, a core genus of the Lauraceae family, has important economic uses in eastern Asia and North America. However, its historical diversification has not been clarified. In this study, we report nine newly sequenced Lindera plastomes. The plastomes of these nine Lindera species range from 152,211 (L. nacusua) to 152,968 bp (L. metcalfiana) in length, similar to that of another Lauraceae species, Litsea glutinosa (152,618 bp). The length variation of these plastomes derived from the length variation in the loci ycf1, ycf2, ψycf1, and ndhF-ψycf1. Comparing our sequences with other available plastomes in the Lauraceae indicated that eight hypervariable loci, ihbA-trnG, ndhA, ndhF-rpl32, petA-psbJ, psbK-psbI, rps16, trnS-trnG, and ycf1, could serve as DNA barcodes for species delineation, and that the inverted repeats (IRs) showed contraction/expansion. Further phylogenetic analyses were performed using 32 complete plastomes of Lauraceae and seven barcodes from 14 additional species of Lindera and related species in the core Lauraceae. The results showed that these Lindera species grouped into two or four sub-clades, and that two Litsea species and Laurus nobilis were located in the same sub-clade as five Lindera species. These data support a close relationship between the genera Laurus, Lindera, and Litsea, and suggest that Lindera is polyphyletic.

DNA barcoding: an efficient tool to overcome authentication challenges in the herbal market

The past couple of decades have witnessed global resurgence of herbal-based health care. As a result, the trade of raw drugs has surged globally. Accurate and fast scientific identification of the plant(s) is the key to success for the herbal drug industry. The conventional approach is to engage an expert taxonomist, who uses a mix of traditional and modern techniques for precise plant identification. However, for bulk identification at industrial scale, the process is protracted and time-consuming. DNA barcoding, on the other hand, offers an alternative and feasible taxonomic tool box for rapid and robust species identification. For the success of DNA barcode, the barcode loci must have sufficient information to differentiate unambiguously between closely related plant species and discover new cryptic species. For herbal plant identification, matK, rbcL, trnH-psbA, ITS, trnL-F, 5S-rRNA and 18S-rRNA have been used as successful DNA barcodes. Emerging advances in DNA barcoding coupled with next-generation sequencing and high-resolution melting curve analysis have paved the way for successful species-level resolution recovered from finished herbal products. Further, development of multilocus strategy and its application has provided new vistas to the DNA barcode-based plant identification for herbal drug industry. For successful and acceptable identification of herbal ingredients and a holistic quality control of the drug, DNA barcoding needs to work harmoniously with other components of the systems biology approach. We suggest that for effectively resolving authentication challenges associated with the herbal market, DNA barcoding must be used in conjunction with metabolomics along with need-based transcriptomics and proteomics.

ITS and trnH-psbA as Efficient DNA Barcodes to Identify Threatened Commercial Woody Angiosperms from Southern Brazilian Atlantic Rainforests

The Araucaria Forests in southern Brazil are part of the Atlantic Rainforest, a key hotspot for global biodiversity. This habitat has experienced extensive losses of vegetation cover due to commercial logging and the intense use of wood resources for construction and furniture manufacturing. The absence of precise taxonomic tools for identifying Araucaria Forest tree species motivated us to test the ability of DNA barcoding to distinguish species exploited for wood resources and its suitability for use as an alternative testing technique for the inspection of illegal timber shipments. We tested three cpDNA regions (matK, trnH-psbA, and rbcL) and nrITS according to criteria determined by The Consortium for the Barcode of Life (CBOL). The efficiency of each marker and selected marker combinations were evaluated for 30 commercially valuable woody species in multiple populations, with a special focus on Lauraceae species. Inter- and intraspecific distances, species discrimination rates, and ability to recover species-specific clusters were evaluated. Among the regions and different combinations, ITS was the most efficient for identifying species based on the 'best close match' test; similarly, the trnH-psbA + ITS combination also demonstrated satisfactory results. When combining trnH-psbA + ITS, Maximum Likelihood analysis demonstrated a more resolved topology for internal branches, with 91% of species-specific clusters. DNA barcoding was found to be a practical and rapid method for identifying major threatened woody angiosperms from Araucaria Forests such as Lauraceae species, presenting a high confidence for recognizing members of Ocotea. These molecular tools can assist in screening those botanical families that are most targeted by the timber industry in southern Brazil and detecting certain species protected by Brazilian legislation and could be a useful tool for monitoring wood exploitation.

A renaissance in herbal medicine identification: from morphology to DNA

Numerous adverse reactions have arisen following the use of inaccurately identified medicinal plant ingredients, resulting in conditions such as aristolochic acid nephropathy and herb-induced poisoning. This problem has prompted increased global concern over the safety of herbal medicines. DNA barcoding, a technique aiming at detecting species-specific differences in a short region of DNA, provides a powerful new tool for addressing this problem. A preliminary system for DNA barcoding herbal materials has been established based on a two-locus combination of ITS2+psbA-trnH barcodes. There are 78,847 sequences belonging to 23,262 species in the system, which include more than 95% of crude herbal drugs in pharmacopeia, such as those of China, Japan, Korea, India, USA, and Europe. The system has been widely used in traditional herbal medicine enterprises. This review summarizes recent key advances in the DNA barcoding of medicinal plant ingredients (herbal materia medica) as a contribution towards safe and efficacious herbal medicines.

Identification of ethnomedicinal plants (Rauvolfioideae: Apocynaceae) through DNA barcoding from northeast India

BACKGROUND

DNA barcode-based molecular characterization is in practice for plants, but yet lacks total agreement considering the selection of marker. Plant species of subfamily Rauvolfioideae have long been used as herbal medicine by the majority of tribal people in Northeast (NE) India and at present holds mass effect on the society. Hence, there is an urgent need of correct taxonomic inventorization vis-à-vis species level molecular characterization of important medicinal plants.

OBJECTIVE

To test the efficiency of matK in species delineation like DNA barcoding in Rauvolfiadae (Apocynaceae).

MATERIALS AND METHODS

In this study, the core DNA barcode matK and trnH-psbA sequences are examined for differentiation of selected ethnomedicinal plants of Apocynaceae. DNA from young leaves of selected species was isolated, and matK gene (~800 bp) and trnH-psbA spacer (~450 bp) of Chloroplast DNA was amplified for species level identification.

RESULTS

The ~758 bp matK sequence in comparison to the trnH-psbA showed easy amplification, alignment, and high level of discrimination value among the medicinal Rauvolfioidae species. Intergenic spacer trnH-psbA is also exhibited persistent problem in obtaining constant bidirectional sequences. Partial matK sequences exhibited 3 indels in multiple of 3 at 5 end. Evidently, generated matK sequences are clustered cohesively, with their conspecific Genbank sequences. However, repeat structures with AT-rich regions, possessing indels in multiple of 3, could be utilized as qualitative molecular markers in further studies both at the intra-specific and shallow inter-specific levels like the intergenic spacers of CpDNA.

CONCLUSION

matK sequence information could help in correct species identification for medicinal plants of Rauvolfioideae.