Predicting quantitative phytochemical markers in single Echinacea plants or clones from their DNA fingerprints

DNA barcoding, microarrays and next generation sequencing: recent tools for genetic diversity estimation and authentication of medicinal plants

DNA barcoding, microarray technology and next generation sequencing have emerged as promising tools for the elucidation of plant genetic diversity and its conservation. They are proving to be immensely helpful in authenticating the useful medicinal plants for herbal drug preparations. These newer versions of molecular markers utilize short genetic markers in the genome to characterize the organism to a particular species. This has the potential not only to classify the known and yet unknown species but also has a promising future to link the medicinally important plants according to their properties. The newer trends being followed in DNA chips and barcoding pave the way for a future with many different possibilities. Several of these possibilities might be: characterization of unknown species in a considerably less time than usual, identification of newer medicinal properties possessed by the species and also updating the data of the already existing but unnoticed properties. This can assist us to cure many different diseases and will also generate novel opportunities in medicinal drug delivery and targeting.

Chicoric acid: chemistry, distribution, and production

Though chicoric acid was first identified in 1958, it was largely ignored until recent popular media coverage cited potential health beneficial properties from consuming food and dietary supplements containing this compound. To date, plants from at least 63 genera and species have been found to contain chicoric acid, and while the compound is used as a processing quality indicator, it may also have useful health benefits. This review of chicoric acid summarizes research findings and highlights gaps in research knowledge for investigators, industry stakeholders, and consumers alike. Additionally, chicoric acid identification, and quantification methods, biosynthesis, processing improvements to increase chicoric acid retention, and potential areas for future research are discussed.

Subtracted diversity array identifies novel molecular markers including retrotransposons for fingerprinting Echinacea species

Echinacea, native to the Canadian prairies and the prairie states of the United States, has a long tradition as a folk medicine for the Native Americans. Currently, Echinacea are among the top 10 selling herbal medicines in the U.S. and Europe, due to increasing popularity for the treatment of common cold and ability to stimulate the immune system. However, the genetic relationship within the species of this genus is unclear, making the authentication of the species used for the medicinal industry more difficult. We report the construction of a novel Subtracted Diversity Array (SDA) for Echinacea species and demonstrate the potential of this array for isolating highly polymorphic sequences. In order to selectively isolate Echinacea-specific sequences, a Suppression Subtractive Hybridization (SSH) was performed between a pool of twenty-four Echinacea genotypes and a pool of other angiosperms and non-angiosperms. A total of 283 subtracted genomic DNA (gDNA) fragments were amplified and arrayed. Twenty-seven Echinacea genotypes including four that were not used in the array construction could be successfully discriminated. Interestingly, unknown samples of E. paradoxa and E. purpurea could be unambiguously identified from the cluster analysis. Furthermore, this Echinacea-specific SDA was also able to isolate highly polymorphic retrotransposon sequences. Five out of the eleven most discriminatory features matched to known retrotransposons. This is the first time retrotransposon sequences have been used to fingerprint Echinacea, highlighting the potential of retrotransposons as based molecular markers useful for fingerprinting and studying diversity patterns in Echinacea.

A taxonomist's view on genomic authentication

A brief history of taxonomy, for the most part plant oriented, is provided, which demonstrates the use of morphology early on, through the stages when different technologies became available at different times until the present use of genomic tools. Genomic authentication facilitates with greater precision than ever before the identification of an organism or part thereof. In this chapter I made an attempt to stress that, in general, but more so for genomic authentication, the use of the variation inherent in taxa down to the lowest level of the hierarchy of classification needs to be used to achieve a high degree of correct authentication.

The use of phylogeny to interpret cross-cultural patterns in plant use and guide medicinal plant discovery: an example from Pterocarpus (Leguminosae)

BACKGROUND

The study of traditional knowledge of medicinal plants has led to discoveries that have helped combat diseases and improve healthcare. However, the development of quantitative measures that can assist our quest for new medicinal plants has not greatly advanced in recent years. Phylogenetic tools have entered many scientific fields in the last two decades to provide explanatory power, but have been overlooked in ethnomedicinal studies. Several studies show that medicinal properties are not randomly distributed in plant phylogenies, suggesting that phylogeny shapes ethnobotanical use. Nevertheless, empirical studies that explicitly combine ethnobotanical and phylogenetic information are scarce.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we borrowed tools from community ecology phylogenetics to quantify significance of phylogenetic signal in medicinal properties in plants and identify nodes on phylogenies with high bioscreening potential. To do this, we produced an ethnomedicinal review from extensive literature research and a multi-locus phylogenetic hypothesis for the pantropical genus Pterocarpus (Leguminosae: Papilionoideae). We demonstrate that species used to treat a certain conditions, such as malaria, are significantly phylogenetically clumped and we highlight nodes in the phylogeny that are significantly overabundant in species used to treat certain conditions. These cross-cultural patterns in ethnomedicinal usage in Pterocarpus are interpreted in the light of phylogenetic relationships.

CONCLUSIONS/SIGNIFICANCE

This study provides techniques that enable the application of phylogenies in bioscreening, but also sheds light on the processes that shape cross-cultural ethnomedicinal patterns. This community phylogenetic approach demonstrates that similar ethnobotanical uses can arise in parallel in different areas where related plants are available. With a vast amount of ethnomedicinal and phylogenetic information available, we predict that this field, after further refinement of the techniques, will expand into similar research areas, such as pest management or the search for bioactive plant-based compounds.

Identifying commercially relevant Echinacea species by AFLP molecular markers

The rising interest in medicinal plants has brought several species of the genus Echinacea to the attention of many scientists. Echinacea angustifolia, E. pallida, and E. purpurea are the most important for their immunological properties, well known and widely used by the native Americans. The three species are easily distinguishable on the basis of their morphological characteristics, but it would be difficult, if not impossible, to distinguish them in commercial preparations of ground, dry plant parts of E. purpurea (the most valuable species for chemotherapeutic properties) mixed with the other two species. Species-specific molecular markers could be useful to address this issue. In the present work, using fresh material collected from cultivated Echinacea spp., AFLP analysis was used to discriminate the three species and to detect species-specific DNA fragments. By using 14 primer combinations it was possible to detect a total of 994 fragments, of which 565 were polymorphic. Overall, 89 fragments were unique to E. purpurea, 32 to E. angustifolia, and 26 to E. pallida. E+CAC/M+AAT or E+CAC/M+AGC alone provided 13, 9, and 4 or 7, 5, and 5 specific fragments for E. purpurea, E. angustifolia, and E. pallida, respectively. A validation trial to confirm the results was carried out on bulked samples of 23 accessions covering most of the genetic diversity of the three species. The results are discussed in terms of practical applications in the field of popular medicine, detecting frauds, and implications for the genus Echinacea.

Relationships among genetic makeup, active ingredient content, and place of origin of the medicinal plant Gastrodia tuber

Gastrodia tuber and its component gastrodin have many pharmacological effects. The chemical fingerprints and gastrodin contents of eight Gastrodia populations were determined, and the genomic DNA polymorphism of the populations was investigated. Genetic distance coefficients among the populations were calculated using the DNA polymorphism data. A dendrogram of the genetic similarities between the populations was constructed using the genetic distance coefficients. The results indicated that the genomic DNA of Gastrodia tubers was highly polymorphic; the eight populations clustered into three major groups, and the gastrodin content varied greatly among these groups. There were obvious correlations among genetic makeup, gastrodin content, and place of origin. The ecological environments in Guizhou and Shanxi may be conducive to evolution and to gastrodin biosynthesis, and more suitable for cultivation of Gastrodia tubers. These findings may provide a scientific basis for overall genetic resource management and for the selection of locations for cultivating Gastrodia tubers.

Quantitative determination of soybean meal content in compound feeds: comparison of near-infrared spectroscopy and real-time PCR

Standard methods for determining the raw material content of compound feed are little exploited, except for the identification of meat and bone meal in feeds. In this work, near-infrared (NIR) spectroscopy and real-time polymerase chain reaction (PCR) were applied in order to establish new and fast methods for quantification of soybean meal content in compound feeds. The best prediction quality was achieved by using a model based on NIR spectroscopy (R2 = 0.9857, standard error of cross-validation 1.1065). Furthermore, a sensitive qualitative detection method by using the real-time PCR was developed (R2 = 0.976, slope -3.7599). Finally, the differences between the real-time PCR result and the NIR spectroscopy result for a given sample were also treated, and we found that the NIR spectroscopy method provided quite accurate results which approach closely those of the real-time PCR method.

Comparative Molecular and Phytochemical Study of the Tree SpeciesSantalum austrocaledonicum (Santalaceae) Distributed in the New-Caledonian Archipelago

We have tried to elucidate the origin of phytochemical variation in trees by studying concomitantly the chemical and microsatellite variations in Santalum austrocaledonicum. Eight natural populations were sampled in the New-Caledonian archipelago, a total of 157 individuals being analyzed. The main components, as revealed by gas chromatography (GC), were alpha- and beta-santalol (as in other sandalwood species), although the level of (Z)-lanceol was particularly high. Most of the chemical variation was observed within populations (83.7%). With microsatellites, the variation between populations was more pronounced (32% of the total variation). Although the chemical variation between populations was small, we investigated the effects of genetic drift and migration by comparing the chemical- and molecular-differentiation patterns. The poor congruence between neighbor-joining trees, confirmed by the non-significant Mantel test between the molecular and chemical distance matrices (R=0.26, P=0.12), showed that genetic drift and migration are not the main evolutionary forces acting on chemical differentiation between populations. We could not find any effect of soil and rainfall conditions neither. Although the impact of drift and migration cannot be discounted in rationalizing between-population differentiation, the low variation among populations could result from a stabilizing selection caused by the same phytopathogen charge across the natural range.

Comparative molecular and phytochemical investigation of Leontodon autumnalis (Asteraceae, Lactuceae) populations from Central Europe

Previous analyses of Leontodon autumnalis L. revealed the existence of two chemotypes. In the current study molecular and phytochemical methods were combined to investigate 24 Central European populations of L. autumnalis. The focus of this study was the correlation of molecular and phytochemical characters at the intraspecific level. DNA fingerprint profiles of 183 individuals were obtained by random amplified polymorphic DNA (RAPD) providing 77 molecular markers. Contents of phenolics and sesquiterpenoids of flowering heads and sub-aerial parts were quantified by HPLC-DAD analyses. HPLC results were evaluated by principal component analysis. Geographic distribution of the two detected chemotypes partially overlapped. Phylogenetic groupings displayed in an unrooted neighbor-joining tree calculated from the RAPD data matrix were correlated with the geographical origin of the plant material. However, genetic profiles neither correlated with the two chemotypes nor with the morphologically based subspecies of L. autumnalis recognized by some authors. The presented data imply that the morphotypes are of multiple origins or due to different ecological growing conditions rather than genetically determined and that phytochemical races are induced by a limited number of genetical differences, which might have occurred independently in different lineages of the L. autumnalis group.

Does domestication mimic speciation? 1. A population-genetic analysis ofHordeum spontaneumandHordeum vulgarebased on AFLP and evolutionary considerations

To answer the question whether Hordeum spontaneum K. Koch. and Hordeum vulgare L. are conspecific taxonomic entities or not”, we carried out an investigation with amplified restriction fragment length polymorphism (AFLP™) using H. vulgare cultivars, H. spontaneum from the Fertile Crescent, and material from China, primarily Xizang (Tibet), containing landraces and accessions identified morphologically as Hordeum agriocrithon Åberg. and H. spontaneum. Population genetic analyses and discriminant analyses were based on three groupings, H. vulgare, H. spontaneum, and H. agriocrithon, determined from morphology. To independently find groups, cluster analyses were carried out followed by population-genetic analyses and discriminant analyses of the clusters. The results of population-genetic analyses of morphologically based groups were not very different from those of comparable analyses of groups inferred from clustering. Based on 795 AFLP bands scored on 506 individuals, genetic diversity was 30% higher within H. spontaneum than within H. agriocrithon or H. vulgare. The variation among the three entities was 27.3% (FCT= 0.27) and among populations within the three was 40.4% (FSC= 0.56) leaving 32.3% (FST= 0.68) within populations/accessions. Three entities were clearly defined by clustering and supported by discriminant analyses, and then nomenclaturally formulated, two as species and one as an interspecific hybrid. The first, H. spontaneum, comprises populations in the Near East, the second, H. vulgare, comprises the cultivars, and the third, H. ×agriocrithon, comprises all barley landraces and hybrids from China as well as hybrids from the Near East. We discuss evolutionary perspectives of speciation and conclude that barley cultivars form a species distinct from the wild progenitor, H. spontaneum. This analysis may highlight the dilemma regarding other cultivated plants and domesticated animals, a still unresolved evolutionary–taxonomic problem.

Sequence assessment of comigrating AFLPTM bands in Echinacea -- implications for comparative biological studies

The extent of sequence identity among clones derived from monomorphic and polymorphic AFLPTM polymorphism bands was quantified. A total of 79 fragments from a monomorphic band of 273 bp and 48 fragments from a polymorphic band of 159 bp, isolated from individuals belonging to different populations, varieties, and species of Echinacea, were cloned and sequenced. The monomorphic fragments exhibited above 90% sequence identity among clones within samples. Sequence identity within variety ranged from 82.78% to 94.87% and within species from 75.82% to 98.9% and was 57.97% in the genus. The polymorphic fragments exhibited much less sequence identity. In some instances, even two clones from the same fragment were different in their size and sequence. Within sample, clone sequence identity ranged from 100% to 51.57%, within variety from 33.33% to 100% in one variety, and from 23.66% to 45% within species and was as low as 1.25% within the genus. In addition, sequences of the same size were aligned to verify the nature of their sequence dissimilarity/similarity. Within each size group, identical sequences were found across species and varieties. In general, comigrating bands cannot be considered homologous. Thus, the use of AFLPTM band data for comparative studies is appropriate only if the results emanating from such analyses are considered as approximations and are interpreted as phenotypic but not genotypic.

Analysis of diversity of natural populations and commercial lines ofEchinaceausing AFLP

An analysis of diversity of Echinacea native to North America, using amplified fragment length polymorphism (AFLP®), was carried out to complement a previously undertaken taxonomic revision of Echinacea that employed multivariate morphometrics. A total of 53 940 AFLP fragments, of which 40 455 were polymorphic, were scored on 435 individual plants from 58 populations consisting of ±10 individuals per population. The resulting polymorphism was sufficient to distinguish each plant. A monomorphic AFLP band and a polymorphic AFLP band that migrated at the same position, taken from samples of four species and eight varieties, were cloned, and multiple clones were sequenced. The polymorphic band at the same position across fragments was not identical, with identity as low as 23% compared with 50% identity of the monomorphic band, both of which were at the 100% threshold of sequence similarity. Thus, the AFLP banding profiles, irrespective of their sequence identity, were treated as phenotypes for population genetic, discriminant, and phylogenetic analyses. Variance components within populations and among populations within species were of equal magnitude, but the partitioned variation was slightly higher among varieties than among populations within varieties. Since no species-specific or variety-specific AFLP fingerprints were found, canonical discriminant analysis was conducted, resulting in support for four species but not for the varieties. Similar results were obtained with cluster and principal coordinate analyses, based on genetic distances. To achieve identification using AFLP fingerprints, various classificatory analyses were performed, followed by bootstrapping for validation. An example to identify an unknown plant at the species level with a minimum of 10 AFLP fragments, with greater than 82% overall correct classification, is provided. Phylogenetic analysis of all 435 individuals supported only Echinacea purpurea (L.) Moench and Echinacea laevigata (C.L. Boynton & Beadle) as separate entities, and only the three Echinacea atrorubens varieties and Echinacea pallida var. tennesseensis (Beadle) Binns, B.R. Baum & Arnason.Key words: Echinacea, population genetic analysis, multivariate analysis, AFLP band homologies.