Chemotypic Variation Research Articles

Population genetics of lichen-forming fungi – a review

AbstractPopulation genetics investigates the distribution of genetic variation in natural populations and the genetic differentiation among populations. Lichen-forming fungi are exciting subjects for population genetic studies due to their obligate symbiosis with a green-algal and/or cyanobacterial photobiont, and because their different reproductive strategies could influence fungal genetic structures in various ways. In this review, first, I briefly summarize the results from studies of chemotype variation in populations of lichen-forming fungi. Second, I compare and evaluate the DNA-based molecular tools available for population genetics of lichen-forming fungi. Third, I review the literature available on the genetic structure of lichen fungi to show general trends. I discuss some fascinating examples, and point out directions for future research.

The molecular basis of host plant selection in Melaleucaquinquenervia by a successful biological control agent

Melaleuca quinquenervia (Cav) S.T. Blake (broadleaf paperbark) is an Australian tree that has become a serious weed in many places around the world. Two insects Oxyops vitiosa (the melaleuca weevil), and Boreioglycaspis melaleucae (the melaleuca psyllid), which were introduced to Florida as part of a biological control programme, have been very effective in reducing survival and reproduction of this weed. There are two terpene chemotypes of M. quinquenervia ; one rich in the sesquiterpene E-nerolidol whereas the other is rich in viridiflorol. Viridiflorol is a strong feeding deterrent for the melaleuca weevil and retards larval development. The larvae therefore avoid the viridiflorol-rich chemotype, in contrast, female melaleuca psyllids prefer to oviposit on these leaves. To identify the molecular basis of these preferences, we isolated and characterised two terpene synthases from the viridiflorol-rich chemotype, both of which utilise farnesyl pyrophosphate and have the same product profile. Chemotypic variation in terpenes in M. quinquenervia is under strong genetic control and the reproductive potential of each chemotype is limited by a different insect. These insects could, therefore, be selective agents for the maintenance of chemotypic variation in M. quinquenervia.

Pentacyclic triterpenoids from the medicinal herb, Centella asiatica (L.) Urban.

Centella asiatica accumulates large quantities of pentacyclic triterpenoid saponins, collectively known as centelloids. These terpenoids include asiaticoside, centelloside, madecassoside, brahmoside, brahminoside, thankuniside, sceffoleoside, centellose, asiatic-, brahmic-, centellic- and madecassic acids. The triterpene saponins are common secondary plant metabolites and are synthesized via the isoprenoid pathway to produce a hydrophobic triterpenoid structure (aglycone) containing a hydrophilic sugar chain (glycone). The biological activity of saponins has been attributed to these characteristics. In planta, the Centella triterpenoids can be regarded as phytoanticipins due to their antimicrobial activities and protective role against attempted pathogen infections. Preparations of C. asiatica are used in traditional and alternative medicine due to the wide spectrum of pharmacological activities associated with these secondary metabolites. Here, the biosynthesis of the centelloid triterpenoids is reviewed; the range of metabolites found in C. asiatica, together with their known biological activities and the chemotype variation in the production of these metabolites due to growth conditions are summarized. These plant-derived pharmacologically active compounds have complex structures, making chemical synthesis an economically uncompetitive option. Production of secondary metabolites by cultured cells provides a particularly important benefit to manipulate and improve the production of desired compounds; thus biotechnological approaches to increase the concentrations of the metabolites are discussed.

Chemotypic variations of the essential oils of Mentha taxa collected in the Marmara region of Turkey

The genus Mentha L. (Lamiaceae) is represented by 16 taxa in the Flora of Turkey [1,2]. Eleven taxa belonging to 8 species (including hybrids) have been investigated for essential oils. The oils obtained by hydrodistillation using a Clevenger apparatus were analysed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). In our ongoing research into compositions of Mentha taxa in Turkey, we had previously reported on the mint oils of Northern Turkey [3]. In this study over 100 oil samples of the following taxa were investigated: M. pulegium, M. aquatica, M. piperita nm. citrata, M. rotundifolia, M. x dumetorum, M. x villosa-nervata, M. spicata var. spicata, M. spicata var. tomentosa, M. longifolia subsp. longifolia, M. longifolia subsp. typhoides. Chemotypic variations are discussed based on the previous and present results.

Chemical variation of Usnea longissima Ach. in the central Oregon Coast Range

The lichenized ascomycete Usnea longissima occurs in cool forests with coastal climates in Europe, Asia and North America and is threatened throughout its range. The Pacific Northwest region of North America is considered a stronghold of this species. While many studies have focused on the ecology of U. longissima, knowledge of the secondary chemistry of U. longissima is sparse for the region. The objectives of this study were to analyze collections of U. longissima for chemotypic variation using thin-layer chromatography and to examine ecological and geographic patterns of chemotype variation within the central Oregon Coast Range. Three major chemotypes were found within the study area with some additional chemotypic variation documented throughout the global range of U. longissima . The most common chemotype (chemotype 1: usnic, barbatic and norbarbatic acids) accounted for 70.9% of samples, with the other 2 chemotypes accounting for 24% (chemotype 2: usnic and diffractaic acids) and 4.2% (chemotype 3: usnic and a minor unknown acid) of samples. Chemotype 2 generally occurred farther west and at higher elevations than chemotype 1. Different chemotypes may deserve protection to ensure the persistence and genetic variation of U. longissima throughout its current range.

Chemotypic variation of essential oils in the medicinal plant, Anemopsis californica

Anemopsis californica (Saururaceae) commonly called yerba mansa, is an important medicinal plant in many deserts in the southwestern region of North America. Populations of A. californica, collected throughout New Mexico, were examined for chemical variability in roots and rhizomes for select monocyclic (cymene, limonene, piperitone and thymol) and bicyclic (α-pinene, 1,8-cineole and myrtenol) monoterpenoid and phenylpropanoid (methyleugenol, isoeugenol and elemicin) derived essential oil components. Three distinct chemotypes were detected using a hierarchical clustering analysis on the concentration of 10 different analytes in three individuals from each of 17 populations. One chemotype was characterized by high elemicin concentrations, a second chemotype by high methyleugenol concentrations and the third by high piperitone and thymol concentrations. Steam distilled oil was used to screen for anticancer bioactivity. A. californica root oils demonstrated anti-proliferative activity against AN3CA and HeLa cells in vitro but no activity against lung, breast, prostate or colon cancer cells. The IC 50 values for the root oil were 0.056% and 0.052% (v/v) for the AN3CA and HeLa cells, respectively.

Association between chemical and genetic variation of Vitex rotundifolia populations from different locations in China: its implication for quality control of medicinal plants

Vitex rotundifolia is a widely distributed plant species that has been extensively used in traditional Chinese medicine. Its fruits, Fructus Viticis, are recorded as Manjingzi in the Pharmacopoeia of the People's Republic of China. For the effective quality control of its medicinal values reflected by chemical variation patterns, in addition to the relationship with genetic diversity, analyses based on high-performance liquid chromatographic (HPLC) fingerprinting and inter simple sequence repeat (ISSR) molecular markers were carried out, involving 14 V. rotundifolia populations from different locations in China. The HPLC data showed considerable variation of chemical constituents among the V. rotundifolia populations. The hierarchical clustering analysis further revealed four major groups based on their chemotype variation. Abundant genetic diversity was detected among the V. rotundifolia populations that also were clustered into four groups based on their ISSR data. It is important to point out that the genetic variation pattern revealed by molecular markers was closely associated with that indicated by chemical constitutes in the fruits of V. rotundifolia. This finding provides a solid basis for the combined use of chemical and genetic fingerprints in efficiently evaluating qualities and choosing favourable chemotypes with appropriate pharmacological properties of V. rotundifolia, in addition to establishing good agricultural practices for medicinal plants.

Assessment and Implications of Intraspecific and Phenological Variability in Monoterpenes of Scots Pine (Pinus sylvestris) Foliage

Scots pine populations contain individuals with widely differing amounts and composition of monoterpenes and exist as one of two chemotypes: with or without delta3-carene. We investigated the significance for ecological studies of two types of variation in monoterpenes: (1) the inherent variability in the concentration of monoterpenes or their relative amounts in needles of seedlings, saplings, and mature trees; and (2) phenological variation in developing needles. The relative composition of needle monoterpenes in 5-year-old saplings changed during the needle development period until the final composition was reached upon needle maturity. Changes in composition depended on chemotype. Needles of the "no-delta3-carene" chemotype had higher absolute concentrations of alpha-pinene, beta-pinene, camphene, and total monoterpenes than "delta3-carene" chemotype. For the "delta3-carene" chemotype, the relative concentration of delta3-carene during the needle growing season and immediately after emergence of seedlings was higher compared to that reached at needle maturity. Repeated removal of single needles (at weekly intervals during growth) from 5-year-old saplings did not influence the composition of monoterpenes. Within a natural Scots pine dominated woodland, 18% of mature Scots pines (N=574) belonged to the "no-delta3-carene" chemotype. Chemotypic variation within populations means that the statistical power with which differences in monoterpene concentrations can be detected is lower when sampling from the whole population compared to sampling within chemotypes. Reduction of this background variation and accounting for chiral variation if present, would significantly aid efficiency, interpretation, and understanding of processes in chemical and ecological research. One method for achieving this is the screening of plants for chemotypes before the establishment of experiments or field sampling regimes. We present a summary of suitable analytical methods for needle tissue that facilitates this prior screening.

Chemical composition of flavonoids and styrylpyrones and the genetic variability of isozymes in natural populations of Cryptocarya mandioccana Meisner (Lauraceae)

The chemical composition of leaves of 57 trees of Cryptocarya mandioccana from three populations of southeastern Brazil was investigated through HPLC, assaying six flavonoids, seven styrylpyrones, and seven unidentified compounds. From 51 of the former trees, genotypes were obtained from 40 polymorphic loci of 19 isozymes. Cluster analyses of the phytochemical and genetical variation revealed that trees exhibited four chemotypes and five clusters from isozymes, respectively. Discriminant analyses from selected variables of the isozymic and chemical data sets were performed, respectively, in relation to the four chemotypes and the five isozyme clusters. The classification of individuals presented respective error estimates of 9.16% and 13.57%, indicating that the genetic data could explain the clusters from chemotypes and vice versa at acceptable error levels. Linear regressions with Dummy variable showed significant association of locus Skdh-2 with quercetin-3- O-β- d-glucopyranoside and cryptofolione, indicating that its alleles would be responsible for the chemotype variation between individuals.

(390) Chemotype Variation among Black Cohosh Populations

Black cohosh [Actaea racemosa L.; syn. Cimicifuga racemosa (L.) Nutt.] is a medicinal plant native to America and the woodlands of eastern North America. The roots and rhizomes of black cohosh, used by Native Americans to ease childbirth and treat menstrual cramps, rheumatism, headaches, coughs, asthma, and snakebites, are currently popular as an herbal remedy in the United States and Europe for the relief of discomfort associated with menopause. To determine chemical variation among populations of this perennial plant, root samples from 33 locations within the natural range of the species, ranging from Massachusetts to South Carolina and west to Missouri and Tennessee, were collected and chemically analyzed by HPLC-PDA using a C-18 reversed phase column (Phenomenex) for separation of the chemical constituents. The constituents were identified by comparison with commercial standards, including actein, methyl-beta-arabinopyranoside, caffeic acid, cimicifugoside, cimicifugoside H1, cimiracemoside A, 26 deoxyactein, ferulic acid, isoferulic acid, kaempferol, formononetin, and others. Chemically, an extract of the root and rhizome is known to contain at least three major natural product groups: cycloartenal-type triterpenes, phenolics, and flavonoids. Chemical constituents, especially formononetin, varied among the populations.

Essential Oils of Mentha Species from Northern Turkey

Out of 8 species and 15 taxa (including hybrids) of Mentha existing in the flora of Turkey, 8 taxa belonging to 6 species were investigated for essential oils. Of 272 samples collected from 181 stations in northern Turkey, 85 were subjected to water distillation and GC/MS analysis. The taxa investigated were as follows: Mentha pulegium, M. suaveolens, M. aquatica, M. spicata var. spicata, M. longifolia ssp. longifolia, M. longifolia ssp. typhoides, M. x dumetorium, M. x villosa-nervata. The authors discuss chemotypic variations based on the results of essential oil analysis, soil analysis and chromosome counts.

Genetic control of kavalactone chemotypes in Piper methysticum cultivars

The chemical composition of 121 cultivars of Piper methysticum originating from 51 Pacific islands, were investigated using HPLC. The results obtained for six major kavalactones (demethoxy-yangonin, dihydrokavain, yangonin, kavain, dihydromethysticin and methysticin) were submitted to cluster analysis and six distinct chemotypes were identified. Three field experiments demonstrated that chemotypes are not affected by environmental factors but are controlled genetically. Analysis of the isozyme variation for eight enzyme systems, revealed that these cultivars exhibited only three zymotypes. These are so similar that the differences in malate dihydrogenase and diaphorase could be explained as mutations. Few genes are thought to be responsible for the chemotype variation between cultivated clones. Because all cultivars are decaploids and sterile, it is suggested that mutagenesis might be used to induce genetic variability and to improve cultivar chemotypes.

Chemotypic Variation in Indian Spearmint*

Our investigation has substantiated that Indian spearmint exists in the form of three chemotypes, the common one being rich in limonene and carvone while the other two being rich in piperitenone epoxide

POPULATION STUDIES AMONG SONORAN DESERT SPECIES OF PARMELIA SUBG. XANTHOPARMELIA (PARMELIACEAE)

Species of Parmelia subg. Xanthoparmelia exhibit partial morphological convergence in a region of sympatry in the northern portion of the Sonoran Desert. Within the isidiate morph of the population, chemotypic variation is present. These chemotypes exhibit habitat selection among different rock substrates within a region of relatively uniform climate and topography. Partial habitat selection is also demonstrable for the chemotypes of the nonisidiate morph in the population. Other morphological characters are useful in segregating portions of the isidiate and nonisidiate morphs into chemically distinct groups that have previously been assumed to represent only chemotypic variation.

Population Studies Among Sonoran Desert Species of Parmelia subg. Xanthoparmelia (Parmeliaceae)

Species of Parmelia subg. Xanthoparmelia exhibit partial morphological convergence in a region of sympatry in the northern portion of the Sonoran Desert. Within the isidiate morph of the population, chemotypic variation is present. These chemotypes exhibit habitat selection among different rock substrates within a region of relatively uniform climate and topography. Partial habitat selection is also demonstrable for the chemotypes of the nonisidiate morph in the population. Other morphological characters are useful in segregating portions of the isidiate and nonisidiate morphs into chemically distinct groups that have previously been assumed to represent only chemotypic variation.