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PubMed2004

Polyphyletic origin of pyrrolizidine alkaloids within the Asteraceae. Evidence from differential tissue expression of homospermidine synthase.

The evolution of pathways within plant secondary metabolism has been studied by using the pyrrolizidine alkaloids (PAs) as a model system. PAs are constitutively produced by plants as a defense against herbivores. The occurrence of PAs is restricted to certain unrelated families within the angiosperms. Homospermidine synthase (HSS), the first specific enzyme in the biosynthesis of the necine base moiety of PAs, was originally recruited from deoxyhypusine synthase, an enzyme involved in the posttranslational activation of the eukaryotic initiation factor 5A. Recently, this gene recruitment has been shown to have occurred several times independently within the angiosperms and even twice within the Asteraceae. Here, we demonstrate that, within these two PA-producing tribes of the Asteraceae, namely Senecioneae and Eupatorieae, HSS is expressed differently despite catalyzing the same step in PA biosynthesis. Within Eupatorium cannabinum, HSS is expressed uniformly in all cells of the root cortex parenchyma, but not within the endodermis and exodermis. Within Senecio vernalis, HSS expression has been previously identified in groups of specialized cells of the endodermis and the adjacent root cortex parenchyma. This expression pattern was confirmed for Senecio jacobaea as well. Furthermore, the expression of HSS in E. cannabinum is dependent on the development of the plant, suggesting a close linkage to plant growth.

Alkyl and Aryl Transferases↗
PubMed2005

Maternal effects and heterosis influence the fitness of plant hybrids.

Here we tested two possible nonexclusive explanations for the maintenance of a hybrid swarm between Senecio jacobaea and Senecio aquaticus; first, that genotype-by-environment interactions involving water and nutrient clines are involved in hybrid fitness, and second, heterosis in early hybrid generations may provide an initial hybrid advantage that contributes to hybrid persistence. In three climate chamber studies, fitness and root growth were measured for parental species and natural and artificial F1 hybrids, in order to determine whether hybrids occur in habitats where they are more fit than parental species. Natural hybrids, which are generally back-crossed to S. jacobaea, always equaled S. jacobaea in growth characteristics. Maternal effects played a role in the fitness of F1 hybrids, with offspring from S. jacobaea mothers exhibiting higher fitness than those from S. aquaticus mothers, and compared with parental species and natural hybrids. Natural hybrids are not distributed in zones where they are most fit with respect to nutrient and water regimes. Superior fitness of early generation hybrids may contribute to hybrid swarm stability.

Biomass↗
PubMed2002

Toxic pyrrolyzidine alkaloids from three mongolian plants. a possible risk for cattle poisoning.

Ten pyrrolizidine alkaloids (PA) were isolated from Senecio ambraceus, Senecio arcticus, and Nonea pulla growing on Mongolian pastures and meadows. Because of the contained toxic PA, these plants are suspected of causing cattle poisoning, which is reported in the literature and also in personal reports from local farmers and herdsmen. The structures of the PA were elucidated using spectroscopical methods. S. ambraceus contains the toxic PA senecionine, seneciphylline, and otosenine. In S. arcticus, senecionine can be found too, besides the non-toxic PA platyphylline, neoplatyphylline, and acetylplatyphylline. Nonea pulla is shown to contain the 0-7 isomers lycopsamine and intermedine as well as their 0-7-acetylderivatives. Besides the first mentioned acetylplatyphylline, all PA were already described in the literature.

Animals↗
PubMed2000

A phylogeny of Packera (Senecioneae; asteraceae) based on internal transcribed spacer region sequence data and a broad sampling of outgroups.

A phylogeny of Packera is presented based on sequence data from the internal transcribed spacer region of nuclear ribosomal DNA of 26 species (28 populations) of Packera and 23 outgroup taxa, including representatives of all three subtribes of the Senecioneae. The results support a Mexican origin for Packera, with its closest relatives found among Old World taxa in the subtribe Senecioninae, such as Senecio jacobaea and Pericallis. Packera species from the west coast of the United States, previously included in the section Bolanderi of Greenman, are part of a basal assemblage including species of Greenman's Mexican section Sanguisorboidei. The rest of Packera separates into two sister groups, one containing species from the Arizona-New Mexico region and the other containing more geographically diverse taxa. Among the outgroups, New World Senecio species are monophyletic and two Tussilaginoid assemblages are strongly supported; the Tephroseroid group (Tephroseris and Sinosenecio) plus Petasites combine with the Luina complex to form a clade of north temperate taxa, and the four Mexican genera (Psacalium, Robinsonecio, Barkleyanthus, and Pittocaulon) form a monophyletic group.

Asteraceae↗
PubMed1983

An evaluation of acetone extracts from six plants in the Ames mutagenicity test.

Acetone extracts from six plants were evaluated for mutagenic activity with the Salmonella/mammalian-microsome mutagenicity test (Ames) utilizing tester strains TA98 and TA100 and in the presence and absence of induced rat liver microsomes. Extracts from alfalfa (Medicago sativa), lettuce (Lactuca sativa) and thread-leaf groundsel (Senecio longilobus) produced only negative responses. Comfrey (Symphytum officinale) and tansy ragwort (Senecio jacobaea) extracts produced toxic responses that were abolished in the presence of the microsomal bioactivation system. Bracken (Pteridium aquilinum) and tansy ragwort extracts produced positive responses following bioactivation with the liver microsomal system. The results suggest that the Ames mutagenicity test may be of some value in initial evaluations for potential toxic effects of plants consumed by animals and man.

Acetone↗
PubMed2001

Development of enzyme-linked immunosorbent assays for the hepatotoxic alkaloids riddelliine and riddelliine N-oxide.

Pyrrolizidine alkaloid-containing plants are widely distributed throughout the world and are particularly common in the genus Senecio. The structural types and concentrations of the alkaloids vary among plant species. In addition, within a species of plant, concentrations vary with environment and location. Many pyrrolizidine alkaloids are toxic and cause poisoning in livestock and in humans. Rapid, sensitive, and specific diagnostic techniques are needed to identify poisoned animals and to determine the particular plants and conditions under which livestock are likely to be poisoned. In this study, two competitive inhibition enzyme-linked immunosorbent assays for riddelliine, riddelliine N-oxide, and other closely related pyrrolizidine alkaloids were developed using polyclonal antibodies. One assay is class specific toward the free base forms of the pyrrolizidine alkaloids; the other assay showed cross-reactivity to both the free base and N-oxide forms of the alkaloids. The assay with the lowest limit of detection had an I(50) of 803.9 pg with a limit of detection of 47.5 pg for riddelliine. Spike and recovery studies for riddelliine in bovine blood ranged from 45 to 74%. The assay that showed cross-reactivity between the N-oxide and free base forms of the pyrrolizidine alkaloids allowed estimation of the total pyrrolizidine alkaloid content in Senecio riddellii in admixture with alfalfa. These findings suggest that these techniques will be excellent tools to diagnose poisoned animals and identify highly toxic plants.

Animals↗
PubMed2002

Development and optimization of methods for using sex pheromone for monitoring the mealybug Planococcus ficus (Homoptera: Pseudococcidae) in California vineyards.

The sex pheromone of the vine mealybug Planococcus ficus Signoret has been identified as a single component, lavandulyl senecioate. Racemic lavandulyl senecioate was as attractive to male mealybugs as the insect-produced (S)-enantiomer, indicating that the unnatural enantiomer is not inhibitory. Lavandulol, which also was found in extracts from virgin females, antagonized attraction of males at higher doses. Rubber septum lures loaded with 10- to 1,000-microg doses of the pheromone were equally attractive, and lures loaded with 100 microg of racemic pheromone remained attractive for at least 12 wk under field conditions. Delta traps were more effective than double-sided sticky cards and minimized captures of nontarget insects. Pheromone-baited traps had an effective range of at least 50 m. Comparison of visual sampling methods and sampling of males with pheromone-baited traps revealed that trap catches were significantly correlated with the results from visual sampling methods, and with economic damage.

Alkenes↗
PubMed2004

Conformational evaluation and detailed 1H and 13C NMR assignments of eremophilanolides.

Extensive application of 1D and 2D NMR methodology, combined with molecular modeling, allowed the complete 1H and 13C NMR assignments of eremophilanolides from Senecio toluccanus. Comparison of the experimental 1H, 1H coupling constant values with those generated employing a generalized Karplus-type relationship, using dihedral angles extracted from MMX and DFT calculations, revealed that the epoxidized eremophilanolides 1 and 2 show conformational rigidity at room temperature, whereas molecules 3-6, containing an isolated double bond, are conformationally mobile.

Carbon Isotopes↗
PubMedDate not supplied

Evaporative light scattering detection of pyrrolizidine alkaloids.

A reverse-phase high-performance liquid chromatography method utilizing evaporative light scattering detection (ELSD) has been developed for the simultaneous detection of hepatotoxic pyrrolizidine alkaloids with and without chromophores, namely, riddelliine, riddelliine N-oxide, senecionine, senecionine N-oxide, seneciphylline, retrorsine, integerrimine, lasiocarpine and heliotrine. Pyrrolizidine alkaloids were detected in five plant extracts (Senecio spartioides, S. douglasii var. longilobus, S. jacobaea, S. intergerrimus var. exaltatus and Symphytum officinale). The detection of heliotrine (which does not contain a chromophore) was much improved by ELSD compared with photodiode array detection.

Chromatography, High Pressure Liquid↗
PubMed2005

Relative importance of fertiliser addition to plants and exclusion of predators for aphid growth in the field.

Herbivore dynamics and community structure are influenced both by plant quality and the actions of natural enemies. A factorial experiment manipulating both higher and lower trophic levels was designed to explore the determinants of colony growth of the aphid Aphis jacobaeae, a specialist herbivore on ragwort Senecio jacobaea. Potential plant quality was manipulated by regular addition of NPK-fertiliser and predator pressure was reduced by interception traps; the experiment was carried out at two sites. The size and persistence of aphid colonies were measured. Fertiliser addition affected plant growth in only one site, but never had a measurable effect on aphid colony growth. In both habitats the action of insect predators dominated, imposing strong and negative effects on aphid colony performance. Ants were left unmanipulated in both sites and their performance on the aphid colonies did not significantly differ between sites or between treatments. Our results suggest that, at least for aphid herbivores on S. jacobaea, the action of generalist insect predators appears to be the dominant factor affecting colony performance and can under certain conditions even improve plant productivity.

Analysis of Variance↗
PubMed2003

Stomatal conductance in a tropical xerophilous shrubland at a lava substratum.

Diurnal variation in leaf stomatal conductance (gs) of three xerophilous species (Buddleia cordata, Senecio praecox and Dodonaea viscosa) was measured over a 10-month period during the dry and wet seasons in a shrubland that is developing in a lava substratum in Mexico. Averaged stomatal conductances were 147 and 60.2 (B. cordata), 145 and 24.8 (D. viscosa) and 142.8 and 14.1 mmol m(-2) s(-1) (S. praecox) during the wet and dry season respectively. Leaf water potential (Psi) varied in a range of -0.6 to -1.2 (S. praecox), -0.6 to -1.8 (B. cordata) and -0.9 to -3.4 MPa (D. viscosa) during the same measurement periods. Stomata were more sensitive to changes in irradiance, air temperature and leaf-air vapour pressure difference in the rainy season than the dry season. Although stomatal responses to Psi were difficult to distinguish in any season (dry or rainy), data for the entire period of measurement showed a positive correlation, stomata tending to open as Psi increased, but there is strong evidence of isohydric behaviour in S. praecox and B. cordata. A multiplicative model relating gs to environmental variables and to Psi accounted for 79%-83% of the variation of gs in three sites (pooled data); however, the performance of the model was poorer (60%-76%) for individual species from other sites not included in the pooled data.

Adaptation, Physiological↗
PubMed1984

Effect of seneciphylline and senecionine on hepatic drug metabolizing enzymes in rats.

The effect of oral administration of the pyrrolizidine alkaloids, seneciphylline and senecionine, from Senecio vulgaris (Compositae) on activities of hepatic epoxide hydrase, glutathione-S-transferase, aminopyrine-N-demethylase and arylhydrocarbon hydroxylase (AHH) was investigated in microsomes of young male albino rats. Seneciphylline significantly increased the activities of epoxide hydrase and glutathione-S-transferase but caused reduction of cytochrome P-450 and related monooxygenase activities. Senecionine failed to stimulate epoxide hydrase while it diminished the activities of glutathione-S-transferase, aminopyrine demethylase and AHH. Seneciphylline and senecionine could not produce any prominent in vitro effect on the hepatic drug metabolizing enzymes under study, except slight stimulation of epoxide hydrase activity by both the alkaloids and slight reduction of aminopyrine demethylase activity by senecionine.

Aminopyrine N-Demethylase↗
PubMed2003

Insecticides in Chinese medicinal plants: survey leading to jacaranone, a neurotoxicant and glutathione-reactive quinol.

Sixty-two plant species from central China were purported to have insecticidal activity. Adult house fly (Musca domestica) toxicity assays were used to identify the two most active plants and guide the chromatographic isolation of the insecticidal components. The active ingredient of Senecio palmatusPall. (Asteraceae) was characterized as methyl (1-hydroxy-4-oxocyclohexa-2,5-dien-1-yl)acetate (jacaranone) (1), previously known to have insect antifeedant activity. Mono- and bisglutathione (GSH) adducts are formed on incubation of 1 with GSH and rat liver GSH S-transferase. The toxic action of 1 in mice (intraperitoneal LD(50) = 150-200 mg/kg) is associated with both neurological signs and GSH depletion in liver 90 min after treatment. Paeonia suffruticosa var. papaveracea (Andr.) Kerner (Paeoniaceae) was the other active plant found here to have 2'-hydroxy-4'-methoxyacetophenone (paeonol) (2) as an insecticidal ingredient in the root and in one case, for the whole plant, contaminated with S-tert-butylthiomethyl O,O-diethyl phosphorodithioate (terbufos) (3), a synthetic anticholinesterase insecticide.

Animals↗
PubMed2002

Does natural selection promote population divergence? A comparative analysis of population structure using amplified fragment length polymorphism markers and quantitative traits.

Divergent natural selection is considered an important force in plant evolution leading to phenotypic differentiation between populations exploiting different environments. Extending an earlier greenhouse study of population differentiation in the selfing annual plant Senecio vulgaris, we estimated the degree of population divergence in several quantitative traits related to growth and life history and compared these estimates with those based on presumably neutral molecular markers (amplified fragment length polymorphisms; AFLPs). This approach allowed us to disentangle the effects of divergent selection from that of other evolutionary forces (e.g. genetic drift). Five populations were examined from each of two habitat types (ruderal and agricultural habitats). We found a high proportion of total genetic variance to be among populations, both for AFLP markers (phiST = 0.49) and for quantitative traits (range of QST: 0.26-0.77). There was a strong correlation between molecular and quantitative genetic differentiation between pairs of populations (Mantel's r = 0.59). However, estimates of population differentiation in several quantitative traits exceeded the neutral expectation (estimated from AFLP data), suggesting that divergent selection contributed to phenotypic differentiation, especially between populations from ruderal and agricultural habitats. Estimates of within-population variation in AFLP markers and quantitative genetic were poorly correlated, indicating that molecular marker data may be of limited value to predict the evolutionary potential of populations of S. vulgaris.

DNA, Plant↗
PubMed1999

Homospermidine synthase, the first pathway-specific enzyme of pyrrolizidine alkaloid biosynthesis, evolved from deoxyhypusine synthase.

Pyrrolizidine alkaloids are preformed plant defense compounds with sporadic phylogenetic distribution. They are thought to have evolved in response to the selective pressure of herbivory. The first pathway-specific intermediate of these alkaloids is the rare polyamine homospermidine, which is synthesized by homospermidine synthase (HSS). The HSS gene from Senecio vernalis was cloned and shown to be derived from the deoxyhypusine synthase (DHS) gene, which is highly conserved among all eukaryotes and archaebacteria. DHS catalyzes the first step in the activation of translation initiation factor 5A (eIF5A), which is essential for eukaryotic cell proliferation and which acts as a cofactor of the HIV-1 Rev regulatory protein. Sequence comparison provides direct evidence for the evolutionary recruitment of an essential gene of primary metabolism (DHS) for the origin of the committing step (HSS) in the biosynthesis of pyrrolizidine alkaloids.

Alkyl and Aryl Transferases↗
PubMed2003

Argentinian plant extracts with relaxant effect on the smooth muscle of the corpus cavernosum of guinea pig.

Extracts of different polarity from Baccharis trimera, Haplopappus rigidus Huperzia saururus, Maytenus ilicifolia, Satureja parvifolia and Senecio eriophyton were tested for their relaxant activity on smooth muscle using L-phenylephrine precontracted strips of corpus cavernosum obtained from Guinea pigs. Highly significant and dose dependent results were obtained with the dichloromethane extracts of H. saururus (87% of relaxation at the dose of 10 mg/ml), S. parvifolia (95% of relaxation at 2.5 mg/ml) and S. eriophyton (94% of relaxation at 5 mg/ml). Similar effects were observed with the methanol extracts of H. saururus (88% of relaxation at 10 mg/ml) and S. parvifolia (84% of relaxation at 10 mg/ml). These results were comparable to those obtained with the dichloromethane and methanol extracts of the well known Mexican species Turnera diffusa. Moreover, the aqueous extract of H. rigidus and the aqueous and methanol extracts of S. eriophyton were highly effective in a dose dependent manner (more than 90% of relaxation at the dose of 10 mg/ml). Significant results, but with a lower overall relaxant activity (about 70% of relaxation at 10 mg/ml), could also be obtained with the aqueous extract of S. parvifolia and with the dichlormethane and methanol extracts of B. trimera and M. ilicifolia. The positive controls with Sildenafil citrate at doses ranging from 0.35 to 35 microg/ml yielded moderate effects (up to 46% of relaxation at 35 microg/ml). The effects observed in the present study seem to validate the folk medicinal use of the tested plants and open new ways in the search for natural products with vasodilatory effects.

Animals↗
PubMed2004

Disentangling food quality from resistance against parasitoids: diet choice by a generalist caterpillar.

The relative importance of food quality and enemy-reduced space is a central but unresolved issue in the evolutionary ecology of host use by phytophagous insects. Indeed, a practical obstacle to experimentally disentangling the functional roles of these factors is the host specificity of insect herbivores, particularly toxic plant specialists. In this study, we employ a toxic plant generalist to uniquely disentangle these alternative explanations. We experimentally demonstrate that the value of enemy-reduced space supersedes that of food quality in determining the diet and host preference of the polyphagous woolly bear caterpillar Grammia geneura (Lepidoptera: Arctiidae). Caterpillars sacrificed superior growth efficiency in choosing a mixed diet that included toxic host plants and provided resistance against parasitoids. The resistance of individual caterpillars was associated with the relative amount of defensive plants eaten as well as with the sequestration of pyrrolizidine alkaloids from one such plant (Senecio longilobus).

Ambrosia↗