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Molecular characterization of a seed transmitted clavicipitaceous fungus occurring on dicotyledoneous plants (Convolvulaceae).

Ergoline alkaloids (syn. ergot alkaloids) are constituents of clavicipitaceous fungi (Ascomycota) and of one particular dicotyledonous plant family, the Convolvulaceae. While the biology of fungal ergoline alkaloids is rather well understood, the evolutionary and biosynthetic origin of ergoline alkaloids within the family Convolvulaceae is unknown. To investigate the possible origin of ergoline alkaloids from a plant-associated fungus, 12 endophytic fungi and one epibiotic fungus were isolated from an ergoline alkaloid-containing Convolvulaceae plant, Ipomoea asarifolia Roem. & Schult. Phylogenetic trees constructed from 18S rDNA genes as well as internal transcribed spacer (ITS) revealed that the epibiotic fungus belongs to the family Clavicipitaceae (Ascomycota) whereas none of the endophytic fungi does. In vitro and in vivo cultivation on intact plants gave no evidence that the endophytic fungi are responsible for the accumulation of ergoline alkaloids in I. asarifolia whereas the epibiotic clavicipitaceous fungus very likely is equipped with the genetic material to synthesize these compounds. This fungus resisted in vitro and in vivo cultivation and is seed transmitted. Several observations strongly indicate that this plant-associated fungus and its hitherto unidentified relatives occurring on different Convolvulaceae plants are responsible for the isolated occurrence of ergoline alkaloids in Convolvulaceae. This is the first report of an ergot alkaloid producing clavicipitaceous fungus associated with a dicotyledonous plant.

Ascomycota↗

Testing the phylogenetic position of a parasitic plant (Cuscuta, Convolvulaceae, asteridae): Bayesian inference and the parametric bootstrap on data drawn from three genomes.

Previous findings on structural rearrangements in the chloroplast genome of Cuscuta (dodder), the only parasitic genus in the morning-glory family, Convolvulaceae, were attributed to its parasitic life style, but without proper comparison to related nonparasitic members of the family. Before molecular evolutionary questions regarding genome evolution can be answered, the phylogenetic problems within the family need to be resolved. However, the phylogenetic position of parasitic angiosperms and their precise relationship to nonparasitic relatives are difficult to infer. Problems are encountered with both morphological and molecular evidence. Molecular data have been used in numerous studies to elucidate relationships of parasitic taxa, despite accelerated rates of sequence evolution. To address the question of the position of the genus Cuscuta within Convolvulaceae, we generated a new molecular data set consisting of mitochondrial (atpA) and nuclear (RPB2) genes, and analyzed these data together with an existing chloroplast data matrix (rbcL, atpB, trnL-F, and psbE-J), to which an additional chloroplast gene (rpl2) was added. This data set was analyzed with an array of phylogenetic methods, including Bayesian analysis, maximum likelihood, and maximum parsimony. Further exploration of data was done by using methods of phylogeny hypothesis testing. At least two nonparasitic lineages are shown to diverge within the Convolvulaceae before Cuscuta. However, the exact sister group of Cuscuta could not be ascertained, even though many alternatives were rejected with confidence. Caution is therefore warranted when interpreting the causes of molecular evolution in Cuscuta. Detailed comparisons with nonparasitic Convolvulaceae are necessary before firm conclusions can be reached regarding the effects of the parasitic mode of life on patterns of molecular evolution in Cuscuta.

Base Sequence↗

Down the slippery slope: plastid genome evolution in Convolvulaceae.

Cuscuta (dodder) is the only parasitic genus found in Convolvulaceae (morning-glory family). We used long PCR approach to obtain large portions of plastid genome sequence from Cuscuta sandwichiana in order to determine the size, structure, gene content, and synteny in the plastid genome of this Cuscuta species belonging to the poorly investigated holoparasitic subgenus Grammica. These new sequences are compared with the tobacco chloroplast genome, and, where data are available, with corresponding regions from taxa in the other Cuscuta subgenera. When all known plastid genome structural rearrangements in parasitic and nonparasitic Convolvulaceae are considered in a molecular phylogenetic framework, three categories of rearrangements in Cuscuta are revealed: plesiomorphic, autapomorphic, and synapomorphic. Many of the changes in Cuscuta, previously attributed to its parasitic mode of life, are better explained either as plesiomorphic conditions within the family, i.e., conditions shared with the rest of the Convolvulaceae, or, in most cases, autapomorphies of particular Cuscuta taxa, not shared with the rest of the species in the genus. The synapomorphic rearrangements are most likely to correlate with the parasitic lifestyle, because they represent changes found in Cuscuta exclusively. However, it appears that most of the affected regions, belonging to all of these three categories, have probably no function (e.g., introns) or are of unknown function (a number of open reading frames, the function of which, if any, has yet to be discovered).

Base Sequence↗

Elimination of ergoline alkaloids following treatment of Ipomoea asarifolia (Convolvulaceae) with fungicides.

Ergoline alkaloids are constituents of Clavicipitaceous fungi living on Poaceae plants. Ergoline alkaloids as well as volatile oil are also present in Ipomoea asarifolia Roem. & Schult (Convolvulaceae). Treatment of this plant with two fungicides (Folicur, Pronto Plus) eliminates the ergoline alkaloids but not the volatile oil. Elimination of ergoline alkaloids occurs concomitantly with loss of fungal hyphae associated with secretory glands on the upper leaf surface of the Ipomoea plant. Our observations suggest that accumulation of ergoline alkaloids in the Convolvulaceae may depend on the presence of a plant-associated fungus.

Ergolines↗

Calystegines as chemotaxonomic markers in the Convolvulaceae.

An extended GC-MS study of 129 convolvulaceous species belonging to 29 genera (all 12 tribes) including the results of a previous survey (65 spp.) revealed the occurrence of one to six polyhydroxy alkaloids of the nortropane type (calystegines) in 62 species belonging to 22 genera of all tribes except the unique parasitic Cuscuteae. The large genus Ipomoea turned out to comprise calystegine-positive species in at least eight out of ten sections checked. The number of the calystegines used as reference compounds has been increased from seven (previous survey) to 11 (present study). Furthermore, the results concerning these additional four alkaloids could also be completed for all species of the previous survey. The plant material (epigeal vegetative parts and/or roots, flowers, fruits/seeds) was obtained from collections in the wild from a wide range of tropical, subtropical, and temperate locations of all continents as well as from cultivation in the greenhouse. All plant organs turned out to be potential locations for the occurrence of these metabolites though they are detectable often only in certain organs of a given species. Three genera (Cuscuta, Operculina, Polymeria) might have lost the ability to synthesize these plesiomorphic characters in the course of the evolution since the examination of several different organs and/or provenances of five species each failed to show calystegines as constituents. Nevertheless, the present data clearly demonstrate that the occurrence of calystegines is an almost consistent trait in the Convolvulaceae in principle, from basal to most advanced tribes.

Alkaloids↗

Re-assignment of the Affinities of the Fossil Pollen Type Tricolpites trioblatus Mildenhall and Pocknall to Wilsonia (Convolvulaceae) and a reassessment of the ecological interpretations.

Tricolpites trioblatus Mildenhall and Pocknall was described from Upper Miocene-Pliocene sediments of New Zealand and attributed to the Hebe complex (Scrophulariaceae), which is common in the New Zealand vegetation, especially in montane and subalpine habitats. Pollen in Miocene-Pliocene sediments in central Australia is identified with T. trioblatus, and the depositional situations included shallow lakes, with fresh or brackish waters, sometimes becoming saline. The affinities of T. trioblatus are re-examined in the light of these disparate environments in Australia and New Zealand. It has been found that all the fossil grains examined are more comparable to pollen of Wilsonia, and perhaps Cressa (Convolvulaceae), than to those of the Hebe complex. Wilsonia and Cressa are found in salt marshes, hence affinities with them are ecologically more credible for central Australia. T. trioblatus is found in late Eocene sediments deposited under episodic marine transgressions; an environment likely to stimulate the evolution of new species tolerant to saline conditions.

Journal Article↗

Alkaloidal components in the poisonous plant, Ipomoea carnea (Convolvulaceae).

Natural intoxication of livestock by the ingestion of Ipomoea carnea (Convolvulaceae) sometimes occurs in tropical regions of the world. Polyhydroxylated alkaloids were isolated from the leaves, flowers, and seeds of the poisonous plant and characterized. Chromatographic separation of the leaf extract resulted in the isolation of swainsonine (1), 2-epi-lentiginosine (2), calystegines B(1) (3), B(2) (4), B(3) (5), and C(1) (6), and N-methyl-trans-4-hydroxy-l-proline (7). The contents of 1 in the fresh leaves and flowers were 0.0029 and 0.0028%, respectively, whereas the contents of 1, 3, and 4 in the seeds were approximately 10 times higher than those in the leaves and flowers. Alkaloids 3, 4, and 6 showed a potent inhibitory activity toward rat lysosomal beta-glucosidase, with IC(50) values of 2.1, 0.75, and 0.84 microM, respectively, and alkaloid 5 was a moderate inhibitor of alpha- and beta-mannosidases. Although alkaloid 1 is known as a powerful inhibitor of lysosomal alpha-mannosidase (IC(50) = 0.02 microM), alkaloid 2, which has been thought to be an intermediate in the biosynthesis of 1, was also a potent inhibitor of alpha-mannosidase with an IC(50) value of 4.6 microM.

Alkaloids↗

Indonesian medicinal plants. XV. Chemical structures of five new resin-glycosides, merremosides a, b, c, d, and e, from the tuber of Merremia mammosa (Convolvulaceae).

Five new resin-glycosides, named merremosides a (1), b (2), c (3), d (4), and e (5), were isolated from the tuber of Merremia mammosa (LOUR.) HALLIER f. (Convolvulaceae), an Indonesian medicinal plant. The structures of 1, 2, 3, 4, and 5 have been elucidated on the basis of chemical and physiochemical evidence, including syntheses of (11S)-(+)- and (11R)-(--)-jalapinolic acid (16b and 18b) and the glycosidic acid designated as merremoside i (6).

Carbohydrate Sequence↗

Indonesian medicinal plants. XVI. Chemical structures of four new resin-glycosides, merremosides f, g, h1, and h2, from the tuber of Merremia mammosa (Convolvulaceae).

Four new resin-glycosides named merremosides f (6), g (7), h1 (8), and h2 (9) were isolated from the tuber of Merremia mammosa (Lour.) Hallier f. (Convolvulaceae), an Indonesian medicinal plant. Their chemical structures have been elucidated on the bases of their chemical and physicochemical properties.

Carbohydrate Sequence↗

Indonesian medicinal plants. XIX. 1) Chemical structures of four additional resin-glycosides, mammosides A, B, H1, and H2, from the tuber of Merremia mammosa (Convolvulaceae).

Four new resin-glycosides, named mammosides A (10), B (11), H1 (12), and H2 (13), were isolated from the tuber of Merremia mammosa (Convolvulaceae), a Jamu raw material. Their chemical structures have been elucidated on the bases of chemical and physicochemical evidence, including synthesis of a glycosidic acid designated as mammoside I.

Carbohydrate Sequence↗

Anti-inflammatory and antispasmodic activity of Ipomoea imperati (Vahl) Griseb (Convolvulaceae).

Ipomoea imperati (Convolvulaceae) lives on the sandy shores of the Brazilian coast and in other areas of the world. The anti-inflammatory activity of a methanol-water extract of the leaves of I. imperati was investigated in experimental models of acute and subchronic inflammation. Topical application of the extract (10 mg/ear) inhibited mouse ear edema induced by croton oil (89.0 +/- 1.3% by the lipid fraction with an IC50 of 3.97 mg/ear and 57.0 +/- 1.3% by the aqueous fraction with an IC50 of 3.5 mg/ear) and arachidonic acid (42.0 +/- 2.0% with an IC50 of 4.98 mg/ear and 31.0 +/- 2.0% with an IC50 of 4.72 mg/ear). Phospholipase A2, purified from Apis mellifera bee venom, was also inhibited by the extract (5.0 mg/ml lipid and aqueous fraction) in vitro in a dose-dependent manner (85% by the lipid fraction with an IC50 of 3.22 mg/ml and 25% by the aqueous fraction with an IC50 of 3.43 mg/ml). The methanol-water extract of I. imperati (1000 mg/kg) administered by the oral route also inhibited the formation of cotton pellet-induced granulomas (73.2 +/- 1.2% by the lipid fraction and 56.14 +/- 2.7% by the aqueous fraction) and did not cause gastric mucosal lesions. I. imperati extracts (10 mg/ml) also inhibited in a dose-dependent manner the muscle contractions of guinea pig ileum induced by acetylcholine and histamine (IC50 of 1.60 mg/ml for the lipid fraction and 4.12 mg/ml for the aqueous fraction). These results suggest the use of I. imperati as an anti-inflammatory and antispasmodic agent in traditional medicine.

Animals↗

Variation of breeding system, floral rewards, and reproductive success in clonal Calystegia species (Convolvulaceae).

The reproductive biology of four Japanese Calystegia species (Convolvulaceae) was studied to examine the effects of clonality and population structure on reproductive success. Calystegia soldanella, C. hederacea, and C. japonica are self-incompatible, while C. sepium is self-compatible but needs pollinator services for self-pollination. The showy, bisexual flowers of Calystegia offer pollen and nectar that attract many kinds of insects such as bees and syrphid flies. Clones of C. soldanella often formed mats just above the high tide line on beaches and produced a great number of seeds. Calystegia hederacea and C. japonica were distributed as patches of separate clones and often failed to transfer pollen grains among clones. Fruit and seed sets in C. hederacea and C. japonica were not limited by pollinators but by the number of compatible pollen grains. Although C. sepium clones were also distributed in patches, high and stable fecundity was achieved by self-compatibility and pollinator attraction. We suggest that self-compatibility in C. sepium has evolved under fertilization limitation caused by geitonogamy or facilitated selfing.

Journal Article↗

Chemotaxonomy of the pantropical genus Merremia (Convolvulaceae) based on the distribution of tropane alkaloids.

The occurrence and distribution of tropane and biogenetically related pyrrolidine alkaloids in 18 Merremia species of paleo-, neo-, and pantropical occurrence have been studied. The extensive GC-MS study included members of almost all sections of the genus and has been carried out with epigeal vegetative parts as well as with roots. It comprises altogether 74 tropanes and 13 pyrrolidines including nicotine. Along with datumetine known already from a solanaceous species, the study led to the isolation (from M. dissecta and M. guerichii, respectively) and structure elucidation (spectral data) of four novel 3alpha-acyloxytropanes, merresectines A-D: 3alpha-(4-methoxybenzoyloxy)nortropane (A), 3alpha-kurameroyloxytropane (B), 3alpha-nervogenoyloxytropane (C), 3alpha-[4-(beta-D-glucopyranosyloxy)-3-methoxy-5-(3-methyl-2-butenyl)benzoyloxy]tropane (beta-d-glucoside of D). Moreover, the novel 3alpha,6beta-di-(4-methoxybenzoyloxy)tropane (merredissine) has been isolated from M. dissecta and structurally elucidated. In addition the structures of datumetine and merresectine A could be confirmed by synthesis. Spectral data for two known 3alpha-acyloxytropanes (merresectine E beta-D-glucoside, 4'-dihydroconsabatine) and one known 3beta-acyloxytropane (concneorine) are documented for the first time. The structures of three further merresectines (F-H) have been determined by mass spectrometry. Furthermore, the linkage (2',3- and 2',4-, respectively) of two position isomer N-methylpyrrolidinylhygrines was proven by synthesis. The results of the study contribute to the solution of infrageneric taxonomic problems. Whereas all species yield pyrrolidine alkaloids without suitably differentiating results the diverging occurrence of tropane alkaloids leads to three groups of sections: (1) taxa free of tropanes, (2) taxa with simple tropanes, and (3) taxa with merresectines in addition to simple tropanes.

Alkaloids↗

Phylogenetic relationships of the sweetpotato in Ipomoea series Batatas (Convolvulaceae) based on nuclear beta-amylase gene sequences.

Phylogenetic relationships of 13 accessions and a cultivar representing the sweetpotato, Ipomoea batatas (L.) Lam., and its wild progenitors, were investigated using the nucleotide sequence variation of a nuclear-encoded beta-amylase gene. A 1.1-1.3 kb fragment of the gene spanning two exons separated by a long intron was PCR-amplified, cloned, and sequenced. Exon sequences proved highly conservative, while intron sequences yielded large differences. Intron analyses grouped species in a phylogenetic context according to the presence of two genome types: A and B. These groups are consistent with results of previous analyses, save for the novel placement of I. tiliacea, among the A-genome species. Sequences specific to both A and B genome species have been identified. Exon sequences indicate that I. ramosissima and I. umbraticola are quite different from other A-genome species. Placement of I. littoralis is questionable; its intron is similar to other B-genome species, but its exons are quite different. Exon evolution indicates that the B-genome has evolved faster than the A-genome. Interspecific intron and exon variation indicates I. trifida, I. tabascana, and I. batatas form a monophyletic group.

Cell Nucleus↗