Mistletoe Research Papers - Academia.edu (original) (raw)

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to... more

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as ‘‘ornithophilic’’ by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.

— A survey was conducted at Botswana University of Agriculture and natural Resources at Sebele content farm to determine the intensity and level of mistletoe infestation in tree species. The intensity and the total number of trees per... more

— A survey was conducted at Botswana University of Agriculture and natural Resources at Sebele content farm to determine the intensity and level of mistletoe infestation in tree species. The intensity and the total number of trees per tree species infected by the parasitic weed were determined. Acacia eriobola, Acacia mellifera, Terminalia sericea, Ziziphus mucronata, Schinus molle, Acacia tortilis, Acacia erubesens and Acacia flekii hosted the highest number of mistletoe. Results revealed significant variation in level of mistletoe infestation between tree species. A 100% infestation was recorded in some tree species such as Acacia eriobola and Ziziphus mucronata. Severely infested indigenous tree species were dying, whereas most of the exotic tree species were either not infested or have very little number of mistletoe on them. The variation observed could be due to the fact that indigenous species the frequently visited by dispensers looking for food and shelter than exotic species. In addition, there is a possibility that the mistletoe species co-evolved with the indigenous tree species and the vector may be well established on the host tree species than on exotic species.

The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We... more

The relationship between mistletoes and birds has been studied from the perspectives of mutualism and seed dispersal. Here, we emphasize the role that avian dispersers play as agents of mistletoe seed transmission to plant hosts. We describe the patterns of transmission of the seeds of Tristerix aphyllus, an endophytic Chilean mistletoe, on two of its columnar cacti hosts (Eulychnia acida and Echinopsis skottsbergii) by the Chilean Mockingbird Mimus thenca. In north-central Chile, these cacti grow in relatively discrete subpopulations on north-facing slopes. We measured variation in seed transmission within 10 subpopulations varying in species composition, host density, parasite density, parasite prevalence (defined as the percentage of hosts infested in a given population), and disperser abundance. Seed transmission was independent of species, but was strongly de- pendent on prior parasitism. Parasitized individuals received seeds much more frequently than expected from their relative abundance. We found no correlation between the density of hosts and seed transmission. We found strong positive correlations, however, between parasite prevalence and seed transmission to both parasitized and nonparasitized hosts. Seed transmission of T. aphyllus seeds by M. thenca appeared to be frequency- rather than density- dependent. Seed transmission was also tightly and positively correlated with the abundance of seed-dispersing birds at each site. Because bird abundance and parasite prevalence were correlated, we conducted path analysis to disentangle their relative effect on seed trans- mission. A model including only the direct effect of bird abundance and the indirect effect of parasite prevalence through bird abundance explained roughly the same variance as a full model including both the direct and indirect effects of bird abundance and prevalence on seed transmission. Apparently, variation in bird abundance was the main determinant of variation in transmission. We suggest that mistletoes, host plants, and the birds that disperse mistletoe seeds are systems well suited for studies of the ecological and evolu- tionary dynamics of disease transmission.

In anthroposophical medicine, total extracts of Viscum album (mistletoe) have been developed to treat cancer patients. The oldest such product is Iscador. Although Iscador is regarded as a complementary cancer therapy, it is the most... more

In anthroposophical medicine, total extracts of Viscum album (mistletoe) have been developed to treat cancer patients. The oldest such product is Iscador. Although Iscador is regarded as a complementary cancer therapy, it is the most commonly used oncological drug in Germany. To determine whether Iscador treatment prolongs survival time of patients with carcinoma of the colon, rectum, or stomach; breast carcinoma with or without axillary or remote metastases; or small cell or non-small-cell bronchogenic carcinoma; and to explore synergies between Iscador treatment and psychosomatic self-regulation. Prospective nonrandomized and randomized matched-pair studies nested within a cohort study. General community in Germany. 10,226 cancer patients involved in a prospective long-term epidemiological cohort study, including 1668 patients treated with Iscador and 8475 who had taken neither Iscador nor any other mistletoe product (control patients). Iscador. Survival time. In the nonrandomized...

Mistletoe extracts have been shown to provide deoxyribonucleic acid (DNA)-stabilizing effects in human peripheral blood mononuclear cells (PBMC) in vitro. We investigated the effect of a mistletoe extract on PBMC with and without... more

Mistletoe extracts have been shown to provide deoxyribonucleic acid (DNA)-stabilizing effects in human peripheral blood mononuclear cells (PBMC) in vitro. We investigated the effect of a mistletoe extract on PBMC with and without concomitant treatment with cyclophosphamide and compared mitochondrial activity and replication of normal PBMC with that of a T-cell leukemia cell line. The experiments were performed with PBMC of healthy blood donors and the T-cell leukemia Jurkat cell line. Cells were pre-incubated with mistletoe extract for 60 to 65 hours. 4-hydroperoxycyclophosphamide (4-hpc, precursor of 4-hydroxycyclophosphamide) was added for 2 hours, after which mitochondrial activity and replication were measured. All experiments were randomized and blinded. Cell mitochondrial activity and replication were assessed with spectrophotometric analysis of WST-1 reduction and BrdU incorporation. The application of 4-hpc consistently reduced mitochondrial activity and replication of PBMC ...

The high parenteral toxicity of mistletoe lectin ML-1, a type-2 RIP (ribosome inactivating protein), with LD 50 values of 5 to 10 g/kg BW, seriously limits its use as a cytotoxic agent in cancer therapy. As RIP proteins are generally... more

The high parenteral toxicity of mistletoe lectin ML-1, a type-2 RIP (ribosome inactivating protein), with LD 50 values of 5 to 10 g/kg BW, seriously limits its use as a cytotoxic agent in cancer therapy. As RIP proteins are generally better tolerated when given orally, we investigated the effects of ML-1 on growth, gut and body metabolism and composition by feeding rats diets containing 67 or 200 mg ML-1 kg 1 BW for 10 days. Although ML-1 depressed voluntary feed intake and reduced growth rate, none of the rats lost weight during the experiment. ML-1 had no effect on the digestibility of proteins and other components of the diet but because of increased urinary nitrogen losses, the overall N balance and total body N content were reduced, particularly at the higher dose of ML-1. Body fat was also reduced, probably due to the depression of circulating insulin levels. Some organs were affected by oral ML-1: there was hypertrophy of the pancreas and lungs and, most importantly, a dramatic dose-dependent hyperplastic growth of the small intestine, probably due to the avid binding and endocytosis of ML-1 by gut epithelial cells. The plasma level of tumour necrosis factor-was significantly increased by oral ML-1 and there was a similar, though not significant, rise in Interleukin-1 levels. These similarities in cytokine release by oral and intraperitoneal ML-1 suggest that the oral route may be as effective in tumor suppression as the parenteral. As orally given ML-1 was well tolerated by rats with an extended nontoxic dose range over that of parenteral ML-1, the possible advantages in therapy offered by this route could now be profitably explored. (J. Nutr. Biochem. 9:31-36, 1998) © Elsevier Science Inc. 1998

2,6-Dimethylocta-2,7-diene-1,6-diol 6-O-[6'-O-beta-D-apiofuranosyl]-beta-D-glucopyranoside (1) was isolated from Viscum album ssp. album.

Ribosome-inactivating proteins having antitumor and immunomodulatory properties constitute the active principle of widely used mistletoe therapy in Europe. This is the first report of the four isoforms of Himalayan mistletoe... more

Ribosome-inactivating proteins having antitumor and immunomodulatory properties constitute the active principle of widely used mistletoe therapy in Europe. This is the first report of the four isoforms of Himalayan mistletoe ribosome-inactivating proteins (HmRips) from Viscum album parasitized on wild apple inhabiting NW Himalayas. HmRips were purified by affinity chromatography and four isoforms were separated by ion-exchange chromatography. HmRip 1, 2, 3, and 4 have isoelectric points of 6.6, 6.1, 5.2, and 4.7, respectively. Disulfide linked toxin and lectin subunits of HmRip 1 and 2 isoforms have molecular weights of 28 and 34 kDa while those of HmRip 3 and 4 have 28 and 32 kDa. The isoforms lacked blood group specificity and showed positive activity with seven mammalian erythrocyte types but did not show any activity with avian erythrocyte type. Lectin activity of HmRips remained unchanged for a wide range of temperatures (0–65 °C) and pH (3–9). Unlike other type II Rips, the HmRip 1, 2, and 4 showed unique affinity towards l-rhamnose, meso-inositol, and l-arabinose while HmRip 3 has specificity to gal/galNAc. Sugar binding studies with 22 sugars also suggested that the C-4 hydroxyl of galactose might be the critical site involved in sugar binding of HmRips. Type II Rips are known to be galactoside specific and do not have affinity for l-rhamnose and meso-inositol. However, HmRip 1, 2, and 4 having equal affinity for galactose and l-rhamnose do not strictly fit into any of the four structural classes of the lectins and represent a new class of type II Rips and plant lectins.

Identifying natural selection in wild plant populations is a challenging task, as the reliability of selection coefficients depends, among other factors, on the critical assumption of data independence. While rarely examined, selection... more

Identifying natural selection in wild plant populations is a challenging task, as the reliability of selection coefficients depends, among other factors, on the critical assumption of data independence. While rarely examined, selection coefficients may be influenced by the spatial and genetic dependence among plants, which violates the independence criterion , leading to biased selection estimates. In this study, we examine the extent to which frugivore-mediated selection coefficients are influenced by spatial and genetic information. We used Generalized Additive Models to deal with spatial and relatedness issues. We compared the fit of the Lande and Arnold multivariate model with models including spatial , genetic relatedness, and spatial + genetic relatedness corrections. Our results indicate that fit in standard models was substantially increased after including the spatial structure. Likewise, the model including the genetic relatedness accounted for a variance fraction not explained by spatial structure, which permitted the identification of significant selection acting upon fruit size, a trait not detected under selection otherwise, and dealt better with autocorrelation that any other model. The model including spatial and genetic effects altogether accounted for 65% of the variance, compared to 13% of the standard model. The spatial structure and genetic relatedness played an important role in this system. As genetic effects revealed significant selection upon fruit traits otherwise hidden under standard selection estimates, field studies that control for plant dependency may provide more realistic selection estimates in natural plant populations.

The primary structure of the B chain of the N-acetyl-D-galactosamine-recognizing mistletoe lectin-3 (ML-3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC-separation and Edman degradation and... more

The primary structure of the B chain of the N-acetyl-D-galactosamine-recognizing mistletoe lectin-3 (ML-3B) has been deduced from proteolytic digest peptides of the purified glycoprotein, their HPLC-separation and Edman degradation and confirmation of the peptide sequences by MALDI-MS. ML-3B consists of 262 amino acid residues including 10 cysteine moieties. The structure and linkage of the carbohydrate side chains, connected to two N-glycosylation sites at positions Asn95 and Asn135 of the lectin, were determined by a combination of glycosidase treatment and MALDI-MS of corresponding glycopeptide fragments. The sequence alignment reveals a high homology with other B chains of type-II RIPs, although there are remarkable differences in the D-galactose-specific mistletoe lectin-1B chain. The recently published primary structure of the mistletoe lectin-3A chain1 and the now available primary sequence of the 3B chain allowed the construction of a preliminary homology model of ML-3. The model demonstrates, unequivocally, that ML-3 is a member of the type-II RIP family with rigid conservation of the enzymatic active site of the A chain and an identical overall protein fold. Specific amino acid residue exchanges and the different glycosylation pattern in comparison with ML-1 are discussed and related to the properties of the two glycoproteins. The knowledge of the complete primary structure of mistletoe lectin-3 is a major contribution towards more insight into the mechanism of the biological activity of commercial mistletoe preparations. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to... more

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.