Nuclear DNA Metabolism in the Tip of the Cortical Strands of Viscum album L

The tips of the cortical strands of Viscum album were investigatedby autoradiographic and cytophotometric methods. It is shown that DNA synthesis and mitotic activity of the sub-apicalmeristematic cells are constant during the whole year. Theirnuclear DNA content varies from 2C to 4C values. The elongated cells which cover the meristematic zone are characterizedby no DNA synthesis, no mitotic activity and a 2C nuclear DNAcontent. They are ‘blocked’ in the presyntheticphasc G₁ of their cellular cycle, without polyploidy. The relationship between polyploidy and secretion is discussed. Viscum album, mistletoe, nucleus, DNA, polyploidy     

云杉矮槲寄生内寄生系统的解剖学研究

采用石蜡切片和显微观察的方法,以被云杉矮槲寄生侵染的青海云杉枝条为材料,从解剖学水平观察云杉矮槲寄生的内寄生系统。结果表明:云杉矮槲寄生的内寄生系统由分布在寄主皮层内的皮层根和镶嵌在寄主木质部中的吸根组成。皮层根可以沿着寄主枝条,通过挤压寄主皮层细胞的方式扩展,并穿透寄主表皮层形成云杉矮槲寄生的寄生芽;在靠近或接触寄主次生韧皮部时形成吸根,吸根顶端细胞定向穿透寄主韧皮部和形成层,侵染木质部,并沿木射线方向生长。当云杉矮槲寄生侵入寄主以及皮层根向外生长时,寄主表皮层发生加厚现象。随着云杉矮槲寄生侵染部位的寄主皮层细胞数增多,引起枝条膨大。研究认为,云杉矮槲寄生可以进行系统侵染,反映了云杉矮槲寄生与其寄主在组织水平上的相互作用。     

Le Phloème des Cordons Corticaux duViscum album L. (Loranthacées)

Résumé Les cordons corticaux duViscum album L. (Loranthacée) sont étudiés en microscopie photonique et électronique. La présence d'un tissu phloémien comprenant des cellules criblées et des cellules compagnes est, pour la première fois, démontrée. Les éléments criblés sont anucléés, pauvres en cytoplasme dégénérescent et possèdent des plages criblées avec des pores obstrués par des P-protéines. Par contre, les cellules compagnes ont un noyau volumineux et un cytoplasme dense. Ces caractéristiques ultrastructurales sont comparées à celles décrites dans le phloème des plantes autotrophes. Chez les Phanérogames parasites, la différenciation d'un véritable tissu phloémien semble liée au degré de parasitisme qu'elles ont atteint.

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Phloem in the cortical strands ofViscum album L. (Loranthaceae)

Summary The cortical strands ofViscum album L. (Loranthaceae) were investigated at the light and electron microscopic levels. The occurrence of phloem in its endophytic system is registered for the first time. It consists of sieve tubes and companion cells. The former are enucleated cells with degenerescent cytoplasm, sieve plates and P-protein occluding the pores. The companion cells possess a large nucleus and a dense cytoplasm. These features are compared with those encountered in the phloem of autotrophic plants. Among the parasitic Phanerogames, the differentiation of phloem seems related to the parasitic level reached by these plants.

     

Étude cytologique et cytochimique de l'extrémité des cordons corticaux duViscum album. Mise en évidence d'une sécrétion mucilagineuse

Résumé L'extrémité des cordons corticaux duViscum album est étudiée en microscopie photonique et électronique.Les cellules subapicales sont isodiamétriques et possèdent un volumineux noyau dans un cytoplasme dense. Elles se divisent fréquemment et montrent de très nombreux noyaux marqués après incorporation de thymidine tritiée. Ces aspects cytologiques, cytochimiques et métaboliques permettent d'affirmer que ce massif cellulaire correspond au méristème subterminal responsable de la croissance des cordons corticaux.Les cellules allongées situées en avant de cette zone méristématique présentent les caractéristiques ultrastructurales de cellules sécrétnces. La nature polysaccharidique de la substance sécrétée est démontrée. Après la technique à l'acide periodique-TCH-protéinate d'argent, le produit de sécrétion est localisé dans des vésicules golgiennes avant d'être déversé dans l'espace péricellulaire. L'existence d'une éventuelle homologie entre ces cellules allongées et les cellules externes de la coiffe des racines des végétaux autotrophes est discutée.

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Cytological and cytochemical study of the cortical strands ofViscum album L. (Loranthaceae). Evidence for a mucilaginous secretion

Summary The tip of the cortical strands ofViscum album were investigated at the light and electron microscopic levels.Subapical cells are isodiametric and possess a large nucleus and a dense cytoplasm. They divide frequently and show numerous labelled nuclei after incorporation of tritiated thymidine. Cytological, cytochemical and metabolic aspects allow us to consider this region to be the meristem of the cortical strands which is responsible for subterminal growth.Elongated cells with ultrastructural features of secreting cells cover this zone. The substance secreted is polysaccharidic and can be visualized in Golgi vesicles after the periodic acid-TCH-silver protein technique. These cells which protect the subterminal meristem of the cortical strands and secrete mucilage are compared with the external cells of the root cap of autotrophic Phanerogams.

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Ce travail a été effectué dans le cadre de l'équipe de recherche associée au C. N. R. S.: « Cytologie expérimentale des cellules méristématiques et de leurs dérivées », no. 0616.     

The Endophytic System of Arceuthobium minutissimum, the Indian Dwarf Mistletoe

The Indian dwarf mistletoe, Arceuthobium minutissimum Hook f.is the most diminutive dicotyledonous stem parasite on Pinusexcelsa. The endophytic system is well developed, having a largenumber of anastomosing strands in the cortex and sinkers penetratingthe medullary rays in wood. The cortical strand is protostelicwith the central tracheary elements, the vessels, surroundedby paren-chymatous cells. An earlier report of absence of vesselsseems to be erroneous. The growth of the cortical strands iseffected by an apical cell. The sinkers typically associatedwith the rays of host, are composed of parenchymatous cellsand tracheary elements including vessels. They make contactswith the cells of the ray through pits present in the trachearyelements. The sinkers cause hypertrophy and even fusion of twoor more rays to form a composite medullary ray. The tracheidsof the host tissue also become stunted and contorted in shape.These observations are in agreement with those of other investigatorson American host species for Arceuthobium.     

Induction of tumor necrosis factor expression by a lectin fromViscum album

Summary A purified lectin (MLI) fromViscum album was used to test whether peripheral monocytes from human blood can be activated for the production of tumour necrosis factor (TNF). Cytotoxic activity was detected in the supernatant of MLI-stimulated monocyte cultures. This cytotoxic activity was completely inhibited by monoclonal antibodies to TNF. Small amounts of soluble TNF protein were measured in a TNF-specific enzyme-linked immunospecific assay system. Strong expression of TNF mRNA was induced in human monocytes as well as in macrophage cultures from C3H/HeJ mice having a low response to endotoxin after 2 h of stimulation. Both chains of the MLI were found to induce TNF mRNA equally well in human monocytes. In macrophages of endotoxin-low-responder mice the toxic A chain was a better inducer of TNF mRNA than the galactose-specific lectin B chain. Thus, MLI has immunomodulating effects in activating monocytes/macrophages for inflammatory responses.     

The gene space of European mistletoe (Viscum album)

European mistletoe (Viscum album) is a hemiparasitic flowering plant that is known for its very special life cycle and extraordinary biochemical properties. Particularly, V. album has an unusual mode of cellular respiration that takes place in the absence of mitochondrial complex I. However, insights into the molecular biology of V. album so far are very limited. Since the genome of V. album is extremely large (estimated 600 times larger than the genome of the model plant Arabidopsis thaliana) it has not been sequenced up to now. We here report sequencing of the V. album gene space (defined as the space including and surrounding genic regions, encompassing coding as well as 5′ and 3′ non-coding regions). mRNA fractions were isolated from different V. album organs harvested in summer or winter and were analyzed via single-molecule real-time sequencing. We determined sequences of 39 092 distinct open reading frames encoding 32 064 V. album proteins (designated V. album protein space). Our data give new insights into the metabolism and molecular biology of V. album, including the biosynthesis of lectins and viscotoxins. The benefits of the V. album gene space information are demonstrated by re-evaluating mass spectrometry-based data of the V. album mitochondrial proteome, which previously had been evaluated using the A. thaliana genome sequence. Our re-examination allowed the additional identification of nearly 200 mitochondrial proteins, including four proteins related to complex I, which all have a secondary function not related to respiratory electron transport. The V. album gene space sequences are available at the NCBI.     

Wood charcoal and seeds as indicators for animal husbandry in a wetland site during the late mesolithic�Cearly neolithic transition period (Swifterbant culture, ca. 4600�C4000 b.c.) in NW Belgium

Analysis of wood charcoal and seeds from ??Doel sector M??, a Swifterbant site (ca. 4600?C4000 b.c.) from NW Belgium, provides information on the environment, plant food subsistence, animal husbandry practices and seasonality of this wetland camp site during the mesolithic?Cneolithic transition period. The results of the analyses of both charcoal and seeds show that the site was located on the top of a sand ridge covered by an upper riverbank forest with Quercus sp., Tilia sp., Ulmus sp. and Fraxinus excelsior, and surrounded by Alnus woodland. Seeds and fruits of Quercus sp., Cornus sanguinea, Corylus avellana, Malus sylvestris and Prunus spinosa probably represent food plants. High numbers of Viscum album charcoal fragments and Hedera helix seeds suggest the use of these plants as leaf fodder, and thus animal husbandry at the site. In terms of seasonality, the use of both Viscum album and Hedera helix is a strong indication that these wetland campsites were occupied during winter/early spring.     

Multiply branched replicative intermediates in E. coli and bacteriophage lambda

Summary Multiple branched DNA fragments present in a fast sedimenting complex comprising a minute fraction of the E. coli genome have been isolated. Similar structures were also observed among bacteriophage DNA replicative intermediates after infection of synchronized E. coli cells. These structures were found to be associated with the amino acid and thymidine starvation steps required for synchronization and originate either by initiation from secondary sites or by snap-back of daughter strands containing substantial single stranded regions in the vicinity of the growing point.     

Seed treatment with aqueous extract of Viscum album induces resistance to pearl millet downy mildew pathogen

Abstract

Downy mildew (Sclerospora graminicola [Sacc.] Schroet.) is a serious agricultural problem for pearl millet (Pennisetum glaucum [L.] R. Br.) grain production under field conditions. Six medicinally important plant species Azadirachta indica, Argemone mexicana, Commiphora caudata, Mentha piperita, Emblica officinalis and Viscum album were evaluated for their efficacy against pearl millet downy mildew. Seeds of pearl millet were treated with different concentrations of aqueous extract of the plants to examine their efficacy in controlling downy mildew. Among the plant extracts tested, V. album treatment was found to be more effective in enhancing seed quality parameters and also in inducing resistance against downy mildew disease. Germination and seedling vigor was improved in seeds treated with V. album extracts over control. Seeds treated with 10% concentration of V. album showed maximum protection against downy mildew disease under greenhouse and field conditions. The downy mildew disease protection varied from 44–70% with different concentrations. Leaf extract of V. album did not inhibit sporulation and zoospore release from sporangia of Sclerospora graminicola, indicating that the disease-controlling effect was attributed to induced resistance. Seed treatment with V. album extract increased pearl millet grain yield considerably. In V. album, treated pearl millet seedlings increased activities of peroxidase, and phenylalanine ammonia-lyase enzyme was detected. FTIR analysis of V. album extracts showed the presence of amides and other aromatic compounds which are antimicrobial compounds involved in plant defense.     

cDNA-derived identification of novel thionin precursors in Viscum album that contain highly divergent thionin domains but conserved signal and acidic polypeptide domains

The existence of new thionin variants in Viscum album has been deduced from cDNA sequences. Unlike the viscotoxins and related thionins previously found in different members of the Viscaceae, these novel thionins contain eight rather than six cysteine residues. In this respect they resemble thionins described previously from various cereals and from Pyrularia pubera, which also contain eight cysteine residues at identical positions. All of the new thionins of V. album are encoded as higher-molecular-weight precursors consisting of a signal peptide, a thionin domain and an acidic polypeptide domain. While the deduced amino acid sequences of the thionin domains of different precursor molecules are highly divergent, the two other domains are conserved among all of the variants and are distinct from the corresponding domains of thionin precursors of other plant species.     

Modulating glycosidase degradation and lectin recognition of gold glyconanoparticles

Glyconanoparticles (GNPs) are water-soluble carbohydrate-functionalized gold nanoclusters with a promising potential to serve as versatile tools in studies ranging from basic chemical glycobiology to clinical applications. In this paper we evaluate the influence of ligand density and presentation on the recognition by protein receptors by examining the interaction of lactose-functionalized GNPs with two different galactose-specific carbohydrate-binding proteins: an enzyme, Escherichia coli β-galactosidase, and a lectin, Viscum album agglutinin. The results suggest that the proper selection of ligand densities and spacers in GNP functionalization is an important requisite to match the topological requirements of the target receptor while escaping glycosidase degradation.     

The upward shift in altitude of pine mistletoe (Viscum album ssp. austriacum) in Switzerland—the result of climate warming?

Pine mistletoe (Viscum album ssp. austriacum) is common in natural Scots pine (Pinus sylvestris L.) forests in the alpine Rhone Valley, Switzerland. This semi-parasite, which is regarded as an indicator species for temperature, increases the drought stress on trees and may contribute to the observed pine decline in the region. We recorded mistletoes on representative plots of the Swiss National Forest Inventory ranging from 450 to 1,550 m a.s.l. We found mistletoe on 37% of the trees and on 56% of all plots. Trees infested with mistletoe had a significantly higher mortality rate than non-infested trees. We compared the current mistletoe occurrence with records from a survey in 1910. The current upper limit, 1,250 m, is roughly 200 m above the limit of 1,000–1,100 m found in the earlier survey 100 years ago. Applying a spatial model to meteorological data we obtained monthly mean temperatures for all sites. In a logistic regression mean winter temperature, pine proportion and geographic exposition significantly explained mistletoe occurrence. Using mean monthly January and July temperatures for 1961–1990, we calculated Skres plant respiration equivalent (RE) and regressed it against elevation to obtain the RE value at the current mistletoe elevation limit. We used this RE value and temperature from 1870–1899 in the regression and found the past elevation limit to be at 1,060 m, agreeing with the 1910 survey. For the predicted temperature rise by 2030, the limit for mistletoe would increase above 1,600 m altitude.     

Polycentric vascular rays in Suaeda monoica and the control of ray initiation and spacing

Summary The early-formed xylem of Suaeda monoica Forssk. ex J. F. Gmel (Chenopodiaceae) is temporarily rayless. Vascular rays differentiate during later stages of its xylem ontogeny. The rays in Suaeda are heterogeneous, and some of them are aggregated. The mature xylem of this species is characterized by two unique types of vascular rays: (1) rays with several inside initiation centres of small cells formed by local frequent cell divisions in the cambium, and (2) huge xylem rays with radial phloem strands that are connected to the axial phloem. The spacing of the xylem rays is not even, and possible mechanisms controlling ray spacing are discussed. Our observations indicate that rays do not have an inhibitory zone around them in which ray initiation is prevented. The initiation of radial patterns of small cells which appear like inside rays within a large vascular ray suggests that initiation and spacing of rays is controlled by radial signal flows in relationship with axial signal fluxes.     

Chemical constituents of Viscum album var. meridianum

Twenty known compounds were isolated from Viscum album L. var. meridianum Danser. As major compounds, flavanones, flavanone glycosides and triterpenenes could be chemotaxonomic markers for the genus Viscum according to our study and literatures.     

Flavonoid evidence for allopolyploidy in the Chenopodium album aggregate (Amaranthaceae)

The flavonoid chemistry of 16 species of Chenopodium was investigated, with an emphasis on C. album and its relatives. The chief compounds seen were 3-O-glycosides of quercetin, kaempferol and isorhamnetin. The latter two classes show a mutually exclusive distribution among the diploid and all but one tetraploid species. C. polyspermum is unusual in possessing O-methylation at the 4-, 6- and 7-positions, and C. murale is the only taxon to have 7-O-glycosylation. Acylated glycosides are common. C. album and related hexaploid taxa display a single flavonoid profile, providing no support for the recognition of more than one species. The hexaploid flavonoid profile represents an almost perfect summation of those of the diploids, C. suecicum and C. ficifolium. This apparent additive inheritance supports the hypothesis that these species (or taxa very similar to them) are involved in the ancestry of C. album. Chromosome numbers are reported for 14 of the species.     

Die Verteilung der leitenden Strukturen in der Achse vonClematis vitalba (Ranunculaceae)

The vascular pattern and its origin are described in connection with the differentiation of ground tissue in the shoot. Leaf arrangement ofClematis vitalba L. is decussate, and the vascular pattern appears rather simple at first: From internode to internode six strands—three from each leaf—alternate. About six internodes from the shoot apex, the pattern is completed by accessory strands which do not leave the axis and differentiate near the primary bark and exactly between the old strands. The formation of the acessory strands is not caused by the enlargement of the axis alone, because the balance between ground and vascular tissue is already regulated by the enlargement of the primary strands.

Zweiter Beitrag der Serie Die Sproßentwicklung vonClematis vitalba (Ranunculaceae) vgl. den ersten Beitrag:Schnettker (1976).     

Mechanism of stimulation of human natural killer cytotoxicity by arabinogalactan fromLarix occidentalis

Cultures of human peripheral blood mononuclear cells (PBMC) as well as cultures of preseparated peripheral non-adherent cells (PNAC) and monocytes showed enhancement of natural killer (NK) cytotoxicity against K562 tumor cells when pretreated with arabinogalactan fromLarix occidentalis for 48–72 h. Lack of enhanced responses of PBMC (37% of donors) did not necessarily mean that PNAC and monocyte cultures were also non-responsive to arabinogalactan treatment. Moreover, PBMC, PNAC and monocytes of individual donors could exhibit various responses to arabinogalactan when cultures derived from bleedings after intervals of several months were assayed. Arabinogalactan-mediated enhancement of NK cytotoxicity was not initiated directly but was found to be governed by the cytokine network. Generally, arabinogalactan pretreatment induced an increased release of interferon (IFN), tumor necrosis factor , interleukin-1 (IL-1) and IL-6 but only IFN was involved in enhancement of NK cytotoxicity since cytotoxicity enhancement of PBMC and PNAC but not that of monocytes could be blocked when anti-IFN antibodies were present during pretreatment. The presence of anti-IL-2 antibodies completely blocked NK cytotoxicity enhancement of PBMC and only moderately that of PNAC and monocytes. This blocking effect was also observed when no detectable increase of IL-2 release could be recorded. The receptor specificity of arabinogalactan is not well characterized. Initial information obtained from comparative studies indicated that arabinogalactan presumably interacts with a receptor that showed specificity for a NK-cytotoxicity-enhancing oligo-saccharide fromViscum album extracts since the action of both components was not synergistic but rather competitive.     

Distribution, frequency and host patterns of European mistletoe (Viscum album subsp. album) in the major city of Lodz, Poland

The frequency of parasitism of the European mistletoe, Viscum album L. subsp. album, in the city of Lodz, a typical major city in Poland, was investigated. The infection prevalence and intensity of the mistletoe Viscum album subsp. album on its main host, Acer saccharinum as a function of host size was also investigated. The parasite showed a strong preference for alien, planted tree species (i.e. A. saccharinum, Populus×canadensis and Robinia pseudoacacia). In 2009–2011, V. album subsp. album was observed on 28 host taxa of trees and shrubs, which represents the highest diversity of host trees in a single locality in the Poland. Within the studied area 2147 trees were infested by mistletoe. The distribution of mistletoes (V. album subsp. album) among A. saccharinum hosts is significantly aggregated. The intensity of mistletoe infection in the silver maple trees was affected by the individual tree characteristics, such as the height of the tree. The overall level of aggregation as indicated by the variance to mean ratio of mistletoe numbers per host fell within the midrange of values found in other published studies of host-mistletoe interactions. The higher mistletoe infection prevalence in taller trees results from differential dispersal of mistletoe seeds to tall trees as well as differential survival of established mistletoes on tall trees. The incidence of mistletoe was higher in city centre (zone of high density development) than it was on the outskirts of a city (outer marginal zone). It was found that the abundant occurrence of mistletoe was recorded in the stands of increased nitrogen input, while other stands have little or no mistletoe infection present. Thus, this mistletoe species uses both passive and active uptake, which may be a selective advantage in a nutrient-poor environment or on a nutrient-deficient host species.