The ultrastructure of dwarf mistletoe (Arceuthobium spp.) sinker cells in the region of the host secondary vasculature

1985 ◽  
Vol 63 (5) ◽  
pp. 889-898 ◽  
Author(s):  
M. Carol Alosi ◽  
Clyde L. Calvin
Keyword(s):  
Cell Walls ◽  
Lipid Bodies ◽  
Dwarf Mistletoe ◽  
Sieve Cell ◽  
The Common ◽  
Host Parasite ◽  
Sieve Pores

Sinker cells showed ultrastructural similarities in three species of Arceuthobium on three different hosts despite differences in season of collection and fixation. All species had abundant osmiophilic lipid bodies, plastids with prolamellarlike bodies, mitochondria with large nucleoids, chromocentric nuclei, and peculiar saccules associated with plasmodesmatal fields. Xylem may not be continuous through sinkers. Apoplastic continuity between host and parasite is afforded by fused cellulosic cell walls. Pitlike wall thinnings and "half-plasmodesmata" are found between juxtaposed host and parasite cells. One-sided, imperforate sieve pores were noted between a sieve cell and a contiguous sinker cell. However, symplastic isolation of the host and parasite seems likely. Therefore, nutrients may be absorbed from the common host–parasite apoplast. Mobilization of nutrients out of the endophytic system to the aerial shoots is thought to be facilitated by differential starch storage in the parasite body.

scholarly journals Erythraeid larvae parasitizing dragonflies in Zambia—description of Leptus (Leptus) chingombensis sp. nov. with data on biology and ecology of host-parasite interactions

2019 ◽  
Vol 24 (5) ◽  
pp. 790
Author(s):  
Rafał Bernard ◽  
Magdalena Felska ◽  
Joanna Mąkol
Keyword(s):  
Dna Barcode ◽  
Morphological Characteristics ◽  
Parasite Load ◽  
Ventral Side ◽  
Habitat Conditions ◽  
Local Character ◽  
Host Parasite Interactions ◽  
Group Variation ◽  
The Common ◽  
Host Parasite

A survey of odonate fauna in Zambia (Central Province, Luano District) resulted in discovery of ectoparasitic larvae of Leptus (L.) chingombensis sp. nov. (Trombidiformes: Parasitengona, Erythraeidae) on four species of dragonflies (Odonata) representing four different families assigned to Zygoptera and Anisoptera. The morphological characteristics of the new species is supported with DNA barcode sequence. Despite some intra-group variation related to relatively large sample, the morphological and genetic consistence confirm the common specific identity of the material. A brief comparison of Leptus spp. hitherto known from the Afrotropic as larvae is given. Supplementary data to the descriptions of Leptus (L.) bicristatus Fain et Elsen, 1987, Leptus (L.) aldonae Haitlinger, 1987 and Leptus (L.) soddagus Haitlinger, 1990, based on examination of type material, are provided. In the case of L. (L.) chingombensis sp. nov., the parasite load reached high, previously not recorded for Odonata–terrestrial Parasitengona association values, attaining at 44 and 49 larvae. Clear topic preferences towards the ventral side of the host’s body were recorded, with an additional tendency to distal parts of synthorax and the ventral depression of the abdomen. We hypothesize that the infestation did not take place synchronously at dragonflies emergence, but consisted in repeated infestation events during the recurrent appearance of dragonflies in the contact microhabitat occupied by Leptus. The very local character of the finding along with the regular appearance of larvae parasitizing dragonflies, obviously favoured by specific habitat conditions, no doubts confirms the non-accidental nature of the phenomenon.

Host–parasite distributions under changing climate: Tsuga heterophylla and Arceuthobium tsugense in Alaska

2012 ◽  
Vol 42 (4) ◽  
pp. 642-656 ◽  
Author(s):  
Tara M. Barrett ◽  
Greg Latta ◽  
Paul E. Hennon ◽  
Bianca N.I. Eskelson ◽  
Hailemariam Temesgen
Keyword(s):  
Logistic Models ◽  
Tsuga Heterophylla ◽  
Climate Scenarios ◽  
Degree Days ◽  
Dwarf Mistletoe ◽  
Southeast Alaska ◽  
Modeling Approaches ◽  
Abundance And Distribution ◽  
Forested Ecosystems ◽  
Host Parasite

Dwarf mistletoes ( Arceuthobium species) influence many processes within forested ecosystems, but few studies have examined their distribution in relation to climate. An analysis of 1549 forested plots within a 14.5 million ha region of southeast Alaska provided strong indications that climate currently limits hemlock dwarf mistletoe ( Arceuthobium tsugense (Rosendahl) G.N. Jones) to a subset of the range of its primary tree host, western hemlock ( Tsuga heterophylla (Raf.) Sarg.), with infection varying from a high of 20% of trees at sea level to only 5% by 200 m elevation. Three types of modeling approaches (logistic, most similar neighbors, and random forests) were tested for the ability to simultaneously predict abundance and distribution of host and pathogen as a function of climate variables. Current distribution was explained well by logistic models using growing degree-days, indirect and direct solar radiation, rainfall, snowfall, slope, and minimum temperatures, although accuracy for predicting A. tsugense presence at a particular location was only 38%. For future climate scenarios (A1B, A2, and B1), projected increases for A. tsugense habitat over a century ranged from a low of 374% to a high of 757%, with differences between modeling approaches contributing more to uncertainty than differences between climate scenarios.

Wilts caused by Verticillium species. A cytological survey of vascular alterations in leaves

1982 ◽  
Vol 60 (6) ◽  
pp. 825-837 ◽  
Author(s):  
Jane Robb ◽  
Alexandra Smith ◽  
Lloyd Busch
Keyword(s):  
Electron Microscopy ◽  
Cell Walls ◽  
Sem Analysis ◽  
Disease Symptoms ◽  
Vascular Tissues ◽  
Transmission Electron ◽  
Tem Method ◽  
Cytological Alterations ◽  
Host Parasite ◽  
Leaf Symptoms

Plants that are infected with fungi of the species Verticillium frequently develop foliar disease symptoms which may include one or more of the following: flaccidity, drying, chlorosis leading to necrosis, vascular browning, epinasty, and leaf abscission. A number of ultrastructural and chemical alterations occur in the vascular tissues of such leaves: deposition of brown pigments, coating of xylem vessel walls with abnormal material (i.e., lipid-rich coatings or fibrillar coatings), plugging of xylem vessels with gums, gels or tyloses, degeneration of parenchyma cells, and accumulation of abnormal electron dense materials in primary and secondary cell walls. Different host–parasite combinations exhibit different leaf symptoms and different cytological alterations. The purpose of the present survey was to determine whether the extent of any of the possible vascular alterations in leaves could be correlated with the wilting tendency of the host.Chrysanthemums, snapdragons, eggplants, sunflowers, potatoes, sycamore maples and hedge maples were infected with V. dahliae; alfalfa and hops were infected with V. albo-atrum. When leaf symptoms were well advanced, samples were taken from the major lateral leaf veins and were prepared for light (LM) and transmission electron microscopy (TEM) or scanning electron microscopy (SEM). The various types of alterations in the vascular tissues were identified by a correlated LM–TEM method and (or) SEM analysis and for each sample vein the proportion of vessels affected by each type of alteration was calculated. Four leaf samples, each from different plants, were analysed for each host. The visual symptoms, including vascular browning, were estimated subjectively. The degree of leaf flaccidity was correlated positively with the proportion of lipid-coated vessels and inversely with the degree of vascular browning. No other correlations were observed.

Anatomy and ultrastructure of the endophytic system of Pilostyles thurberi (Rafflesiaceae)

1985 ◽  
Vol 63 (7) ◽  
pp. 1231-1240 ◽  
Author(s):  
Job Kuijt ◽  
D. Bray ◽  
A. R. Olson
Keyword(s):  
Cell Types ◽  
Sieve Element ◽  
Cell Type ◽  
Discontinuous System ◽  
Sieve Elements ◽  
The Third ◽  
Sieve Plates ◽  
Host Parasite ◽  
Anatomy And Ultrastructure ◽  
Sieve Pores

The endophytic system of Pilostyles thurberi Gray consists of initially uniseriate filaments which develop into an anastomosing complex of larger cortical strands and radial sinkers. In the cortical strands three cell types are recognized, two of which differ largely in the density of the cytoplasm, the shape of the nucleus, and the degree to which the cytoplasm becomes plasmolyzed during fixation. The nuclei of both cell types contain two nucleoli which are physically connected by a nucleolar bridge. The third cell type demonstrates sieve plates, including a calloselike substance in the sieve pores and is consequently considered to be a sieve element. The sieve elements appear to form a discontinuous system and are regarded as a vestigial cell type. Plasmodesmal connections across the host–parasite interface have not been observed.

scholarly journals A novel thermostable prokaryotic fucoidan active sulfatase PsFucS1 with an unusual quaternary hexameric structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Dalgaard Mikkelsen ◽  
Hang Thi Thuy Cao ◽  
Thomas Roret ◽  
Nanna Rhein-Knudsen ◽  
Jesper Holck ◽  
...  
Keyword(s):  
Cell Walls ◽  
Sea Cucumber ◽  
Functional Characterization ◽  
Structural Data ◽  
Ring Structure ◽  
Optimal Temperature ◽  
Brown Seaweeds ◽  
Dimer Interface ◽  
The Common ◽  
Novel Protein

AbstractFucoidans are sulfated, fucose-rich marine polysaccharides primarily found in cell walls of brown seaweeds (macroalgae). Fucoidans are known to possess beneficial bioactivities depending on their structure and sulfation degree. Here, we report the first functional characterization and the first crystal structure of a prokaryotic sulfatase, PsFucS1, belonging to sulfatase subfamily S1_13, able to release sulfate from fucoidan oligosaccharides. PsFucS1 was identified in the genome of a Pseudoalteromonas sp. isolated from sea cucumber gut. PsFucS1 (57 kDa) is Ca2+ dependent and has an unusually high optimal temperature (68 °C) and thermostability. Further, the PsFucS1 displays a unique quaternary hexameric structure comprising a tight trimeric dimer complex. The structural data imply that this hexamer formation results from an uncommon interaction of each PsFucS1 monomer that is oriented perpendicular to the common dimer interface (~ 1500 Å2) that can be found in analogous sulfatases. The uncommon interaction involves interfacing (1246 Å2) through a bundle of α-helices in the N-terminal domain to form a trimeric ring structure. The high thermostability may be related to this unusual quaternary hexameric structure formation that is suggested to represent a novel protein thermostabilization mechanism.

scholarly journals Social hosts evade predation but have deadlier parasites

2021 ◽  
Author(s):  
Jason Walsman ◽  
Mary J. Janecka ◽  
David R. Clark ◽  
Rachael D. Kramp ◽  
Faith Rovenolt ◽  
...  
Keyword(s):  
Social Behaviour ◽  
Evolutionary Ecology ◽  
Group Living ◽  
Common Garden ◽  
Virulence Evolution ◽  
The Common ◽  
Trinidadian Guppy ◽  
Host Parasite ◽  
Predator Defence ◽  
Insight Into

AbstractParasites exploit hosts to replicate and transmit, but overexploitation kills both host and parasite1: parasite virulence evolves to balance these costs and benefits. Predators can in theory shift this balance by consuming hosts2–4. However, the non-consumptive effects of predators may be as important as their consumptive effects5. Here, we use an eco-coevolutionary model to show that predators select for host grouping, a common anti-predator, defensive social behaviour6. Host grouping simultaneously increases parasite transmission, thus within-host parasite competition, and therefore favours more exploitative, virulent, parasites7. When parametrized with data from the guppy-Gyrodactylus spp. system, including our experimentally demonstrated trade-off between virulence and transmission, our model accurately predicted the common garden-assayed virulence of 18 parasite lines collected from four Trinidadian guppy populations under different predation regimes. The quantitative match between theory and data lends credence to the model’s insight that the non-consumptive, social behaviour pathway is entirely responsible for the observed increase in virulence with predation pressure. Our results indicate that parasites play an important, underappreciated role in guppy evolutionary ecology. Moreover, group living is a common anti-predator defence6 and our general model accommodates host-parasite interactions across taxa: its insight into the interactions among predation, sociality, and virulence evolution may apply broadly. Our results additionally suggest that social distancing, by reducing host-host contact, can select for less virulent parasites and pathogens.

Parental Stress and Prechilling Effects on Pennsylvania Smartweed (Polygonum pensylvanicum) Achenes

Weed Science ◽  
1982 ◽  
Vol 30 (3) ◽  
pp. 243-248 ◽  
Author(s):  
James L. Jordan ◽  
David W. Staniforth ◽  
Catalina M. Jordan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Zea Mays ◽  
Parental Stress ◽  
Cell Walls ◽  
Lipid Bodies ◽  
Transmission Electron ◽  
Polygonum Pensylvanicum ◽  
Scanning Electron

Pennsylvania smartweed (Polygonum pensylvanicum L.) achenes were harvested from plants growing either free from competition or in competition with corn (Zea mays L. ‘Pioneer 3780′) plants. Seeds were dormant when harvested. After 15 weeks of prechilling, 4 and 35% of the seeds germinated from plants with and without corn competition, respectively; after 30 weeks of prechilling, more than 92% of all seeds germinated. Scanning electron microscopy revealed that the carpel walls of achenes from plants with corn competition were porous with many channels. Carpel walls of achenes from plants without corn competition were without pores and channels. Transmission electron microscopy showed more lipid bodies in the embryo epidermal cells of seeds from plants with corn competition. Cell walls of embryos from non-prechilled seeds from plants with corn competition contained lipoidosomes that traversed cell walls. Lipoidosomes did not occur in cells of prechilled seeds.

Preliminary Microscopic Investigations of the Digesta Derived From Foliage of Eucalyptus-Ovata (Labill) in the Digestive-Tract of the Common Ringtail Possum, Pseudocheirus-Peregrinus (Marsupialia)

1986 ◽  
Vol 34 (2) ◽  
pp. 157 ◽  
Author(s):  
TP Obrien ◽  
A Lomdahl ◽  
G Sanson
Keyword(s):  
Cell Walls ◽  
Faecal Pellets ◽  
Partial Digestion ◽  
Gut Function ◽  
Pseudocheirus Peregrinus ◽  
The Common ◽  
Eucalyptus Ovata ◽  
Micro Organisms ◽  
Microscopic Investigations ◽  
Ringtail Possum

A method is described that stabilizes vacuolar tannins in unchewed leaves of Eucalyptus ovata. This method, with light microscopy and electron microscopy, was used to study the fate of digesta in the gut of the common ringtail possum Pseudocheirus peregrinus. Normal animals (fed fresh foliage and practising coprophagy) were compared with animals denied access either to fresh foliage or to soft faecal pellets in the week before they were killed. Both manipulations appear to disturb gut function and create a need for caution in interpreting the observations. Nonetheless the results demonstrate some tanning of leaf cytoplasts in the ringtail possum, but the quantitative significance of the dietary losses so incurred is difficult to estimate. Partial digestion of cell walls and tanned cytoplasts occurs in the caecum, where massive populations of micro-organisms become attached to digestion-resistant tissue components. These 'microbial rafts' are reingested as soft pellets by coprophagy and the bacteria largely digested.

Studies on the association between Noteia anomala and Hormosira banksii (Phaeophyta)

1980 ◽  
Vol 28 (2) ◽  
pp. 239 ◽  
Author(s):  
ND Hallam ◽  
MN Clayton ◽  
D. Parish
Keyword(s):  
Cell Walls ◽  
Close Contact ◽  
Light And Electron Microscopy ◽  
Biological Significance ◽  
Adjacent Cell ◽  
Tide Pool ◽  
Prolonged Culture ◽  
The Common ◽  
The Relationship ◽  
Sexually Mature

Anatomical, ultrastructural, ecological and physiological aspects of the relationship between the common brown alga, Hormosira banksii, and the obligate epiphyte Notheia anomala are described. The highest frequencies of infection by N. anomala occur in sexually mature H. banksii in tide-pool populations. Male and female H. banksii are equally affected, and the most common sites of infection are the receptacles where N. anomala attaches around the ostiole rather than within the conceptacle. Prolonged culture of N. anomala was only possible with media containing a filtered extract of the receptacles of the host species. Light and electron microscopy of the regions of thallus connecting N. anomala and H. banksii showed a wedge-shaped incursion of N. anomala in the H. banksii thallus, and very close contact between the adjacent cell walls of host and epiphyte, but there were no protoplasmic connections. The biological significance of the relationship between N. anomala and H. banksii is discussed.

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