Insect epidermis: polarity patterns after grafting result from divergent cell adhesions between host and graft tissue

Development ◽  
1990 ◽  
Vol 110 (4) ◽  
pp. 1071-1079
Author(s):  
K. Nubler-Jung ◽  
B. Mardini
Keyword(s):  
Cell Sheet ◽  
Intermediate Stage ◽  
Epidermal Cells ◽  
Host Cells ◽  
Planar Polarity ◽  
Differentiated Cells ◽  
Local Sequence ◽  
Two Factors ◽  
Insect Epidermis ◽  
Graft Tissue

Insect epidermal cells display planar polarity (i.e. polarity in the plane of the cell sheet) by secreting oriented cuticular denticles and bristles before each moult. We investigate how cell polarities in an abdominal segment are uniformly oriented towards the posterior of the animal. Recently we have shown for the cotton bug Dysdercus that, in 180 degrees-rotated grafts pretreated with colchicine, graft cells tend to adopt the orientation prevailing in surrounding host cells via an intermediate stage with outward oriented denticles (Nubler-Jung and Grau, 1987). Here we show that, in untreated grafts that were transposed along the anteroposterior segment axis, the denticles also always tend to point outwards. This independence of the polarity pattern from the direction of transposition is compatible neither with a gradient model for polarity control, nor with the assumption that epidermal cells orient according to the local sequence of distinctly differentiated cells. Instead we found that outward orientation of graft denticles correlates with an elongation of epidermal cells along a host-graft border with divergent cell adhesiveness. We therefore propose that outward orientation in a graft results from a combination of two factors: epidermal cells stretch along an interface with divergent cell adhesiveness, and they form a denticle perpendicular to their long axis. By analogy, the normal anteroposterior orientation of denticles in a segment may result because epidermal cells tend to elongate parallel to the segment boundary and to form denticles perpendicular to this mediolateral cell elongation, i.e. along the anteroposterior segment axis.

A light and electron microscope study of the fungal endophytes in the sporophyte and gametophyte of Lycopodium cernuum with observations on the gametophyte–sporophyte junction

1992 ◽  
Vol 70 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Jeffrey G. Duckett ◽  
Roberto Ligrone
Keyword(s):  
Root Nodules ◽  
Fungal Endophytes ◽  
Fungal Endophyte ◽  
Peninsular Malaysia ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Material ◽  
Intercellular Spaces ◽  
Host Cytoplasm ◽  
Fungal Associations

The ventral epidermal cells of the photosynthetic, surface-living gametophytes of Lycopodium cernuum, collected from moist shaded banks in Peninsular Malaysia, contain an aseptate fungus. In some cells the hyphae are thick walled and form coils encapsulated by a thin layer of host wall material. In others the fungus is thin walled and shows limited differentiation into larger trunk hyphae and arbuscules. The adjacent host cytoplasm, separated from the fungus by a granular interfacial matrix, contains numerous chloroplasts, mitochondria, and microtubules. The hyphae contact the substratum via the ventral walls of the epidermal cells and the rhizoids are free from infection. In the protocorm and root nodules, aseptate hyphae initially colonize mucilage-filled schizogenous intercellular spaces. Subsequent invasion of the host cells is associated with the development of massive overgrowths of host wall material. The fungal associations in L. cernuum share a mixture of attributes otherwise found in different angiosperm mycorrhizae and in mycotrophic relationships in liverworts. Wall ingrowths are present in both the gametophyte and sporophyte cells in the placenta of L. cernuum. The very limited development of the placenta, compared with L. appressum, certain bryophytes and ferns, the diminutive size, and early senescence of the gametophytes of L. cernuum are all linked to the presence of the protocorm. This massive absorptive organ, homologous to a foot, in terms of its position in sporophyte ontogeny, but external to the parent gametophyte, derives its nutrition partly from photosynthesis and partly from its fungal endophyte. Key words: chloroplasts, Lycopodium, mycorrhiza, pteridophytes, root nodules, symbiosis, transfer cells.

New class of polyomavirus mutant that can persist as free copies in F9 embryonal carcinoma cells

1986 ◽  
Vol 6 (11) ◽  
pp. 3920-3927
Author(s):  
K Ariizumi ◽  
H Ariga
Keyword(s):  
Embryonal Carcinoma ◽  
Regulatory Region ◽  
Host Cells ◽  
Circular Dna ◽  
New Class ◽  
Differentiated Cells ◽  
Copy Numbers ◽  
Undifferentiated Cells ◽  
Ec Cells ◽  
F9 Embryonal Carcinoma Cells

A small circular DNA was found extrachromosomally in a clone of F9 embryonal carcinoma (EC) cells at high copy numbers per cell. The DNA was cloned in plasmid pUC19. Restriction endonuclease analyses of the DNA indicated that the DNA (fPyF9) was a mutant of polyomavirus (Py) DNA and had a mutation in a noncoding regulatory region. There have been many reports on the isolation of Py mutants capable of replication in undifferentiated cells. However, fPyF9 was different from other Py mutants in the following aspects: it was harbored stably as a free copy at 1 X 10(4) to 5 X 10(4) copies per cell in EC cells; it replicated in undifferentiated cells better than in differentiated cells; it was extremely rearranged in the sequences of the enhancer B domain; and it carried in the enhancer B domain three copies of an exogenous sequence which does not exist in Py strain A2. From these observations, we propose a new class of Py EC mutant which has an autonomous state similar to that of plasmid and small circular DNA in host cells.

scholarly journals Ultrastructure of the Infection of Sorghum bicolor by Colletotrichum sublineolum

2001 ◽  
Vol 91 (2) ◽  
pp. 149-158 ◽  
Author(s):  
P. S. Wharton ◽  
A. M. Julian ◽  
R. J. O'Connell
Keyword(s):  
Cell Wall ◽  
Sorghum Bicolor ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Thickening ◽  
Fungal Cell ◽  
Resistant Cultivars ◽  
Ultrastructural Studies ◽  
Opaque Material ◽  
Colletotrichum Sublineolum

Ultrastructural studies of the infection of susceptible and resistant cultivars of Sorghum bicolor by Colletotrichum sublineolum were conducted. Initial penetration events were the same on both susceptible and resistant cultivars. Germ tubes originating from germinated conidia formed globose, melanized appressoria, that penetrated host epidermal cells directly. Appressoria did not produce appressorial cones, but each penetration pore was surrounded by an annular wall thickening. Inward deformation of the cuticle and localized changes in staining properties of the host cell wall around the infection peg suggests that penetration involves both mechanical force and enzymic dissolution. In compatible interactions, penetration was followed by formation of biotrophic globular infection vesicles in epidermal cells. Filamentous primary hyphae developed from the vesicles and went on to colonize many other host cells as an intracellular mycelium. Host cells initially survived penetration. The host plasma membrane invaginated around infection vesicles and primary hyphae and was appressed tightly to the fungal cell wall, with no detectable matrix layer at the interface. Necrotrophic secondary hyphae appeared after 66 h and ramified through host tissue both intercellularly and intracellularly, forming hypostromatic acervuli by 114 h. Production of secondary hyphae was accompanied by the appearance of electron-opaque material within infected cells. This was thought to represent the host phytoalexin response. In incompatible interactions, infection vesicles and primary hyphae were formed in epidermal cells by 42 h. However, they were encrusted with electron-opaque material and appeared dead. These observations are discussed in relation to the infection processes of other Colletotrichum spp. and the host phytoalexin response.

scholarly journals Modification of cell surface glycoprotein: addition of fucosyl residues during epidermal differentiation.

1982 ◽  
Vol 95 (2) ◽  
pp. 626-631 ◽  
Author(s):  
J D Zieske ◽  
I A Bernstein
Keyword(s):  
Cell Surface ◽  
Lectin Binding ◽  
Epidermal Cells ◽  
Epidermal Differentiation ◽  
Surface Glycoprotein ◽  
Basal Cells ◽  
Cell Surface Glycoprotein ◽  
Similar Treatment ◽  
Differentiated Cells ◽  
Cell Layers

When cutaneous sections from the newborn rat were treated with alpha-fucosidase, Ulex europeus agglutinin I (UEA) binding to the cell surface of the differentiated cells in the epidermis was diminished and there was an appearance in these cell layers of binding by Bandeiraea simplicifolia I-B4 lectin (BS I-B4), which normally is specific for the basal cells. A similar treatment with alpha-galactosidase resulted in a loss of BS I-B4 binding, but had no effect on UEA binding. Glycoproteins isolated from the membranes of epidermal cells showed a threefold increase in the ratio of binding to UEA versus BS I-B4 affinity columns as the proteins were derived from the more differentiated cell populations. These data suggest that alpha-fucosyl residues are added to the glycoproteins on the cell surfaces of differentiated cells, thus blocking alpha-galactosyl residues and changing the lectin binding specificity as epidermal cells move out of the basal cell layer.

scholarly journals Ultrastructure of the Penetration and Infection of Pansy Roots by Thielaviopsis basicola

2000 ◽  
Vol 90 (8) ◽  
pp. 843-850 ◽  
Author(s):  
Charles W. Mims ◽  
Warren E. Copes ◽  
Elizabeth A. Richardson
Keyword(s):  
Filter Paper ◽  
Germ Tube ◽  
Epidermal Cells ◽  
Host Cells ◽  
Thielaviopsis Basicola ◽  
Cortical Cells ◽  
Infection Structures ◽  
Transmission Electron ◽  
Papilla Formation ◽  
Potting Media

Transmission electron microscopy was used to study the penetration and infection of pansy roots by Thielaviopsis basicola. Events observed in 7- to 10-day-old roots produced on moist filter paper differed slightly from those in roots from 4-week-old plants washed free of potting media prior to inoculation. By 3 h postinoculation (PI), epidermal cells of roots produced on filter paper exhibited aggregated cytoplasm and papilla formation in response to germ tube tips. The presence of callose in papillae was demonstrated using immunogold labeling. Papilla formation was not effective in preventing host cell penetration. A slender infection hypha emerged from a germ tube tip and grew through a papilla. Its tip then expanded to form a globose infection vesicle. By 6 h PI, infection hyphae emerged from infection vesicles, and invaded host cells showed signs of necrosis. By 8 h PI, infection hyphae had grown into cortical cells in spite of papilla formation in these cells. By 24 h PI, distinctive intracellular hyphae were present in necrotic cortical cells. In washed roots, most epidermal cells failed to respond to invasion. Hyphae simply grew through these cells and contacted cortical cells that exhibited aggregated cytoplasm and papillae formation. Infection structures similar to those produced in epidermal cells from roots grown on filter paper then formed in cortical cells of washed roots. The fact that T. basicola formed infection structures only in cells that responded to invasion suggests that T. basicola has a more complex relationship with its host than would be expected in a nectrotrophic pathogen. We believe that T. basicola is best described as a necrotrophic hemibiotroph.

A histological study of interactions between avirulent races of stem rust and wheat containing resistance genes Sr5, Sr6, Sr8, or Sr22

1979 ◽  
Vol 57 (4) ◽  
pp. 324-331 ◽  
Author(s):  
R. Rohringer ◽  
W. K. Kim ◽  
D. J. Samborski
Keyword(s):  
Resistance Genes ◽  
Stem Rust ◽  
Chinese Spring ◽  
Histological Study ◽  
Fungal Growth ◽  
Triticum Aestivum L ◽  
Epidermal Cells ◽  
Host Cells ◽  
Colony Development ◽  
Mesophyll Cells

Primary leaves of wheat (Triticum aestivum L.) with and without resistance genes Sr5, Sr6, Sr8, or Sr22 were inoculated with avirulent races of stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn.) and examined by fluorescence microscopy. In leaves containing the Sr5 gene for resistance, both epidermal and mesophyll cells fluoresced when interacting with the fungus, indicating incompatibility. In leaves containing the Sr6 gene, interacting epidermal cells did not fluoresce and incompatibility was expressed only in mesophyll cells.When the effect of the Sr5 gene was studied in leaves with different genetic backgrounds, it was found that most colonies developed only one or two haustorial mother cells in leaves containing this gene in Prelude, Marquis, or Reliance backgrounds, when examined up to 72 h after incubation. Conversely, in leaves with the Chinese Spring background, one-third of the colonies continued to grow and they produced macroscopically visible lesions. Our observations indicated that the Chinese Spring genotype partially altered the expression of the Sr5 gene in mesophyll but not in epidermal cells. In contrast, the Sr6 gene was more effective in the Chinese Spring background than in the Prelude background.Rust development in leaves with or without the Sr8 gene was the same up to 60 h after incubation, when incompatibility in resistant plants was first detected by the appearance of fluorescing host cells. By 72 h, mean colony size in resistant leaves was smaller than that in susceptible leaves, evidently because growth of runner hyphae was inhibited. Apparently, the P8 gene for avirulence was not expressed until colonies had reached considerable size. In leaves containing the Sr22 gene for resistance, the sequence of histological events was similar to that in leaves containing Sr8, but fluorescing host cells appeared later (72 h) and colony growth was inhibited only at 96 h after incubation. In both of these interactions, fluorescing host cells developed at the periphery of colonies when incompatibility was expressed. The host-parasite interaction in cells invaded before that time remained compatible even at later stages of colony development. In leaves containing the Sr5 or the Sr8 gene, but not in those with the Sr6 gene, the growth of some colonies was inhibited although they were not associated with fluorescing host cells. Evidently, host-cell necrosis was closely associated with reduced fungal growth in interactions involving Sr6, but not in interactions involving the resistance genes Sr5 and Sr8.

Electron microscopy of susceptible and resistant near-isogenic (sr6/Sr6) lines of wheat infected by Puccinia graminis tritici. II. Expression of incompatibility in mesophyll and epidermal cells and the effect of temperature on host–parasite interactions in these cells

1979 ◽  
Vol 57 (23) ◽  
pp. 2617-2625 ◽  
Author(s):  
D. E. Harder ◽  
R. Rohringer ◽  
D. J. Samborski ◽  
S. R. Rimmer ◽  
W. K. Kim ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Epidermal Cells ◽  
Host Cells ◽  
Effect Of Temperature ◽  
Temperature Sensitive ◽  
Structural Abnormality ◽  
Mesophyll Cells ◽  
Backcross Line ◽  
Chinese Spring Wheat ◽  
Host Parasite

Primary leaves of near-isogenic lines of Chinese Spring wheat, either with or without the temperature-sensitive resistance gene Sr6, were inoculated with an avirulent race of stem rust, maintained at 19, 26, or 28 °C, and harvested 1–4 days after inoculation. The infected tissues were examined with an electron microscope to determine the effects of these temperatures on the expression of the Sr6 gene. At 26 °C in the Sr6 line about one-half of the haustoria in mesophyll cells were disorganized or collapsed. None of the haustoria in epidermal cells showed any structural abnormality. In the susceptible (sr6) line, most haustoria were structurally normal at 26 °C whether they were in mesophyll or epidermal cells. There were no signs of disorganization or necrosis of infected host cells of either (Sr6 or sr6) line at 26 °C. At 28 °C in both lines, all haustoria in mesophyll cells were necrotic or collapsed, but those in epidermal cells were not. No host cell necrosis was observed in genotypically resistant leaves. At 19 °C, most haustoria and invaded mesophyll cells in the Sr6 line were necrotic. In the invaded epidermal cells neither haustoria nor host protoplasts were necrotic. In contrast, in a backcross line of Marquis wheat containing resistance gene Sr5 and infected with an avirulent race, both invaded mesophyll and epidermal cells were necrotic.

scholarly journals Exploring the maturation of a monocytic cell line using self-organizing maps of single-cell Raman spectra

2020 ◽  
Author(s):  
Sayani Majumdar ◽  
Mary L Kraft
Keyword(s):  
Single Cell ◽  
Raman Spectra ◽  
Macrophage Polarization ◽  
Intermediate Stage ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Self Organizing Maps ◽  
Differentiated Cells ◽  
20 Nm ◽  
Self Organizing

ABSTRACTPhorbol myristate acetate (PMA)-differentiated THP-1 cells are routinely used in lieu of primary macrophages to study macrophage polarization during host-pathogen interactions and disease progression. The phenotypes of the THP-1 macrophages are influenced by the level and duration of PMA stimulation, and possibly also by the presence of adhesion factors. Here, we use self-organizing maps (SOMs) of single-cell Raman spectra to probe the effects of PMA stimulation conditions and adhesion factors on THP-1 cell differentiation. Raman spectra encoding for biochemical composition were acquired from individual cells on substrates coated with fibronectin or poly-L-lysine before and after stimulation with 20 nM or 200 nM PMA for two different time intervals. SOMs that show the extent of spectral dissimilarity were constructed. For all stimulation conditions, the SOMs indicated the spectra acquired from cells after 3 d treatment had diverged from those of untreated cells. The SOMs also showed treatment with 200 nM PMA for 3 d produced both fully and partially differentiated cells on both adhesion factors, whereas the outcome of 20 nM PMA treatment for 3 d depended on the adhesion factor. Treatment of THP-1 cells on fibronectin with 20 nM PMA for 3 d produced both partially and fully differentiated cells, but this treatment induced an intermediate stage of differentiation when applied to THP-1 cells on poly-L-lysine. Thus, the transition of THP-1 monocytes into macrophage-like cells may be modulated by integrin-binding interactions. Furthermore, the composite of culture and stimulation conditions may confound the comparison of results from separate studies.

scholarly journals Electron tomography visualization of HIV-1 fusion with target cells using fusion inhibitors to trap the pre-hairpin intermediate

2020 ◽  
Author(s):  
Mark S. Ladinsky ◽  
Priyanthi N.P. Gnanapragasam ◽  
Zhi Yang ◽  
Anthony P. West ◽  
Michael S Kay ◽  
...  
Keyword(s):  
Electron Tomography ◽  
Intermediate Stage ◽  
Viral Envelope ◽  
Host Cells ◽  
Target Cells ◽  
Virus Infectivity ◽  
Viral Fusion ◽  
Fusion Inhibitors ◽  
Viral Egress ◽  
Hiv 1

AbstractFusion of HIV-1 with the membrane of its target cell, an obligate first step in virus infectivity, is mediated by binding of the viral envelope (Env) spike protein to its receptors, CD4 and CCR5/CXCR4, on the cell surface. The process of viral fusion appears to be fast compared with viral egress and has not been visualized by electron microscopy (EM). To capture fusion events for EM, the process must be slowed or stopped by trapping Env-receptor binding at an intermediate stage. Here we describe using fusion inhibitors to trap HIV-1 virions attached to target cells by Envs in an extended pre-hairpin intermediate state. Electron tomography revealed HIV-1 virions bound to TZM-bl cells by 2-4 narrow spokes, with slightly more spokes present when evaluated with mutant virions that lacked the Env cytoplasmic tail. These results represent the first direct visualization of the hypothesized pre-hairpin intermediate and improve our understanding of Env-mediated HIV-1 fusion and infection of host cells.

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