Cellular differentiation in Venturia inaequalis ascospores during germination and penetration of apple leaves

1987 ◽  
Vol 65 (12) ◽  
pp. 2549-2561 ◽  
Author(s):  
K. J. Smereka ◽  
W. E. Machardy ◽  
A. P. Kausch
Keyword(s):  
Time Course ◽  
Venturia Inaequalis ◽  
Ultrastructural Changes ◽  
Wall Material ◽  
Dense Matrix ◽  
Mechanical Pressure ◽  
Selective Staining ◽  
Infection Hypha ◽  
Dome Shape ◽  
Host Tissues

The penetration of the apple leaf cuticle by ascospores of Venturia inaequalis was studied by using ultrastructural and cytochemical techniques. A time-course developmental sequence is presented. Attachment of ascospores to the leaf surface appears to be by a mucilaginous substance and is followed by germination and penetration pore formation. The penetration pore is a circular opening adjacent to the leaf. It appears to form by degradation of the fungal wall and is bordered by a thickening of fungal wall material. Above the penetration pore, an infection sac forms from invagination and extension of the fungal plasmalemma. This structure has been reported only in V. inaequalis. Infection sac development initiates when the fungal plasmalemma appears to be forced into a dome shape. The dome flattens out and the membrane folds back upon itself, circumscribing the margin of the pore. The folded membrane becomes apposed, resulting in a circular belt of junctional structures which morphologically resemble molluscan septate junctions. As the infection sac enlarges, additional junctions form wherever the infection sac membrane abuts with the fungal plasmalemma. Selective staining with phosphotungstic acid revealed that the infection sac membrane becomes differentiated from the fungal plasmalemma. The infection sac enlarges and accumulates a dense matrix that appears to penetrate into the cuticle, causing ultrastructural changes in host tissues. The infection hypha, which is an extension of the infection sac membrane, breaches the cuticle without any apparent mechanical pressure.

Ultrastructural Changes of the Symbiotic Chlorella-Like Alga Isolated from Hydra Viridis

1982 ◽  
Vol 40 ◽  
pp. 320-321
Author(s):  
K.W. Lee ◽  
R.H. Meints ◽  
D. Kuczmarski ◽  
J.L. Van Etten
Keyword(s):  
Time Course ◽  
Reciprocal Cross ◽  
Ultrastructural Level ◽  
Ultrastructural Changes ◽  
Symbiotic Relationship ◽  
Cell Recognition ◽  
Green Hydra ◽  
Different Strains ◽  
Hydra Viridis

The physiological, biochemical, and ultrastructural aspects of the symbiotic relationship between the Chlorella-like algae and the hydra have been intensively investigated. Reciprocal cross-transfer of the Chlorellalike algae between different strains of green hydra provide a system for the study of cell recognition. However, our attempts to culture the algae free of the host hydra of the Florida strain, Hydra viridis, have been consistently unsuccessful. We were, therefore, prompted to examine the isolated algae at the ultrastructural level on a time course.

scholarly journals Comparative Time-Course Physiological Responses and Proteomic Analysis of Melatonin Priming on Promoting Germination in Aged Oat (Avena sativa L.) Seeds

2021 ◽  
Vol 22 (2) ◽  
pp. 811
Author(s):  
Huifang Yan ◽  
Peisheng Mao
Keyword(s):  
Antioxidant Capacity ◽  
Avena Sativa ◽  
Proteomic Analysis ◽  
Time Course ◽  
Intact Cell ◽  
Membrane Integrity ◽  
Acid Synthesis ◽  
Ultrastructural Changes ◽  
Oat Seeds ◽  
Aged Seeds

Melatonin priming is an effective strategy to improve the germination of aged oat (Avena sativa L.) seeds, but the mechanism involved in its time-course responses has remained largely unknown. In the present study, the phenotypic differences, ultrastructural changes, physiological characteristics, and proteomic profiles were examined in aged and melatonin-primed seed (with 10 μM melatonin treatment for 12, 24, and 36 h). Thus, 36 h priming (T36) had a better remediation effect on aged seeds, reflecting in the improved germinability and seedlings, relatively intact cell ultrastructures, and enhanced antioxidant capacity. Proteomic analysis revealed 201 differentially abundant proteins between aged and T36 seeds, of which 96 were up-accumulated. In melatonin-primed seeds, the restoration of membrane integrity by improved antioxidant capacity, which was affected by the stimulation of jasmonic acid synthesis via up-accumulation of 12-oxo-phytodienoic acid reductase, might be a candidate mechanism. Moreover, the relatively intact ultrastructures enabled amino acid metabolism and phenylpropanoid biosynthesis, which were closely associated with energy generation through intermediates of pyruvate, phosphoenolpyruvate, fumarate, and α-ketoglutarate, thus providing energy, active amino acids, and secondary metabolites necessary for germination improvement of aged seeds. These findings clarify the time-course related pathways associated with melatonin priming on promoting the germination of aged oat seeds.

scholarly journals Patterns of Gene Expression Upon Infection of Soybean Plants by Phytophthora sojae

2004 ◽  
Vol 17 (10) ◽  
pp. 1051-1062 ◽  
Author(s):  
Pat Moy ◽  
Dinah Qutob ◽  
B. Patrick Chapman ◽  
Ian Atkinson ◽  
Mark Gijzen
Keyword(s):  
Gene Expression ◽  
Time Course ◽  
Phytophthora Sojae ◽  
Gene Microarray ◽  
Pathogenesis Related ◽  
Soybean Plants ◽  
Related Proteins ◽  
Phytoalexin Biosynthesis ◽  
Host Tissues ◽  
Mixed Samples

To investigate patterns of gene expression in soybean (Glycine max) and Phytophthora sojae during an infection time course, we constructed a 4,896-gene microarray of host and pathogen cDNA transcripts. Analysis of rRNA from soybean and P. sojae was used to estimate the ratio of host and pathogen RNA present in mixed samples. Large changes in this ratio occurred between 12 and 24 h after infection, reflecting the rapid growth and proliferation of the pathogen within host tissues. From the microarray analysis, soybean genes that were identified as strongly upregulated during infection included those encoding enzymes of phytoalexin biosynthesis and defense and pathogenesis-related proteins. Expression of these genes generally peaked at 24 h after infection. Selected lipoxygenases and peroxidases were among the most strongly downregulated soybean genes during the course of infection. The number of pathogen genes expressed during infection reached a maximum at 24 h. The results show that it is possible to use a single microarray to simultaneously probe gene expression in two interacting organisms. The patterns of gene expression we observed in soybean and P. sojae support the hypothesis that the pathogen transits from biotrophy to necrotrophy between 12 and 24 h after infection.

scholarly journals Particle Assembly and Ultrastructural Features Associated with Replication of the Lytic Archaeal Virus Sulfolobus Turreted Icosahedral Virus

2009 ◽  
Vol 83 (12) ◽  
pp. 5964-5970 ◽  
Author(s):  
Susan K. Brumfield ◽  
Alice C. Ortmann ◽  
Vincent Ruigrok ◽  
Peter Suci ◽  
Trevor Douglas ◽  
...  
Keyword(s):  
Time Course ◽  
Plaque Assay ◽  
Ultrastructural Changes ◽  
Progeny Virus ◽  
Particle Assembly ◽  
Virus Particles ◽  
Transmission Electron ◽  
Archaeal Viruses ◽  
Infected Cells ◽  
Sulfolobus Turreted Icosahedral Virus

ABSTRACT Little is known about the replication cycle of archaeal viruses. We have investigated the ultrastructural changes of Sulfolobus solfataricus P2 associated with infection by Sulfolobus turreted icosahedral virus (STIV). A time course of a near synchronous STIV infection was analyzed using both scanning and transmission electron microscopy. Assembly of STIV particles, including particles lacking DNA, was observed within cells, and fully assembled STIV particles were visible by 30 h postinfection (hpi). STIV was determined to be a lytic virus, causing cell disruption beginning at 30 hpi. Prior to cell lysis, virus infection resulted in the formation of pyramid-like projections from the cell surface. These projections, which have not been documented in any other host-virus system, appeared to be caused by the protrusion of the cell membrane beyond the bordering S-layer. These structures are thought to be sites at which progeny virus particles are released from infected cells. Based on these observations of lysis, a plaque assay was developed for STIV. From these studies we propose an overall assembly model for STIV.

An ultrastructural study of pollen development in tomato (Lycopersicon esculentum). I. Tetrad to early binucleate microspore stage

1993 ◽  
Vol 71 (8) ◽  
pp. 1039-1047 ◽  
Author(s):  
P. L. Polowick ◽  
V. K. Sawhney
Keyword(s):  
Endoplasmic Reticulum ◽  
Lycopersicon Esculentum ◽  
Ultrastructural Study ◽  
Pollen Development ◽  
Pollen Wall ◽  
Ultrastructural Changes ◽  
Dense Matrix ◽  
Tetrad Stage ◽  
Microspore Stage ◽  
Electron Dense Matrix

Microspores undergo considerable ultrastructural changes between the tetrad and early binucleate microspore stages of microsporogenesis in tomato (Lycopersicon esculentum). Pollen wall deposition began late in the tetrad stage, and by the early microspore stage a lamellar foot layer and tectum were deposited. Sculpturing of the tectum was evident by the early binucleate microspore stage. Dictyosomes and vesicles were abundant during the period of pollen wall formation. Plastids were associated with the endoplasmic reticulum (ER) to form plastid–ER complexes, from the late tetrad to the vacuolate microspore stage. At the vacuolate microspore stage, endoplasmic reticulum independent of plastids was also observed, and at the early binucleate microspore stage ER was not associated with plastids. Free ribosomes were evenly distributed throughout the cytoplasm until the vacuolate microspore stage when they were organized into polysomes. Mitochondria were spherical to ellipsoid, with an electron-dense matrix and swollen cristae, until the early binucleate microspore stage when they were highly elongate and became convoluted. Key words: Lycopersicon esculentum, microsporogenesis, pollen development, tetrads, tomato, ultrastructure.

Ultrastructural changes in posterior midgut cells associated with blood feeding in adult female Rhodnius prolixus Stal (Hemiptera: Reduviidae)

1983 ◽  
Vol 61 (11) ◽  
pp. 2574-2586 ◽  
Author(s):  
P. F. Billingsley ◽  
A. E. R. Downe
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Blood Meal ◽  
Apical Cell ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
Ultrastructural Changes ◽  
Dense Matrix ◽  
Apical Surface ◽  
Posterior Midgut

Modifications of posterior midgut cells of Rhodnius prolixus following a meal of rabbit blood are described. Prominent stacks and whorls of rough endoplasmic reticulum become redistributed following a blood meal but later reform during the postfeeding period. Lysosomes undergo internal structural changes and apparent fluctuations in their number per cell as a result of blood meal ingestion. Before blood feeding, the apical surface of the midgut cells show a typical arrangement of a plasma membrane covered on the lumenal surface by a glycocalyx. After a blood meal, a more complex organisation appears, consisting of two plasma membranes separated by an electron-dense matrix. The lumenal apical membrane proliferates during the digestion period to form loosely organised extracellular membrane layers which may function as a peritrophic membrane. Changes in the rough endoplasmic reticulum and lysosomes and modifications to the apical cell surface appear to coincide with previously described proteinase activity cycles in the posterior midgut of R. prolixus. The implications of these results are discussed and are compared with similar ultrastructural events from haematophagous Diptera.

Ultrastructural changes in tissues of larval Elateridae (Coleoptera) infected with the fungus Metarrhizium anisopliae

1971 ◽  
Vol 17 (2) ◽  
pp. 281-289 ◽  
Author(s):  
R. Y. Zacharuk
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Fat Body ◽  
Malpighian Tubule ◽  
Malpighian Tubules ◽  
The Other ◽  
Host Cells ◽  
Ultrastructural Changes ◽  
Host Death ◽  
Host Tissues

The ultrastructural changes that occur in the cells of the hypodermis, fat body, Malpighian tubule, midgut, ventral abdominal ganglion, and muscle during mycoses in three species of elaterid larvae infected with Metarrhizium anisopliae are described. The fungus penetrated all the above tissues before host death in most of the larvae examined. In some infected larvae, however, particularly in the smaller individuals or species, only the hypodermal and fat tissues were penetrated before death. Changes in fine structure appear in all the tissues soon after the fungus enters the hemocoel, even when no fungal growths are present near the host cells. In general, there is initially an increase in the number of lysosomes and of endoplasmic reticulum and ribosomes, followed by a vesiculation of the endoplasmic reticulum and of the cristae of the mitochondria and a progressive vacuolation of the cytoplasm. In some tissues the mitochondria increase in number before vesiculation. Glycogen granules and lipid and oil inclusions disappear rapidly during mycosis. Clear, membrane-limited vacuoles become particularly abundant in the Malpighian tubules and the midgut, suggesting increased secretion of fluids into their lumens. At or soon after death, the lysosomes disappear and all the membranous structures of the cells are disrupted, and laminated or whorled bodies of thickened membranes become numerous. Disintegration of all tissues, including muscle and nerve, was extensive in some larvae that were still capable of some sluggish movement before fixation for the study. It is suggested that the fungus incites lysosome production by the host tissues along with the other initial changes observed, and that final disintegration of the host tissues is by a process of autohistolysis.

Ultrastructural changes in the myxamoebae of Physarum polycephalum in response to a microcyst-inducing concentration of mannitol

1984 ◽  
Vol 62 (2) ◽  
pp. 272-280 ◽  
Author(s):  
Lynda M. Williams ◽  
Jean-G. Lafontaine
Keyword(s):  
Cell Wall ◽  
Osmotic Potential ◽  
Physarum Polycephalum ◽  
Morphological Changes ◽  
Ruthenium Red ◽  
Ultrastructural Changes ◽  
Wall Material ◽  
Cell Wall Material ◽  
Cell Coat ◽  
Ruthenium Red Staining

The response of axenically cultured Physarum polycephalum myxamoebae to a microcyst-inducing concentration of mannitol (0.5 M) has been studied for both log-phase and maximum-concentration cultures. Results indicate that mannitol alone is not sufficient to induce encystment; a population effect is also necessary. Myxamoebae may continue to divide in the presence of mannitol if this effect is absent. Early ultrastructural changes have been noted indicating that the primary mode of action of mannitol is via the change in osmotic potential of the medium. Nuclear and cytoplasmic ultrastructural changes during the encystment process are documented. Recovery of log-phase cells to undergo mitosis involves definite morphological changes, which are also described. Ruthenium red staining was utilised to emphasize changes in the cell coat and indicate possible sites of accumulation of cell wall material.

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