Ultrastructure of conidium germination of Cochliobolus carbonus

1974 ◽  
Vol 52 (11) ◽  
pp. 2335-2340 ◽  
Author(s):  
Gordon M. Murray ◽  
Douglas P. Maxwell
Keyword(s):  
Germ Tube ◽  
Tube Wall ◽  
Outer Electron ◽  
Spherical Form ◽  
Innermost Layer ◽  
Apical Vesicles ◽  
Conidium Germination ◽  
Central Pore ◽  
Septal Pores ◽  
Germ Tubes

Multiseptate conidia of Cochliobolus carbonus germinate in water by one or two polar germ tubes. The septa between cells within a conidium contain a central pore, which is plugged before germination but open during germination, so that all cells are interconnected. During germination, vacuoles enlarge, endoplasmic reticulum profiles increase in number, and mitochondria change from a spherical form with loosely arranged cristae to an elongated form with closely packed cristae. The conidium wall consists of an inner electron-translucent layer and an outer electron-opaque layer. The germ tube wall is continuous with the innermost layer of the conidium wall. Shortly after germination, a septum with a central pore forms in the germ tube by invagination where it emerges from the conidium. The germ tube wall is surrounded by a fibrillar sheath. The presence of apical vesicles in the germ tube tip is confirmed. The associations of Woronin bodies with septal pores and microbodies, of lipids with vacuoles, and of microbodies with lipids and vacuoles are discussed.

Ultrastructure and lipid identification during conidium germination of Stemphylium sarcinaeforme

1976 ◽  
Vol 22 (1) ◽  
pp. 92-100 ◽  
Author(s):  
Gordon M. Murray ◽  
Douglas P. Maxwell
Keyword(s):  
Endoplasmic Reticulum ◽  
Acid Phosphatase ◽  
Total Lipid ◽  
Germ Tube ◽  
Tube Wall ◽  
Dry Weight ◽  
Lipid Bodies ◽  
Conidium Germination ◽  
Germ Tubes ◽  
Qualitative Changes

Multicelled conidia of Stemphylium sarcinaeforme germinate in water forming several germ tubes. Individual cells within conidia are connected by pores which are plugged in ungerminated conidia and open in germinated ones. During germination, vacuoles enlarge, endoplasmic reticulum profiles increase in number, and mitochondria change from spherical to elongate. The germ tube wall is laid down at the site of emergence from the conidium. Shortly after germination, a septum with a central pore forms where the germ tube emerged. The germ tube wall is surrounded by a fibrillar sheath. Lipid bodies are closely associated with vacuoles during germination. The ultrastructural location of lipid was found by extraction of conidia with lipid solvents. Total lipid decreases from 14.4% of the dry weight of ungerminated conidia to 13.4% of the dry weight of conidia germinated for 10 h. No qualitative changes occurred in the major lipid classes of conidia during germination. The activities of lipase and acid phosphatase were detected in ungerminated and germinated conidia.

Ultrastructure of conidia, conidium germination, and appressorium development in the plant pathogenic fungus Colletotrichum truncatum

1991 ◽  
Vol 69 (11) ◽  
pp. 2455-2467 ◽  
Author(s):  
C. Gerald Van Dyke ◽  
Charles W. Mims
Keyword(s):  
Germ Tube ◽  
Pathogenic Fungus ◽  
Freeze Substitution ◽  
Colletotrichum Truncatum ◽  
Dialysis Membrane ◽  
The Matrix ◽  
Single Nucleus ◽  
Conidium Germination ◽  
Matrix Spread ◽  
Germ Tubes

Nongerminating conidia of Colletotrichum truncatum were coated with copious amounts of a finely fibrillar extracellular matrix. This matrix spread out onto the dialysis membrane used as a substrate in this study. Each thin-walled conidium contained a single nucleus that underwent mitosis 1–2 h following placement of aqueous suspensions of conidia on membranes. A septum subsequently developed near the middle of the conidium, creating two uninucleate cells. Just prior to or during septum development a germ tube emerged laterally, usually near one end of the conidium. The nucleus moved into the germ tube and underwent mitosis. One daughter nucleus remained in the germ tube, the other moved back into the conidium. Developing germ tubes appeared to produce large amounts of electron-dense, fibrillar material that coated their surfaces. This material blended into the remnants of the matrix initially coating conidia and could not be clearly differentiated from the latter material. Germ tubes grew to various lengths before forming appressoria. Appressorium differentiation began shortly after the germ-tube tip curved sharply. A septum developed to delimit the tip that differentiated into a swollen appressorium. By 6 h following initial hydration of conidia, appressoria were melanized and the surrounding extracellular material had condensed onto their surfaces, forming an electron-dense coating that appeared to stick appressoria to dialysis membranes. A tiny penetration peg developed from an apparently wall-less region on the underside of the mature appressorium and, in some instances, grew a short distance into the dialysis membrane. Key words: electron microscopy, freeze substitution, conidia, appressoria.

Development of primary germ tubes by conidia of Blumeria graminis f.sp. hordei on leaf epidermal cells of Hordeum vulgare

2002 ◽  
Vol 80 (10) ◽  
pp. 1121-1125 ◽  
Author(s):  
H H Edwards
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Hordeum Vulgare ◽  
Host Cell ◽  
Germ Tube ◽  
Tube Wall ◽  
Blumeria Graminis ◽  
Transmission Electron ◽  
Host Cell Wall ◽  
Germ Tubes

Development of primary germ tubes from conidia of Blumeria graminis f.sp. hordei on primary leaf segments of Hordeum vulgare was investigated from 3 to 13 h postinoculation (hpi) using transmission electron microscopy. By 3 hpi, the primary germ tube wall that makes contact with the host cuticle develops a small protrusion that breaches the host cuticle and touches the host cell wall but does not penetrate any further. This protrusion is the cuticular peg. From 3 to 13 hpi, the cuticular peg swells, becomes quite electron dense, and finally develops a loose fibrillar texture. The structure of the primary germ tube with the terminal cuticular peg is consistent with the hypothesis that it allows the conidium to absorb water and solutes present in the host cell wall.Key words: powdery mildew, barley, ultrastructure.

Anastomosis of germ tubes and migration of nuclei in germ tube networks of the soybean rust pathogen, Phakopsora pachyrhizi

2011 ◽  
Vol 132 (2) ◽  
pp. 163-167 ◽  
Author(s):  
R. Vittal ◽  
H. -C. Yang ◽  
G. L. Hartman
Keyword(s):  
Germ Tube ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Rust Pathogen ◽  
And Migration ◽  
Germ Tubes

Resistance mechanisms in Lycopersicon spp. to tomato powdery mildew (Oidium neolycopersici)

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. S141-S144 ◽  
Author(s):  
A. Lebeda ◽  
B. Mieslerová ◽  
L. Luhová ◽  
K. Mlíčková
Keyword(s):  
Germ Tube ◽  
Leaf Surface ◽  
Resistance Mechanism ◽  
Resistance Mechanisms ◽  
Host Tissue ◽  
Tissue Response ◽  
Limited Information ◽  
Oidium Neolycopersici ◽  
Conidium Germination ◽  
Tomato Powdery Mildew

Limited information on the resistance mechanisms in Lycopersicon spp. to Oidium neolycopersici is still available. Macroscopically the resistance is characterized by a very low amount of mycelium development and a lack of sporulation. The leaf surface did not effectively inhibite conidium germination, however significant differences in germ tube and appressorium development were recorded. A large variation was observed in host tissue response. The prevailing resistance mechanism was hypersensitivity (HR). Considerable changes of peroxidase and catalase activities during pathogenesis were detected among tested wild Lycopersicon spp. There was positive correlation between increasing of peroxidase activity and extent of necrosis. Histochemistry showed large differences in production of superoxid ions, H<sub>2</sub>O<sub>2</sub> and peroxidase in Lycopersicon spp. with various level of resistance.

Ascospore germination, growth in culture, and imperfect spore formation in Cookeina sulcipes and Phillipsia crispata

1975 ◽  
Vol 53 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. W. Paden
Keyword(s):  
Germ Tube ◽  
Outer Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Spore Surface ◽  
No Formation ◽  
Ascospore Germination ◽  
Germ Tubes

Ascospores of Cookeina sulcipes germinate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores of Phillipsia crispata germinate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture both C. sulcipes and P. crispata form arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

Carbon dioxide induces endotrophic germ tube formation in Candida albicans

1990 ◽  
Vol 36 (4) ◽  
pp. 249-253 ◽  
Author(s):  
Ruth C. Mock ◽  
Jordan H. Pollack ◽  
Tadayo Hashimoto
Keyword(s):  
Carbon Dioxide ◽  
Candida Albicans ◽  
Sodium Bicarbonate ◽  
Key Words ◽  
Germ Tube ◽  
Tube Formation ◽  
Chemical Inducers ◽  
Tube Emergence ◽  
Ph Range ◽  
Germ Tubes

Candida albicans formed germ tubes when exposed to air containing 5 to 15% carbon dioxide (CO2). The CO2-mediated germ tube formation occurred optimally at 37 °C in a pH range of 5.5 to 6.5. No germ tubes were produced at 25 °C, even when the optimal concentration of CO2 (10%) was present in the environment. The requirement of CO2 for germ tube formation could be partially substituted by sodium bicarbonate but not by N2. Carbon dioxide was required to be present throughout the entire course of germ tube emergence suggesting that its role is not limited to an initial triggering of morphogenic change. We suggest that carbon dioxide may be a common effector responsible for the germ tube promoting activity of certain chemical inducers for C. albicans. Key words: Candida albican germ tubes, CO2-induced germ tube formation, endotrophic germ tube formation.

scholarly journals Regulation of Pathogenic Spore Germination by CgRac1 in the Fungal Plant Pathogen Colletotrichum gloeosporioides

2011 ◽  
Vol 10 (8) ◽  
pp. 1122-1130 ◽  
Author(s):  
Iris Nesher ◽  
Anna Minz ◽  
Leonie Kokkelink ◽  
Paul Tudzynski ◽  
Amir Sharon
Keyword(s):  
Cell Division ◽  
Plant Pathogen ◽  
Germ Tube ◽  
Colletotrichum Gloeosporioides ◽  
Fluorescent Protein ◽  
Nuclear Division ◽  
Simultaneous Formation ◽  
Content Type ◽  
Germ Tubes

ABSTRACT Colletotrichum gloeosporioides is a facultative plant pathogen: it can live as a saprophyte on dead organic matter or as a pathogen on a host plant. Different patterns of conidial germination have been recognized under saprophytic and pathogenic conditions, which also determine later development. Here we describe the role of CgRac1 in regulating pathogenic germination. The hallmark of pathogenic germination is unilateral formation of a single germ tube following the first cell division. However, transgenic strains expressing a constitutively active CgRac1 (CA-CgRac1) displayed simultaneous formation of two germ tubes, with nuclei continuing to divide in both cells after the first cell division. CA-CgRac1 also caused various other abnormalities, including difficulties in establishing and maintaining cell polarity, reduced conidial and hyphal adhesion, and formation of immature appressoria. Consequently, CA-CgRac1 isolates were completely nonpathogenic. Localization studies with cyan fluorescent protein (CFP)-CgRac1 fusion protein showed that the CgRac1 protein is abundant in conidia and in hyphal tips. Although the CFP signal was equally distributed in both cells of a germinating conidium, reactive oxygen species accumulated only in the cell that produced a germ tube, indicating that CgRac1 was active only in the germinating cell. Collectively, our results show that CgRac1 is a major regulator of asymmetric development and that it is involved in the regulation of both morphogenesis and nuclear division. Modification of CgRac1 activity disrupts the morphogenetic program and prevents fungal infection.

Emergence of the aeciospore germ tubes of Cronartium coleosporioides (=Peridermium stalactiforme) as observed by scanning electron microscope

1970 ◽  
Vol 48 (9) ◽  
pp. 1692-1692 ◽  
Author(s):  
Y. Hiratsuka
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Germ Tube ◽  
Germ Tubes ◽  
Scanning Electron

Germ tubes of Cronartium coleosporioides Arth. (= Peridermium stalactiforme Arth. and Kern) emerged between processes through short irregular slits. Germ tube walls were folded when they emerged and expanded after the emergence.

Behavior of Fusarium roseum 'Sambucinum' under carbon starvation conditions in relation to survival in soil

1969 ◽  
Vol 15 (1) ◽  
pp. 117-126 ◽  
Author(s):  
G. J. Griffin ◽  
T. Pass
Keyword(s):  
Latent Period ◽  
Direct Observation ◽  
Germ Tube ◽  
Carbon Starvation ◽  
Glucose Medium ◽  
Glucose Depletion ◽  
High Germination ◽  
Germ Tubes ◽  
Starvation Conditions ◽  
Exogenous Source

Direct observation of washed macroconidia of F. roseum 'Sambucinum' infested in rewetted soil and incubated at 6 °C indicated that germination increased to 79% at 4 days and increased slowly thereafter. Lysis of germ tubes was inhibited and most germ tubes were not lysed even after 48 days incubation. Small two- or three-celled macroconidia were commonly produced on germ tubes. In contrast, peak germination (39%) occurred at 2 days in rewetted soil incubated at 25 °C with germ tube lysis occurring rapidly between 4 and 8 days. Only sparse sporulation was observed. After 9 months, survival of F. roseum 'Sambucinum' was much greater in soil incubated at 6 °C than at 25 °C.Macroconidia required an exogenous source of carbon for high germination and formed one- or two-celled chlamydosporic macroconidia in media lacking exogenous carbon. After 9 months incubation under carbon starvation conditions at 25 °C chlamydosporic macroconidia had a longer latent period and a much slower rate of germination than macroconidia. Germinated macroconidia formed two- or three-celled macroconidia within 24 h when transferred to media lacking exogenous carbon. Four-celled macroconidia were produced by F. roseum 'Sambucinum' in a dilute glucose medium before exhaustion of the glucose while F. solani 'Coeruleum' formed chlamydospores in this medium after glucose depletion. Behavior of F. roseum 'Sambucinum' under carbon starvation conditions is similar to behavior in rewetted soil in the mode of sporulation and in the formation of chlamydosporic macroconidia, but differs by a lack of appreciable germination and by a greatly reduced lysis of fungal structures.

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