THE CYTOLOGY OF INFECTION STRUCTURE DEVELOPMENT IN UREDIOSPORE GERM TUBES OF UROMYCES PHASEOLI VAR. TYPICA (PERS.) WINT.

1967 ◽  
Vol 45 (4) ◽  
pp. 447-450 ◽  
Author(s):  
Ramesh Maheshwari ◽  
A. C. Hildebrandt ◽  
P. J. Allen
Keyword(s):  
Nuclear Division ◽  
In Vitro Differentiation ◽  
Structure Development ◽  
Infection Structures ◽  
Uromyces Phaseoli ◽  
Mother Cells ◽  
Germ Tubes ◽  
Infection Hypha ◽  
Feulgen Technique

Urediospores of Uromyces phaseoli var. typica (Pers.) Wint. race 32 Arth. germinated on mineral oil – nitrocellulose membranes and sequentially developed appressoria, vesicles, and infection hyphae. The nuclear behavior during in vitro differentiation of infection structures was studied by use of the Feulgen technique. The two urediospore nuclei divided in the germ tube before the formation of appressorium. This was followed by a second division of the four daughter nuclei in the appressorium, and occasionally by a third division of the eight nuclei in the vesicle and infection hypha. Haustorial mother cells were formed in infection hyphae in vitro and contained from two to five nuclei. In contrast, nuclear division did not occur in germ tubes where growth continued linearly. Infection structures that developed in vitro resembled those produced during infection of the host by urediospores of other species of rust fungi.

Structural studies of the development of infection structures of cowpea rust, Uromyces phaseoli var. vignae. I. Nucleoli and nuclei

1978 ◽  
Vol 56 (6) ◽  
pp. 648-661 ◽  
Author(s):  
Michèle C. Heath ◽  
I. Brent Heath
Keyword(s):  
Mother Cell ◽  
Cell Formation ◽  
Structural Studies ◽  
Nucleolar Activity ◽  
Infection Structures ◽  
Uromyces Phaseoli ◽  
Living Material ◽  
Mother Cells ◽  
Germ Tubes ◽  
Infection Hypha

Light microscopical observations of living germ tubes and infection structures of cowpea rust were combined with an ultrastructural study to show that a nucleolus was present in the interphase nucleus at all stages of development from uredospore germination through to new uredospore formation. Vacuolate nucleoli were common in germ tubes but only nonvacuolate nucleoli were observed at other stages of fungal development. When grown on oil-containing collodion membranes, germinating uredospores, germ tubes, appressoria, and infection hyphae without haustorial mother cells all contained nucleoli composed primarily of nongranular material. Predominantly granular nucleoli were observed in developing uredospores and all parasitic stages in the leaf after the formation of the first haustorial mother cell. However, the fact that granular nucleoli were also seen in a membrane-grown infection hypha after haustorial mother cell formation suggested that the host was not required to stimulate the resumption of nucleolar activity. Electron-opaque patches, presumed to be condensed chromatin, were most prominent in the nucleoplasm of haustorial mother cells and virtually absent in germinating uredospores and germ tubes. The significance of this observation is discussed. A reduction in nuclear volume was observed in living material prior to cytokinesis in the appressorium and the substomatal vesicle. Evidence suggested that this reduction was produced by the expulsion of part of the nucleoplasm, plus the nucleolus, during mitosis rather than before as suggested for other rusts. Nuclei of haustorial mother cells and haustoria were also smaller than those in intercellular hyphae but the mechanism by which this was achieved could not be determined.

Structural studies of the development of infection structures of cowpea rust, Uromyces phaseoli var. vignae. II. Vacuoles.

1979 ◽  
Vol 57 (17) ◽  
pp. 1830-1837 ◽  
Author(s):  
I. Brent Heath ◽  
Michèle C. Heath
Keyword(s):  
Control System ◽  
Structural Studies ◽  
Developmental Pathway ◽  
Infection Structures ◽  
Uromyces Phaseoli ◽  
Mother Cells ◽  
Germ Tubes

During development of infection structures of cowpea rust, Uromyces phaseoli var. vignae, migration of cytoplasm from one structure to the next is accompanied by production of vacuoles. The developmental pathway of these vacuoles appears to differ in different sites of production. In germinating uredospores, appressoria, and substomatal vesicles, their development includes the formation and enlargement of electron-opaque globule-containing vesicles, termed vacuole precursor vesicles (VPVs). In contrast, in the elongating germ tubes and vacuolating haustorial mother cells, VPVs do not appear during vacuolation. During development of VPVs into vacuoles there seems to be a control system which selectively activates only a portion of the VPV population.

scholarly journals Ultrastructural and Immunochemical Changes During the In Vitro Development of Plasmopara halstedii

2003 ◽  
Vol 93 (8) ◽  
pp. 1023-1030 ◽  
Author(s):  
Sandrine Bouterige ◽  
Guy Tronchin ◽  
Maurice Lesourd ◽  
Agnès Marot-Leblond ◽  
Valérie Molinéro ◽  
...  
Keyword(s):  
Ultrastructural Changes ◽  
Asexual Development ◽  
Direct Examination ◽  
Plasmopara Halstedii ◽  
In Vitro Development ◽  
A Cell ◽  
Mother Cells ◽  
Vitro Development ◽  
Germ Tubes

The asexual phase of the life cycle of Plasmopara halstedii, the causal agent of downy mildew of sunflower, plays a key role in the propagation of the disease. We investigated the morphological and ultrastructural changes that occur during the asexual development of the pathogen. Direct examination of infected cotyledons confirmed the presence of sporangiophores. In contact with water, important ultrastructural changes occurred, affecting the surface of zoosporangia, which became smoother, and their cytoplasm, which differentiated into flagellate zoospores. The subsequent encystment of zoospores was characterized by the synthesis of a cell wall and the loss of the flagella. In addition, two monoclonal antibodies (MAbs) specific for P. halstedii were used to analyze the immunochemical changes associated with these modifications. MAb 16A6, which bound to a 48-kDa glycoprotein, mainly labeled the surface of mobile or encysted zoospores and of mother cells of germ tubes. Conversely, MAb 2F9, which recognized highly glycosylated antigens, labeled the surface of zoosporangia and of flagellate zoospores, but not the encysted zoospores. These results provide new insights into the morphological and ultrastructural changes associated with the release and the encystment of zoospores which may be interesting targets for the development of new antimicrobial products.

Ultrastructure of conidial germ-tube development in vitro by the insect pathogen Entomophaga aulicae

1989 ◽  
Vol 67 (3) ◽  
pp. 754-762 ◽  
Author(s):  
Faye Murrin ◽  
Richard A. Nolan
Keyword(s):  
Germ Tube ◽  
Culture Medium ◽  
Protoplast Formation ◽  
Insect Pathogen ◽  
Liquid Culture Medium ◽  
Cytoplasmic Membranes ◽  
Development In Vitro ◽  
Germ Tubes ◽  
Infection Hypha

In an effort to understand the factors influencing the formation of infection structures by the insect pathogen Entomophaga aulicae, we examined the ultrastructural development of conidial germ tubes formed in vitro under conditions that resemble those producing appressoria and protoplasts during infection. Conidia germinated on formvar in a nonaqueous environment produced a single viable germ tube, which in turn produced appressorium-like structures or secondary conidia, structures similar to those formed on the host. The formation of appressorium-like structures indicates that stimuli for appressorium formation are relatively nonspecific, whereas development of the infection hypha requires different triggers. Conidia germinated in a liquid culture medium, which supports the growth of the protoplast stage of the fungus, produced a single viable germ tube that continued to grow apically. This apical growth was accompanied by the loss of the outer layer of the germ tube wall and the presence of electron-opaque granules in an extensive system of cytoplasmic membranes. Protoplasts did not form directly from these germ tubes and ultrastructural details of tip growth in this medium did not resemble those previously described in infection hyphae prior to protoplast formation in the host.

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