Marburg, Universiẗat, Diss., 2004.

Marburg, Universiẗat, Diss., 2004.

Köln, Universiẗat, Diss., 2004.

A mutant mycelial colony of Ustilago hordei (Pers.) Lagerh.' was studied by light and electron microscopy to compare its general morphology with results obtained from earlier cytological studies. Its ultrastructure is also compared with that of other fungi. The results obtained from light microscopy generally agree with those from earlier work. Cells of the mycelia are very long, irregular in length, and contain numerous mitochondria and one to several nuclei. Electron microscopy reveals the walls of the mycelial cells to be single layered fibrillar structures. In apical regions all the characteristic organelles are present. The elongate mitochondria have plate-like cristae that lie parallel to the long axis of the mitochondri and the outer bounding membrane is often thicker than the inner one; these two features of the mitochondria are both unusual. Endoplasmic reticulum is sparse. Branch hyphae and septae are not present. In differentiated areas there is an increase in the number of vesicles and larger vacuoles. Mitochondria undergo rather unique changes whereby concentric lamellae are formed in a bulge of outer mitochondrial membrane. These concentric lamellae are engulfed by vacuoles in which the lamellae appear to be transformed into tubular bodies. At some point these vacuoles fuse with the plasma membrane and release their contents into the space between the plasma membrane and the cell wall. The vacuoles seem to act as lysosomes. Branch hyphae and septae are present. Degenerate regions are very vacuolated and contain many membranous structures. Few organelles are present. Mitochondria are distorted and their cristae swollen or absent. Dictyosomes and lomasomes are not present throughout the hyphae. / Science, Faculty of / Botany, Department of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1922. / Typescript. With this is bound: Spore germination of Ustilago striaeformis / William Harold Davis. Reprinted from: Phytopathology, vol. XIV, no. 6 (June 1924), p. [251]-266, plates xiv-xvi. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1941. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 88-91).

Pulsed-field gel electrophoresis (PFGE) of the strains representing the 14 races of U. hordei, the causal agent of covered smut on barley, revealed extensive polymorphism in chromosome length and number. The purpose of this study was to determine by two approaches the exact chromosome number for each U. hordei race, and to ascertain whether some strains are aneuploid, using two approaches. A telomere-specific repeat from Fusarium oxysporum was used as a probe onto Southern blots of restriction digests of individual chromosome bands to determine the number of chromosomes contained in each band. Nineteen to twenty-three chromosomes were identified in the strains representing the 14 races of U. hordei. To ascertain the number of chromosomes identified by the telomere-specific probe, chromosome-specific libraries were constructed and linkage groups were established by using chromosome-specific fragments as probes. The homologous chromosomes identified by these probes were typically monosomic with a maximum of 15 percent of variability, but cases of disomy were also observed in some strains. The second objective of this study was to analyze a filamentous mutant of U. hordei, designated fil1-1, that was isolated following heat-shock treatment. The filamentous phenotype is of interest, because it is believed to be involved in pathogenicity. U. hordei is a dimorphic fungus which has yeast like cells that are non pathogenic, while dikaryons produced upon mating are filamentous and pathogenic. Molecular characterization of the fil1-1 mutant showed that it has suffered a 50 kb deletion in a 940 kb chromosome. Genetical and physical analysis placed the fill mutation near the terminus of one arm of the 940 kb chromosome. The filamentous phenotype reverted to the sporidial wild type in presence of cyclic AMP. Biochemical analyses revealed that the intracellular level of cyclic AMP is three-fold lower in the mutant phenotype than in the wild type. These results indicate that cyclic AMP is an important determinant in fungal morphogenesis. / Graduation date: 1998

Univ., Diss., 2009--Marburg.

Univ., Diss., 2009--Marburg.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1953. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [147]-167).