| Summary: | One of the major aims of the study was to characterise spore germination using light microscopy and to investigate the role and relative importance of each of the three conidial cells for successful germination. Analysis of germ tube growth rate showed that there are two modes of germination: a conidium produces either a single germ tube or two slightly slower growing germ tubes. Results from scanning electron microscopy and fluorescence microscopy studies suggest that germ tube emergence is asymmetric and directed towards the substratum. A method was developed by which individual conidial cells could be selectively killed, using localised laser irradiation, a technique which has not been previously used with fungal cells. The data suggest that isolated apical and basal cells are able to germinate and form appressoria. The middle cell never germinated, even when it was the only living cell in a conidium. Furthermore, there was evidence that the apical cell, which germinates most frequently, exerts "apical dominance" over the basal cell. Very little is known about organelle morphology and distribution within living fungal spores, and even less is known abut organellar dynamics during spore germination. Another major aim of this study was to characterise organellar organisation and dynamics in living and potentially pathogenic conidia throughout germination. The analysis used confocal microscopy and vital stains. To obtain biologically meaningful results, an <i>in vitro</i> system which mimicked <i>in vivo</i> conditions as closely as possible was developed and optimised for confocal microscopy. A range of potentially vital dyes were screened as organelle stains in living conidia during germination. Nuclei (stained with SYTO 11), vacuolar compartments (stained with cDFFDA), mitochondria (stained with Rhodamine 123), and the apical vesicle cluster (stained with FM4-64) were identified and characterised during germination. Each cell was shown to contain a single nucleus that changed position within the cell during germination but otherwise did not exhibit extensive movement.
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