Budding patterns during the cell cycle of the maize smut pathogen Ustilago maydis

Abstract

Haploid sporidia of the dimorphic phytopathogen Ustilago maydis (D.C.) Corda reproduce by budding once each cell cycle. Homogeneous log-phase sporidial cultures were generated by serial passage in liquid culture, and the growth characteristics and percentages of budded cells were determined for the cultures. The characteristics of budding were determined for individual cells by light and electron microscopy. Buds emerged only from the poles of mother cells, and cells could select either a previously used bud site, or a new bud site, each cycle. Time-lapse photomicroscopy indicated that, on solid medium, the first two buds emerged from new cells at a point distal to the site of attachment to the mother cell. In subsequent cell cycles, the buds tended to emerge from alternate poles of the mother cell. The cells used multiple bud sites at each pole. In addition, transmission and scanning electron microscopy revealed a series of annulations (bud scars) at the base of some buds, indicating that cells also used the same budding site many times. This versatility in selecting bud sites indicates that budding likely depends on complex regulatory pathways for determining cellular polarity. Key words: Ustilago maydis, bud, polarity, cell cycle, morphogenesis, yeast.

Role of Hsl7 in Morphology and Pathogenicity and Its Interaction with Other Signaling Components in the Plant Pathogen Ustilago maydis

“…Another possible explanation of the directional-growth phenotype is a defect in cell separation. In U. maydis cells, budding alternates between the poles of cells, where one daughter cell buds and completely separates from the mother cell before the next daughter cell begins budding from the opposite pole (26). If mother and daughter cells do not correctly separate, then the cells will remain connected and grow in a linear fashion, mimicking pseudohyphal cells in appearance.…”

Pathocycles: Ustilago maydis as a model to study the relationships between cell cycle and virulence in pathogenic fungi

“…Similar to S. cerevisiae, veg-etative growing U. maydis cells normally produce one polar bud per cell cycle (Jacobs et al 1994), which is formed at one apex, usually oV center from the tip (budding angle around 35°, Straube et al 2003). However, two main diVerences distinguish bud formation in both yeasts.…”

The machinery for cell polarity, cell morphogenesis, and the cytoskeleton in the Basidiomycete fungus Ustilago maydis—A survey of the genome sequence☆

“…The mechanism by which one of the cell poles is chosen versus the other is not known. Cells are able to bud at new sites at the cell poles or use a previously chosen site for budding as in apiculate yeasts (Jacobs et al, 1994). In some respects this pattern resembles the bipolar budding pattern of S. cerevisiae.…”