Evaluating yeast filamentous growth at the single-cell level

Budding yeast can undergo filamentous growth in response to nutrient limitation. Filament formation can be examined under glucose-limiting conditions by the single-cell invasive growth assay, or under nitrogen-limiting conditions with the pseudohyphal growth assay, both described here. The single-cell assay allows robust quantitation of changes in budding pattern and cell length, and most cells in the population show the response. The pseudohyphal growth assay reveals filamentous patterns in larger microcolonies and adjoining subpopulations of cells. Historically, the single-cell assay has been used to study filamentous growth in haploid cells and the pseudohyphal growth assay in diploid cells. However, both assays can be used in either cell type.