Chromatin and Cell Wall Staining of Schizosaccharomyces pombe

Abstract

Fission yeasts grow by tip extension, maintaining a constant width until they reach a critical size threshold and divide. Division by medial fission—which gives these yeast their name—generates a new end that arises from the site of cytokinesis. The old end, which was produced during the previous cell cycle, initiates progression of the new cell cycle, and in G2, the new end is activated in a process termed new-end takeoff (NETO). In this protocol, the fluorescent stains calcofluor and 4′,6-diamidino-2-phenylindole (DAPI) are used to give a rapid and informative assessment of morphogenesis and cell-cycle progression in the fission yeast Schizosaccharomyces pombe. Calcofluor reveals the timing of NETO because it stains the birth scars that are generated at new ends by cytokinesis less efficiently than the rest of the cell wall. Intense calcofluor staining of the septum and measurement of cell length are also widely used to identify dividing cells and to gauge the timing of mitotic commitment. Staining nuclei with DAPI identifies mono- and binucleated cells and complements the calcofluor staining procedure to evaluate the stages of the cell cycle and identify mitotic errors. Equally simple DAPI staining procedures reveal chromatin structure in higher resolution, facilitating more accurate staging of mitotic progression and characterization of mitotic errors.