FIG. 4.

Rvs161p functions in cell-cell fusion during mating. Shown are matings between two wild-type haploids (panels A and B) or between two rvs161Δ mutant haploids (panels C to F) visualized by fluorescence/differential interference contrast optics. Cell nuclei are stained with the fluorescent dye 4′,6′-diamidino-2-phenylindole. Cell-cell fusion allows cytoplasmic mixing and the nuclei of each mating partner meet at the site of cell fusion to fuse and create a single diploid nucleus. In the case of rvs161Δ × rvs161Δ matings, delays in cell-cell fusion (apparent by differential interference contrast) result in delays in nuclear fusion. This leads to the persistence of two nuclei. In panels C and D nuclear fusion is taking place despite incomplete removal of the intervening cell wall (partial Fus⁻ phenotype) and in panels E and F nuclear fusion has been completely blocked by the inability to remove intervening cell wall (full Fus⁻ phenotype). (Reproduced from reference 21 by copyright permission of the Rockefeller University Press.)