Fig 3.

Nuclear positioning during mating in the wild type (A) and kar7 mutant (B). DIC, differential interference contrast. a mating type cells producing Nop1-GFP and α mating type cells producing Nop1-mCherry were cocultured on MS mating medium. The two fluorescent signals were observed to merge, indicating that cytosolic fusion occurs during the process of a-α opposite-sex mating. The two nuclei remain separated in the dikaryotic hyphae. In the basidium, the two nuclei migrate toward each other and karyogamy occurs, resulting in diploidization. Meiosis follows, and chains of basidiospores are produced (A). In the crosses between two kar7 mutants, the dikaryotic hyphae produced are similar to those in the wild type; however, in the mutant basidia, the two congressed nuclei do not undergo fusion, resulting in a failure to proceed into meiosis or produce spore progeny (B). Scale bar = 5 μm.