Dikaryotic

Dikaryotic describes cells or hyphae that contain two genetically distinct haploid nuclei within each cell. This condition results from plasmogamy, the fusion of cytoplasm between two compatible fungal hyphae, while the nuclei do not immediately fuse (no karyogamy). The dikaryotic stage is a hallmark of many fungi, especially basidiomycetes, and also occurs in some ascomycetes.

In dikaryotic mycelium, the two nuclei coexist in each cell and divide synchronously during mitosis, with each daughter cell containing one nucleus of each genotype. Septa with pores allow limited cytoplasmic exchange but help maintain two separate nuclei. Clamp connections in many basidiomycetes aid the distribution of nuclei to new cells.

The dikaryotic phase is typically transient relative to the haploid and diploid phases. It persists until karyogamy occurs, producing a diploid zygote that immediately undergoes meiosis to generate haploid spores. In basidiomycetes, the dikaryotic mycelium often forms fruiting bodies, where basidia facilitate karyogamy and meiosis within the basidium. In some fungi, a prolonged dikaryotic stage precedes sexual reproduction.

Etymology and scope: dikaryon means “two nuclei.” The term is used for the stage or organism carrying two distinct nuclei per cell; it is not the same as diploid tissue, which contains paired homologous chromosomes within a single nucleus. The occurrence and length of the dikaryotic phase vary among fungal taxa.