Using the 'Buller phenomenon' in experimental evolution studies of basidiomycetes

A. The standard life cycle of a heterothallic basidiomycete fungus. Sexual spores germinate (upper left) give rise to a haploid monokaryon. Two compatible monokaryons can fuse, upon which they reciprocally exchange nuclei, without cytoplasmic mixing (down left). This leads to the formation of the dikaryon (grey, right), all cells of which have two different nuclei, and which is a cytoplasmic mosaic. The dikaryon can produce mushrooms (schematically drawn on the grey dikaryon), the sexual fruiting bodies, where a short diploid stage is immediately followed by meiosis and sexual spore formation. The insert shows how the two nuclei in a dikaryotic cell are distributed over cells during cell division via the formation of clamp connections. B. The monokaryons exhibit two clearly distinct behaviors in a mating, accepting a nucleus, and donating a nucleus, which can be considered as female and male roles, respectively.