Unilateral nuclear migration in Basidiomycetes: pheromone interaction, genomic conflicts and mating-system reversion

Unilateral nuclear migration (UNM) is a striking deviation from the normal reciprocal exchange of nuclei in mating between otherwise compatible monokaryons in Basidiomycetes. UNM has rarely been subject to systematical investigation. Here, we examine the scientific history of UNM in Basidiomycetes and evaluate the explanations brought forward. We suggest that UNM could have an evolutionary role in mating-system reversion from tetrapolarity by assuring a more stable (reciprocal) nuclear migration.