The mechanism of nuclear migration in Basidiomycetes

In various fungi genetically marked nuclei implanted in a mycelium of a different genotype can, after an interval of hours, be recovered centimeters away from the implant. Such immigrant nuclei, besides dividing and colonizing the established mycelium, undergo intercellular migration with astonishing speed. Nuclear migration and mating behaviour are regulated genetically by incompatibility factors. In 1964, two hypotheses were proposed as possible mechanisms for nuclear migration in Basidiomycetes. The propulsion hypothesis assumes that the nuclei are self-propelled, and the flow hypothesis assumes that the nuclei are carried passively in actively streaming protoplasm. Two experimental designs were formulated to differentiate between the two hypotheses. One design was successfully applied, and the results obtained are consistant with the flow hypothesis. The other involved technical difficulties which have not been overcome.