Induction of autogamy by transfer of macronuclear karyoplasm in Paramecium tetraurelia.

Macronuclear karyoplasm was transplanted from pre-autogamous donor cells (clonal age, 22 fissions) into the macronucleus of young recipient cells (2 fissions after autogamy occurred) by means of microinjection. A reciprocal experiment was carried out by injecting karyoplasm from young clonal age donors into pre-autogamous recipients. In the case of karyoplasm transfer from pre-autogamous donors to young recipients, autogamy occurred early in 67% of injected cells, whereas reciprocal injections had no influence on the onset of autogamy, and all of the injected cells underwent autogamy. Such results indicate a distinct role of pre-autogamous cells of macronucleus in the induction of autogamy.