Summary: Time-lapse cinematography and immunofluorescence microscopy were used to study cellular events during amoebal fusions and sexual plasmodium development in Amoebal fusions occurred frequently in mixtures of strains heteroallelic or homoallelic for the mating-type locus , but plasmodia developed only in the -heteroallelic cultures. These observations confirmed that controls development of fusion cells rather than cell fusion. Analysis of cell pedigrees showed that, in both types of culture, amoebae fused at any stage of the cell cycle except mitosis. In -heteroallelic fusion cells, nuclear fusion occurred in interphase about 2 h after cell fusion; interphase nuclear fusion did not occur in -homoallelic fusion cells. The diploid zygote, formed by nuclear fusion in -heteroallelic fusion cells, entered an extended period of cell growth which ended in the formation of a binucleate plasmodium by mitosis without cytokinesis. In contrast, no extension to the cell cycle was observed in -homoallelic fusion cells and mitosis was always accompanied by cytokinesis. In -homoallelic cultures, many of the binucleate fusion cells split apart without mitosis, regenerating pairs of uninucleate amoebae; in the remaining fusion cells, the nuclei entered mitosis synchronously and spindle fusion sometimes occurred, giving rise to a variety of products. Immunofluorescence microscopy showed that -heteroallelic fusion cells possessed two amoebal microtubule organizing centres, and that most zygotes possessed only one; amoebal microtubule organization was lost gradually over several cell cycles. In -homoallelic cultures, all the cells retained amoebal microtubule organization.


Article metrics loading...

Loading full text...

Full text loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error