Post-fusion somatic incompatibility in plasmodia of Physarum polycephalum

Area of Science:

• Cell Biology
• Mycology
• Genetics

Background:

• Cell fusion in myxomycetes can lead to incompatibility reactions.
• The 'killer' and 'sensitive' strain system in Physarum polycephalum provides a model for studying cellular interactions.

Purpose of the Study:

• To investigate the cellular and nuclear events during the incompatibility reaction between 'killer' and 'sensitive' strains of Physarum polycephalum.
• To characterize the fate of nuclei from both strains following fusion.

Main Methods:

• High-resolution autoradiography was employed to track nuclear behavior.
• Microscopic observation was used to assess nuclear and cytoplasmic changes.

Main Results:

• Sensitive strain nuclei are selectively damaged, vacuolated, and eliminated from the cytoplasm.
• Nuclear damage manifests as chromatin condensation and nucleolar segregation.
• Nuclear envelopes exhibit blebbing, and endoplasmic reticulum vesicles increase.
• Multiple nuclear fusions occur between genetically similar and dissimilar nuclei.
• Mean nuclear diameter increases significantly post-reaction, with population size normalizing later.
• Fusion near killer strain mitosis results in neutral heterokaryons that convert to killer phenotype.

Conclusions:

• The incompatibility reaction in Physarum polycephalum involves targeted elimination of sensitive nuclei.
• Nuclear fusion dynamics and cellular responses are key features of this incompatibility.
• Mitotic stage influences the outcome of incompatible fusions, leading to phenotypic conversion.