Septin-containing barriers control the differential inheritance of cytoplasmic elements

Area of Science:

• Cell biology
• Molecular biology
• Genetics

Background:

• Haploid cell fusion in Saccharomyces cerevisiae creates zygotes with unique cellular dynamics.
• The zygote midzone plays a critical role in the segregation of cellular components during early development.
• Understanding the spatial and temporal regulation of organelle and complex redistribution is key to cell division.

Purpose of the Study:

• To investigate the role of the septin annulus in the zygote midzone.
• To characterize the differential redistribution of supramolecular complexes and organelles during zygote development.
• To explain the preferential inheritance of single mitochondrial genotypes in terminal zygotic buds.

Main Methods:

• Microscopy techniques to observe supramolecular complexes and organelles in yeast zygotes.
• Genetic crosses involving strains with and without the PSI+ prion.
• Analysis of protein and organelle movement dynamics relative to septin localization.

Main Results:

• The septin annulus in the zygote midzone differentially affects the redistribution of complexes and organelles.
• Redistribution of supramolecular complexes (polysomes, Sup35p-GFP [PSI+]) is delayed compared to soluble proteins.
• Mitochondrial encounter is delayed until septin relocation, enabling preferential inheritance of a single mitochondrial genotype in buds.

Conclusions:

• Septin-mediated delays in the zygote midzone are crucial for regulating the inheritance patterns of cellular components.
• The rate of redistribution dictates the uniformity of complex and organelle inheritance.
• This mechanism provides a molecular basis for the observed mitochondrial inheritance bias in yeast zygotes.