Homolog pairing and meiotic progression in Coprinus cinereus

Area of Science:

• Cell Biology
• Genetics
• Mycology

Background:

• Meiosis is a fundamental process for sexual reproduction, involving precise chromosome pairing and segregation.
• Understanding homolog pairing dynamics is crucial for comprehending genetic stability and recombination.
• The basidiomycete Coprinus cinereus provides a model system for studying synchronous meiotic events.

Purpose of the Study:

• To investigate the timing and characteristics of homologous chromosome pairing during synchronous meiosis in Coprinus cinereus.
• To determine if chromosome size influences the rate of homologous pairing.
• To examine the relationship between chromosome pairing, chromatin condensation, and nucleolar fusion.

Main Methods:

• Fluorescence in situ hybridization (FISH) was employed to visualize and analyze homologous chromosome pairing.
• Spread preparations of meiotic nuclei were used to examine nuclei at various time points post-karyogamy.
• Two probes targeting the same homologous pair were utilized to assess pairing extent.

Main Results:

• Homologous chromosome pairing initiates rapidly following karyogamy, with significant pairing observed by 4 hours post-karyogamy.
• Chromosome size (1 Mb vs. 2.5 Mb) did not affect the speed of homologous association.
• Interstitial, single-copy sites can stably associate before nucleolar fusion.
• Chromatin condensation increases post-pairing, leading to stable compaction during the pachytene stage.

Conclusions:

• Homologous chromosome pairing is a rapid and efficient process in Coprinus cinereus meiosis.
• The observed chromatin condensation and stable compaction at pachytene are integral to successful meiotic progression.
• These findings contribute to a deeper understanding of the molecular mechanisms governing meiotic chromosome dynamics.