An ameiotic mutant of Coprinus cinereus halted prior to pre-meiotic S-phase

Area of Science:

• Mycology
• Genetics
• Developmental Biology

Background:

• Coprinus cinereus is a model organism for studying fungal development and genetics.
• Meiosis is a critical process for sexual reproduction in fungi, involving DNA replication and chromosome segregation.
• Understanding the genetic regulation of meiosis is essential for comprehending fungal life cycles.

Purpose of the Study:

• To investigate the function of a newly identified dominant mutation, Mar, in Coprinus cinereus.
• To determine the effect of the Mar mutation on key developmental stages, particularly meiosis and fruiting body formation.
• To elucidate the molecular mechanism underlying the Mar mutation's impact on DNA replication and development.

Main Methods:

• Isolation and characterization of five Coprinus cinereus monokaryons with the Mar mutation.
• Formation of dikaryons by mating Mar-bearing and normal monokaryons.
• Analysis of fruiting body development, including basidia and karyogamy.
• DNA polymerase assays using extracts from Mar-bearing dikaryons.
• Radioactive labeling (32P) to assess DNA and RNA synthesis in cap tissue.

Main Results:

• Dikaryons formed with Mar-bearing monokaryons exhibited aborted fruiting bodies with a failure in basidial karyogamy.
• The Mar mutation was found to likely prevent pre-meiotic DNA replication, as indicated by low DNA synthesis in polymerase assays.
• Limited incorporation of 32P into DNA and RNA was observed in Mar-bearing fruiting body tissue at the pre-meiotic stage.
• Aborted fruiting bodies resembled those of normal cultures treated with cycloheximide or high temperature prior to S-phase.
• Mar-bearing monokaryons failed to form fruiting bodies under nutritional stress, unlike normal monokaryons.

Conclusions:

• The Mar mutation in Coprinus cinereus disrupts meiosis by inhibiting pre-meiotic DNA replication.
• This defect leads to developmental abnormalities, including aborted fruiting bodies and failure of karyogamy.
• The Mar mutation highlights a critical regulatory point in the transition to meiosis and impacts fungal development under stress conditions.