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Mitochondrial inheritance in Aspergillus nidulans
A Coenen1, J H Croft, M Slakhorst
1Department of Genetics, Agricultural University, Wageningen, The Netherlands. Alex Coenen@PopGen@E1.WAU.NL
Abstract:
Mitochondrial chloramphenicol and oligomycin resistance mutations were used to investigate mitochondrial inheritance in A. nidulans. Mitochondrial RFLPs could not be used to distinguish between paternal and maternal mitochondria because none were detected in the 54 isolates investigated. Several thousand ascospores from each of 111 hybrid cleistothecia from 21 different crosses between 7 heterokaryon incompatible isolates were tested for biparental inheritance. All mitochondrial inheritance was strictly uniparental. Not one instance of paternal inheritance of mitochondria was observed. The implications of our results for the theory that uniparental inheritance evolved to avoid cytoplasmic conflict are discussed. Possible explanations for the maintenance of strict uniparental inheritance of mitochondria in an inbreeding homothallic organism are suggested. The chloramphenicol resistance marker was inherited preferentially to the oligomycin resistance marker probably due to the inhibited energy production of mitochondria with the oligomycin resistance mutation. The maternal parent was determined for 93 hybrid cleistothecia from 17 crosses between 7 different strains. Contrary to previous reports A. nidulans strains functioned as both maternal and paternal parent in most crosses.
Insights
Mitochondrial inheritance in Aspergillus nidulans is strictly uniparental, with no paternal transmission observed. This study explores the reasons for this phenomenon and discusses the implications for theories on cytoplasmic inheritance.
Area of Science:
- Genetics
- Molecular Biology
- Mycology
Background:
- Mitochondrial inheritance patterns are crucial for understanding cellular evolution and genetic disease.
- Aspergillus nidulans, a model organism, has been studied for its genetic mechanisms, including mitochondrial inheritance.
Purpose of the Study:
- To investigate the mode of mitochondrial inheritance in Aspergillus nidulans using drug resistance markers.
- To determine if biparental inheritance occurs and to identify the maternal and paternal parents in crosses.
Main Methods:
- Utilized chloramphenicol and oligomycin resistance mutations as genetic markers for mitochondria.
- Analyzed thousands of ascospores from multiple crosses to assess inheritance patterns.
- Employed mitochondrial RFLPs, though they proved ineffective for distinguishing parental origins.
Main Results:
- All observed mitochondrial inheritance in Aspergillus nidulans was strictly uniparental, with no instances of paternal inheritance detected.
- The chloramphenicol resistance marker showed preferential inheritance over the oligomycin resistance marker.
- Contrary to prior research, A. nidulans strains acted as both maternal and paternal parents in most crosses.
Conclusions:
- Strict uniparental mitochondrial inheritance in A. nidulans may have evolved to prevent cytoplasmic conflict.
- The study suggests potential explanations for maintaining this strict inheritance in an inbreeding organism.
- Re-evaluation of parental roles in A. nidulans crosses is warranted based on these findings.