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Escape from het-6 incompatibility in Neurospora crassa partial diploids involves preferential deletion within the
M L Smith1, C J Yang, R L Metzenberg
1Biology Department, Carleton University, Ottawa, Ontario, Canada. mysmith@ccs.carleton.ca
Genetics
|October 1, 1996
Summary
In Neurospora crassa, self-incompatibility "escape" in partial diploids was linked to DNA deletions. These deletions, varying in size, consistently involved a specific region, suggesting a mechanism similar to tumor suppressor gene loss in humans.
Area of Science:
- Genetics
- Molecular Biology
- Mycology
Background:
- Self-incompatibility in *Neurospora crassa* is regulated by het loci.
- Partial diploids heterozygous for het-6 alleles (het-6OR/het-6PA) exhibit incompatibility.
- Translocations can create duplicated genomic regions, influencing genetic interactions.
Purpose of the Study:
- To investigate the genetic and molecular mechanisms underlying "escape" from het-6 incompatibility in *Neurospora crassa* partial diploids.
- To characterize the nature and extent of genomic alterations associated with this escape phenomenon.
Main Methods:
- Construction of self-incompatible partial diploids using a translocation strain.
- Phenotypic analysis of growth rates to identify "escape" strains.
- Molecular characterization using Restriction Fragment Length Polymorphisms (RFLPs) and chromosomal electrophoresis.
- Analysis of deletions in relation to the het-6 locus.
Main Results:
- Approximately 25% of partial diploids showed increased growth, indicating escape from het-6 incompatibility.
- Escape strains predominantly retained the het-6 allele from the normal chromosome II (LGII) position (80%) or the translocated position (16%).
- Molecular analyses revealed that escape is consistently associated with deletions of duplicated DNA segments, ranging from 70 kbp to the entire 270-kbp translocated region.
Conclusions:
- Mitotic deletions are the primary mechanism for "escape" from het-6 incompatibility in *Neurospora crassa* partial diploids.
- These deletions always encompass a hypothesized 35-kbp region containing the het-6 gene.
- The observed deletion spectrum parallels mechanisms seen in the loss of tumor suppressor genes and the hprt gene in humans, suggesting conserved pathways for genomic instability.