期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：10
页码：6032-6036
DOI：10.1073/pnas.77.10.6032
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要："Stoppers" are a class of Neurospora crassa extranuclear mutants characterized by gross deficiencies of cytochromes b and aa3 and an unusual growth phenotype which involves irregular periods of growth andnongrowth. In the present work, mtDNAs from all four stopper mutants were found to contain deletions or insertions detectable by restriction enzyme analysis. [stp] mtDNA consists predominantly of defective molecules which retain a 16-megadalton segment (EcoRI-1, -4, and -6) of wild-type mtDNA (40 megadaltons). The other stopper mutants show smaller alterations: [stp A18t]-618, a 0.35-kilobase deletion in EcoRI-7b; [stp B2]-651, a 4-kilobase insertion in EcoRI-2; and [stp A]-574, a 5-kilobase deletion in EcoRI-2 and -10. Based on these results, we propose that "stop-start" growth results from competition between certain defective mtDNAs which have a tendency to predominate and low concentrations of less defective mtDNA species which must be retained to sustain growth. Three additional extranuclear mutants ("nonstoppers") have also been found to contain deletions in mtDNA. Remarkably, the defective mtDNA species in two of these mutants ([poky]H1-10 and [SG-3]-551) retain different sizes (18 and 13 megadlatons, respectively) of the same region retained in [stp] mtDNA (i.e., EcoRI-1, -4, and -6). The findings suggest that production of defective mtDNAs in Neurospora is nonrandom with a preferred mechanism leading to retention of this segment. It may be significant that the retained segment contains both mitochondrial rRNA genes and most mitochondrial tRNA genes. These deletion mutants may provide a tool for genetic mapping of Neurospora mtDNA.
