An Analysis Of The Mitochondrial And Nuclear Genomes Of Two Basidiomycetes, Coprinus Cinereus And Coprinus Stercorarius (fungi, Dna Transfer).

The structure and organization of mitochondrial DNA from two basidiomycete species, Coprinus cinereus and Coprinus stercorarius, were analyzed by mapping of restriction enzyme sites and determining the order of nine mitochondrial genes by Southern hybridization, using isolated fragments of Saccharomyces cerevisiae petite DNAs. The mitochondrial genome sizes (43.3 and 91.1 kilobase pairs, respectively), restriction site patterns, and gene orders for these two species all differ significantly. Additionally, one of these nine genes, varl, appears to be absent in the C. cinereus mitochondrial genome. The relationship between these two species was assessed by measuring mitochondrial and nuclear DNA sequence divergence by thermal elution of DNA duplexes from hydroxylapatite. These genomes were found to be quite divergent. Only a small fraction of either nuclear or mitochondrial DNA, perhaps corresponding to the coding sequences, was capable of reassociating. Those sequences capable of reassociating were found to have a 15% divergence for the mitochondrial genomes and a 7-15% divergence for the nuclear genomes, depending on the reassociation criterion. The nuclear genomes of these two species were hybridized with DNA from nine mitochondrial genes of S. cerevisiae in order to detect homologies that might indicate DNA transfer between mitochondria and the nucleus. Nuclear homologies were found to four genes in both species and, additionally, to varl in C. cinereus. The homologies to the four common gene probes were localized to various regions of the nuclear ribosomal DNA (rDNA) repeat unit in both species. The varl homology was not found within this repeat unit. Analysis of one of these rDNA homologies at the level of DNA sequencing revealed only a 38 base pair region of the rDNA with 65.8% homology to the yeast cytochrome oxidase subunit 1 gene probe. Although this low level of homology is not indicative of a mitochondrial-nuclear DNA transfer event, further investigation of the other rDNA homologies may provide such evidence.PhDBiological SciencesMolecular biologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127779/2/8521007.pd