|Budget Amount *help
¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1998 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1997 : ¥1,900,000 (Direct Cost : ¥1,900,000)
The aim of this study is to elucidate the mechanism for inter-molecular recombination between parental mitochondrial DNAs (mtDNAs) occurring in sexual cross of higher basidiomycete, Pleurotus ostreatus (Jacq. : FR.) Kummer. The recombination sites in each parental mtDNA for generation of new BamHI fragment, REC-A (7.0 kb), were estimated by construction of the physical maps and by Southern-blot analysis using REC-A DNA as a probe, and their nucleotide sequences were determined. Such recombinational regions in parental mtDNAs possessed more than 2 kb of consensus sequences with each other, which were split by one and two regions with nonconsensus sequences (1.2 to 1.7 kb in size), respectively. While, the nucleotide sequences of the region around REC-A in recombinant mtDNA was consist of consensus and all nonconsensus sequences recognized in both parental mtDNAs, suggesting that the polymorphism around the REC-A was caused by integrations of the regions with nonconsensus sequences contained in one parental mtDNA into the other. Part of consensus sequences between parental mtDNAs indicated homology to exonic sequences of the cytochrome oxidase subunit 1 (cx1) genes of fungi, and also each nonconsensus sequences were homologous to the sequences of group I intron located in the cx1 genes of fungi. Each intron possessed ORF which encoded a LAGI-DADG motif, characteristic of the endonucleases involved in group I intron mobility. These results indicate that the mechanism of recombination for generating the REC-A fragment is elucidated by the gene-conversion, achieved by the mobility of the introns within the cx1 gene locus. Furthermore, by comparison of the physical maps among parental and recombinant mtDNAs, it was suggested that the similar manner of recombinations between parental mtDNAs were occurred in other recombination sites.