| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1999: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
The mitochondrial genomes (mt-genomes) of the higher basidiomycetes have very little molecular genetic information regarding overall genome structure or gene structure and function. The aim of this study is to evaluate the overall structure of mt-genomes of the higher basidiomycete Pleurotus ostreatus and to clarify the basis for mitochondrial DNA restriction fragment length polymorphism (RFLP) in natural populations of this fungus. I thereupon determined the complete nucleotide sequence of two types (strain no.-5 17 type and -286 type) mt-genomes of this fungus. The two mt-genomes are 71,948 and 72,466 base pairs circular molecules and I observed that they are very A + T rich (about 73%). By searching for genes in the strain no. 517 type mt-genome using the programs BLAST and tRNA-scan, a total of 55 possible genes were identified. These included genes for two species of ribosomal RNA, 26 genes of transfer RNA (tRNA) and 14 open reading frames(ORFs) for functionally known proteins and
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13 ORFs predicted as possible genes, excluding intronic ORFs. The gene content of P.ostreatus mt- genome is considered to be virtually the same as that of the other fungal mt- genomes that have been reported. The number of tRNA genes encoded in the mt- genome was not sufficient to support the synthesis of mitochondrial protein, suggesting that the undetectable tRNA genes in the mt-genome may be nuclear- encoded and imported from the cytoplasm. Comparing the two mt-genome structures, no differences were found between the two mt-genomes analyzed in terms of gene content, gene order and the direction for the translation of each gene. However, in a comparison of differences in sequence between the two mt- genomes, multiple small-size insertions/deletions and point mutations were found mainly in the interspacer region of genes, some of which produced new restriction sites. Moreover, large fragments of insertions/deletions longer than 1 kb were also found both in the interspacer regions of genes and in the intrageneric regions, where there were different intronic sequences. This indicates, in particular, that the difference of intronic sequences contained each mt-genome is the primary basis for the production of the RFLP observed in both. Less
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