Intraspecific Comparison of Three Complete Mitochondrial Genome Sequences from the Oyster Mushroom, Pleurotus ostreatus

摘要

Mitochondria, ATP-producing organelles in cells, have their own independent genomes called the mitochondrial (mt) genome. The effects of the mt genome structure on cellular phenotype during the fruiting body formation of basidiomycetes are presumably important; however, these effects have not been elucidated. Intraspecific variation of mt genome structures, which is indispensable information for assessing the effects of mt genome structure, has been assessed mainly by using restriction fragment length polymorphism (RFLP) patterns. Here, we used complete mt genome sequences of Pleurotus ostreatus isolates to examine intraspecific variation among mt genome structure among three genome types, Ⅰ (accession number: AB573642), Ⅱ (accession number; AB573692), and III (NC_009905), and compared this variation with that determined using RFLP patterns. The mt genome of each P. ostreatus type was a circular DNA molecule ranging in size from 71 947 bp (type Ⅰ) to 73 242 bp (type III). Each of the genomes contained 14 common mt genes, one ribosomal small subunit protein 3 gene, one RNA polymerase gene (only in type Ⅲ), two DNA polymerase genes, and two rRNA genes. Twenty-four tRNA genes were determined to form a common set among the three types of mt genomes. The type Ⅰ mt genome had two additional tRNA genes. The gene orders in each mt genome were almost identical, but each had different open reading frames (ORFs) and introns. Comparison of nucleotide sequences showed that there were many substitutions and indels in the intergenic regions. Furthermore, nucleotide sequence differences were observed in gene-coding regions, the majority of which were related to polymorphisms in amino-acid coding sequences. These results indicated both conservation of mt genome primary structure in P. ostreatus species and sequence polymorphisms that corresponded to the mtDNA RFLPs.