Abstract
The complete nucleotide sequence (501,020 bp) of the mitochondrial genome from cytoplasmic male-sterile (CMS) sugar beet was determined. This enabled us to compare the sequence with that previously published for the mitochondrial genome of normal, male-fertile sugar beet. The comparison revealed that the two genomes have the same complement of genes of known function. The rRNA and tRNA genes encoded in the CMS mitochondrial genome share 100% sequence identity with their respective counterparts in the normal genome. We found a total of 24 single nucleotide substitutions in 11 protein genes encoded by the CMS mitochondrial genome. However, none of these seems to be responsible for male sterility. In addition, several other ORFs were found to be actively transcribed in sugar beet mitochondria. Among these, Norf246 was observed to be present in the normal mitochondrial genome but absent from the CMS genome. However, it seems unlikely that the loss of Norf246 is causally related to the expression of CMS, because previous studies on mitochondrial translation products failed to detect the product of this ORF. Conversely, the CMS genome contains four transcribed ORFs (Satp6presequence, Scox2-2 , Sorf324 and Sorf119) which are missing from the normal genome. These ORFs, which are potential candidates for CMS genes, were shown to be generated by mitochondrial genome rearrangements.
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Acknowledgements
We gratefully acknowledge Drs. Yuji Kishima and Yoshinori Nishita for technical advice and continuous encouragement, and Dr. Takahiko Tsudzuki for drawing the Figures. This work was done in part at the Research Center for Molecular Genetics, Hokkaido University, and was supported in part by Grants in Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and a grant from the Program for Promotion of Basic Research Activities for Innovative Biosciences, Japan. A. E. was the recipient of a Japanese Government (Monbusho) Scholarship.
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Satoh, M., Kubo, T., Nishizawa, S. et al. The cytoplasmic male-sterile type and normal type mitochondrial genomes of sugar beet share the same complement of genes of known function but differ in the content of expressed ORFs. Mol Genet Genomics 272, 247–256 (2004). https://doi.org/10.1007/s00438-004-1058-9
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DOI: https://doi.org/10.1007/s00438-004-1058-9