Sequence and transcript analysis of the Nco2.5 Ogura-specific fragment correlated with cytoplasmic male sterility in Brassica cybrids

Abstract
Sequence analysis of the Ogura-specific mitochondria) DNA (mtDNA) fragment isolated previously from Brassica cybrids carrying Ogura cytoplasmic male sterility (cms) revealed a tRNAfMet sequence, a putative 138 amino acid open reading frame (orf138), and a 158 amino acid ORF (orf158) previously observed in mitochondria) genomes from several other plant species. Transcription mapping showed that both ORFs are present on a 1.4 kb cms-specific transcript. The orf158 sequence is also transcribed in fertile plants on a different mRNA, and thus is unlikely to be related to cms. On the other hand, fertile revertant plants lack transcripts of the orf138 sequence, whose possible role in the mechanism of Ogura cms is discussed.