PCR Amplification of the Mitochondrial DNA Sequence Specific to the Male-sterile and Normal Cytoplasm in Onion

We compared the transcriptional properties of mitochondrial DNA (mtDNA) from a pair of male-sterile (S cytoplasm)/maintainer (N cytoplasm) lines together with the nuclear-restored plants. The transcriptional patterns of the mitochondrial genes, cob and cox1, were different between N and S cytoplasm. We cloned and sequenced the cob gene from both N and S onion. The Scob gene diverged from the Ncob gene 56 bp 5' to the initiation codon. This upstream region of the Scob gene was homologous to a part of ORF1708 of the tobacco chloroplast DNA. We designed primers to amplify the upstream regions of the cob by PCR. A 414-bp DNA fragment was amplified from the total DNA of `2935A' (S cytoplasm) and a 130-bp DNA fragment was amplified from that of `2935B' (N cytoplasm) using a pair of primers specific to S cytoplasm and nor cytoplasm, respectively.