Cross hybridization between organelle RNAs and mitochondrial and chloroplast genomes in Brassica

Mitochondrial and chloroplast RNAs from male fertile and cytoplasmically male sterile Brassica napus cultivars were labelled by in organello uptake and incorporation of ³²P-UTP. Filter hybridization techniques indicated substantial sequence homology between mitochondrial transcripts and chloroplast DNA restriction fragments. The converse was also found, i.e., hybridization of chloroplast transcripts to mitochondrial DNA restriction fragments, although to a lesser degree. The data suggest that the large number of homologous sequences present in mitochondrial and chloroplast genomes remain transcriptionally active after transfer and integration into the other organellar genome.