In organello mitochondrial DNA and RNA synthesis in fertile and cytoplasmic male sterile Zea mays L

An in organello system is described in which radioactive nucleoside triphosphates are linearly incorporated into maize mitochondrial DNA and RNA for more than 60 minutes at 37 °C. The nuclear control over plasmid-like mitochondrial DNAs observed in vivo is faithfully duplicated in this system. These plasmid-like DNAs are replicated and transcribed very efficiently. In organello transcription included most of, if not the entire, mitochondrial genome, which suggests that the great sequence complexity in maize mitochondrial DNA is not necessarily derived from extensive noncoding regions. Regulation over cytoplasmic expression is indicated by the quantitative but not qualitative variation in transcription between mitochondrial chromosome segments isolated from different cytoplasms. This system provides a tool in studying regulation of organellar gene expression and DNA synthesis as well as evidence that higher plant mitochondrial messenger RNA is polyadenylated.