Supernumerary DNAs in Plant Mitochondria. In: Hohn B, Dennis ES, editors. Genetic Flux in Plants. Vienna: Springer; 1985. pp. 91-109. [DOI: 10.1007/978-3-7091-8765-4_6]

High-frequency transfer of linear DNA containing 5'-covalently linked terminal proteins: electroporation of bacteriophage PRD1 genome into Escherichia coli

Using electroporation with the phage PRD1 genome, we set up a high-frequency DNA transfer system for a linear dsDNA molecule with 5'-covalently linked terminal proteins. The transfer was saturated when more than 100 ng of PRD1 genome was used. Electroporation efficiency was about four orders of magnitude higher than that obtained with transfection. Removal of the terminal protein abolished plaque formation, which could not be rescued by supplying the terminal protein or phage DNA polymerase or both in trans.

A comparison of cytoplasmic revertants to fertility from different CMS-S maize sources

The mitochondrial genome organizations of a number of independent culture-derived fertile CMS-S revertants with the nuclear genotype W182BN were compared to spontaneous field revertants with the genotypes WF9, M825/Oh07 and 38-11. Regions of the genome around sequences homologous to the terminal repeats of the linear S1 and S2 episomes characteristic of CMS-S mitochondria were used as hybridization probes on Southern blots of BamHI and SalI digested mitochondrial DNA. The results obtained suggest that the nuclear, not the cytoplasmic, genotype of the parent plant affects the type of novel mitochondrial DNA organization found in the revertant. The DNA reorganization during reversion from CMS-S in tissue culture appears to be similar to that observed in spontaneous revertants obtained during the normal plant life-cycle. Unlike the situation for reversion from CMS-T, no common DNA sequence or reading frame appeared to be lost or disrupted in revertants.

Transcription of the S-2 maize mitochondrial plasmid

Mitochondria from S (male-sterile) and RU (male-fertile) maize cytoplasms contain both autonomous plasmids and copies of plasmid sequences integrated into the mitochondrial genome. The S-2 plasmid in S, which appears essentially the same as the R-2 plasmid in RU, contains two large open reading frames (ORFs) that may encode gene products required for plasmid maintainance and replication. Transcripts from both ORF1 and ORF2 are readily detected in cytoplasms having free plasmids. The 5' ends of these RNAs, which are transcribed from opposite ends of the plasmid, correspond to nucleotide position 32 within each of the 208 bp terminal inverted repeats (IRs). In Normal (fertile) and Revertant S (now fertile) cytoplasms that have only integrated copies of the S-2 sequence, transcripts from the S-2 ORFs are either present in greatly reduced amounts, or not detectable. The loss of transcriptional activity is correlated with deletions of, or nucleotide changes within, the IRs associated with the integrated S-2 ORFs. Evidence for transcription of non-plasmid DNA adjacent to integrated IRs suggests that both free-plasmid and integrated forms of the plasmid IR have promoter-like activity.