Relationships Among Plasmid-Like DNAs of the Maize Mitochondria
In addition to the high molecular weight DNA normally encountered in maize mitochondria, several cytoplasms contain plasmid-like DNAs. In the S cytoplasm (cms-S), two plasmid-like DNAs are found, S-1 and S-2, which are about 6.4 and 5.4 kilobases (kb) long, respectively (Pring et al., 1977). Electron microscopy has shown that these molecules have a linear configuration with defined ends. However, these observations do not rule out the possibility that linearity could have arisen by the breakage of native circular molecules. Additional studies have demonstrated novel sequence arrangements in that both S-1 and S-2 are terminated by inverted repeats, which are about 0.2 kb long (Levings and Pring, 1979). About 1.7 kb of terminally located sequence homology exist between the S-1 and S-2 DNAs. The common sequences involve 1.5 kb, including the inverted repeat, at one end, and at the other end, the 0.2 kb inverted repeat.
KeywordsMaize Recombination Timothy
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