A new type of plasmid from a wild isolate of Dictyostelium species: the existence of closely situated long inverted repeats.

A circular plasmid having high copy number was found in a wild isolate of Dictyostelium species. Gel electrophoresis, electron microscopy and Southern blot hybridization revealed that the plasmid, named pDG1, is 4.5 Kb (1.5 micron) in size with closely situated long inverted repeats. The plasmid seems to be located in the nuclei. It was not a derivative of ribosomal DNA. The possible correlation of the plasmid with the putative intermediate DNA of retrotransposon DIRS-1 found in Dictyostelium discoideum is discussed.