title: Characterization of two circular plasmids from the marine diatom Cylindrotheca fusiformis: plasmids hybridize to chloroplast and nuclear DNA.
abstract: This paper reports the discovery and initial characterization of two small plasmids, pCf1 and pCf2, in the marine diatom Cylindrotheca fusiformis. Extracted diatom DNA separates into two bands in CsCl-Hoechst 33258 dye gradients. Upon agarose gel electrophoresis of a sample of the upper band of the gradient we observed, in addition to high molecular weight (genomic) chloroplast and mitochondrial DNA, pairs of lower molecular weight bands. These bands contained two species of circular plasmid DNA molecules, as shown by electron microscopy. The nucleotide composition of the plasmids, and chloroplast and mitochondrial DNAs is similar, as indicated by their co-banding in the gradients. They were cloned, and their restriction maps determined, showing that pCf1 is 4.27 and pCf2 4.08 kb in size. By hybridization analysis, we showed that pCf1 and pCf2 share regions of similarity, but not identity. Neither plasmid hybridizes with mitochondrial DNA. Both plasmids hybridize with chloroplast DNA, and pCf2 also hybridizes with nuclear DNA.
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093.
authors.forename: J D
authors.initials: JD
authors.lastname: Jacobs
authors.forename: J R
authors.initials: JR
authors.lastname: Ludwig
authors.forename: M
authors.initials: M
authors.lastname: Hildebrand
authors.forename: A
authors.initials: A
authors.lastname: Kukel
authors.forename: T Y
authors.initials: TY
authors.lastname: Feng
authors.forename: R W
authors.initials: RW
authors.lastname: Ord
authors.forename: B E
authors.initials: BE
authors.lastname: Volcani
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism*; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000648:ultrastructure; D004272:DNA, Mitochondrial / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000235:genetics; D056890:Eukaryota / Q000235:genetics*; D008854:Microscopy, Electron; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D015183:Restriction Mapping
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA