Circular plasmid DNAs from the red alga Gracilaria chilensis

Abstract

Total cellular DNA extracted from eight red algal species (from the genera Gracilaria, Gracilariopsis, Porphyra and Gymnogongrus) was centrifuged on Hoechst dye/CsCl gradients. In five species, plasmid-like DNAs banded with the A+T rich organellar DNAs in the CsCl gradients. Based on their electrophoretic migration in different agarose gels, the plasmid-like DNAs are circular. This is the first report of putative plasmid DNAs in the red algae outside the genus Gracilaria. Two similar Gracilaria chilensis plasmid-like DNAs of 3.8 and 3.4 kb (GC2 and GC3) were cloned in pUC19. The cloned GC2 DNA did not hybridize to either the organellar or nuclear genomes of G. chilensis, suggesting that GC2 is a true plasmid. GC2 did hybridize to the plasmid of one other red algal species, Gracilaria sordida.