title: Plasmids from two morphologically distinct cyanobacterial strains share a novel replication origin.
abstract: A 2.9-kbp replication origin from a plasmid endogenous to the filamentous cyanobacterium Fremyella diplosiphon UTEX 481 was genetically characterized and sequenced. Deletion analysis of the 2.9-kbp DNA fragment delimited the minimum region necessary for replication in F. diplosiphon Fd33 to approximately 2.5 kbp. DNA sequence analysis revealed that the F. diplosiphon plasmid replication origin is structurally very similar to and shares significant identity with the 1.75-kbp replication origin reported for plasmid pDU1, isolated from the morphologically distinct cyanobacterium Nostoc sp. strain PCC 7524. Each cyanobacterial plasmid replication origin includes a large open reading frame that predicts a conserved protein of unknown function; the predicted proteins of the replication origins are of similar sizes and 30% identical in amino acid sequence. Each cyanobacterial plasmid replication origin also possesses a region of dyad symmetry approximately 300 bp upstream of the conserved open reading frame.
authors.affiliation: Department of Plant Biology, Carnegie Institution of Washington, Stanford, California 94305.
authors.forename: M R
authors.initials: MR
authors.lastname: Schaefer
authors.forename: G G
authors.initials: GG
authors.lastname: Chiang
authors.forename: J G
authors.initials: JG
authors.lastname: Cobley
authors.forename: A R
authors.initials: AR
authors.lastname: Grossman
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D015183:Restriction Mapping; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D004269:DNA, Bacterial