title: Extrachromosomal DNA isolated from tomato big bud and Candidatus Phytoplasma australiense phytoplasma strains.
abstract: The nucleotide sequences of two extrachromosomal elements from tomato big bud (TBB) and one extrachromosomal element from Candidatus Phytoplasma australiense (Ca. P. australiense) phytoplasmas were determined. Both TBB plasmids (3319 and 4092 bp) contained an open reading frame ( approximately 570 bp) with homology to the rolling circle replication initiator protein (Rep). This gene was shorter than the rep genes identified from other phytoplasma plasmids, geminiviruses and bacterial plasmids. Both TBB extrachromosomal DNAs (eDNAs) encoded a putative DNA primase (dnaG) gene, a chromosomal gene required for DNA replication and which contains the conserved topoisomerase/primase domain. We speculate that the replication mechanism for the TBB phytoplasma eDNA involves the dnaG gene instead of the rep gene. The Ca. P. australiense eDNA (3773 bp) was shown to be circular and contained four open reading frames. The rep gene was encoded on ORF 1 and had homology to both plasmid (pLS1) and geminivirus-like domains.
authors.affiliation: Charles Darwin University, Darwin, NT 0909, Australia. lucy.tran-nguyen@cdu.edu.au
authors.forename: L T T
authors.initials: LT
authors.lastname: Tran-Nguyen
authors.forename: K S
authors.initials: KS
authors.lastname: Gibb
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D016000:Cluster Analysis; D019915:DNA Primase / Q000235:genetics; D017931:DNA Primers; D004261:DNA Replication / Q000235:genetics*; D004269:DNA, Bacterial / Q000302:isolation & purification*; D015180:Electrophoresis, Gel, Two-Dimensional; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D045582:Phytoplasma / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D019915:DNA Primase