title: Evolution of the chloroplast genome.
abstract: We discuss the suggestion that differences in the nucleotide composition between plastid and nuclear genomes may provide a selective advantage in the transposition of genes from plastid to nucleus. We show that in the adenine, thymine (AT)-rich genome of Borrelia burgdorferi several genes have an AT-content lower than the average for the genome as a whole. However, genes whose plant homologues have moved from plastid to nucleus are no less AT-rich than genes whose plant homologues have remained in the plastid, indicating that both classes of gene are able to support a high AT-content. We describe the anomalous organization of dinoflagellate plastid genes. These are located on small circles of 2-3 kbp, in contrast to the usual plastid genome organization of a single large circle of 100-200 kbp. Most circles contain a single gene. Some circles contain two genes and some contain none. Dinoflagellate plastids have retained far fewer genes than other plastids. We discuss a similarity between the dinoflagellate minicircles and the bacterial integron system.
authors.affiliation: Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK. c.j.howe@bioc.cam.ac.uk
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Howe
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Barbrook
authors.forename: V Lila
authors.initials: VL
authors.lastname: Koumandou
authors.forename: R Ellen R
authors.initials: RE
authors.lastname: Nisbet
authors.forename: Hamish A
authors.initials: HA
authors.lastname: Symington
authors.forename: Tom F
authors.initials: TF
authors.lastname: Wightman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000235:genetics; D001482:Base Composition; D018742:DNA, Chloroplast / Q000235:genetics*; D004141:Dinoflagellida / Q000235:genetics; D019143:Evolution, Molecular; D016678:Genome; D008969:Molecular Sequence Data; D018087:Plastids / Q000235:genetics*
chemical_list: D018742:DNA, Chloroplast